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The quantification of upland runoff for subsurface drainage design Runesson, Deborah 1986

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THE QUANTIFICATION OP UPLAND RUNOFF FOR SUBSURFACE DRAINAGE DESIGN By DEBORAH RUNESSON B . S c , Lakehead U n i v e r s i t y , 1982 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF BIO-RESOURCES ENGINEERING) We accept t h i s t h e s i s as conforming t/jo the r e p a i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1986 ° Deborah Runesson, 1986 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department or by h i s o r her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of Bio-Resources Engineering The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date April 18, 1986 i i ABSTRACT Accurate upland r u n o f f and peak flow estimates are c r u c i a l f o r s u c c e s s f u l subsurface drainage design i n adjacent lowland a g r i c u l t u r a l r e g i o n s . Three techniques used i n drainage design, namely the SCS Curve Number approach f o r r u n o f f e s t i m a t i o n , and the SCS u n i t hydrograph procedure and the R a t i o n a l formula f o r peak flow e s t i m a t i o n were eva l u a t e d . A s m a l l upland r e s e a r c h watershed was e s t a b l i s h e d at A g r i c u l t u r e Canada's A g a s s i z Research S t a t i o n , Farm #2, i n the e a s t e r n end of the Lower F r a s e r V a l l e y of B r i t i s h Columbia. The use of d i g i t a l e l e v a t i o n models to a s s i s t i n watershed a n a l y s i s was reviewed through the development of a model f o r the Research watershed. F i n d i n g s showed that the SCS Curve Number approach underestimated r u n o f f . The R a t i o n a l formula p r o v i d e d the best estimates of peak flow. The use of a d i g i t a l e l e v a t i o n model pro v i d e d r e q u i r e d parameters f o r the v a r i o u s methods t e s t e d , and showed high p o t e n t i a l f o r f u r t h e r use i n watershed q u a n t i f i c a t i o n . i i i TABLE OF CONTENTS PAGE ABSTRACT i i LIST OF TABLES v i i i LIST OE FIGURES x ACKNOWLEDGEMENT x i i i A. INTRODUCTION ! 1 B. OVERVIEW OF THEORY AND PROCEDURES 4 B.1. Watershed q u a n t i f i c a t i o n - c o n v e n t i o n a l approaches 4 B . 2 . D i g i t a l e l e v a t i o n m o d e l l i n g 5 B. 2 . a . types of d i g i t a l e l e v a t i o n models 6 B . 2 . a . i . the i r r e g u l a r DEM 6 B . 2 . a . i i . the contour DEM 7 B . 2 . a . i i i . the p r o f i l e DEM 7 B. 2 . a . i v . the g r i d DEM 8 B. 2.b. a p p l i c a t i o n of d i g i t a l e l e v a t i o n models 10 C. RUNOFF ESTIMATION PROCEDURES 16 C. 1. Hydrograph a n a l y s i s 16 C . 2 . S o i l C o n s e r v a t i o n S e r v i c e curve number method ... 24 C. 2 . a . l a n d use and treatment c l a s s e s 2 4 C . 2 . b . h y d r o l o g i c s o i l groups 2 5 C . 2 . c . antecedent s o i l moisture c o n d i t i o n 2 7 C . 2 . d . r u n o f f e s t i m a t i o n 28 C 3 . P h y s i c a l l y "based r a i n f a l l - r u n o f f models 2 9 C.J.a. model s t r u c t u r e 3 2 C. 3 . a . i . i n t e r c e p t i o n / d e p r e s s i o n s t o r e 3 2 i v C 3 - a . i i . n e a r - s u r f a c e ( i n f i l t r a t i o n ) s t o r e 33 C3«a.iii. v a r i a b l e c o n t r i b u t i n g area component r e l a t e d t o subsurface s o i l water storage 34 C3.a.iv. delayed subsurface flow 34 C.J.a.v. overland flow 35 C.3«b. model theory 36 C. 3 . C . model c a l i b r a t i o n 42 C 3 . c i . overland flow, i n t e r c e p t i o n and i n f i l t r a t i o n parameters 42 C . J . c i i . subsurface storage parameters 47 C 3 . c i i i . channel r o u t i n g procedures 48 C3«d.. a n a l y z i n g catchment topography 49 C . 3 • d.. i . r e c t a n g u l a r planes 50 C3«d.ii. r e c t a n g u l a r curved flow s u r f a c e 50 C . 3 . d . i i i . convergent plane s e c t i o n 51 D. PEAK FLOW ESTIMATION 53 D.1. Time of c o n c e n t r a t i o n 53 D. 2. S o i l C o n s e r v a t i o n S e r v i c e u n i t hydrograph method . 54 D. 2.a. peak discharge of the u n i t hydrograph 55 D-3. R a t i o n a l formula 57 D.3-a. overview of use and development 57 E. WATERSHED DESCRIPTION 61 E. 1. H i s t o r i c a l landuse 61 E.2. N a t i v e v e g e t a t i o n 62 E.3. General c l i m a t e 63 E.4. S o i l s 63 E.4.a. upland s o i l s 65 E.4-a.i. S l o l l i c u m S e r i e s 65 E . 4 . a . i i . Poignant S e r i e s ( o r t h i c "brown wooded) .. 66 E . 4 . a . i i i . I s a r S e r i e s ( o r t h i c r e g o s o l ) 67 E.4-a.iv. H a r r i s o n s e r i e s (degraded a c i d brown) .. 68 E.4.a.v. Ryder s e r i e s ( o r t h i c a c i d wooded s o i l ) .. 69 E.4-"b. lowland s o i l s 70 E.4-b.i. Gibson Muck (organic s o i l ) 70 E . 4 - b . i i . Banford muck (or g a n i c s o i l ) 71 E. 4 - " b . i i i . Annis (rego g l e y s o l ) 72 E.4.b.iv. H a t z i c ( o r t h i c humic g l e y s o l s o i l ) 73 E.4.b.v. H j o r t h s e r i e s 74 P. PROCEDURES 76 P.1. Watershed q u a n t i f i c a t i o n 76 P.1.a. c r e a t i o n of a d i g i t a l data base 77 P.1.b. a n a l y t i c a l software 80 P. 1 .b. i . a rea 80 P. 1 . b . i i . p r o f i l e s 82 P.2. Runoff e s t i m a t i o n 83 P.2.a. f i e l d i n s t r u m e n t a t i o n 83 P.2.b. hydrograph s e p a r a t i o n 86 P.2.c. r u n o f f measurement from hydrographs 87 P.2.d. S o i l C o n s e r v a t i o n S e r v i c e Curve Number method 87 P.2.e. model c a l i b r a t i o n 95 P.2.e.i. s p r i n k l i n g i n f i l t r o m e t e r design 95 P . 2 . e . i i . s p r i n k l i n g i n f i l t r o m e t e r c a l i b r a t i o n v i procedures 9 9 F. 3 - Peak flow e s t i m a t i o n 1 0 2 F . 3 « a . time of c o n c e n t r a t i o n d e t e r m i n a t i o n 1 0 2 F . 3 - a . i . Nomograph 1 0 2 F . 3 - a . i i . Kerby formula 1 0 3 F . 3 « a . i i i . Flow v e l o c i t y method 1 0 3 F . 3 - a . i v . K i r p i c h formula 1 0 5 F . 3 - a . v . Lag method 106 F . 3 - b . SCS u n i t hydrograph procedure 1 0 7 F .3.C R a t i o n a l formula method 108 F . 3 - d . weir c a l i b r a t i o n 1 0 9 G. RESULTS AND DISCUSSION 1 1 0 G . 1 . D i g i t a l E l e v a t i o n Model performance 1 1 0 G. 1.a. data c o l l e c t i o n techniques 1 1 0 G . 1.b. DEM c r e a t i o n 1 1 0 G . 1.c. area comparisons 1 2 1 G . 1.d. p r o f i l i n g performance 1 2 3 G . 2 . Runoff comparisons 1 2 5 G . 2.a. watershed curve numbers 1 2 5 G . 2.b. r u n o f f estimates 128 G . 3 . TOPMODEL e v a l u a t i o n 1 3 4 G . 4 - Peak flow comparisons 1 3 9 G . 4-a. time of c o n c e n t r a t i o n - h y d r a u l i c l e n g t h .... 1 3 9 G . 4-b. time of c o n c e n t r a t i o n 1 4 0 G . 4 - C . peak flow estimates 1 4 4 H. CONCLUSIONS 1 5 0 v i i I. REFERENCES 155 APPENDICIES 160 APPENDIX A ( a e r i a l photographs) 161 APPENDIX B (contour map) 164 APPENDIX C (DEM programs) 166 APPENDIX D ( r e c e s s i o n a n a l y s i s ) 176 APPENDIX E (hydrograph s e p a r a t i o n ) 184 APPENDIX F (storm data) 204 v i i i LIST OF TABLES PAGE 1. Minimum i n f i l t r a t i o n r a t e s f o r s o i l h y d r o l o g i c groups 27 2. A v a i l a b l e Moisture C o n d i t i o n c l a s s i f i c a t i o n 28 3- S o i l s e r i e s c l a s s i f i c a t i o n 65 4. CN valu e s f o r AMC c l a s s I I to be used i n the curve number method 89 5. Curve numbers as adjus t e d f o r AMC 92 6. G u i d e l i n e s f o r the d e t e r m i n a t i o n of the di s c h a r g e c o e f f i c i e n t C i n the r a t i o n a l formula 109 7. Sun angles f o r the A g a s s i z Research Watershed 113 8. Area comparisons 122 9- Comparison of d i s t a n c e s along the h y d r a u l i c l e n g t h . 1 2 3 1 0 . Curve Numbers f o r the upland r e g i o n of the Ag a s s i z Research Watershed 1 2 5 11. Curve Numbers f o r the Pan r e g i o n of the A g a s s i z Research Watershed 126 12. Curve Numbers f o r the Ag a s s i z Research Watershed ... 128 13- Runoff estimates based on the SCS Curve Number method and hydrograph a n a l y s i s 129 14. Curve Numbers and t estimates u s i n g the Lag method . 141 1 5 ' Time of c o n c e n t r a t i o n estimates 141 16. t and t as estimated from hydrograph a n a l y s i s .... 1 4 3 P c 1 7 . E s t i m a t i o n of the r u n o f f c o e f f i c i e n t C f o r the Aga s s i z Research Watershed 1 4 5 Peak flow estimates 1 4 7 X LIST OF FIGURES PAGE 1. Barnes method - l o g a r i t h m i c p l o t t i n g of a hydrograph showing method of r e c e s s i o n a n a l y s i s 1 9 2 . Some simple baseflow s e p a r a t i o n procedures 2 1 3 . S e p a r a t i o n of complex hydrograph u s i n g r e c e s s i o n curve 2 2 4 - A schematic r e p r e s e n t a t i o n of the sub-basin model .. 3 2 5 . S p r i n k l i n g i n f i l t r o m e t e r 4 3 6 . R e s u l t s from a s p r i n k l i n g i n f i l t r o m e t e r experiment, Landshaw sub-basin 4 5 7 . Expected nature of r e s u l t s from i n f i l t r o m e t e r experiments i n t e r p r e t e d i n terms of the storage based i n f i l t r a t i o n component of the model 4 7 8 . A c / A vs a/tang f o r i d e a l i z e d s i d e s l o p e s 5 2 9 - Dimensionless c u r v i l i n e a r u n i t hydrograph and e q u i v a l e n t t r i a n g u l a r hydrograph 5 7 1 0 . D i g i t a l p lanimeter and 1 : 5 0 0 0 s t e r e o p l o t t e d map ... 7 7 1 1. D i g i t i z e r set-up at the UBC Computing Centre 7 8 1 2 . Weir and water l e v e l r e c o r d e r ( l o o k i n g north) 8 4 1 3 . Close up of water l e v e l r e c o r d e r set-up ( l o o k i n g SE) 8 5 1 4 . Graph f o r determining r u n o f f curve numbers of f o r e s t -range complexes i n western U n i t e d S t a t e s : herbaceous and oak-aspen complexes 9 1 1 5 . Graph f o r determining r u n o f f curve numbers of f o r e s t -range complexes i n western U n i t e d S t a t e s : j u n i p e r -grass and sage-grass complexes 9 1 x i 16. Curve number graph f o r the c o n v e r s i o n of r a i n f a l l i n t o r u n o f f 93 17- Diagram of I n f i l t r o m e t e r Chamber 96 18. Base of i n f i l t r o m e t e r chamber 97 19. I n f i l t r o m e t e r stand 97 20. M i n i p l o t (base) f o r i n f i l t r o m e t e r 98 21. F i e l d s et up of the s p r i n k l i n g i n f i l t r o m e t e r apparatus 99 22. C a l i b r a t i o n Curve f o r s p r i n k l i n g i n f i l t r o m e t e r 100 23. Nomograph f o r e s t i m a t i n g time of c o n c e n t r a t i o n 103 24. V e l o c i t i e s f o r upland method of e s t i m a t i n g T Q 105 25 • Raw image 111 26. S y n t h e t i c image of Research Watershed on February 7 at noon (azimuth 174°, e l e v a t i o n 25°) 112 27. May 1 9:00 a.m 114 28. May 1 1:00 p.m 114 29. May 1 5:00 p.m 115 30. May 1 7:00 p.m 115 31• Contour maps f o r the top h a l f of the r e s e a r c h watershed i l l u s t r a t i n g v a r i o u s contour i n t e r v a l s ... 116 32. S y n t h e t i c image from Feb.7 40 m contour i n t e r v a l .. 117 33- S y n t h e t i c image from Feb.7 100m contour i n t e r v a l .. 118 34- S y n t h e t i c image f o r Feb.7 at noon combined with the raw image and a 100m contour o v e r l a y 119 35- P i x e l s i n an image - fo u r times enlargement 120 36. P i x e l s i n an image - e i g h t times enlargement 120 P r o f i l e f o r h y d r a u l i c l e n g t h of A g a s s i z Research ACKNOWLEDGEMENT The author expresses thanks to Dr. S.T. Chieng f o r s e r v i n g as t h e s i s a d v i s o r , as w e l l as Dr. J . Keng, and Dr. D. G o l d i n g f o r s e r v i n g as committee members. I wish to express a p p r e c i a t i o n to Marc Majka f o r h i s computer a s s i s t a n c e i n the D i g i t a l E l e v a t i o n M o d e l l i n g component of t h i s r e s e a r c h . Thanks are a l s o extended to B r i a n Harding of A g r i c u l t u r e Canada f o r h i s a s s i s t a n c e i n m o n i t o r i n g the f i e l d equipment. F i n a l l y , I am e s p e c i a l l y g r a t e f u l to my husband U l f f o r h i s advice and f i e l d a s s i s t a n c e , as w e l l as f o r h i s encouragement throughout my graduate s t u d i e s . 1 A. INTRODUCTION Adequate land drainage has l o n g been reco g n i z e d as the most s i g n i f i c a n t l i m i t i n g f a c t o r to a g r i c u l t u r a l development i n the Lower E r a s e r V a l l e y . Although t h i s i s a r e l a t i v e l y s m a l l a g r i c u l t u r a l area, i t i s i n t e n s i v e l y farmed and accounts f o r about 50$ of the Province's a g r i c u l t u r a l revenues (Baehr 1980). There are two b a s i c drainage c o n d i t i o n s i n the Lower E r a s e r V a l l e y : 1) f l a t lands ( s l o p e l e s s that 0.5$) such as i n Richmond, D e l t a , and p a r t s of P i t t Meadow and C h i l l i w a c k , and 2) upland areas producing r u n o f f onto a g r i c u l t u r a l lowlands such as Surrey, P o r t Langley, Matsqui P r a i r i e , and p a r t s of P i t t Meadow and C h i l l i w a c k . Due to expansion of a g r i c u l t u r a l p r o d u c t i o n i n t o the f r i n g e s of the lowland and i n t o the upland, i t i s important to c o n s i d e r the p o t e n t i a l e f f e c t s of upland r u n o f f on lowland a g r i c u l t u r a l drainage systems. There are many r u n o f f e s t i m a t i o n techniques with v a r y i n g complexity, ease of use, accuracy, a p p l i c a b i l i t y , c o s t , as w e l l as form: d e t e r m i n i s t i c , s t o c h a s t i c , c o n ceptual, t h e o r e t i c a l , black-box,and continuous or event based. In drainage design one i s concerned that a model can provide an accurate estimate of upland r u n o f f w i t h i n a reasonable time and budget. One such model th a t shows p o t e n t i a l f o r f u l f i l l i n g these c r i t e r i a i s the S o i l C o n s e r v a t i o n S e r v i c e Curve Number Method. Recent r e s e a r c h i n r u n o f f e s t i m a t i o n has been i n the d i r e c t i o n of p h y s i c a l l y based d e t e r m i n i s t i c m o d e l l i n g , where the 2 ru n o f f , time to peak, and peak discharge are dependent on the geomorphology of the b a s i n . TOPMODEL (topography based h y d r o l o g i c model) (Beven and K i r k b y 1976; Beven 1977; Beven and Ki r k b y 1979; Beven and Wood 1983; Beven e_t a l . 1984; Hornberger et a l . 1985) may pro v i d e an o p e r a t i o n a l approach i n drainage design. Peak discharge e s t i m a t i o n i s r e q u i r e d f o r s u r f a c e drainage system design as w e l l as the design of o u t l e t d i t c h e s f o r subsurface systems. Two commonly used techniques are the S o i l C o n s e r v a t i o n S e r v i c e U n i t Hydrograph method, and the R a t i o n a l Formula. The o b j e c t i v e s o f t h i s r e s e a r c h are: 1) to explore the f e a s i b i l i t y of u s i n g a d i g i t a l e l e v a t i o n model f o r watershed q u a n t i f i c a t i o n i n drainage design procedures, 2) to eva l u a t e the s o i l c o n s e r v a t i o n s e r v i c e curve number method of r u n o f f e s t i m a t i o n i n a s m a l l upland watershed w i t h a l a r g e degree of f o r e s t cover i n the Lower F r a s e r V a l l e y , 3) to evaluate the r a t i o n a l formula and s o i l c o n s e r v a t i o n u n i t hydrograph procedure f o r peak discharge e s t i m a t i o n i n same watershed, 4) to evaluate a p h y s i c a l l y - b a s e d d e t e r m i n i s t i c r u n o f f model: TOPMODEL. Thi s t h e s i s addresses the above o b j e c t i v e s by v e r i f y i n g the methods and techniques commonly used i n r u n o f f and peak flow e s t i m a t i o n with f i e l d data c o l l e c t e d at A g r i c u l t u r e Canada farm #2 near A g a s s i z , B r i t i s h Columbia. The problem of watershed 3 q u a n t i f i c a t i o n i s addressed through the c r e a t i o n and use of a d i g i t a l e l e v a t i o n model (DEM). The use of d i g i t a l e l e v a t i o n models i s f a s t becoming an i n t e g r a l component of Geographic Information Systems (GIS), as w e l l as p r o v i n c i a l and f e d e r a l mapping programs; thereby a t o p i c a l approach f o r the a g r i c u l t u r a l community to c o n s i d e r . 4 B. OVERVIEW OP THEORY AND PROCEDURES  B.1. Watershed q u a n t i f i c a t i o n - c o n v e n t i o n a l approaches One of the f i r s t steps i n p r e p a r i n g a farm water management scheme i s to "become acquainted w i t h the f i e l d and watershed c h a r a c t e r i s t i c s , namely the topography. The c o n v e n t i o n a l approach i n v o l v e s f i e l d i n s p e c t i o n , s u r v e y i n g of the f i e l d area, p l u s review of a v a i l a b l e map sheets f o r ge n e r a l watershed • i n f o r m a t i o n such as area, s l o p e , and h y d r a u l i c d i s t a n c e s . The most common map a v a i l a b l e f o r t h i s purpose i s the 1:50 000 N a t i o n a l Topographic S e r i e s (NTS) map sheet, u n l e s s s p e c i a l i n t e r e s t maps have been produced. For a s m a l l watershed under study f o r an on-farm subsurface drainage system, o f t e n the accuracy of the NTS map sheet i s not adequate (a 1:50 000 map sheet i s not intended f o r d e t a i l e d f e a t u r e e x t r a c t i o n ) . The map i s not produced w i t h the same p r e c i s i o n as a l a r g e s c a l e map, thus the contour l e v e l or l o c a t i o n may be i n a c c u r a t e . A contour i n t e r v a l of 40 meters does not allow f o r i d e n t i f i c a t i o n of s m a l l depressions and seepage zones which are important i n r u n o f f e s t i m a t i o n . Any measurements of area from a two dimensional map sheet do not i n c o r p o r a t e s l o p e , t h e r e f o r e i n a mountainous watershed the area can be h i g h l y underestimated. The same i s tr u e of d i s t a n c e s measured. The study of topographic map sheets may be augmented w i t h a e r i a l photo i n t e r p r e t a t i o n , u s i n g standard p r o v i n c i a l M i n i s t r y of Environment b l a c k and white a e r i a l photography. T h i s a d d i t i o n a l a n a l y s i s (dependent upon the s c a l e of the photography) 5 can add important i n f o r m a t i o n m i s s i n g from the s m a l l s c a l e maps. Measurements can s t i l l not be taken d i r e c t l y from the photographs, e s p e c i a l l y i n areas of extreme t e r r a i n due to the severe r e l i e f displacement (the s h i f t i n the photographic p o s i t i o n of an image caused by the r e l i e f of the o b j e c t under study, i . e . i t ' s e l e v a t i o n w i t h r e s p e c t to a s e l e c t e d datum). An orthophoto (a photograph showing images i n t h e i r t rue o r t h o g r a p h i c p o s i t i o n s i . e . p l a n i m e t r i c a l l y c o r r e c t ) takes out t h i s displacement to allow d i r e c t measurement of t e r r a i n f e a t u r e s , but they are not w i d e l y a v a i l a b l e i n the Province'. I f a h i g h p r o f i l e r e s ource p r o j e c t has been developed i n the area of i n t e r e s t f o r drainage work, orthophotos may have been produced. B.2. D i g i t a l e l e v a t i o n m o d e l l i n g Another avenue f o r determining watershed c h a r a c t e r i s t i c s i s the use of a D i g i t a l T e r r a i n Model (DTM), a l s o r e f e r r e d to as a D i g i t a l E l e v a t i o n Model (DEM). A d i g i t a l t e r r a i n model (DTM) c o n s i s t s of a set of numbers that r e p r e s e n t s the s p a t i a l d i s t r i b u t i o n of a p r o p e r t y of the t e r r a i n ( C o l l i n s 1975). T h i s may i n c l u d e coded i n f o r m a t i o n on any s o r t of t e r r a i n f e a t u r e s ( s o i l type, f o r e s t cover, geology, etc.) as l o n g as t h i s i n f o r m a t i o n i s r e f e r e n c e d to s p e c i f i c h o r i z o n t a l c o o r d i n a t e s , and i s i n numerical form. The type of DTM developed and a p p l i e d i n t h i s t h e s i s i s one i n which the e l e v a t i o n Z i s given as a f u n c t i o n of the h o r i z o n t a l c o o r d i n a t e s X and Y, consequently o f t e n r e f e r r e d to as a d i g i t a l e l e v a t i o n model (DEM). 6 The widespread acceptance of the advantages of map data i n d i g i t a l form i s due to numerous reasons i n c l u d i n g : 1) with d i g i t a l technology, computational p r o c e s s i n g , d r a f t i n g and s c r i b i n g , changes of s c a l e and p r o j e c t i o n s can be achieved at a f r a c t i o n of the manual co s t , 2) advances i n computer technology and the decrease i n hardware cost make i t p o s s i b l e to design i n t e g r a t e d , m u l t i f u n c t i o n a l systems that can e f f i c i e n t l y do a l a r g e volume of work i n one o p e r a t i o n , 3) producers of d i g i t a l mapping data are b u i l d i n g data bases, p r i m a r i l y to support t h e i r own purposes, and secondly to allow f o r the exchange of data between v a r i o u s groups a c c o r d i n g to a s t a n d a r d i z e d d i g i t a l data base s t r u c t u r e , 4) d i g i t a l mapping technology p r o v i d e s the means f o r a c h i e v i n g a higher degree of accuracy throughout a l l stages from data a c q u i s i t i o n by computer-aided photogrammetric c o m p i l a t i o n to r e p r e s e n t a t i o n by automated d r a f t i n g / s c r i b i n g (Allam 1982). B.2.a. types of d i g i t a l e l e v a t i o n models D i f f e r e n t types of DEMs may be d i s t i n g u i s h e d by the r e g u l a r i t y of the c o o r d i n a t e spacings: B.2.a.i. the i r r e g u l a r DEM In t h i s type none of the c o o r d i n a t e s occur i n r e g u l a r l y spaced v a l u e s . A common example i s the product of a t r a n s i t and s t a d i a survey i n which the rodman s e l e c t s ground p o i n t s at which there i s a change i n slope or some d i s t i n c t f e a t u r e . T h i s type of DEM gives an adequate d e s c r i p t i o n of the topography w i t h the 7 s m a l l e s t number of p o i n t s . I t a l s o r e q u i r e s the g r e a t e s t number of d e c i s i o n s by humans i n i t s p r o d u c t i o n . I r r e g u l a r DEM's can a l s o be d e r i v e d photogrammetrically (with a s t e r e o p l o t t e r ) , but i t i s not a common p r a c t i c e to do so. B . 2 . a . i i . the contour DEM In t h i s type the values of Z are e q u a l l y spaced and the model i s c r e a t e d i n the contour mode ( i . e . each contour l e v e l i s t r a c e d i n d i v i d u a l l y ) . The p o i n t s to be recorded can be chosen by i n s p e c t i o n , thereby may be pl a c e d more c l o s e l y i n h i l l y or rough t e r r a i n , and f a r apart i n f l a t areas. T h i s may be done manually u s i n g a d i g i t i z e r with a l a r g e s c a l e map of the watershed ( i n p o i n t mode as d e s c r i b e d above) or i n run mode which accepts a continuous stream of data a l o n g the contour at equal d i s t a n c e s or equal time i n t e r v a l s . The contour DEM may a l s o be cr e a t e d when the a c t u a l s t e r e o p l o t t i n g of the a e r i a l photos takes p l a c e . A d i g i t a l output i s sent to a computer r a t h e r than d i r e c t p l o t t i n g of the contour map u s i n g a mechanical pantograph. T h i s e l i m i n a t e s one g e n e r a t i o n of map p r o d u c t i o n . B . 2 . a . i i i . the p r o f i l e DEM In t h i s type the values of e i t h e r X or Y are e q u a l l y spaced. The model i s generated by t r a c i n g t r a n s e c t s a l o n g a contour map, or scanning a photogrammetric model along e q u a l l y spaced p r o f i l e s . P r o f i l e DEMs are commonly used i n c i v i l e n g i n e e r i n g f o r the computation of volumes of earth-work. They may e q u a l l y w e l l be a p p l i e d i n a g r i c u l t u r a l e n g i n e e r i n g f o r c a l c u l a t i n g earth-work volumes f o r s u r f a c e drainage systems. 8 The s i n g l e r e g u l a r DEMs produced by p r o f i l i n g and by c o n t o u r i n g seem to be e q u a l l y r a p i d i n p r o d u c t i o n and e q u a l l y accurate i n t h e i r r e p r e s e n t a t i o n of the t e r r a i n . The growth of i n t e r e s t i n orthophotography w i l l probably i n c r e a s e i n t e r e s t i n p r o f i l e DEMs because most e x i s t i n g orthophotoscopes are designed f o r orthophoto p r o d u c t i o n i n the p r o f i l e mode (DEMs are by-products of o f f - l i n e o r t h o p r o d u c t i o n ) . However, i n c r e a s e d i n t e r e s t and use of automated systems w i l l l e a d towards adoption of the g r i d DEM below. B.2.a.iv. the g r i d DEM T h i s i s a s p e c i a l case of the p r o f i l e DEM i n which the s p a c i n g of the h o r i z o n t a l c o o r d i n a t e v a l u e s along the p r o f i l e are constant. For a model that i s l i m i t e d to a given number of p o i n t s , the g r i d DEM i s i n h e r e n t l y f u r t h e r removed from the r e a l t e r r a i n s u r f a c e than e i t h e r the contour or p r o f i l e DEM, j u s t as these are f u r t h e r removed than the i r r e g u l a r DEM. In terms of computer storage, the g r i d DEM i s most economical because i t c o n s i s t s only of a l i s t of Z v a l u e s . When u s i n g a contour map and d i g i t i z e r to manually input Z values f o r an e n t i r e watershed i n t o the computer, i t i s much p r e f e r r e d to use the contour method. Operator f a t i g u e i s much l e s s as compared to t r a c i n g t r a n s e c t s or p r o f i l e s which may be spaced at\ i n t e r v a l s as l i t t l e as 1mm on a base map. T h i s again r e s u l t s i n higher accuracy of the data base ( C o l l i n s 1975). The accuracy of the i n v e r s e process of r e c o n s t r u c t i n g the 9 t e r r a i n , or the accuracy of d e r i v i n g numerical v a l u e s from the DEM, depends upon the DEM d e n s i t y ; the c l o s e n e s s of s p a c i n g of the contours, p r o f i l e s , or g r i d p o i n t s . Once the data base i s formed, i t must be considered as t r u e . No smoothing algorithmns should be a p p l i e d t o a l t e r contours, although e d i t i n g c a p a b i l i t y i s a d e f i n i t e advantage f o r the c o r r e c t i o n of i n c o r r e c t data entry or a r t i f a c t s . With the i n c r e a s i n g use of computer-based d i g i t i z i n g u n i t s ( e s p e c i a l l y w i t h micro-computers), there has been a s t r o n g and welcome t r e n d towards the p r o d u c t i o n of d i g i t a l t o pographic data by means of: 1) d i g i t i z i n g photogrammetrically-produced graphic p l o t s u s i n g manual d i g i t i z i n g t a b l e s , semi-automatic l i n e f o l l o w i n g systems or automated r a s t e r scanning systems, and 2) d i r e c t photogrammetric instruments i n t e r f a c e d to d i g i t a l computers (Allam 1982). Once the data has been c o l l e c t e d , a workable format must be c r e a t e d . For example, the data c o l l e c t e d from d i g i t i z i n g contour l i n e s w i l l be i n the form of a l i s t i n g of X and Y c o - o r d i n a t e s f o r s p e c i f i e d Z l e v e l s . There are v a r i o u s s c h o o l s of thought on t h i s matter : c r e a t i o n of a t r i a n g u l a t e d i r r e g u l a r network (TIN), c r e a t i o n of a g r i d , or c r e a t i o n of a TIN then c o n v e r t i n g i t to a g r i d . The TIN was developed by Dr. T. Poiker i n the e a r l y 1970's at Simon F r a s e r U n i v e r s i t y i n B r i t i s h Columbia. The method i n v o l v e s t r i a n g u l a t i o n between data p o i n t s to c r e a t e a t r i a n g u l a r network. Advantages of the t r i a n g u l a r s u b d i v i s i o n are: 10 1) r e p r o d u c t i o n of the g r e a t e s t p o s s i b l e number of f i n e d e t a i l s from a continuous s u r f a c e , 2) s i n c e o r i g i n a l data are used d i r e c t l y , the ground s u r f a c e 'is b e t t e r approximated as compared to u s i n g a s q u a r e - g r i d i n t e r p o l a t i o n , 3) computing time i s much lower than i n square g r i d methods which ev a l u a t e b r e a k l i n e s ( i . e . watershed d i v i d i n g l i n e s ) (Huegli et a l . 1984). A g r i d model ( r e g u l a r DTM) i s b u i l t of meshes which form a square shaped g r i d i n p l a n i m e t r y . The h e i g h t s of the g r i d p o i n t s are i n t e r p o l a t e d from the h e i g h t s of g i v e n r e f e r e n c e p o i n t s . In photogrammetry, g r i d models are more f r e q u e n t l y a p p l i e d than t r i a n g l e models . T h e i r main advantage i s the r e g u l a r s t r u c t u r e of the data, which makes the use of the DEM e a s i e r and more e f f i c i e n t (Ebner and R e i s s 1984; C o l l i n s 1979). The square g r i d i s p a r t i c u l a r l y u s e f u l f o r f a s t computation of areas and volumes. The g r i d must have a d e n s i t y s u f f i c i e n t to r e p r e s e n t the t e r r a i n adequately. This d e n s i t y depends on the nature of the f e a t u r e s to be represented, and on the p r e c i s i o n that i s r e q u i r e d f o r d e p i c t i n g the t e r r a i n s u r f a c e or f o r c a l c u l a t i n g e l e v a t i o n -dependent q u a n t i t i e s . The g r i d r e s o l u t i o n should be maintained f o r a l l subsequent a n a l y s i s u s i n g the DEM. I t i s p r e d i c t e d t h a t geographic data bases w i l l f o l l o w the g r i d format ( C o l l i n s 1979). B.2.b. a p p l i c a t i o n of d i g i t a l e l e v a t i o n models The i n c r e a s e d a p p r e c i a t i o n of the advantages of map data i n d i g i t a l form i s a c c e l e r a t i n g the a p p l i c a t i o n of d i g i t a l mapping 11 and automated cartography. Numerous government mapping and resource agencies (at v a r i o u s l e v e l s ) , i n s t i t u t i o n s , and p r i v a t e i n d u s t r y throughout the world are a c t i v e l y engaged i n computer-aided map c o m p i l a t i o n and p r o d u c t i o n . The advantages are to o b t a i n a higher l e v e l of e f f i c i e n c y , cost e f f e c t i v e n e s s and improved responsiveness i n the p r o d u c t i o n of maps, c h a r t s and r e l a t e d i n f o r m a t i o n . The F e d e r a l Government of Canada (Department of Energy, Mines & Resources) i s i n v o l v e d i n de v e l o p i n g and implementing hardware and software systems, recommending standards, and p r o v i d i n g DEM data "bases on a n a t i o n a l s c a l e . The F e d e r a l Government has produced DEM base maps f o r n e a r l y a l l of Southern O n t a r i o , and a l a r g e p o r t i o n of Labrador, Quebec, Northwest O n t a r i o , and the Northwest T e r r i t o r i e s (at v a r i o u s g r i d s i z e s ) . The standard map s c a l e they are c o n v e r t i n g to d i g i t a l format (DEM's) i s 1:50 000 (Wong 1985). The Water Management Systems D i v i s i o n of the Inland Waters D i r e c t o r a t e , Environment Canada, have u t i l i z e d d i g i t a l t e r r a i n data i n r i v e r system mo n i t o r i n g i n the Peace-Athabasca D e l t a m o d e l l i n g s t u d i e s . The hydrodynamic approach to m o d e l l i n g as opposed to the h y d r o l o g i c a l r o u t i n g approach r e q u i r e s the a d d i t i o n a l model input of surveyed cross s e c t i o n s , both f o r the channel and f l o o d p l a i n s . In complex r i v e r networks s u b j e c t to c o n s i d e r a b l e overbank f l o o d i n g , d i g i t a l t e r r a i n data p r o v i d e the most e f f i c i e n t and r e l i a b l e means of adequately r e p r e s e n t i n g topographic f e a t u r e s i n a hydrodynamic model ( F a r l e y 1985). 1 2 The A l b e r t a p r o v i n c i a l government has embarked on a ten year program to implement a Geographic Information System: coverage of the e n t i r e p r o v i n c e with DEMs at a 1:20 000 s c a l e ( g r i d format) p r o v i d i n g base maps, as w e l l as de v e l o p i n g thematic o v e r l a y s f o r resource i n f o r m a t i o n such as mi n e r a l s , s o i l type, f o r e s t cover, p u b l i c lands etc (Langford 1986). They are now i n t h e i r f o u r t h year of the p r o j e c t . Government d i r e c t i v e s have been i s s u e d to p r i v a t e i n d u s t r y r e g a r d i n g the format and standards r e q u i r e d i n DEM p r o d u c t i o n , and submitted DEMs are c u r r e n t l y b e i n g reviewed. I t i s t h e i r i n t e n t i o n to make the system a c c e s s i b l e on micro-computers, and a prototype study u s i n g a base sheet (DEM) and thematic o v e r l a y s i s b e i n g t e s t e d on an IBM-PCXT. The Inventory Branch of the B r i t i s h Columbia F o r e s t S e r v i c e have developed and are s u c c e s s f u l l y implementing a province-wide d i g i t a l data base of f o r e s t stand i n f o r m a t i o n (at 1:20 000 s c a l e ) . They p l a n to complete t h e i r Geographic Information System (GIS) by o b t a i n i n g d i g i t a l e l e v a t i o n data. T h i s has most commonly been done through photogrammetric procedures, but the M i n i s t r y hopes to use high r e s o l u t i o n imagery (ten meter ground r e s o l u t i o n ) from the French s a t t e l i t e SPOT (Hedgey 1986). The GIS i s to be based on an IBM-PC image a n a l y s i s system, e v e n t u a l l y w i t h one per d i s t r i c t o f f i c e . The P r o v i n c i a l M i n i s t r y of the Environment i n B r i t i s h Columbia are a l s o i n v o l v e d i n r e v i e w i n g software and p r o p o s i n g a system f o r the co n v e r s i o n of the p r o v i n c e ' s topographic maps i n t o 13 d i g i t a l format f o r the eventual adoption of a m i n i - and micro-based computer system. The proposed program i s c a l l e d TRIM, T e r r a i n Resource Inventory Mapping, a t h r e e year, 15 m i l l i o n d o l l a r program funded by the BC government to produce 1:20 000 d i g i t a l maps (10m contour i n t e r v a l ) c o n t a i n i n g topography, p l a n i m e t r y , and c a d a s t r e . The work i s to be c a r r i e d out through the p r i v a t e s e c t o r , with s p e c i f i c a t i o n s , data storage and d i s s e m i n a t i o n , and a d m i n i s t r a t i o n the r e s p o n s i b i l i t y of the Surveys and Resource Mapping Branch, M i n i s t r y of Environment (Sondheim 1986). The s t a r t date i s scheduled f o r the b e g i n n i n g of the 1986 f i s c a l year. Raw DTM data w i l l be c o l l e c t e d from s t e r e o a e r i a l photographs (1:60 000 s c a l e ) u s i n g an analogue or a n a l y t i c a l s t e r e o p l o t t e r operated by a photogrammetrist. The M i n i s t r y has r e c e n t l y completed an accuracy e v a l u a t i o n p r o j e c t of the v e r t i c a l mapping accuracy obtained w i t h commercially a v a i l a b l e hardware and software i n the p r o d u c t i o n of d i g i t a l e l e v a t i o n models. I t was undertaken to determine whether proposed 1:20 000 t o p o g r a p h i c accuracy standards i n B r i t i s h Columbia are r e a l i s t i c u s i n g present photogrammetric technology a p p l i e d to 1:60 000 b l a c k and white photography. The study showed that the proposed accuracy standards f o r spot and i n t e r p o l a t e d r e l i e f data are r e a l i s t i c f o r g e n t l e topography, but may f r e q u e n t l y not be met f o r mountainous t e r r a i n . The present standards may not adequately address the problem of extreme e r r o r s (Sondheim 1986). I t should be noted t h a t t h i s study only evaluated two procedures of data c o l l e c t i o n : 14 a r e g u l a r g r i d p a t t e r n , and i r r e g u l a r p o i n t s converted to a t r i a n g u l a t e d i r r e g u l a r network. A l l v a r i a b l e s were not h e l d constant i n comparison of the methods, so recommendations of one method over an other are not a b s o l u t e . A l s o , a c c u r a c i e s o b t a i n a b l e from l a r g e s c a l e photography, say 1:20 000 or 1:10 000 going to a 1:10 000, or 1:5 000 s c a l e DEM w i t h the same 10 m contour i n t e r v a l were not evaluated (a more reasonable procedure f o r mountainous regions and watershed a n a l y s i s f o r drainage design, but too l a r g e of a s c a l e f o r complete p r o v i n c i a l coverage). I t i s a n t i c i p a t e d that one may be a b l e to purchase a tape or f l o p p y d i s k e t t e from the P r o v i n c i a l Government c o n t a i n i n g a DEM e q u i v i l a n t to a 1:20 000 map sheet (a p o s i t i o n a l f i l e c o n t a i n i n g XYZ v a l u e s , p o s s i b l y i n g r i d format) (Sawayama 1985). In the U n i t e d S t a t e s , the U.S. G e o l o g i c a l Survey (USGS) through i t s N a t i o n a l Mapping Program has p r o v i d e d a major program of d i g i t a l mapping and t e c h n i c a l a s s i s t a n c e . The DEM i s a by-product of the USGS orthophoto mapping program t h a t transforms photo c o o r d i n a t e s i n t o model c o o r d i n a t e s through automatic c o r r e l a t i o n by the G e s t a l t Photo Mapper II (a Canadian product) ( A l l d e r e_t a l . 1982). DEM f i l e s may be purchased as standard 7.5-minute quadrangles at 30-meter i n t e r v a l s from the N a t i o n a l Center i n V i r g i n i a (White 1981). As i l l u s t r a t e d above, the concept and use of d i g i t a l e l e v a t i o n models i s not new, but has gained enormous development e f f o r t s and f u n d i n g commitment over the past few y e a r s . With the r a p i d improvements i n computer technology and software systems, 15 p l u s the i n c r e a s e d awareness of p o t e n t i a l b e n e f i t s , DEMs are bound to become standard t o o l s of resource managers and p l a n n e r s . For these reasons, the f e a s i b l i l i t y of u s i n g a DEM i n a g r i c u l t u r a l hydrology f o r watershed q u a n t i f i c a t i o n was evaluated i n t h i s t h e s i s . 1 6 C. RUNOFF ESTIMATION PROCEDURES C.1. Hydrograph a n a l y s i s The hydrograph can he regarded as an i n t e g r a l e x p r e s s i o n of the p h y s i o g r a p h i c and c l i m a t i c c h a r a c t e r i s t i c s t h a t govern the r e l a t i o n s between r a i n f a l l and r u n o f f of a p a r t i c u l a r drainage b a s i n (Chow 1964). The water which c o n s t i t u t e s streamflow and c r e a t e s the discharge hydrograph may reach the stream channel by s e v e r a l paths from the p o i n t where i t f i r s t reaches the ground as p r e c i p i t a t i o n . The three main routes of t r a v e l t r a d i t i o n a l l y d e s c r i b e d are overland flow, i n t e r f l o w , and groundwater flow: 1) o v e r l a n d flow or s u r f a c e r u n o f f : overland flow i s t h a t water which t r a v e l s over the ground s u r f a c e to a channel (any d e p r e s s i o n which may c a r r y a s m a l l r i v u l e t of water i n t u r b u l e n t flow d u r i n g a r a i n and f o r a s h o r t time a f t e r w a r d s ) . Such channels are numerous, and the d i s t a n c e water must t r a v e l o verland i s g e n e r a l l y s m a l l . Overland flow t h e r e f o r e reaches the channel i n a s h o r t time p e r i o d , and may be an important element i n the f o r m a t i o n of f l o o d peaks when e x i s t i n g i n reasonable amounts. 2) i n t e r f l o w or subsurface flow: some of the water which i n f i l t r a t e s the s o i l s u r f a c e may move l a t e r a l l y through the upper s o i l l a y e r s u n t i l i t enters a stream channel, thus c a l l e d s ubsurface flow. Subsurface flow moves much more s l o w l y than the s u r f a c e r u n o f f . 17 3) groundwater flow or base flow: p r e c i p i t a t i o n t h a t p e r c o l a t e s down to the groundwater t a b l e may e v e n t u a l l y discharge i n t o the streams as groundwater flow i f the water t a b l e i n t e r s e c t s the stream channels of the b a s i n . The hydrograph a n a l y s i s technique r e l i e s on the s e p a r a t i o n of the hydrograph i n t o at l e a s t two components, and t h i s i s at i t s best an e m p i r i c a l s e p a r a t i o n (Raudkivi 1979). These two components are base flow and storm or d i r e c t r u n o f f . E i t h e r may c o n t a i n a c e r t a i n amount of the subsurface flow ( L i n s l e y et a l . 1982). A t y p i c a l simple hydrograph r e s u l t i n g from an i s o l a t e d p e r i o d of r a i n f a l l c o n s i s t s of a r i s i n g limb, c r e s t segment, and f a l l or r e c e s s i o n limb. The shape of the r i s i n g limb i s i n f l u e n c e d mainly by the storm c h a r a c t e r i s t i c s . The shape of the r e c e s s i o n i s l a r g e l y independent of the c h a r a c t e r i s t i c s of the storm c a u s i n g the r i s e . The p o i n t of i n f l e c t i o n on the f a l l i n g s i d e of the hydrograph i s commonly assumed to mark the time at which s u r f a c e i n f l o w to the channel system ceases. T h e r e a f t e r , the r e c e s s i o n curve r e p r e s e n t s withdrawl of water from storage w i t h i n the b a s i n . I f there i s no s u r f a c e i n f l o w i n t o the channel system, the r e c e s s i o n curve r e p r e s e n t s subsurface and base flow c o n t r i b u t i o n s . Since there i s no ready b a s i s f o r d i s t i n g u i s h i n g between d i r e c t and groundwater flow i n a stream at any i n s t a n t , and s i n c e d e f i n i t i o n s of these components are r e l a t i v e l y a r b i t r a r y , the method of s e p a r a t i o n i s e q u a l l y a r b i t r a r y ( L i n s l e y e_t a l . 1 982). 18 I f the base flow i s assumed e i t h e r to i n c l u d e or to exclude the e n t i r e p o r t i o n of the subsurface flow, s e v e r a l forms of r e c e s s i o n curve a n a l y s i s may be used f o r base flow d e t e r m i n a t i o n and f o r base flow s e p a r a t i o n from the d i r e c t r u n o f f of a hydrograph (Chow 1964). Barnes ( l i n s l e y et a l . 1982) suggests t h a t the r e c e s s i o n can be approximated by three s t r a i g h t l i n e s on a semilogarithm!c p l o t . The t r a n s i t i o n from one l i n e to the next i s o f t e n so gradual that i t i s d i f f i c u l t to s e l e c t the p o i n t s of change i n slope (due to the h e t e r o g e n e i t y of the t y p i c a l catchment). The s l o p e of the l a s t p o r t i o n of the r e c e s s i o n should represent the c h a r a c t e r i s t i c r e c e s s i o n constant f o r groundwater s i n c e , presumably, both i n t e r f l o w and s u r f a c e r u n o f f have ceased. By p r o j e c t i n g t h i s s lope backward i n time ( f i g . 1 ) and r e p l o t t i n g the d i f f e r e n c e between the p r o j e c t e d l i n e and the t o t a l hydrograph, a r e c e s s i o n which c o n s i s t s l a r g e l y of i n t e r f l o w i s obtained. A s l o p e a p p l i c a b l e to i n t e r f l o w i s now determined, and the process can be repeated to e s t a b l i s h the r e c e s s i o n c h a r a c t e r i s t i c s of s u r f a c e r u n o f f . 19 F i g u r e 1: Barnes method - l o g a r i t h m i c p l o t t i n g of a hydrograph showing method of r e c e s s i o n a n a l y s i s ( L i n s l e y et a l . 1982) The above technique r e p r e s e n t s a degree of refinement r a r e l y used f o r e n g i n e e r i n g problems. The base-flow r e c e s s i o n curve i s most f r e q u e n t l y used. One method to c o n s t r u c t t h i s curve i s to piec e together s e c t i o n s of r e c e s s i o n s from v a r i o u s storms u n t i l a composite curve i s obtained which covers the necessary range of flow r a t e s . The r e c e s s i o n curve may a l s o be developed by p l o t t i n g values of the i n i t i a l flow (q r t) a g a i n s t flow (q,) at O u some f i x e d time (t) l a t e r . However, as r u n o f f i s normally considered to be d i v i d e d i n t o only two p a r t s : d i r e c t r u n o f f and base flow, and both p a r t s may c o n t a i n a c e r t a i n amount of the subsurface r u n o f f ; base-flow 20 s e p a r a t i o n i s u s u a l l y made i n an a r b i t r a r y manner and i t i s not s i g n i f i c a n t to even consi d e r the exact amount (which i s unknown anyway) to be i n c l u d e d i n or excluded from the base flow (Chow 1964). For a p p l i c a t i o n of the u n i t hydrograph concept, the method of s e p a r a t i o n should be such t h a t the time base of d i r e c t r u n o f f remains r e l a t i v e l y constant from storm to storm. T h i s may be achieved by t e r m i n a t i n g the d i r e c t r u n o f f at a f i x e d time a f t e r the peak of the hydrograph. The f i x e d time i n days N may be approximated by N=bA 0' 2 [1] where A i s the drainage area and b i s a c o e f f i c i e n t . The value of b i s 0.8 when A i s i n square k i l o m e t e r s and u n i t y when A i s i n square m i l e s . The f i x e d time, N, may be b e t t e r estimated by e v a l u a t i n g storm hydrographs, m a i n t a i n i n g the t o t a l time at a reasonable l e n g t h ( L i n s l e y et a l . 1982 ; Chow 1964). The most w i d e l y used s e p a r a t i o n procedure c o n s i s t s of extending the r e c e s s i o n e x i s t i n g b e f o r e the storm to a p o i n t under the peak of the hydrograph (AB, F i g . 2 ). From t h i s p o i n t a s t r a i g h t l i n e i s drawn to the hydrograph at a p o i n t N days a f t e r the peak (as d e f i n e d above). The re a s o n i n g given f o r t h i s procedure i s that as the stream r i s e s , t here i s flow from the stream i n t o the banks; t h e r e f o r e , base flow should decrease u n t i l stages i n the stream begin to drop and bank storage r e t u r n s to the channel. The simple way to make a base-flow s e p a r a t i o n i s to draw a 21 s t r a i g h t l i n e from the p o i n t of r i s e to an a r b i t r a r y p o i n t (N days) on the lower p o r t i o n of the r e c e s s i o n segment of the hydrograph (AC, F i g . 2 ) . A t h i r d method of s e p a r a t i o n i s i l l u s t r a t e d by l i n e ADE ( P i g . 2 ) . T h i s l i n e i s c o n s t r u c t e d by p r o j e c t i n g the r e c e s s i o n of the groundwater a f t e r the storm back under the hydrograph to a p o i n t under the i n f l e c t i o n p o i n t of the f a l l i n g limb. An a r b i t r a r y r i s i n g limb i s sketched from the p o i n t of r i s e of the hydrograph to connect w i t h the p r o j e c t e d base-flow r e c e s s i o n ( L i n s l e y et a l . 1958). Days » P i g u r e 2: Some simple baseflow s e p a r a t i o n procedures ( L i n s l e y ejt a l . 1982) 22 Complex hydrographs r e s u l t i n g from two or more c l o s e l y spaced b u r s t s of r a i n f a l l are more d i f f i c u l t to analyse. I t i s necessary to separate the r u n o f f caused by i n d i v i d u a l b u r s t s of r a i n f a l l i n a d d i t i o n to s e p a r a t i n g d i r e c t r u n o f f from base flow. I f a base-flow s e p a r a t i o n such as l i n e ABC of F i g u r e [2] i s used, b u r s t s of r a i n f a l l are d i v i d e d by p r o j e c t i n g the s m a l l segment of r e c e s s i o n between peaks u s i n g a t o t a l - f l o w r e c e s s i o n curve f o r the b a s i n ( l i n e AB, F i g . 3). D i r e c t r u n o f f f o r the two p e r i o d s of r a i n i s given by areas I and I I . There must be two c l e a r l y d e f i n e d peaks with a s h o r t segment of r e c e s s i o n f o l l o w i n g the f i r s t i n order to do t h i s type of s e p a r a t i o n . l l i l I l I i i r ' ' ' ' ' i i i i 1 i 1 L Jime » F i g u r e 3: S e p a r a t i o n of complex hydrograph u s i n g r e c e s s i o n curve ( L i n s l e y et a l . 1982) 23 Area under a discharge hydrograph r e p r e s e n t s volume of r u n o f f (Q): v o l = / Qdt [2] The area under the curve may he c a l c u l a t e d by i n t e g r a t i n g the hydrograph curve. I t may a l s o be determined by manually determining the enclosed area below the hydrograph and baseflow s e p a r a t i o n l i n e . 24 C.2. S o i l C o n s e r v a t i o n S e r v i c e curve number method The U n i t e d S t a t e s S o i l C o n s e r v a t i o n S e r v i c e (SCS) has developed a set of e m p i r i c a l curves to r e l a t e storm p r e c i p i t a t i o n to d i r e c t r u n o f f (see f i g u r e 16). The procedure was developed i n the e a r l y 1950's and has become a w i d e l y used and accepted means f o r e s t i m a t i n g stormflow volumes f o r design and n a t u r a l events i n s m a l l ungauged watersheds (Hope and Schulze 1982). The primary input parameter of the SCS model i s the r u n o f f curve number (CN). The curve number i s a w e i g h t i n g f a c t o r which r e f l e c t s the importance of three major parameters: the l a n d use and treatment c l a s s , the s o i l h y d r o l o g i c group, and the antecedent moisture c o n d i t i o n . C.2.a. land use and treatment c l a s s e s In the SCS method of r u n o f f e v a l u a t i o n , the e f f e c t s of s u r f a c e c o n d i t i o n s are evaluated by means of l a n d use and treatment c l a s s e s . Land use i s the watershed cover and i t i n c l u d e s every k i n d of v e g e t a t i o n , l i t t e r and mulch, and f a l l o w (bare s o i l ) as w e l l as n o n - a g r i c u l t u r a l uses such as water s u r f a c e s ( l a k e s , swamps, etc.) and impervious s u r f a c e s (roads, r o o f s , e t c . ) . Land treatment a p p l i e s mainly to a g r i c u l t u r a l l a n d uses and i t i n c l u d e s mechanical p r a c t i c e s such as c o n t o u r i n g or t e r r a c i n g , and management p r a c t i c e s such as g r a z i n g c o n t r o l or crop r o t a t i o n . Land use and treatment c l a s s e s are obtained e i t h e r by o b s e r v a t i o n or by measurement of p l a n t and l i t t e r d e n s i t y and 25 extent on sample areas. In areas where commercial f o r e s t covers a l a r g e p a r t of the watershed, U.S. F o r e s t S e r v i c e procedures f o r determining f o r e s t h y d r o l o g i c c o n d i t i o n s are used (USDA 1972). C.2.b. h y d r o l o g i c s o i l groups The h y d r o l o g i c s o i l group measures the a b i l i t y of s o i l s to absorb water through i n f i l t r a t i o n . The g r e a t e r the i n f i l t r a t i o n , the l e s s the d i r e c t r u n o f f . The premise i n a s s i g n i n g s o i l s to a p a r t i c u l a r h y d r o l o g i c group i s that s o i l s with comparable depth, o r g a n i c matter content, s t r u c t u r e , and degree of s w e l l i n g when s a t u r a t e d , w i l l respond e s s e n t i a l l y the same d u r i n g a r a i n s t o r m w i t h e x c e s s i v e i n t e n s i t i e s . The f o u r h y d r o l o g i c groups o u t l i n e d are: A. (low r u n o f f p o t e n t i a l - overland f l o w ) . S o i l s having h i g h i n f i l t r a t i o n r a t e s even when thoroughly wetted and c o n s i s t i n g c h i e f l y of deep, w e l l to e x c e s s i v e l y drained sands or g r a v e l s . These s o i l s have a high r a t e of water t r a n s m i s s i o n (e.g. deep sand, deep l o e s s , aggregated s i l t s ) , thus overland flow r a r e l y o ccurs. B. S o i l s h a ving moderate i n f i l t r a t i o n r a t e s when thoroughly wetted and c o n s i s t i n g c h i e f l y of moderately deep to deep, moderately w e l l to w e l l d r a i n e d s o i l s with moderately f i n e to moderately coarse t e x t u r e s . These s o i l s have a moderate r a t e of water t r a n s m i s s i o n (e.g. shallow l o e s s , sandy loam) and g e n e r a l l y do not produce overland flow. C. S o i l s having slow i n f i l t r a t i o n r a t e s when thoroughly wetted 26 and c o n s i s t i n g c h i e f l y of s o i l s w i t h a l a y e r t h a t impedes downward movement of water, or s o i l s w i t h moderately f i n e to f i n e t e x t u r e . These s o i l s have a slow r a t e of water t r a n s m i s s i o n (e.g. c l a y loams, shallow sandy loam, s o i l s low i n org a n i c content, and s o i l s u s u a l l y high i n c l a y ) thereby prone to pro d u c i n g overland flow. D. (high r u n o f f p o t e n t i a l ) S o i l s having very slow i n f i l t r a t i o n r a t e s when thoroughly wetted and c o n s i s t i n g c h i e f l y of c l a y s o i l s w ith high s w e l l i n g p o t e n t i a l , s o i l s with a permanent high water t a b l e , s o i l s w i t h a claypan or c l a y l a y e r at or near the s u r f a c e , and shallow s o i l s over n e a r l y impervious m a t e r i a l . These s o i l s have a very slow r a t e of water t r a n s m i s s i o n (e.g. heavy p l a s t i c c l a y s , and c e r t a i n s a l i n e s o i l s ) thereby c a u s i n g overland flow. The SCS s o i l group can be i d e n t i f i e d at a s i t e u s i n g one of three ways: 1) s o i l c h a r a c t e r i s t i c s 2) s o i l maps J>) minimum i n f i l t r a t i o n r a t e The minimum r a t e of i n f i l t r a t i o n (as obtained f o r a bare s o i l a f t e r prolonged wetting) i n c o r p o r a t e s the i n f l u e n c e s of both the s u r f a c e and the h o r i z o n s of a s o i l . Table 1 below o u t l i n e s the minimum i n f i l t r a t i o n r a t e s f o r the fo u r h y d r o l o g i c s o i l groups. 27 MINIMUM INFILTRATION RATE Group ( i n / h r ) (cm/hr) A 0.30 - 0.45 0.762 - 1.143 B 0.15 - 0.30 0.381 - 0.762 C 0.05 - 0.15 0.127 - 0.381 D 0.00 - 0.05 0.00 - 0.127 Table 1: Minimum I n f i l t r a t i o n r a t e s f o r s o i l h y d r o l o g i c groups (McCuen 1982) A r e a l extent f o r d i f f e r e n t s o i l groups must be determined through procedures such as p l a n i m e t e r i n g , or i d e a l l y i f a v a i l a b l e from a d i g i t a l e l e v a t i o n model of the watershed. When d e l i n e a t i n g the s o i l groups, a ge n e r a l r u l e i s recommended: two groups are combined only i f one of them covers l e s s than about 3 percent of the h y d r o l o g i c u n i t . Impervious s u r f a c e s should always be handled s e p a r a t e l y because they produce r u n o f f even i f there i s none from D s o i l s . C.2.c. antecedent moisture c o n d i t i o n The antecedent moisture c o n d i t i o n (AMC) measures the dryness of the s o i l and i t s r e a d i n e s s to absorb f u r t h e r water through i n f i l t r a t i o n . Three antecedent moisture c o n d i t i o n s are reco g n i z e d : 1) AMC I - the s o i l i s dry and has the a b i l i t y to absorb l a r g e q u a n t i t i e s of water through i n f i l t r a t i o n , 2) AMC I I - an average c o n d i t i o n i n which the s o i l i s moist but s t i l l has the c a p a c i t y to absorb c o n s i d e r a b l e water, and 3) AMC I I I - the s o i l i s n e a r l y s a t u r a t e d and has n e g l i g i b l e 28 a b i l i t y to absorb f u r t h e r water. The AMC i s determined on the b a s i s of the t o t a l p r e c i p i t a t i o n from the f i v e days p r e c e e d i n g the storm as o u t l i n e d i n t a b l e 2 below: Prededing 5 day p r e c i p i t a t i o n (mm) AMC I AMC II AMC I I I Growing Season < 35 35-0 - 52.5 > 52.5 Dormant Season < 12.5 1 2 . 5 - 2 7 - 5 > 27-5 Table 2: A v a i l a b l e Moisture C o n d i t i o n c l a s s i f i c a t i o n (Smedema and R y c r o f t 1983) The growing season i n the Lower E r a s e r V a l l e y i s considered to be March 1 to November 1, and the dormant season November 1 to March 1. In design procedures the antecedent s o i l moisture c o n d i t i o n i s o f t e n a p o l i c y d e c i s i o n r a t h e r than a statement of a c t u a l s o i l c o n d i t i o n s at the s i t e . ( i . e . AMC II i s assumed i n the growing season, and AMCIII i n the dormant season). C.2.d. r u n o f f e s t i m a t i o n A p p r o p r i a t e curve numbers are chosen f o r a given watershed to r e f l e c t the above c h a r a c t e r i s t i c s . The r e l a t e d r u n o f f i s then c a l c u l a t e d u s i n g r e l a t i o n s h i p s e s t a b l i s h e d by the S o i l C o n s e r v a t i o n S e r v i c e (USDA 1972; McCuen 1982). 29 C . 3 . P h y s i c a l l y "based r a i n f a l l - r u n o f f models Since the 1930's the Horton (1933) i n f i l t r a t i o n approach to ru n o f f p r o d u c t i o n has dominated hydrology and i t s a p p l i c a t i o n s to the p r e d i c t i o n of r i v e r d ischarges and i n land management (Dunne et a l . 1975). The h y d r o l o g i c a l response of catchments to storm r a i n f a l l has t r a d i t i o n a l l y been viewed as predominantly c o n t r o l l e d at the s o i l s u r f a c e . Where the i n f i l t r a t i o n c a p a c i t y of the s o i l i s exceeded, the excess r a i n f a l l w i l l generate the su r f a c e r u n o f f t h a t was assumed t o pro v i d e the bulk of the storm hydrograph. The Horton model of over l a n d flow has been confirmed by repeated f i e l d o b s e r v a t i o n and h y d r a u l i c study i n s e m i a r i d regions and on a g r i c u l t u r a l lands such as those of the Midwestern United S t a t e s . Since the i n f i l t r a t i o n c a p a c i t i e s of s o i l s on a catchment are r a r e l y uniform, the p r o d u c t i o n of Horton overland flow v a r i e s s p a t i a l l y . Hewlett (1961) developed the p a r t i a l - a r e a model of storm r u n o f f based on the o r i g i n a l Horton a n a l y s i s of overland flow, but s u g g e s t i n g that only a sm a l l p o r t i o n of some catchments c o n t r i b u t e s storm r u n o f f . T h i s l e d to f u r t h e r r e s e a r c h e f f o r t s by Betson (1964). In humid r e g i o n s , the i n f i l t r a t i o n c a p a c i t y of the s o i l remains h i g h u n l e s s the dense v e g e t a t i o n cover i s d i s t u r b e d . Hence, Horton o v e r l a n d flow i s co n f i n e d to l o c a t i o n s such as roads, s k i d t r a i l s i n f o r e s t s , some ploughed f i e l d s , a r t i f i c i a l f i l l s , and other areas that have been denuded of t h e i r v e g e t a t i o n . Overland flow can a l s o occur under snowpacks i n 30 areas where the i n f i l t r a t i o n c a p a c i t y i s lowered by the presence of concrete f r o s t i n the s o i l . In humid regions that have not been s e v e r e l y d i s t u r b e d , Horton overland flow does not occur (Dunne et_ a l . 1 975). Under these c o n d i t i o n s , the storm hydrograph may e i t h e r be generated almost e n t i r e l y by subsurface f l o w s , or s a t u r a t i o n overland flow (Beven and Wood 1983). Subsurface stormflow occurs where rainwater enters some zone of a permeable s o i l and d i s p l a c e s s o i l water to the stream ( r e f e r r e d to as t r a n s l a t o r y flow (Hewlett and Hi b b e r t 1967)). Subsurface stormflow may a l s o i n c l u d e some of the storm r a i n f a l l . When subsurface stormflow i s unable to remove a l l the incoming rainwater, the consequent i n c r e a s e i n the amount of water s t o r e d i n the s o i l r a i s e s the water t a b l e to the s o i l s u r f a c e i n swales and on the lower p a r t s of h i l l s l o p e s . Subsurface water can then emerge from the s o i l s u r f a c e as r e t u r n flow, and run overland at much gr e a t e r v e l o c i t i e s than are p o s s i b l e f o r subsurface stormflow. Rain f a l l i n g d i r e c t l y on the sa t u r a t e d area a l s o runs o f f as overland flow. These l a s t two processes may be grouped together as s a t u r a t i o n overland flow. Such areas of s a t u r a t e d s o i l have been shown to expand and co n t r a c t both s e a s o n a l l y and w i t h i n i n d i v i d u a l storm events. A choice i s a v a i l a b l e between an i n f i l t r a t i o n r a t e approach to the p r e d i c t i o n of overland flow (as o r i g i n a l l y d e s c r i b e d by Hewlett (1961) and used i n the model of Engman & Rogowski (1974)), and a s o i l storage based approach i n which the i n f i l t r a t i o n r a t e i s e s s e n t i a l l y c o nsidered t o be n o n - l i m i t i n g 31 such that o verland flow i s p r e d i c t e d when storage c a p a c i t y i s exceeded (Beven and K i r k b y 1979). The d i f f e r e n t views of how catchments respond becomes l a r g e l y a q u e s t i o n of semantics, but the important p o i n t s to reco g n i z e are that catchment storm response may i n v o l v e s i g n i f i c a n t subsurface c o n t r i b u t i o n s , while r u n o f f c o n t r i b u t i n g areas may be h i g h l y dynamic (Beven and Wood 1983). A number of p h y s i c a l l y based d e t e r m i n i s t i c models of the v a r i a b l e c o n t r i b u t i n g area concept of b a s i n response are re p o r t e d i n the l i t e r a t u r e (Beven and K i r k b y 1979). These models, of v a r y i n g degrees of s o p h i s t i c a t i o n and met h o d o l o g i c a l r i g o u r , have been e s s e n t i a l l y based on d i s t r i b u t e d moisture a c c o u n t i n g f o r s o i l elements w i t h i n segments of h i l l s l o p e . The data and computing requirements of these models are so great that they r e s t r i c t t h e i r p r a c t i c a l a p p l i c a t i o n to r e s e a r c h p r o j e c t s where economic c r i t e r i a are l e s s dominant. A l s o , none of the models make l i t t l e use of topographic and s o i l i n f o r m a t i o n , even though both are important i n determining source areas. In de v e l o p i n g a simpler model, Beven and K i r k b y (1976) presented a simple p h y s i c a l l y - b a s e d hydrograph model, TOPMODEL, that attempts to combine the advantages of a lumped r e p r e s e n t a t i o n of average s o i l water response w i t h the d i s t r i b u t e d e f f e c t s of a v a r i a b l e c o n t r i b u t i n g area. The model has s i n c e e x i s t e d i n many forms and has been expanded to i n c l u d e flow r o u t i n g through the channel network. 32 C.^.a. model s t r u c t u r e TOPMODEL (topography-based h y d r o l o g i c a l model), i s based on the combination of s e v e r a l l i n e a r storage components organized i n a s e r i e s c h a i n ( i . e . output from one storage l e v e l becomes input i n t o the n e x t ) . A fundamental assumption of the model i s th a t the catchment under study may be su b d i v i d e d i n t o s e v e r a l subcatchment u n i t s which are r e l a t i v e l y homogeneous i n t h e i r h y d r o l o g i c response and which should t h e r e f o r e be modelled s e p a r a t e l y . The sub-basin model has been formulated from the components as i l l u s t r a t e d i n F i g u r e 4: evaporation precipitation F i g u r e 4 : A schematic r e p r e s e n t a t i o n of the sub-basin model C . 3-a.i. i n t e r c e p t i o n / d e p r e s s i o n s t o r e The i n t e r c e p t i o n / d e p r e s s i o n s t o r e , , has a maximum value S-^  which must be f i l l e d b e fore any i n f i l t r a t i o n takes p l a c e i n t o the lower s t o r e s . E v a p o r a t i o n i s allowed from t h i s s t o r e at the 33 estimated p o t e n t i a l r a t e u n t i l i t i s empty. C .3«a.ii. n e a r - s u r f a c e ( i n f i l t r a t i o n ) s t o r e The n e a r - s u r f a c e ( i n f i l t r a t i o n ) s t o r e , Sg, r e c e i v e s water from the i n t e r c e p t i o n s t o r e , , when the l a t t e r i s f u l l , at a r a t e i equal to the excess r a i n f a l l , u n l e s s the i n f i l t r a t i o n c a p a c i t y i s exceeded. i . e . i > i = i + b/S 0 [3] max 0 ' 2 L^J where i i s the constant leakage r a t e allowed from S 0 to the 0 D 2 e x p o n e n t i a l subsurface s t o r e w i t h i n the area t h a t i s not considered s a t u r a t e d . In t h i s case excess r a i n f a l l ( i - i ) i s con s i d e r e d to max reach the b a s i n o u t l e t by a s u r f a c e route ( i n f i l t r a t i o n excess overland f l o w ) . I f under extreme c o n d i t i o n s a maximum value of near s u r f a c e storage ( i n f i l t r a t i o n s t o r e ) , S c, i s exceeded then again excess water i s considered to reach the sub-basin o u t l e t by a s u r f a c e route ( s a t u r a t i o n excess overland f l o w ) . F u r t h e r l o s s e s due to e v a p o t r a n s p i r a t i o n are allowed from t h i s s t o r e at a d e c r e a s i n g r a t e depending on the l e v e l of the i n f i l t r a t i o n s t o r e , Sg- Thus e a = e r S 2 / S c [4] where e r i s the p o t e n t i a l e v a p o t r a n s p i r a t i o n remaining once the i n t e r c e p t i o n s t o r e S 1 i s depleted, and e i s the a c t u a l l o s s from the i n f i l t r a t i o n s t o r e . 34 C.3«a.iii. v a r i a b l e c o n t r i b u t i n g area component r e l a t e d to  subsurface s o i l water storage Rain f a l l i n g on the c o n t r i b u t i n g s a t u r a t e d area w i l l immediately become overland flow. For a given s a t u r a t e d zone storage l e v e l , S^, the s a t u r a t e d area i s that f o r which l n ( a / t a n g ) > ST/m - S^/m + x [5] x = A - 1 / In (a/tang)dA [6] where: a = area drained / u n i t contour l e n g t h at a p o i n t tang = slope g r a d i e n t at that p o i n t m = a parameter of the e x p o n e n t i a l r e l a t i o n s h i p between storage and l a t e r a l flow X = a constant f o r the subcatchment r e p r e s e n t i n g the average areas f o r (a/tang) given by the above equation. A = t o t a l subcatchment area = the l o c a l s a t u r a t e d storage (assumed s p a t i a l l y constant) = negative moisture d e f i c i t , at complete s a t u r a t i o n = 0 and S^<0 f o r l e s s than f u l l s a t u r a t i o n . 3 The c o n t r i b u t i n g area i s a l s o r e q u i r e d to c a l c u l a t e the overland flow d i s c h a r g e QQJ,: Q o p = i / A c [7] where i = instantaneous r a i n f a l l i n t e n s i t y A = c o n t r i b u t i n g area c to C.3-a.iv. delayed subsurface flow Delayed subsurface flow from the n o n - l i n e a r s a t u r a t i o n s t o r e i s r e p r e s e n t e d as an e x p o n e n t i a l s t o r e f o r which 35 q b = q o e x P ^ S 3 / m ) W where: q^ = the flow r e a c h i n g the channel from the s t o r e q Q = the flow when = 0 ( s o i l i s completely s a t u r a t e d ) (q has the primary f u n c t i o n of a d j u s t i n g the outflow from the e x p o n e n t i a l s t o r e as c a l c u l a t e d u s i n g average storage and the estimated value of m, to he e q u i v a l e n t to the subsurface outflow from the b a s i n as a whole.) m = a constant which c o n t r o l s the s l o p e of the r e c e s s i o n limb of the hydrograph T h i s sequence of storage elements i s assumed to r e p r e s e n t the average response of the s o i l water i n a homogeneous sub-basin u n i t . In t h i s r e s p e c t , each sub-basin i s t r e a t e d as a lumped system. I t i s assumed that the dominant source of quick r e t u r n or s u r f a c e flow i s an area of s u r f a c e s a t u r a t i o n , or v a r i a b l e c o n t r i b u t i n g area, the extent of which v a r i e s w i t h the average l e v e l of subsurface s o i l water storage as represented by the s t o r e (Beven and K i r k b y 1979). C.5»a.v. ov e r l a n d flow The overland flow component may be estimated as d o f = i A c [9] where i i s the instantaneous r a i n f a l l i n t e n s i t y and A i s the 17 c s a t u r a t e d area. E a r l y m o d e l l i n g i n the Crimple Beck catchment i n England (Beven 1977) suggested t h a t even f o r s m a l l sub-basin areas, overland flow t r a v e l times were ca u s i n g a s i g n i f i c a n t delay i n the t i m i n g of sub-basin d i s c h a r g e . A simple overland flow r o u t i n g r o u t i n e was thus i n c l u d e d i n the model based on the 36 expected spread of c o n t r i b u t i n g area i n r e l a t i o n to the topography and a constant o v e r l a n d flow v e l o c i t y OPV. Overland flow w i t h i n the c o n t r i b u t i n g area i s routed at a v e l o c i t y p r o p o r t i o n a l to l o c a l g r a d i e n t , with the parameter OFV as the constant of p o r p o r t i o n a l i t y • The time taken to reach the sub-b a s i n o u t l e t from any p o i n t w i t h i n the p r e d i c t e d c o n t r i b u t i n g area i s given by N x i . Z . OPV tans. I - 1 0 ! i = 1 1 where x^ i s the l e n g t h of the i t h flow path segment of slope tane^, and N i s the number of segments between the p o i n t and the outflow. Por a given value of A , a unique time-delay histogram can be d e r i v e d from the b a s i n topography which allows overland flow to be routed to the o u t l e t (Beven and K i r k b y 1979). In Beven et a l . (1984), a new r o u t i n g procedure was used; a simple n o n - l i n e a r c o n v o l u t i o n r o u t i n g a l g o r i t h m n based on the a t -a - s t a t i o n v e l o c i t y r e l a t i o n s h i p : c ( t ) = CHA * Q ( t ) C H B [11 ] where Q(t) i s the outflow discharge f o r the whole catchment at time t ; CHA and CHB are constants; and c ( t ) i s an average ki n e m a t i c wave v e l o c i t y f o r the channel network which i s assumed to be s p a t i a l l y constant. The r o u t i n g procedure accounts f o r the d i s t r i b u t i o n of p r e d i c t e d subcatchment i n f l o w s with d i s t a n c e a l o n g the channel network (Beven e_t a l . 1984). C 3 * b . model theory TOPMODEL uses r e a d i l y a v a i l a b l e t opographic data i n c o n j u n c t i o n with a l i m i t e d amount of s o i l i n f o r m a t i o n so that 37 not only can the v a r i a t i o n i n b a s i n topography and channel topology be r e a d i l y d e s c r i b e d , but p h y s i c a l l y - b a s e d s o i l parameters can be measured i n any catchment. Since a l l the model parameters can be obtained by d i r e c t measurement f o r a p a r t i c u l a r area, the model should be a p p l i c a b l e to ungauged catchments of up 2 to 500 km , where only r a i n f a l l and e v a p o r a t i o n data are a v a i l a b l e . The model has been designed s p e c i f i c a l l y f o r u n f o r e s t e d catchments with a humid-temperate c l i m a t e ( t h i s r e s t r i c t i o n i s mainly based on the procedures used to i n c o r p o r a t e e v a p o t r a n s p i r a t i o n ) (Beven et a l . 1984). As per Beven and K i r k b y (1979), i t i s assumed t h a t at any p o i n t i n the catchment, downslope flow per u n i t width of s l o p e , q, i s r e l a t e d to s a t u r a t i o n d e f i c i t , S, by: q = K Qexp(-S/m)tanB [ 1 2 ] where k Q i s the s a t u r a t e d c o n d u c t i v i t y at the s o i l s u r f a c e , and m i s a parameter of the r e c e s s i o n curve (subsurface flow parameter). Return flow as w e l l as subsurface flow are governed by t h i s equation (Beven 1985). S a t u r a t i o n d e f i c i t (S) i s d e f i n e d as the storage d e f i c i t below f u l l s a t u r a t i o n due to s o i l drainage alone and e x c l u d i n g the a d d i t i o n a l d e f i c i t s t h a t would r e s u l t from e v a p o t r a n s p i r a t i o n . Thus K Qtan6 i s the t r a n s m i s s i o n c a p a c i t y of the s o i l p r o f i l e at f u l l s a t u r a t i o n , where tanB i s the l o c a l s u r f a c e s l o p e angle. T h i s r e l a t i o n s h i p allows s o i l h y d r a u l i c c o n d u c t i v i t y to vary with depth but assumes that the l o c a l h y d r a u l i c g r a d i e n t i s equal to the s u r f a c e s l o p e angle 38 throughout. Assuming steady s t a t e input r a t e , R, at any p o i n t q = Ra [13] where a i s the upslope area d r a i n e d per u n i t width of slope or contour l e n g t h . Comhining equations [12] and [ 13 ] above, S = -mln(aR / K QtanB) [14] The s a t u r a t e d area may then be d e f i n e d as the area which S < 0 or a/tanB< k Q/R [15] ( n o t i n g t h a t d e f i c i t s are +ve) The average storage d e f i c i t i n the catchment i s given by: A A S = A - 1 / Sda = A - 1 / -mln(aR / K tang)d a [16] 0 0 0 I t i s f u r t h e r assumed t h a t K and m are constant, i . e . t h a t o ' the s o i l i s homogeneous and of a uniform depth then S = -mX - mln(R/K ) [ 17 ] - 1 A where: X = A /In(a/tanB)d o [18] 0 i s a constant f o r the catchment dependent on topography. From equation [ 1 7 ] : ln(R/k ) = -S/m - ln(a/tan&) [19] so t h a t S = -m X + S + mln(atan3) [20] I t i s a l s o assumed t h a t subsurface drainage from the complete 39 b a s i n i s d e s c r i b e d by a s i m i l a r e x p o n e n t i a l f u n c t i o n to equation [12] , i n v o l v i n g the average d e f i c i t S: Q B = Q Q exp(-S/m) or a l s o expressed as: [21] q b = q o e xP^ S 3 / m ) [22] where i s the s a t u r a t e d zone storage, and m i s a parameter of the r e c e s s i o n curve of the catchment and can e a s i l y be estimated from a minimum of discharge measurements. The model of Beven and K i r k b y (1979) i n v o l v e d continuous a c c o u n t i n g f o r the subsurface storage d e f i c i t S, so th a t at any time, g i v e n S and the d i s t r i b u t i o n of ln ( a / t a n g ) i n the catchment, equation [14] based on s t e a d y - s t a t e assumptions, was used to p r e d i c t the dynamic response of the c o n t r i b u t i n g area f o r which S < 0 or: Thi s approach was mo d i f i e d somewhat by Beven and Wood (1983) where t h e i r i n t e r e s t was d i r e c t e d to p r e d i c t i n g the response to i n d i v i d u a l l a r g e storms. E q u a t i o n [14] not only gives a r e l a t i o n s h i p f o r p r e d i c t i n g s a t u r a t e d areas f o r any value of S but a l s o f o r p r e d i c t i n g the s a t u r a t i o n d e f i c i t s anywhere i n the catchment. I f a value of i n i t i a l catchment d i s c h a r g e , i s a v a i l a b l e p r i o r t o the storm, then equations [14] and [15] may be combined to gi v e : Values of S < 0 i n d i c a t e an i n i t i a l s a t u r a t e d area, w h i l e elsewhere the d e f i c i t must be f i l l e d b e f o r e s a t u r a t i o n i s ln(a/tanB) > S/m + X [23] S = m X - mln(a/tane) - mln(Q i/Q ) [24] 40 predicted for each value of ln(a/tane). The saturation deficit approach to predicting variable contributing areas neglects the dynamic response of the subsurface flow system (Beven and Wood 1983). One of the failings of the earlier Beven and Kirkby (1979) model was in its treatment of the.delays in the unsaturated zone in affecting the subsurface response. The use of the i n i t i a l saturation deficit approach outlined above also suggests a convenient way to allow for the effect of the unsaturated zone. For any area of soil at or near saturation, the unsaturated-zone delay will be minimal, and will increase upslope for points of higher i n i t i a l deficit (lower ln(a/tans)). If it is assumed that the delay in the unsaturated zone is directly proportional to deficit at a point, then the input to the saturated zone at that point q v may be described by: q = S /(t.S) [25] •^v uz' d where S is the predicted saturation deficit, t^ is a time delay per unit of deficit; and S is storage in the unsaturated zone * uz in excess of some field capacity value below which vertical flows may be neglected on the time scale of the storm hydrograph. The average residence of the unsaturated zone is effectively t^S. Given the different values of S associated with different values of ln(a/tane), an areally weighted reduction in the catchment average deficit S can be calculated during a time period. Subsurface output in the same time period can be calculated from equation [17] allowing continuous accounting for S. 41 R e c a l c u l a t i o n of the s a t u r a t i o n d e f i c i t s p r e d i c t e d from S at each time step makes allowance f o r downslope flows and, d u r i n g drainage, the recovery of s a t u r a t i o n d e f i c i t s between c l o s e l y spaced events. In t h i s way both s u r f a c e and subsurface responses can be p r e d i c t e d , thereby a v o i d i n g any a r b i t r a r y hydrograph s e p a r a t i o n p r i o r to a n a l y s i s (Beven and Wood 1983). The model has a l s o been m o d i f i e d to account f o r the s p a t i a l v a r i a b i l i t y of s o i l h y d r a u l i c c h a r a c t e r i s t i c s (Beven 1985). S = S.- m Y + min ( Y±^) [26] I I where Y i s a b a s i n constant: v X ' l n ( K ^ ? 7 ) [ 2 7 ] -A i i The use of equation [26] i n a continuous a c c o u n t i n g model assumes that the steady s t a t e r e l a t i o n s h i p s used i n the development are a good approximation to storage r e l a t i o n s h i p s under t r a n s i e n t c o n d i t i o n s . I f t h i s i s a reasonable assumption, equation [26] allows f o r p r e d i c t i o n of the p a t t e r n of s o i l moisture d e f i c i t w i t h i n the catchment, and p a r t i c u l a r l y the s a t u r a t e d c o n t r i b u t i n g area (S^ < 0), from knowledge of topography and s o i l c h a r a c t e r i s t i c s . The b a s i n constant y can be d i v i d e d i n t o a topographic part and a s o i l p art where the f i r s t i n t e g r a l i s the topographic constant x of Beven and K i r k b y (1979): * = i{ln{ tanV ^ " A £ l n ( K ^ £28] 42 C.3 ' C . model c a l i b r a t i o n C.3.c.i. overland flow, i n t e r c e p t i o n and i n f i l t r a t i o n parameters Model c a l i b r a t i o n f o r overland flow, i n t e r c e p t i o n , and i n f i l t r a t i o n parameters ( S D , S , i , and OEV) i n TOPMODEL r e q u i r e s f i e l d e xperimentation u s i n g a s p r i n k l i n g i n f i l t r o m e t e r . A s i n g l e or double r i n g i n f i l t r o m e t e r could not be used f o r the c a l i b r a t i o n . A ground p l o t with a s u f f i c i e n t area f o r g e n e r a t i n g s u r f a c e r u n o f f , and a means of c o l l e c t i n g and measuring t h i s r u n o f f i s imperative f o r parameter d e t e r m i n a t i o n . A s p r i n k l i n g i n f i l t r o m e t e r allows n a t i v e v e g e t a t i o n to remain i n t a c t g i v i n g a more r e p r e s e n t a t i v e e s t i m a t i o n of i n t e r c e p t i o n s t o r e near the ground s u r f a c e . S i m u l a t i n g r a i n f a l l on the ground i n s t e a d of f l o o d i n g w i t h a constant head as i n u s i n g a r i n g set-up i s more r e a l i s t i c , e s p e c i a l l y i n the upland s o i l s where ponding does not u s u a l l y occur (unless i n s m a l l d e p r e s s i o n s ) . The s p r i n k l i n g i n f i l t r o m e t e r used by Beven ( 1 9 7 7 ) i s shown i n f i g u r e 5 below where: a. one wheeled t r o l l e y w i t h motor, pump, pre s s u r e gauge and two 5 - g a l l o n water r e s e r v o i r s b. s p r i n k l e r n o z z l e c. s p r i n k l e r bar d. h e i g h t adjustment f o r s p r i n k l e r bar e. p o l y e t h l e n e wind s h i e l d f . r u n o f f p l o t boundary g. s p l a s h cover over r u n o f f c o l l e c t i o n tube h. r u n o f f c o l l e c t i o n tube - i n t r e n c h 43 i . r u n o f f c o l l e c t i o n p o i n t - i n t r e n c h F i g u r e 5: s p r i n k l i n g i n f i l t r o m e t e r The above apparatus was r e l a t i v e l y p o r t a b l e , w i t h reasonably even ground cover and minimal wind e f f e c t s (Beven 1977). The r a t e s of a p p l i c a t i o n that could be achieved (30 to >200 mm/hr eq u i v a l e n t ) were, however, high i n r e l a t i o n to the range of recorded r a i n f a l l r a t e s i n the Crimple Beck watershed under study. Beven found t h a t the s p r i n k l i n g i n f i l t r o m e t e r could be much improved, i n p a r t i c u l a r to allow lower r a t e s of a p p l i c a t i o n , more r e a l i s t i c drop s i z e s , and v e h i c l e mounted water r e s e r v o i r s . At l e a s t one s p r i n k e r t e s t i s recommended on each major s o i l and v e g e t a t i o n type (Beven and Wood 1983). C a l i b r a t i o n i s performed as f o l l o w s : a) One or more s o i l cores are taken adjacent to the chosen 44 s i t e , f o r a n a l y s i s of near s u r f a c e s o i l water storage (M^) p r i o r to the experiment. h) I n f i l t r o m e t e r apparatus i s set up at the chosen s i t e , and when proper head has been a t t a i n e d i n the i n f i l t r o m e t e r f o r d e s i r e d s p r i n k l i n g r a t e , time i s s t a r t e d and water i s allowed to reach s o i l . c) Once overland flow has begun on the p l o t , the r u n o f f i s c o l l e c t e d at given time p e r i o d s (to c a l c u l a t e the r a t e of r u n o f f / u n i t area) u n t i l a constant r u n o f f r a t e i s obtained. d) When constant r u n o f f i s reached, an estimate of v e l o c i t y of s u r f a c e r u n o f f i s obtained by a p p l y i n g dye at the upslope end of the p l o t and e s t i m a t i n g the t r a v e l l i n g time to the opposite end of the p l o t by eye. T h i s may be more a c c u r a t e l y determined by the a n a l y s i s of r u n o f f samples taken at known times on a f l u o r i m e t e r . e) A measurement of s u r f a c e s l o p e , tan g, at the s i t e allows the parameter OFV to be c a l c u l a t e d from: OPV = - — - — [29] t tang where t = the average time of t r a v e l x = the l e n g t h of the p l o t g = p l o t slope f ) R a i n f a l l i s stopped, and when r u n o f f has ceased a s o i l core i s taken from the c e n t r e of the p l o t (lY^). g) Once a l l r a t e s of flow and s o i l moisture values have been c a l c u l a t e d , a graph of r u n o f f r a t e and i n f i l t r a t i o n r a t e ( i as 4 5 c a l c u l a t e d from s p r i n k l e r a p p l i c a t i o n r a t e - r u n o f f rate) i s drawn ( s i m i l a r to that i n f i g u r e 6). In the s i m p l e s t form of a n a l y s i s the parameter i i s taken as the f i n a l constant i n f i l t r a t i o n r a t e . The maximum value of i n t e r c e p t i o n s t o r e i s taken as the amount of water a p p l i e d "before the constant r u n o f f i s achieved minus the change i n near s u r f a c e s o i l water storage 10 m m / h S p r i n K l t r r o t i 7 0 m m / h x l T * O v e r l a n d H o w I n f i l t r a t i o n 30 M i n u t e s F i g u r e 6: R e s u l t s from a s p r i n k l i n g i n f i l t r o m e t e r experiment, Landshaw sub-basin (Beven and Ki r k b y 1979). I f i n f i l t r a t i o n r a t e s are gr e a t e r than the input ( a r t i f i c i a l p r e c i p i t a t i o n r a t e ) , the parameter ( i n f i l t r a t i o n s t o r e ) i s i n o p e r a t i v e . When measured values of i ( f i n a l constant r o i n f i l t r a t i o n r a t e ) are used i n the model, the i n f i l t r a t i o n s t o r e as a whole has l i t t l e or no e f f e c t on the p r e d i c t e d d i s c h a r g e s and does not p r o v i d e a delay b e f o r e flow reaches the subsurface s t o r e . I f i n f i l t r a t i o n r a t e s are l e s s than the s p r i n k l i n g input r a t e , the l i n e a r i n f i l t r a t i o n s t o r e , ( S 2 ) , serves to model the 46 delay before i n f i l t r a t e d water reaches the subsurface s a t u r a t e d s o i l water s t o r e . E s t i m a t i o n of the parameters b and S Q r e q u i r e s a more complex procedure i n v o l v i n g s e v e r a l spray t e s t s c a r r i e d out a d i f f e r e n t a p p l i c a t i o n r a t e s . Under a constant r a t e of input, i , to the near s u r f a c e s t o r e (as i n the s p r i n k l e r t e s t ) s u r f a c e flow may occur e i t h e r as a r e s u l t of the i n f i l t r a t i o n c a p a c i t y , i , or the t o t a l storage c a p a c i t y , S , b e i n g max c exceeded. I f T i s the time from the s t a r t of the t e s t to the onset of overland flow and T' i s the time r e q u i r e d to f i l l the d e p r e s s i o n storage S^, (that i s T' = S ^ / i ) then f o r i n f i l t r a t i o n excess overland flow i <i [30] max -or from equation [3] i Q + b/S 2 4 i when S 2 = ( T - T ' ) ( i - i 0 ) [31] T h i s assumes that the d e p r e s s i o n storage i s s a t i s f i e d f i r s t , or 1 1 ± o + (T - r ) ( i - [ 3 2 ] or T-T' = ( . * . }2 [33] Eor s a t u r a t i o n excess overland flow, the storage S 2 at the onset of o v e r l a n d flow i s equal to SQ: S c = (T - T ' ) ( i - i Q ) [34] or S T - T' = ( . _ c. ) [35] P l o t t i n g ( i - i ) a g a i n s t log(T-T') f o r t e s t s at d i f f e r e n t 47 a p p l i c a t i o n r a t e s should d i s t i n g u i s h the two mechanisms of overland flow g e n e r a t i o n , and enable the parameters b and S to c be determined from the i n t e r c e p t s on the ( i - i ) a x i s ( f i g u r e 7): F i g u r e 7: Expected nature of r e s u l t s from i n f i l t r o m e t e r experiments i n t e r p r e t e d i n terms of the storage based i n f i l t r a t i o n component of the model (Beven and K i r k b y 1979). The parameter m of the e x p o n e n t i a l subsurface s t o r e i s estimated by making discharge measurements at the subsurface catchment outflow d u r i n g a r e c e s s i o n p e r i o d of zero r a i n f a l l . Any e x i s t i n g discharge measurements w i t h i n the catchment can be i n c o r p o r a t e d i n the a n a l y s i s . The discharge measurements are converted to mm per u n i t area e q u i v a l e n t from which an estimate of change i n average storage l e v e l i n the sub-catchment d u r i n g the p e r i o d of measurement can be c a l c u l a t e d . The use of a winter r e c e s s i o n p e r i o d i s recommended to minimise the e f f e c t of eva p o r a t i o n on the change i n storage which otherwise must be taken i n t o account. l o g ( T - T ' ) \ \ , \ \ \ ^ log b tog S c (L - L o ' C . 3 • c . i i . subsurface storage parameters 4 8 I f the subsurface c o n t r i b u t i o n to drainage from the catchment conforms to the e x p o n e n t i a l s t o r e that i s assumed i n the model, then a graph of c a l c u l a t e d r e l a t i v e storage l e v e l (as the a b c i s s a ) versus l o g Q (measured d i s c h a r g e ) ( a s the o r d i n a t e ) should p l o t as a s t r a i g h t l i n e w i t h a slope of 1/m. Given a value of m f o r a subcatchment, the subsurface parameter Q , can be c a l c u l a t e d from measurements of average s o i l water storage obtained from s o i l cores taken throughout the s o i l p r o f i l e at a number of l o c a t i o n s i n the subcatchment, at a known value of discharge (q-^) per u n i t area from the catchment. S u b s t i t u t i o n i n t o the f o l l o w i n g equation y i e l d s a value of q . S,/m <*b= V 5 [ 3 6 ] The value of the f i n a l subcatchment parameter S , the i n i t i a l * c' value of S^ at the s t a r t of a s i m u l a t i o n run, can be found by s u b s t i t u t i n g a known or estimated value of a c t u a l discharge from the catchment i n t o equation [22], given q Q and m. T h i s procedure i s only s a t i s f a c t o r y i f the s i m u l a t i o n run s t a r t s d u r i n g a r e c e s s i o n p e r i o d such that a l l subcatchment discharge i s d e r i v e d from subsurface drainage and both the i n t e r c e p t i o n and i n f i l t r a t i o n s t o r e s may be assumed to be dry p r o v i d e d that the model i s a s u i t a b l e r e p r e s e n t a t i o n of subcatchment behaviour. E r r o r s i n the i n i t i a l c o n d i t i o n s are q u i c k l y damped out and have been found to have l i t t l e e f f e c t on the s i m u l a t i o n s (Beven 1977). C . ^ . c . i i i . channel r o u t i n g parameters Channel r o u t i n g i s expressed by the flow v e l o c i t y r e l a t i o n s h i p of the f o l l o w i n g equation: 49 C(t) = CHA Q(traD [37] where Q(t) i s the discharge at the outflow of the whole catchment at time t and C(t) i s an average k i n e m a t i c wave v e l o c i t y f o r the network which i s assumed to he s p a t i a l l y constant. The parameters CHA and CHB can he obtained by n o n - l i n e a r r e g r e s s i o n c a l c u l a t i o n s . C.3'd- a n a l y z i n g catchment topography The d e r i v a t i o n of ln(a/tan&) d i s t r i b u t i o n s f o r r e a l catchments w i l l always i n v o l v e some degree of s u b j e c t i v e g e n e r a l i z a t i o n and a b s t r a c t i o n (Beven and Wood 1983). Beven and K i r k b y (1979) used a computerized procedure based on flow l i n e s orthogonal to the contours on l a r g e - s c a l e t o p o g r a p h i c maps as drawn by hand a f t e r p r e l i m i n a r y e v a l u a t i o n of a i r photographs and f i e l d i n s p e c t i o n . T h i s procedure was very time-consuming. With the i n c r e a s i n g a v a i l a b i l i t y of data banks of d i g i t i z e d t o pographic maps at a s c a l e of 1:24 000 or b e t t e r , t h i s p a r t of the a n a l y s i s i s handled a u t o m a t i c a l l y u s i n g a d i g i t i z e r t a b l e t and d i g i t a l e l e v a t i o n model (Beven and Wood 1983). Beven and Wood (1983) have a l s o explored the p o s s i b i l i t y of s u b d i v i d i n g a catchment i n t o a number of i d e a l i z e d flow planes f o r which d i s t r i b u t i o n s of ln(a/tanB) and the parameter x could be d e r i v e d a n a l y t i c a l l y . The a n a l y t i c a l d e r i v a t i o n of topographic c h a r a c t e r i s t i c s i n v o l v e s s u d i v i d i n g a catchment i n t o three d i f f e r e n t types of i d e a l i z e d subcatchments; namely, r e c t a n g u l a r planes, r e c t a n g u l a r curved, and r a d i a l l y convergent s u r f a c e s . The a n a l y t i c a l r e s u l t s f o r these i d e a l i z e d flow s u r f a c e s are given below. 50 C.5»d.i. r e c t a n g u l a r planes The catchment can be represented by a V-shaped r e c t a n g u l a r plane w i t h overland flow l e n g t h L, and stream l e n g t h x; 0<x<L. The d e r i v e d f u n c t i o n s are as f o l l o w s : a/tanB= (L - x)/tanB [38] x = A - 1 / l n ( a / t a n B ) d A = In (L/tanB) - 1 [39] A A / a = 1-(tanB/L)(a/tanP)s [40] where a i s the upslope area d r a i n i n g past that p o i n t per u n i t width of slope or contour l e n g t h , and A Q i s the c o n t r i b u t i n g area f o r t h i s subcatchment where (a/tang)s exceeds the c r i t i c a l (a/tane) f o r s a t u r a t i o n . T h i s l i n e a r r e l a t i o n s h i p f o r A Q / A can be transformed i n t o A C / A vs. l n ( a / t a n & ) . C 5 ' d . i i . r e c t a n g u l a r curved flow s u r f a c e Assuming that the overland flow s u r f a c e can be approximated by the q u a d r a t i c equation: Y = j x 2 + bx [41 ] where j and b can e a s i l y be estimated from topographic map data and x i s measured from the stream. The d e r i v e d f u n c t i o n s are: a/tan8 = (JJ - x ) / ( 2 j x + b) X = l n ( L b b / 2 j ' L / ( 2 j K + b ) k + b , 2 j K ) A / A - [1- (b/L)(a/tanB)] A / A " L1 - 2 j ( a / t a n B ) J [42] [43] [44] 51 C . 5 . d . i i i . convergent plane s e c t i o n Assuming a headwater catchment can be modeled as a convergent plane w i t h angle e and overland flow l e n g t h L, the d e r i v e d f u n c t i o n s are: a/tan3= ( L 2 - x 2)/2xtanB [45] X = l n ( L / 2 t a n s ) - 0 . 5 [46] A /A = L " 2 [ { L 2 + t a n 2 e ( a / t a n B ) 2 } 0 , 5 - t a n B ( a / t a n B ) ] 2 [47] Assuming N-such i d e a l i z e d flow s u r f a c e s ( i = 1,...,N), the cor r e s p o n d i n g v a l u e s f o r the whole catchment are: N - 1 x = (_z A. ) 'sA.x. [48] and N _ 1 N A /A = ( z A ) z A.(A ./A.)(a/tang) [49] c 1=1 1 1=1 1 C 1 1 52 F i g u r e 8 below p l o t s the A /A vs. (a/tang) f o r the three types of i d e a l i z e d p l a n e s . — a / tanfJ L/b. F i g u r e 8: A Q / A V S . a/tang f o r i d e a l i z e d s i d e s l o p e s (Beven and Wood 1983). 53 D. PEAK FLOW ESTIMATION  D.1. Time of c o n c e n t r a t i o n Time of c o n c e n t r a t i o n (t ) i s d e f i n e d as the time r e q u i r e d f o r r u n o f f to t r a v e l from the h y d r a u l i c a l l y most d i s t a n t p a r t of the watershed, to the watershed o u t l e t or some other p o i n t of r e f e r e n c e downstream ( h y d r a u l i c l e n g t h ) ( L u t h i n 1978). In hydrograph a n a l y s i s , the time of c o n c e n t r a t i o n i s the time from the end of e x c e s s i v e r a i n f a l l to the i n f l e c t i o n p o i n t on the f a l l i n g limb of the hydrograph where the r e c e s s i o n curve begins ( r u n o f f c e a s e s ) . The S o i l C o n s e r v a t i o n S e r v i c e p r e s e n t s the f o l l o w i n g r e l a t i o n s h i p s r e l a t e d to the time of c o n c e n t r a t i o n : t = 0.7 t [50] p c with excess d u r a t i o n of p r e c i p i t a t i o n = 0 . 133 t [51] These are augmented with a review by Smedema and R y c r o f t (1983): t p = 0.7 t c [52] t-L = 0.6 t c [53] t r = 1.67 t p [54] The r e f o r e , t , should be 10$ lower than t . ' 1 p where: t = time to peak t = r e c e s s i o n time r t-^ = l a g time As observed values of t are r a r e l y a v a i l a b l e , the designer normally has to make do with estimates of t . Many formulas and nomographs have been developed f o r e s t i m a t i n g t . Almost a l l 54 methods of estimating the time of concentration use the slope, hydraulic length, and some measure of land use. The following methods were selected from the literature to test their accuracy in t estimates as compared to observed t c p values and t estimates: nomograph (Chow 1964), Kerby formula (Chow 1964), flow velocity method (McCuen 1982), Kirpich formula (Smedema and Rycroft 1985; Raudkivi 1979), and the lag method (McCuen 1982). D.2. Soil Conservation Service unit hydrograph method A unit hydrograph is the hydrograph that results from one inch of precipitation excess generated uniformly over the watershed at a uniform rate during a specified period of time. The SCS methods use dimensionless unit hydrographs which are based on extensive analysis of measured data (a dimensionless unit hydrograph is a graph of q./q versus t/t in which q. is the discharge at any time t). Unit hydrographs were evaluated for a large number of actual watersheds and then made dimensionless. An average of these dimensionless unit hydrographs was developed with the following characteristics: 1 ) the time base of the dimensionless unit hydrograph was approximately five times the time-to-peak, 2) approximately 3/8 of the total volume occurred before the t ime-to-peak, 3) the inflection point on the recession limb occurs at approximately 1.7 time the time-to-peak, 4) the unit hydrograph had a curvilinear shape. 55 The c u r v i l i n e a r u n i t hydrograph can be approximated by a t r i a n g u l a r UH t h a t has s i m i l a r c h a r a c t e r i s t i c s . The area under the r i s i n g limb of the two u n i t hydrographs are the same (37.5$) but the time base of the t r i a n g u l a r u n i t hydrograph i s only 8/3 of the time-to-peak (as compared to 5 f o r the c u r v i l i n e a r u n i t hydrograph. D.2.a. peak discharge of the u n i t hydrograph The area under the u n i t hydrograph equates the volume of d i r e c t r u n o f f Q as estimated by the SCS CN approach. Runoff can a l s o be expressed i n terms of time-to-peak (t ), r e c e s s i o n time ( t r ) , and peak d i s c h a r g e ' ( q p ) : Q = l/2q p ( t p + t r ) [55] s o l v i n g f o r q p and r e a r r a n g i n g gives V t - * 1 + t / t £56] p r' p r e p l a c i n g the second term i n the above equation y i e l d s : S * ¥ [57] In order to have q i n c f s , t i n hours, and Q i n inches, i t i s necessary to d i v i d e by the area A i n square miles and to m u l t i p l y by the constant 645-3; a l s o because t r = 1.67 t , equation [57] above becomes: c = « * « [58] P The constant 484 r e f l e c t s a u n i t hydrograph with 3/8 of i t s area under the r i s i n g limb. In mountainous areas, the f r a c t i o n 56 could be expected to be g r e a t e r thus r e f l e c t i n g a constant near 600 (assuming i n c r e a s e d overland f l o w ) . The time-to-peak i n the above equation [58] can be expressed i n terms of the d u r a t i o n of u n i t p r e c i p i t a t i o n excess and the time of c o n c e n t r a t i o n : t c + D = 1.7 t p [59] and D/2 + 0.6 t = t [60] ' c p L J The above two equations are expressed i n f i g u r e 9 below, S o l v i n g equations [59] and [60] f o r D g i v e s : D = 0.133 t [61 ] T h e r e f o r e , t can be expressed i n terms of t Q : t = D/2 + 0.6 t Q = 2/3 t [62] E q u a t i o n [62] then be expressed i n terms of t Q r a t h e r than t 726 AQ r,^i 57 F i g u r e 9: Dimensionless c u r v i l i n e a r u n i t hydrograph and e q u i v a l e n t t r i a n g u l a r hydrograph (McCuen 1982). D.5. R a t i o n a l formula D.5«a. overview of use and development The r a t i o n a l formula had i t s b e g i n n i n g about 130 years ago. The f i r s t paper p u b l i s h e d c o n t a i n i n g the u n d e r l y i n g p r i n c i p l e s was i n 1851, but was l a r g e l y ignored u n t i l 1889 when the method was presented to the American S o c i e t y of C i v i l E n g i neers. In the next few decades, attempts were made to estimate time of c o n c e n t r a t i o n , r u n o f f c o e f f i c i e n t , and r a i n f a l l i n t e n s i t y more a c c u r a t e l y . The development of the i n t e n s i t y - d u r a t i o n - f r e q u e n c y curves p r o v i d e d improved r a i n f a l l i n t e n s i t y estimates, however work on the time of c o n c e n t r a t i o n and r u n o f f c o e f f i c i e n t were 58 l e s s s u c c e s s f u l , as s t i l l i s the case. The past f o r t y years have pr o v i d e d few i f any improvements i n the use of the r a t i o n a l formula, r a t h e r a p r o l i f e r a t i o n of methods to estimate the v a r i o u s f a c t o r s i n the form of equations, graphs, and t a b l e s . T h i s attempt at s i m p l i f i c a t i o n has r e s u l t e d i n some widespread misconceptions i n the use of t h i s formula ( R o s s m i l l e r 1982). The b a s i c p r i n c i p l e u n d e r l y i n g the r a t i o n a l formula i s that the h i g h e s t d i s c h a r g e from the b a s i n occurs i n response to a storm with a d u r a t i o n equal t o the time of c o n c e n t r a t i o n (t ). The r a t i o n a l formula i s based on the f o l l o w i n g assumptions: 1 ) the re c u r r e n c e i n t e r v a l of the peak flow i s the same as tha t of the r a i n f a l l i n t e n s i t y , 2) the r a i n f a l l i s uniform i n space over the drainage area being c o n s i d e r e d , 3) the r a i n f a l l i n t e n s i t y i s uniform throughout the d u r a t i o n of the storm, 4) the c o e f f i c i e n t of r u n o f f i s the same f o r storms of v a r i o u s f r e q u e n c i e s , 5) the c o e f f i c i e n t of r u n o f f i s the same f o r a l l storms on a given watershed. The assumptions of uniform r a i n f a l l i n space and uniform r a i n f a l l i n t e n s i t y are t r u e only f o r s m a l l drainage b a s i n s and sho r t d u r a t i o n storms r e s p e c t i v e l y . T h e r e f o r e , i n a g r i c u l t u r a l drainage system design, the r a t i o n a l formula i s best a p p l i e d to res p o n s i v e types of f i e l d drainage where very l i t t l e 59 t r a n s f o r m a t i o n occurs i n the f i e l d drainage system (the f i e l d drainage hydrograph resembles the hyetograph) (Smedema and R y c r o f t 1983). For example, groundwater drainage (subsurface drainage) u s u a l l y r e s u l t s i n more attenuated hydrographs than shallow flow or s u r f a c e drainage. The r a t i o n a l formula was o r i g i n a l l y developed to estimate peak discharge from s m a l l urban b a s i n s (with a d i s c h a r g e ( r u n o f f ) c o e f f i c i e n t c l o s e to 1.0 r e p r e s e n t i n g the l a r g e percentage of impervious a r e a ) . I t s a p p l i c a t i o n i n a g r i c u l t u r a l drainage system design i s most a p p r o p r i a t e f o r b a s i n s not exceeding 100 - 200 ha. T h e r e f o r e , f o r a s m a l l drainage b a s i n (100 - 200 ha), w i t h c o n d i t i o n s promoting overland flow/or r a p i d i n t e r f l o w ( s l o p i n g l a n d , l e s s permeable s o i l s , development c r e a t i n g impervious s u r f a c e s , g r a z i n g lands w i t h reduced i n f i l t r a t i o n , swampy or p o o r l y drained lowlands, e t c . ) , the r a t i o n a l formula may be q u i t e s u c c e s s f u l l y used to estimate design r u n o f f f o r s u r f a c e drainage systems. Use of the r a t i o n a l formula should be accompanied by the awareness of v a r i o u s r e p o r t e d shortcomings of the method: 1 ) Time of c o n c e n t r a t i o n estimates must i n c l u d e overland flow p l u s time of flow i n open and/or c l o s e d channels (where s i g n i f i c a n t ) to the p o i n t of design. 2) The v a r i o u s equations developed to estimate time of c o n c e n t r a t i o n may vary over a wide range, t h e r e f o r e a weak v a r i a b l e . 3) The r u n o f f c o e f f i c i e n t , C, i s u s u a l l y estimated from a 60 t a b l e of values f o r C. Some t a b l e s only c o n s i d e r one v a r i a b l e ( l a n d u s e ) , and other t a b l e s c o n s i d e r f i v e v a r i a b l e s (land use, s o i l type, s l o p e , antecedent moisture c o n d i t i o n s , and r e c u r r e n c e i n t e r v a l ) . D i f f e r e n t users with d i f f e r e n t t a b l e s can e a s i l y s e l e c t values of C which d i f f e r by 100$, t h e r e f o r e t i s a very weak component of the formula ( R o s s m i l l e r 1982). 4) The r u n o f f c o e f f i c i e n t (C) i s not constant; r a i n f a l l r u n o f f curves are r e p o r t e d to converge at the r a r e r frequency r a i n f a l l events. T h i s i m p l i e s C should be i n c r e a s e d f o r g r e a t e r r e c u r r e n c e i n t e r v a l s ( R o s s m i l l e r 1982). 61 E. WATERSHED DESCRIPTION A l l f i e l d r e s e a r c h was c a r r i e d out a t t h e A g r i c u l t u r e Canada R e s e a r c h Farm #2 w h i c h i s l o c a t e d a t 49.2744°N and 121.7472°W (NTS map sheet 92H/5) i n t h e e a s t e r n end of t h e Lower F r a s e r V a l l e y o f B r i t i s h Columbia. I t w i l l h e r e i n a f t e r be r e f e r r e d t o as the A g a s s i z R e s e a r c h Watershed. L o c a t e d t o t h e west of Bear Mountain, t h e A g a s s i z R e s e a r c h w a t e r s h e d has an a r e a of 474 ha, w i t h a 790 m range of e l e v a t i o n . The w a t e r s h e d i s d i s t i n c t l y d i v i d e d i n t o an u p l a n d and l o w l a n d r e g i o n w i t h a 7:1 u p l a n d t o l o w l a n d r a t i o . Upland s l o p e s v a r y between a p p r o x i m a t e l y 50$ t o 70$. Less t h a n 1$ o f t h e l o w l a n d has been r e c l a i m e d and c u l t i v a t e d f o r f u t u r e c r o p growth. A s u b s u r f a c e d r a i n a g e system was i n s t a l l e d i n 1 982 on h a l f o f t h e c u l t i v a t e d f i e l d . The o u t l e t c o n s i s t s of a s m a l l c h a n n e l i n the l o w l a n d which has been c l e a r e d and m a i n t a i n e d . T h i s l e a d s t o M a r i a S l o u g h and e v e n t u a l l y t o the F r a s e r R i v e r . E.1. H i s t o r i c a l l a n d u s e A h i s t o r i c a l r e v i e w of p r o v i n c i a l a e r i a l photography d a t i n g back t o 1939 shows the s i t e a r e a under c u l t i v a t i o n w i t h c l e a r l y d e f i n e d t r e e - l i n e d d r a i n a g e d i t c h e s t r a v e r s i n g t h e l o w l a n d f i e l d . Over th e y e a r s t h r o u g h t o t h e e a r l y 1960's t h e r e appeared t o be r e a s o n a b l e a t t e m p t s a t f a r m i n g t h e f i e l d a r e a , w i t h v a r i e d s u c c e s s . I t i s o b v i o u s t h a t poor d r a i n a g e i n the l o w l a n d f i e l d has always posed a management c h a l l e n g e . I n t h e l a t e 1960's two new i n t e r c e p t i o n d i t c h e s were e x c a v a t e d , but appeared t o f a l l i n t o l i m i t e d use due t o poor maintenance by t h e next s e r i e s of 62 a e r i a l coverage i n the l a t e 1970's. By 1979 ,a b r i d g e had been c o n s t r u c t e d over the o u t l e t channel, and by 1983, a new drainage d i t c h was excavated. Evidence of the f i r s t l o g g i n g of the upland s i n c e 1939 was n o t i c e d i n the 1965 a e r i a l coverage, on p a r t s of the west s l o p e of Bear Mountain. P r i o r to t h i s , the only c l e a r i n g i n the upland was f o r the o r i g i n a l power l i n e as seen i n the 1952 photos. A new c l e a r i n g f o r a powerline right-of-way was evident i n 1961, and two new powerlines had been c o n s t r u c t e d by 1979 (note - there i s a gap i n photo coverage between 1969 and 1979). The s i t e logged i n 1965 had c o n s i d e r a b l e regrowth (mainly deciduous) by 1979. In J u l y of 1983, p a r t of the area logged i n 1965 had been relogged i n the v i c i n i t y of the power l i n e . D uring the r e s e a r c h p e r i o d l o g g i n g i n the saddle of the upland commenced. E.2. N a t i v e v e g e t a t i o n The A g a s s i z Research Watershed i s i n c l u d e d i n the P a c i f i c Coast S e c t i o n of the Coast F o r e s t Region. In the upland areas p r i o r to l o g g i n g , the f o r e s t cover was dominated by Douglas f i r , western hemlock and western red cedar w i t h the hemlock and cedar predominating on moist s l o p e s and seepage areas. The logged areas support dense deciduous cover dominated by red a l d e r , v i n e and b r o a d l e a f maple i n t e r s p e r s e d with second-growth Douglas f i r and western hemlock. In the lowland, the a l l u v i a l v a l l e y bottom o r i g i n a l l y supported stands of black cottonwood, red a l d e r , b r o a d l e a f maple, western white b i r c h as w e l l as western red cedar, s i t k a spruce, 63 and grand f i r . Most of these stands have been c l e a r e d , and remnants of the o r i g i n a l f o r e s t only occur as s c a t t e r e d pockets on S e a b i r d and some of the i s l a n d s . E3» General c l i m a t e The inshore maritime c l i m a t e of the area i s s t r o n g l y i n f l u e n c e d by the Coast Mountains. Winters are dominated by a l a r g e number of low pressure systems which move onshore from the P a c i f i c Ocean produ c i n g d u l l , m i l d , l o n g d u r a t i o n , low i n t e n s i t y r a i n s . Except f o r r e c h a r g i n g ground water r e s e r v o i r s , the high r a i n f a l l has l i t t l e b e n e f i t and water t a b l e s i n many areas are r a i s e d s u f f i c i e n t l y t o cause severe drainage problems. O c c a s i o n a l l y , p o l a r a i r masses d r a i n i n t o the Lower E r a s e r V a l l e y from the i n t e r i o r of the pr o v i n c e and produce heavy snow f a l l s or f r e e z i n g r a i n when the c o l d i n t e r i o r and damp maritime a i r meet. High p r e s s u r e systems producing warm, sunny weather are common i n the summer. R a i n f a l l i s s h a r p l y c u r t a i l e d and s o i l moisture d e f i c i e n c e s f r e q u e n t l y develop, p a r t i c u l a r l y d u r i n g the important crop growing months of J u l y and August. E.4. S o i l s The s o i l s i n the Ag a s s i z area have developed from u n c o n s o l i d a t e d g e o l o g i c d e p o s i t s of P l e i s t o c e n e or Recent Age. Dep o s i t s vary i n depth from l e s s than a meter i n p a r t s of the mountains to at l e a s t 305 meters i n the v a l l e y bottom. With r e f e r e n c e to the S o i l survey of Ag a s s i z area (Luttmerding and Sprout 1967), the Research watershed can be su b d i v i d e d i n t o the f o l l o w i n g s o i l s e r i e s (as i l l u s t r a t e d on the 64 a i r photo i n Appendix A): SOIL CLASS ^ \ SO - RO S l o l l i c u m - R o c k outcrop GH^S^_^ s o i l complex PT — RO 2) HG~~S Poignant-Rock outcrop s o i l complex 3) T)^- I s a r - H a r r i s o n CaS RD - RD 4) f g 8 P . Ryder p- \ GN n.. 5) — Gibson 6) A ^ ^ B ^ Annis/Banford H 7) ^ — H a t z i c 8) Hj Hj sp. H j o r t h RD - RD; s -PT 9 ) = : — Ryd er-Poignant q ' o-2 F u r t h e r d e t a i l s on the above s o i l c l a s s e s are found i n t a b l e 3. 65 SOIL CLASS CLASSIFICATION PARENT MATERIAL D degraded a c i d brown wooded A e o l i a n dep. mix w i t h c o l l u v i a l slopewash d e p o s i t s 2) o r t h i c a c i d brown wooded A e o l i a n dep. mix w i t h c o l l u v i a l slopewash d e p o s i t s 3) o r t h i c r e g o s o l , degraded a c i d brown A l l u v a i l - c o l l u v i a l f a n d e p o s i t s A l l u v i a l - c o l l u v i a l f a n d e p o s i t s 4) o r t h i c a c i d brown wooded s h a l l o w a e o l i a n d e p o s i t s over g l a c i a l t i l l or bedrock 5) deep muck o r g a n i c d e p o s i t s 6) rego g l e y s o l s h a l l o w muck E r a s e r f l o o d p l a i n d e p o s i t s o r g a n i c d e p o s i t s 7) o r t h i c humic g l e y s o l E r a s e r f l o o d p l a i n d e p o s i t s 8) rego humic g l e y s o l E r a s e r f l o o d p l a i n d e p o s i t 9) o r t h i c a c i d brown wooded A e o l i a n dep. mix w i t h c o l l u v i a l slopewash d e p o s i t s T a b l e 5: S o i l s e r i e s c l a s s i f i c a t i o n E.4«a. u p l a n d s o i l s  E . 4 . a . i . S l o l l i c u m S e r i e s S l o l l i c u m S e r i e s are found between e l e v a t i o n s o f 305 and 762 meters. Topography i s v e r y s t e e p l y t o e x t r e m e l y s l o p i n g ; most g r a d i e n t s between 60 - 90 $. S l o l l i c u m s o i l s have dev e l o p e d from u n s t a b l e , c o a r s e t e x t u r e d c o l l u v i a l d e p o s i t s i n t o w h i c h a s h a l l o w a e o l i a n o v e r l a y has been mixed by windthrow and s o i l c r e e p . T e x t u r e s , b o t h s u r f a c e and 66 subsurface, are coarse and vary from g r a v e l l y sandy loam to g r a v e l l y loamy sand. P r o f i l e s are extremely stony and bedrock u s u a l l y occurs w i t h i n 91 cm of the s o i l s u r f a c e . R o o t i n g depth and moisture p e r m e a b i l i t y i s good u n t i l the u n d e r l y i n g bedrock i s reached then decreases a b r u p t l y (as seen by root mat development and o c c a s i o n a l weak g l e y i n g and m o t t l i n g ) . Most p r o f i l e s are w e l l drained although seepage occurs above and through the upper p a r t of the f r a c t u r e d bedrock. These s o i l s developed under Douglas f i r , cedar and hemlock v e g e t a t i o n , now mostly logged. The s o i l s a l s o support: s m a l l hemlock, Douglas f i r , f i r eweed, willow, b i r c h , a l d e r , b i g l e a f maple, t h i m b l e b e r r y , f a l s e a z a l e a , vaccinuim s p e c i e s , moss, and other regrowth v e g e t a t i o n . None of the S l o l l i c u m s o i l s are s u i t a b l e f o r a g r i c u l t u r a l use due to steep topography and s t o n i n e s s . E . 4 . a . i i . Poignant S e r i e s ( o r t h i c brown wooded) Poignant s o i l s are common between 30 and 457 meter e l e v a t i o n s . They are very s t e e p l y to extremely s l o p i n g with g r a d i e n t s g e n e r a l l y over 50 and commonly ra n g i n g to 90 per cent. These s o i l s have developed on steep, u n s t a b l e s l o p e s . The c o l l u v i a l parent m a t e r i a l i n c l u d e s a e o l i a n and minor g l a c i a l t i l l d e p o s i t s and rock fragments which have been mixed by s o i l creep and windthrow. Surface t e x t u r e s vary from g r a v e l l y sandy loam to loam and g e n e r a l l y become coarser w i t h depth. Stone content i s very high, occupying 50 - 80 $ of the s o i l volume and range i n s i z e from g r a v e l to over one meter i n diameter. Bedrock i s 67 u s u a l l y encountered w i t h i n 91 cm of the s u r f a c e and f r e q u e n t l y outcrops. Drainage ranges from w e l l to moderately w e l l and v a r i e s with the depth of the solum and the amount of seepage from higher e l e v a t i o n s . O r i g i n a l v e g e t a t i o n was mainly c o n i f e r o u s and has mostly been removed by l o g g i n g . Present v e g e t a t i o n c o n s i s t s of a l d e r , v i n e maple, willow, t h i m b l e b e r r y , dogwood, second growth Douglas f i r and hemlock. E . 4 . a . i i i . I s a r S e r i e s ( o r t h i c r e g o s o l ) Regosol s o i l s are w e l l and i m p e r f e c t l y drained s o i l s t h a t l a c k d i s c e r n i b l e h o r i z o n s or i n which development i s l i m i t e d to s l i g h t o r g a n i c accumulation i n the s u r f a c e . The I s a r s o i l occurs on the uplands of the map area between 152 and 304 meter e l e v a t i o n s . They have developed from r e l a t i v e l y recent a l l u v i a l and o c c a s i o n a l l y a l l u v i a l - c o l l u v i a l f a n d e p o s i t s eroded from the mountains. Surface and subsurface t e x t u r e s vary from sandy loam to g r a v e l l y sand and sand and are sometimes weakly s t r a t i f i e d . Cobbles and stones f r e q u e n t l y occupy a l a r g e p a r t of the solum. Pan apexes are steeper and c o a r s e r t e x t u r e d than the f a n aprons which sometimes have a t h i n , f i n e r t e x t u r e d capping mantling the coarse underlay. I s a r s o i l s are w e l l to r a p i d l y d r a i n e d . P r o f i l e development i s n e g l i g i b l e . O r i g i n a l v e g e t a t i o n was mainly c o n i f e r o u s , but logged areas are p r e s e n t l y dominated by a v a r i e t y of deciduous s p e c i e s . 68 Adverse topography and s t o n i n e s s make the I s a r s o i l s u n s u i t a b l e f o r a r a b l e a g r i c u l t u r e on the uplands, but some areas may produce s m a l l amounts of browse. E . 4 . a . i v . H a r r i s o n s e r i e s (degraded a c i d brown) The H a r r i s o n s e r i e s i s a degraded a c i d brown wooded s o i l . T h i s i m p l i e s w e l l to moderately w e l l drained s o i l s , which, under n a t i v e c o n d i t i o n s , are c h a r a c t e r i z e d by o r g a n i c s u r f a c e L-H h o r i z o n s , a l i g h t coloured, e l u v i a t e d Ae h o r i z o n not more than one i n c h t h i c k and one or more reddish-brown Bf or Bm h o r i z o n s . The H a r r i s o n s o i l s occupy a minor acreage on the uplands of the map area between 15 and 45 meter e l e v a t i o n s . T h i s s e r i e s developed from a l l u v i a l and o c c a s i o n a l l y a l l u v i a l - c o l l u v i a l f a n d e p o s i t s o r i g i n a t i n g from the mountains. Most fans have shallow a e o l i a n d e p o s i t s mixed i n t o the s u r f a c e h o r i z o n s by the a c t i o n of windthrow, and s u r f a c e t e x t u r e s g e n e r a l l y vary from g r a v e l l y sandy loam to loam. Cobbles and stones are mixed throughout the p r o f i l e , but are most abundant i n the coarse s u b - s o i l . Drainage i s w e l l to r a p i d . The H a r r i s o n s e r i e s developed under c o n i f e r o u s v e g e t a t i o n dominated by Douglas f i r . Most areas have been logged, and regrowth i n c l u d e s Douglas f i r , v i n e , maple, red a l d e r , cedar, b i r c h , h u c k l e b e r r y , t r a i l i n g b l a c k b e r r y , w i l d strawberry, t h i m b l e b e r r y , soapberry, bracken and moss. On the uplands, the H a r r i s o n s o i l s are g e n e r a l l y u n s u i t a b l e f o r a g r i c u l t u r e due to steep topography, s t o n i n e s s and low moisture h o l d i n g c a p a c i t y . F o r e s t growth i s f a i r to good. 69 E.4»a.v. Ryder s e r i e s ( o r t h i c a c i d brown wooded s o i l ) Ryder s o i l s are mainly r e s t r i c t e d to the n o r t h e a s t upland of the A g a s s i z experimental farm and occur between 23 and 305 meter e l e v a t i o n s . The topography i s s t r o n g l y to very s t e e p l y s l o p i n g and r o l l i n g w i t h most g r a d i e n t s between 10 and 40 percent. The parent m a t e r i a l of the Ryder s e r i e s c o n s i s t s of s i l t y a e o l i a n m a t e r i a l which o v e r l i e s g l a c i a l t i l l or bedrock. Surface t e x t u r e s are u s u a l l y s i l t loam; s u b s o i l t e x t u r e s are s i m i l a r , but vary to loam. The u n d e r l y i n g g l a c i a l t i l l when pre s e n t , i s u s u a l l y g r a v e l l y sandy loam i n t e x t u r e . The depth of the a e o l i a n o v e r l a y i s g e n e r a l l y three or more f e e t . O c c a s i o n a l l y stones and g r a v e l s occur i n the p r o f i l e from windthrow, u n d e r l a y i n g g l a c i a l t i l l or s c a t t e r e d rock outcrops. Roots and moisture p e n e t r a t i o n i s good. The Ryder s e r i e s i s w e l l to moderately w e l l d r a i n e d . Dense deciduous cover has developed s i n c e the o r i g i n a l c o n i f e r o u s v e g e t a t i o n was logged. Earthworm a c t i v i t y i s evident i n the upper p o r t i o n s of some p r o f i l e s . Common v e g e t a t i o n i n c l u d e s Douglas f i r , v i n e and b i g l e a f maple, s t i n g i n g n e t t l e , deer f e r n , bracken, a l d e r , t h i m b l e b e r r y , salmonberry, and t r a i l i n g b l a c k b e r r y . Adverse topography renders most of the Ryder s o i l s u n s u i t a b l e f o r a r a b l e a g r i c u l t u r e , but do have some use as permanent g r a z i n g and browse. Ryder s o i l s are f r i a b l e and e a s i l y c u l t i v a t e d but become droughty d u r i n g dry summers. 70 E.4.b. lowland s o i l s E.4»b.i. Gibson Muck (o r g a n i c s o i l ) Organic s o i l s c o n t a i n 30 percent or more or g a n i c matter and have a depth of at l e a s t 31 cm of c o n s o l i d a t e d or 46 cm of u n c o n s o l i d a t e d o r g a n i c m a t e r i a l . They are very p o o r l y drained and the water t a b l e i s at or near the s u r f a c e f o r s u b s t a n t i a l p a r t s of the year. Muck s o i l s are the only o r g a n i c s o i l s o c c u r r i n g i n the lowlands of the Ag a s s i z map area. Gibson muck occupies s e v e r a l areas on the lowlands between 14 and 21 meter e l e v a t i o n s . The topography i s s l i g h t l y d e p r e s s i o n a l to very g e n t l y s l o p i n g w i t h g r a d i e n t s below two per c e n t . These s o i l s have developed from or g a n i c accumulations of sedges, reeds, mosses, and other o r g a n i c m a t e r i a l which exceed 61 cm i n depth and o v e r l i e heavy t e x t u r e d f l o o d p l a i n sediments. The s u r f a c e h o r i z o n s are w e l l to moderately w e l l decomposed w h i l e u n d e r l y i n g h o r i z o n s are at v a r i o u s stages of decomposition. The mine r a l s u b s o i l i s s t r o n g l y gleyed. P r o f i l e r e a c t i o n i s moderately to extremely a c i d i c . Drainage i s very poor and the water t a b l e i s at or near the s u r f a c e f o r l a r g e p a r t s of the year. Runoff and seepage from higher s u r r o u n d i n g areas and seepage from the E r a s e r R i v e r d u r i n g i t s f r e s h e t stage cause the high water c o n d i t i o n s . Gibson muck i s c l a s s i f i e d as a deep muck with the or g a n i c m a t e r i a l u s u a l l y between two and s i x f e e t i n depth. N a t i v e v e g e t a t i o n i s swamp f o r e s t c o n s i s t i n g of s c a t t e r e d cedar, 71 hemlock, hog b i r c h , hardhack, sweet gale, sedge, skunk cabbage, v a r i o u s grasses and other h y d r o p h y t i c s p e c i e s . Areas of gibson muck which have been rec l a i m e d i n other regions i n the A g a s s i z area are used f o r hay and pasture p r o d u c t i o n . Sedge content of the forage i s u s u a l l y high and the feed value low. I f w e l l managed, these s o i l s are h i g h l y p r o d u c t i v e , e s p e c i a l l y f o r such s p e c i a l i z e d crops as b l u e b e r r y and v e g e t a b l e s . Seepage from h i g h e r areas can o f t e n be reduced by i n t e r c e p t i n g t i l e d r a i n s and d i t c h e s . T i l e d r a i n s or open d i t c h e s are s a t i s f a c t o r y f o r drainage w i t h i n the bog, but the water t a b l e should not be lowered more than i s r e q u i r e d f o r good crop growth. O v e r d r a i n i n g causes e x c e s s i v e subsisdence of the org a n i c d e p o s i t s and o f t e n r e s u l t s i n droughty c o n d i t i o n s d u r i n g the l a t t e r p a r t of the growing season. E . 4 . b . i i . Banford muck (o r g a n i c s o i l s ) Banford muck occurs i n s c a t t e r e d areas on the E r a s e r f l o o d p l a i n between 12 and 21 meter e l e v a t i o n s . As with Gibson muck, i t v a r i e s from d e p r e s s i o n a l to very g e n t l y s l o p i n g with slopes below two percent. U s u a l l y t h i s s e r i e s i s a s s o c i a t e d with the Annis s e r i e s or Gibson muck wit h no d i s t i n g u i s h i n g s u r f a c e or topographic f e a t u r e s between them. S e p a r a t i o n i s based on the depth of the org a n i c d e p o s i t . Banford muck has developed from accumulations of sedges, reeds and other o r g a n i c m a t e r i a l 31 to 61 cm deep, which o v e r l i e heavy t e x t u r e d E r a s e r f l o o d p l a i n sediments. The s u r f a c e h o r i z o n 72 i s w e l l decomposed, while the subsurface o r g a n i c h o r i z o n s are u s u a l l y i n t e r m e d i a t e i n decomposition. The Banford s o i l developed under very p o o r l y drained c o n d i t i o n s . The water t a b l e i s at or near the s o i l s u r f a c e f o r most of the year, with r u n o f f and seepage from s u r r o u n d i n g higher l a n d c o n t r i b u t i n g l a r g e amounts of water. The Banford s o i l (a shallow muck), developed under swampy v e g e t a t i o n c o n s i s t i n g of sedges, reeds, hardhack, sweet ga l e , skunk cabbage, v a r i o u s grasses, s c a t t e r e d willow, cottonwood, cedar and bog b i r c h . Land use i s s i m i l a r to that on Gibson muck. E . 4 . b . i i i . Annis (rego g l e y s o l ) G l e y s o l s o i l s are p o o r l y to very p o o r l y drained s o i l s . The rego g l e y s o l may have a dark coloured A l s u r f a c e h o r i z o n not more than three inches t h i c k , and when c u l t i v a t e d , the plow l a y e r (Ap) i s l i g h t i n c o l o u r . Up to 31 cm of c o n s o l i d a t e d or 46 cm of u n c o n s o l i d a t e d peat or muck may be present on the s u r f a c e . The Annis s o i l s occupy s m a l l , s c a t t e r e d areas between 9 and 17 meter e l e v a t i o n s . The topography i s l e v e l to very g e n t l y u n d u l a t i n g and o f t e n i s d e p r e s s i o n a l i n r e l a t i o n to the surr o u n d i n g l a n d . F i f t e e n to t h i r t y - o n e cm of w e l l decomposed o r g a n i c m a t e r i a l o v e r l a y i n g s i l t y c l a y loam to s i l t y c l a y t e x t u r e d f l o o d p l a i n d e p o s i t s forms the parent m a t e r i a l of these s o i l s . Sand i s u s u a l l y encountered at depth. Annis s o i l s o f t e n form a t r a n s i t i o n zone between m i n e r a l and org a n i c s o i l s . S urface 73 t e x t u r e s are muck. Drainage i s very poor. F l o o d i n g f r e q u e n t l y occurs a f t e r heavy r a i n f a l l and the water t a b l e i s near the s u r f a c e most of the year. D e p r e s s i o n a l areas of Annis muck serve as catchment b a s i n s f o r r u n o f f from higher l a n d . Water p e r c o l a t i o n and r o o t i n g depth i s s e v e r l y r e s t r i c t e d by the heavy massive nature of the s u b s o i l s . P r o f i l e development i s r e s t r i c t e d to o r g a n i c accumulation on the s u r f a c e and s t r o n g g l e y i n g i n the s u b s o i l . N a t i v e v e g e t a t i o n c o n s i s t s of cedar, willow, sedge reeds, hardhack, and other h y d r o p h y t i c s p e c i e s . A l a r g e p o r t i o n of Annis s o i l s are used f o r hay and pasture p r o d u c t i o n . These s o i l s are f r i a b l e and f e r t i l e , but y i e l d s are u s u a l l y poor due to poor drainage which de s t r o y s the legumes and some of the domestic g r a s s e s . Drainage i s r e q u i r e d i n these s o i l s . E.4.b.iv. H a t z i c ( o r t h i c humic g l e y s o l s o i l ) O r t h i c humic g l e y s o l s o i l s are d i s t i n g u i s h e d by poor drainage, a dark coloured Ah h o r i z o n g r e a t e r than 8 cm t h i c k and weakly developed e l u v i a l and/or i l l u v i a l h o r i z o n s which are s t r o n g l y gleyed and mottled. There may be up to 31 cm of c o n s o l i d a t e d or 46 cm of u n c o n s o l i d a t e d peat or muck on the s u r f a c e . The H a t z i c s e r i e s occupies minor acreage between 12 and 15 meter e l e v a t i o n s and has very l e v e l to very g e n t l y s l o p i n g topography w i t h g r a d i e n t s l e s s than two percent. 74 These s o i l s have developed from heavy t e x t u r e d sediments de p o s i t e d by the F r a s e r R i v e r i n q u i e t shallow ponds. S i l t y c l a y and s i l t y c l a y loam are the dominant s u r f a c e t e x t u r e , with u n d e r l y i n g h o r i z o n s somewhat h e a v i e r . C r a c k i n g occurs d u r i n g d r y i n g , but when wet, the s o i l expands thereby r e s t r i c t i n g moisture and root p e n e t r a t i o n . I n t e r n a l and e x t e r n a l drainage are poor due to slow s u r f a c e r u n o f f and r e s t r i c t e d i n t e r n a l moisture movement. The water t a b l e i s at or near the s u r f a c e most of the winter and d u r i n g high water on the P r a s e r R i v e r . P r i o r to c l e a r i n g , o r i g i n a l v e g e t a t i o n c o n s i s t e d of sedge, v a r i o u s grasses, hardhack, w i l l o w , and other s p e c i e s t o l e r a n t to poor drainage. H a t z i c s o i l s are mostly c l e a r e d and u t i l i z e d f o r hay and pasture p r o d u c t i o n . C l o v e r - g r a s s mixtures are used, however c l o v e r s tend to d i e r a p i d l y due to the poor drainage. Drainage i s r e q u i r e d on t h i s s o i l . E.4.b.v. H j o r t h s e r i e s These s o i l s are found i n s i m i l a r t opographic areas as h a t z i c s o i l s . The parent m a t e r i a l i s s i l t y l a t e r a l a c c r e t i o n d e p o s i t s of the P r a s e r R i v e r . In the ridge-and-swale topography these s o i l s occupy the swales and lower s l o p e s of the r i d g e s . Surface t e x t u r e s range from s i l t loam to s i l t y c l a y loam and are u n d e r l a i n by sand and o c c a s i o n a l g r a v e l . These s o i l s are p o o r l y drained, ponding f r e q u e n t l y occurs. N a t i v e v e g e t a t i o n i s mainly deciduous and i n c l u d e s cottonwood, willow, and a l d e r with o c c a s s i o n a l cedar. Shrub 75 cover i s dense and a l i g h t ground cover of sedge and moss e x i s t s . Most areas of H j o r t h s o i l s are c l e a r e d and used f o r hay and pasture p r o d u c t i o n . Drainage i s r e q u i r e d . For a convenient r e f e r e n c e , one can t u r n to the S o i l Management Handbook f o r the F r a s e r V a l l e y (Bertrand and Wood 1983) where s o i l s e r i e s are l i s t e d , and d i v i d e d i n t o s o i l management groups. S o i l l i m i t a t i o n s are presented along with a c l a s s i f i c a t i o n of crop groups based on the l e v e l of management r e q u i r e d to achieve an a c c e p t a b l e l e v e l of p r o d u c t i o n . S o i l Mapping f o r Farm #2 was a l s o performed f o r A g r i c u l t u r e Canada. The upland s o i l s have been c l a s s i f i e d as CUNNINGHAM f i n e sandy loam: w e l l d r a i n e d s o i l s developed on a medium-textured outwash m a t e r i a l . The lowland at the base of the upland area has been c l a s s i f i e d as HICKS muck and t h i n peat:, p o o r l y - d r a i n e d - t o very p o o r l y d r a i n e d s o i l s . The f i e l d area ( f i e l d s 8 & 9) have a mixture of MARIA s i l t y c l a y loam and MARIA s i l t y c l a y . The pocket of w e l l d r a i n e d I s a r - H a r r i s o n s e r i e s s o i l s i d e n t i f i e d i n the 1967 S o i l Survey of A g a s s i z Area was not d e s c r i b e d . T h i s area may serve as a recharge zone f o r the adjacent lowlands - r e d u c i n g s u r f a c e r u n o f f onto the p o o r l y d r a i n e d muck i n the adjacent lowland f i e l d s . 76 E. PROCEDURES  E.1. Watershed q u a n t i f i c a t i o n The standard procedures of watershed q u a n t i f i c a t i o n were performed f o r the A g a s s i z Research Watershed. A 1:50 000 NTS map sheet was used to d e l i n e a t e the watershed boundaries (with r e f e r e n c e to 1:10 000 and 1:20 000 s c a l e a e r i a l photography), and t h i s r e g i o n was then planimeterd to determine watershed area. To improved accuracy and allow d e l i n e a t i o n of the c h a r a c t e r i s t i c r e g i o n s of the watershed, a l a r g e s c a l e 1:5 000 map was s t e r e o p l o t t e d from 1:20 000, 1983 panchromatic a e r i a l photography by A c k e r f e l d t Inc. i n Vancouver ( a e r i a l photography i n Appendix A). The contour i n t e r v a l at t h i s s c a l e f o r a f o r e s t e d r e g i o n was 10 meters. E l e v a t i o n s i n the lowland were c r o s s - r e f e r e n c e d to 1:10 000 s c a l e photography. V e g e t a t i o n boundaries and major landmarks such as the powerlines, and b r i d g e over the d i t c h were i n d i c a t e d . T h i s l a r g e s c a l e map served two purposes i n data c o l l e c t i o n : 1) d i r e c t measurement of watershed areas ( u s i n g a d i g i t a l p lanimeter as seen i n f i g u r e [10] below) plus measurement of h y d r a u l i c l e n g t h , and 2) c r e a t i o n of a d i g i t a l data base. 77 F i g u r e 10: D i g i t a l p l a n i m e t e r and 1:5 000 s t e r e o p l o t t e d map F.1.a. c r e a t i o n of a d i g i t a l d a t a base From t h i s l a r g e - s c a l e map of the A g a s s i z R e s e a r c h Watershed, a d i g i t a l format was c r e a t e d by manually d i g i t i z i n g t he map u s i n g t h e contour method. A T a l o s d i g i t i z e r l o c a t e d a t t h e computer c e n t r e of the U n i v e r s i t y of B r i t i s h Columbia was used. S o f t w a r e p r o v i d e d by the c e n t r e was m o d i f i e d t o a l l o w l a b e l s t o be s e t f o r each co n t o u r l e v e l . The T a l o s d i g i t i z e r and F o r m i c a workboard measures 1.21 meters i n X and 0.91 meters i n Y (48 i n c h e s by 36 i n c h e s ) . The d i g i t i z e r i s s e t i n p o i n t mode, and r e t u r n s p o s i t i v e x and y c o o r d i n a t e measurements i n tho u s a n d t h s of an i n c h r e f l e c t i n g the p o s i t i o n of the c u r s o r c r o s s h a i r s on the w o r k t a b l e when t h e b u t t o n on t h e c u r s o r pad i s p r e s s e d . The d i g i t i z e r i s 78 connected t o a T e k t r o n i x 4010 t e r m i n a l , which e n a b l e s the u s e r t o s i m u l t a n e o u s l y view an image of the map b e i n g d i g i t i z e d . F i g u r e [11] below i l l u s t r a t e s t he d i g i t i z e r s e t - u p used. F i g u r e 11: D i g i t i z e r s e t - u p at the UBC Computing C e n t r e The end product of d i g i t i z i n g was a s e t of 7000 d a t a p o i n t s c o n s i s t i n g o f X,Y,Z c o o r d i n a t e s f o r each d i g i t i z e d p o i n t . These p o i n t s were chosen t o be s t r e f l e c t changes i n topography; namely b e i n g r e l a t i v e l y dense a l o n g curves and i m p o r t a n t c h a r a c t e r i s t i c s . I n o r d e r t o make t h e d i g i t i z e r output u s e f u l , some type of e f f i c i e n t d a t a format and r e f e r e n c i n g system had t o be adopted. A t r i a n g u l a t i o n program f o r c r e a t i n g a t r i a n g u l a t e d i r r e g u l a r network (TIN) w r i t t e n by Dr. J . L i t t l e ( c u r r e n t l y of MIT) was run 79 on a VAX 11/780 minicomputer to c r e a t e a network of t r i a n g l e s between a l l 7000 data p o i n t s f o r the Research Watershed. At t h i s stage, the TIN was converted to a r a s t e r or g r i d to allow f o r program development and more e f f i c i e n t m a n i p u l a t i o n of the data base. Access to an image d i s p l a y system allowed image f i l e s of the DEM to be d i s p l a y e d . E l e v a t i o n s were represented by 255 grey l e v e l s , and d i s p l a y e d i n p i x e l format on a r a s t e r d i s p l a y screen w i t h a r e s o l u t i o n of 512 X 512 p i x e l s . D i f f e r e n t sun angles of azimuth and e l e v a t i o n above the h o r i z o n could be s p e c i f i e d f o r any time of day, or day of the year, to c r e a t e shadows i n the model. A s y n t h e t i c image was c r e a t e d which h i g h l i g h t s t e r r a i n f e a t u r e s and gives some i n d i c a t i o n of sun exposure times and i n t e n s i t y which could be s i g n i f i c a n t i n understanding such processes as s p r i n g snowmelt. Contours could be c r e a t e d f o r any given i n t e r v a l (based on p i x e l grey s c a l e i n t e r v a l ) then e i t h e r d i s p l a y e d as a map on t h e i r own or o v e r l a i d on the s y n t h e t i c image. The r a s t e r d i s p l a y system allowed v i s u a l checking f o r any a r t i f a c t s or problems i n c r e a t i o n of the TIN and g r i d DEM. A g r i d data base was thus c r e a t e d with the o r i g i n i n the upper l e f t corner of the map (NW), and c o - o r d i n a t e s expressed as (row,column) p a i r s . To check the i n t e g r i t y of the d i g i t a l data, a contour map was r e - c r e a t e d from the DEM. A g r a p h i c s package a v a i l a b l e on the mainframe system at UBC , DISSPLA, was used to c r e a t e a contour map. P l o t t i n g was done by t r a n s p o r t i n g the p l o t f i l e t o the IBM-PC (equipped w i t h a Hercules g r a p h i c s board), 80 then u s i n g a t e k t r o n i x t e r m i n a l emulator package to p l o t the map on a ROLAND DXY-880 p l o t t e r (map i n Appendix B). F . 1 . P . a n a l y t i c a l software The development of a d i g i t a l e l e v a t i o n model f o r the Ag a s s i z Research Watershed r e q u i r e d not only a c q u i r i n g a d i g i t a l database f o r the s i t e , but c r e a t i n g the model and de v e l o p i n g a n a l y t i c a l software. Commercial d i g i t a l e l e v a t i o n m o d e l l i n g software does e x i s t , most based on mini-computers and Integraph work s t a t i o n s . Some software i s a v a i l a b l e commercially f o r the micro-computer market, but was not a c c e s s i b l e f o r t h i s r e s e a r c h . In watershed a n a l y s i s f o r the purpose of r u n o f f e s t i m a t i o n , i t i s important to know the watershed area, and be able t o crea t e p r o f i l e s across areas of i n t e r e s t to c a l c u l a t e d i s t a n c e and s l o p e . In t h i s r e s e a r c h two procedures were developed: 1) area d e t e r m i n a t i o n 2) p r o f i l e d e t e r m i n a t i o n . F. 1 . b . i . a r e a As d e s c r i b e d e a r l i e r , DEMs allow the slope of the t e r r a i n to be accounted f o r i n area d e t e r m i n a t i o n . A g r i d of cose f o r each data p o i n t was cr e a t e d . The theory behind u s i n g cose i n area d e t e r m i n a t i o n f o l l o w s : 81 cos(e) = -£ [72] - - o ^ T [73] Area = p * z [74] = p * p cos e [75] A r e a = c ^ T e ™ Area f o r p i x e l s (p = 1) = 33^-5 [77] Area c a l c u l a t i o n i s a two step p r o c e s s . F i r s t a polygon o u t l i n i n g the chosen area must he crea t e d on a g r i d f i l e the same s i z e as the data base ( i n terms of rows and columns). This process i s performed u s i n g the program POLY.C i n Appendix C. The polygon must then he f i l l e d h i g h l i g h t i n g the p i x e l s i n c l u d e d i n the c a l c u l a t i o n s (area i s c a l c u l a t e d f o r each p i x e l i n d i v i d u a l l y then t o t a l l e d ) . The edges of the polygon o f t e n cut through a p i x e l with only a p o r t i o n of i t i n c l u d e d i n the area. To 82 accommodate f o r t h i s , only h a l f the area of a l l perimeter p i x e l s was used. Reference may be made to program AREA.C i n Appendix C f o r program p a r t i c u l a r s . F. 1 . b . i i . p r o f i l e s P r o f i l e s can be cr e a t e d between any two p o i n t s i n the d i g i t a l e l e v a t i o n model. The program NEWPROFI.C r e q u i r e s the f o l l o w i n g i n f o r m a t i o n : DEM s i z e (number of rows and columns), s t a r t i n g and ending p o i n t of the p r o f i l e , p l u s e i t h e r the sampling i n t e r v a l or the number of p o i n t s to sample al o n g the p r o f i l e . Output i s a l i s t of e l e v a t i o n s f o r a l l the sampled p o i n t s . T h i s was imported i n t o a spreadsheet program on the IBM-PC, and made i n t o a graph f i l e f o r p l o t t i n g . Reference may be made to NEWPROFI.C i n Appendix C f o r program p a r t i c u l a r s . 83 F.2. Runoff e s t i m a t i o n 7.2.a. f i e l d i n s t r u m e n t a t i o n The A g a s s i z Research watershed ( A g r i c u l t u r e Canada Farm #2) was chosen f o r t h i s r e s e a r c h p r o j e c t s i n c e i t p r o v i d e d a s m a l l contained watershed with a high per centage of f o r e s t e d upland area, a c o n d i t i o n common f o r a g r i c u l t u r e development i n the lowland f r i n g e s of the Lower F r a s e r V a l l e y . The lowland area had been farmed i n the past as evidenced by h i s t o r i c a l a e r i a l photography, but drainage problems have always posed a management problem. Subsurface drainage had been i n s t a l l e d i n a p o r t i o n of the lowland i n 1982 before t h i s r e s e a r c h began. The t h e s i s r e s e a r c h was i n c o n j u n c t i o n with a c o n t r a c t p r o j e c t w i t h A g r i c u l t u r e Canada. At the onset of t h i s p r o j e c t , there were no discharge measurements f o r the watershed. A r e c t a n g u l a r sharp c r e s t e d weir had been p r e v i o u s l y i n s t a l l e d , but was i n need of r e p a i r . In the summer of^ 1984, a w a t e r l e v e l r e c o r d e r was i n s t a l l e d approximately 16 m upstream from the weir i n a s t r a i g h t u n iform s e c t i o n of the d i t c h . The w a t e r l e v e l r e c o r d e r was supported by a p o l y e t h e l e n e tube mounted i n the d i t c h bed. Holes were d r i l l e d i n t o the tube to allow water l e v e l s to e q u a l i z e w i t h the d i t c h l e v e l . A p l a t f o r m extending to the r e c o r d e r was b u i l t to a l l o w access to the equipment. The tube was secured to the banks of the d i t c h by f o u r a d j u s t i b l e guy-wires to prevent s h i f t i n g or i c e damage as oc c u r r e d the p r e v i o u s winter to the weir. The r e c t a n g u l a r c r e s t e d weir was r e p a i r e d , and the stream 8 4 channel cleaned of weeds with a hack-hoe f o r a d i s t a n c e of approximately seven meters upstream. The f o l l o w i n g two photographs i l l u s t r a t e the weir and water l e v e l r e corder setup. F i g u r e 12 : Weir and water l e v e l r e corder ( l o o k i n g north) 85 F i g u r e 13: Close up of water l e v e l r e c order set-up ( l o o k i n g SE) A S i e r r a - M i s c o t i p p i n g bucket raingage was i n s t a l l e d i n the lowland r e g i o n of the watershed suspended by a p l a t f o r m from the b r i d g e downstream of the weir. A Campbell S c i e n t i f i c 21x micrologger was connected to the raingage to provide a continuous p r e c i p i t a t i o n r e c o r d . The Campbell S c i e n t i f i c micro-computer i n the S o i l Science Department at UBC was used to i n t e r p r e t f i e l d tapes. In a d d i t i o n to the above i n s t r u m e n t a t i o n , two e x i s t i n g groundwater l e v e l r e c o r d e r s i n the drained and undrained f i e l d were monitored. The data c o l l e c t i o n p e r i o d f o r t h i s p r o j e c t was August 1, 1984 to October 1 985. A n a l y s i s of the weekly stage data c h a r t s was done manually 86 (to r e t a i n f u l l r e s o l u t i o n and accuracy due to the s m a l l s c a l e of the r e c o r d i n g c h a r t s ) on an event b a s i s , and t r a n s f e r r e d to spreadsheets on the IBM-PC. P r e c i p i t a t i o n t o t a l s and groundwater l e v e l s f o r both the drained and undrained f i e l d s were a l s o t r a n s f e r r e d from f i e l d graphs to computer spreadsheets. For comparison purposes, the hyetograph, stream d i s c h a r g e hydrograph, and f i e l d groundwater hydrographs were r e - p l o t t e d on a Roland-DXY 880 at the same time i n t e r v a l to allow f o r time to peak d e t e r m i n a t i o n and comparison between the stream and f i e l d hydrographs. F.2.b. hydrograph s e p a r a t i o n In order t o compare r u n o f f estimates from the SCS CN procedures to those measured from the stream hydrographs, the base flow had to be removed (the SCS CN procedures estimates d i r e c t flow only, e x c l u d i n g base f l o w ) . I t was not necessary to determine the volume of base flow f o r the a n a l y s i s procedures. Hydrograph s e p a r a t i o n was performed on a l l storm hydrographs by extending the r e c e s s i o n before the storm to a p o i n t under the peak, then j o i n i n g the hydrograph r e c e s s i o n one day a f t e r the peak (as determined by the r e l a t i o n s h i p N=bA where A i s the drainage area and b i s a c o e f f i c i e n t (b=0.8 when A i s i n km and 2 u n i t y when A i s mi ). In m u l t i - e v e n t storms, the r e c e s s i o n limbs of the hydrograph had to be extended i n some cases to allow f o r the s e p a r a t i o n of base flow f o r a p e r i o d of one day a f t e r the peak. T h i s was accomplished by c r e a t i n g a composite t o t a l storm r e c e s s i o n curve. 87 S i x s i n g l e event storm hydrographs without c o m p l i c a t i n g f a c t o r s such as f r e e z i n g c o n d i t i o n s w i t h r a i n on snow or s n o w f a l l were chosen. The l o g of the discharge was c a l c u l a t e d and p l o t t e d f o r each of these storms, with an i d e n t i c a l time s c a l e f o r each storm. C h a r a c t e r i s t i c segments of the r e c e s s i o n curve were chosen f o r each storm ( s t r a i g h t l i n e segments when p o s s i b l e ) , from d i f f e r e n t d i s c harge l e v e l s . These segments were then p i e c e d together to form a composite t o t a l storm r e c e s s i o n curve ( r e f e r t o appendix D f o r the composite t o t a l storm r e c e s s i o n curve and hydrographs analysed to d e r i v e t h i s , and appendix E f o r the hydrograph s e p a r a t i o n of a l l storms). F.2.c. r u n o f f measurement from hydrographs Once baseflow was separated from the hydrograph, the area above baseflow and under the curve was measured to determine the d i r e c t r u n o f f . T h i s was accomplished u s i n g a d i g i t a l p l a n i m e t e r . The computed volume of r u n o f f was d i v i d e d by the watershed area to give r u n o f f depth i n m i l l i m e t e r s . F.2.d. S o i l C o n s e r v a t i o n S e r v i c e Curve Number method The A g a s s i z Research Watershed, as i n d i c a t e d i n e a r l i e r s e c t i o n s , d i s p l a y s extreme c o n t r a s t s of s l o p e , e l e v a t i o n , landuse, and s o i l c o n d i t i o n . The SCS (USDA 1972) recommends that i f a watershed d i s p l a y s heterogeneous s o i l s , l a n d use or treatment c l a s s e s , i t should be s u b d i v i d e d i n t o a p p r o p r i a t e s e c t i o n s and analysed by one of two methods: 1) determine the CN f o r each s e c t i o n , then c a l c u l a t e a weighted CN f o r the watershed, or 88 2) determine the CN and r e l a t e d r u n o f f f o r each s e c t i o n , then c a l c u l a t e a weighted r u n o f f value f o r the watershed. The method of weighted r u n o f f (Q) gives a more accurate r e s u l t , hut r e q u i r e s more work than the weighted Curve Number procedure. When the r e are l a r g e d i f f e r e n c e s i n CN f o r a watershed, the weighted CN w i l l e i t h e r under or over estimate Q, depending on the s i z e of the storm r a i n f a l l . Weighted Q i s p r e f e r r e d when s m a l l r a i n f a l l s are used and there are two or more widely d i f f e r i n g CNs on the watershed. For c o n d i t i o n s other than these, the method of weighted CN i s l e s s time consuming and almost as a c c u r a t e (USDA 1972). I t was t h e r e f o r e c onsidered a d v i s a b l e to perform a weighted r u n o f f e s t i m a t i o n r a t h e r than f o l l o w a weighted CN approach. The watershed was s u b d i v i d e d i n t o the f o l l o w i n g c h a r a c t e r i s t i c r e g i o n s : f o r e s t e d fan A ( s o i l h y d r o l o g i c c o n d i t i o n A), f o r e s t e d upland B ( s o i l h y d r o l o g i c c o n d i t i o n B) , lowland scrub/marsh, undrained f a l l o w , and drained f a l l o w (Appendix A). Curve numbers f o r the lowland regions of the watershed were estimated u s i n g t a b l e 4 below (based on AMC I I ) . 89 Land Use Description/Treatment/Hydrologic Condition Hydrologic So i l Groui Residential:-^ A B C D Average l o t siz e Average % Imperv; ious 1/8 acre or les s 6S 77 85 90 92 1/4 acre 38 61 75 83 87 1/3 acre 30 57 72 81 86 1/2 acre 25 54 70 80 85 1 acre 20 51 68 79 84 Paved parking l o t s , roofs, driveways, etc 98 98 98 98 Streets and roads: paved with curbs and storm sewers 98 98 98 98 gravel 76 85 89 91 d i r t 72 82 87 89 Commercial and business areas (85V impervious) 89 92 94 95 Industrial d i s t r i c t s (72% impervious) 81 88 91 93 Open Spaces, lawns, parks, golf courses, i cemeteries,etc. good condition: grass cover on 751 or more of the area 39 61 74 80 f a i r condition: grass cover on 50% to 75% of the area 49 69 79 84 Fallow Straight row — 77 86 91 94 Row crops Straight row Poor 72 81 88 91 Straight row Good 67 78 85 89 Contoured Poor 70 79 84 88 Contoured Good 65 75 82 86 Contoured S terraced Poor 66 74 80 82 Contoured 6 terraced ' Good 62 71 78 81 Small grain Straight row Poor 65 76 84 88 Good 63 75 83 87 Contoured Poor 63 74 82 85 Good 61 73 81 84 Contoured 6 terraced Poor 61 72 79 82 Good 59 70 78 81 Close -seeded Straight row Poor 66 77 85 89 legumes Straight row Good 58 72 81 85 or Contoured Poor 64 7S 83 85 rotation Contoured Good SS 69 78 83 meadow Contoured 6 terraced •/Poor 63 73 80 83 Contoured 5 terraced Good 51 67 76 80 Pasture Poor 68 79 86 89 or range F a i r 49 69 79 84 Good 39 61 74 80 Contoured Poor 47 67 81 88 Contoured . F a i r 25 59 75 83 Contoured Good 6 35 70 79 Meadow Good 30 58 71 78 Hoods OT Poor 45 66 77 83 Forest land F a i r 36 60 73 79 Good 25 55 70 77 Farmsteads — . 59 74 82 86 Table 4: CN values f o r AMC c l a s s I I to be used i n the curve number method (USDA 1972) 90 The woods d e s i g n a t i o n i n the above t a b l e r e f e r s to s m a l l i s o l a t e d groves of t r e e s r a i s e d f o r farm or ranch use. Where commercial f o r e s t covers a l a r g e part of the watershed, (such as i n the A g a s s i z Research Watershed - 87$ of the watershed b e i n g upland f o r e s t ) the g u i d e l i n e s f o r n a t i o n a l and commercial f o r e s t -range prepared by the U.S. F o r e s t S e r v i c e (USDA 1972) should be c o n s u l t e d . In the f o r e s t - r a n g e regions of the western U n i t e d S t a t e s , s o i l group, cover type, and cover d e n s i t y are the p r i n c i p a l f a c t o r s used i n e s t i m a t i n g the CN. The nomographs developed f o r e s t i m a t i n g the r u n o f f curve numbers of f o r e s t - r a n g e complexes i n the Western U n i t e d States ( f i g u r e s 14 and 15) were used f o r e s t i m a t i n g the curve numbers f o r the f o r e s t r e g i o n i n the A g a s s i z Research Watershed. Two complexes are i d e n t i f i e d : herbaceous and oak-aspen complexes, and j u n i p e r - g r a s s and sage-grass complexes. These covers are d e f i n e d as f o l l o w s : herbaceous: grass-weed-brush mixtures with brush the minor element, oak-aspen: mountain brush mixtures of oak, aspen, mountain mahogany, b i t t e r brush, maple, and other brush, j u n i p e r - g r a s s : j u n i p e r or pinon with an understory of grass sage-grass: sage with an unde r s t o r y of gr a s s . The amount of l i t t e r i s taken i n t o account when e s t i m a t i n g the d e n s i t y of cover. 100 2 0 i -GBQUP 1 —£a_^ -23 - — « *"* -A M C n \ — — — O a k - A t p t n I 1 i 1 i l i . 0 2 0 4 0 6 0 8 0 100 G R O U N D C O V E R D E N S I T Y IN P E R C E N T F i g u r e 14: Graph f o r determining r u n o f f curve numbers of f o r e range complexes i n western U n i t e d S t a t e s : herbaceous and oak-aspen complexes (USDA 1972). F i g u r e 15". Graph f o r deter m i n i n g r u n o f f curve numbers of f o r e range complexes i n western U n i t e d S t a t e s : j u n i p e r - g r a s s and sage-grass complexes (USDA 1972). 92 The chosen curve numbers f o r a l l r e g i o n s of the watershed were then a d j u s t e d f o r AMC I or AMC I I I when r e q u i r e d u s i n g t a b l e 5 below. CURVE NUMBERS FOR AMC CONDITIONS II I I I I 100 100 100 95 87 99 90 78 98 85 70 97 80 63 94 75 57 91 70 51 87 65 45 83 60 40 79 55 35 75 50 31 70 45 27 65 40 23 60 35 19 55 30 15 50 25 1 2 45 20 9 39 15 7 33 1 0 4 26 5 2 1 7 0 0 0 Table 5: Curve numbers as adjus t e d f o r AMC Curve numbers f o r the watershed were then used to compute r u n o f f u s i n g the f o l l o w i n g r e l a t i o n s h i p s : Q = ( p I °o2.8S) m m P>0.2S [64] where: Q = stormflow(mm) P = storm r a i n f a l l (mm) and S = a catchment storage f a c t o r or p o t e n t i a l maximum r e t e n t i o n (mm) 93 S = - 10) 25.4 [65] where: CN = curve number For each storm event s t u d i e d , a check was made to ensure the storm p r e c i p i t a t i o n was g r e a t e r than the i n i t i a l a b s t r a c t i o n (0.2S). I n i t i a l a b s t r a c t i o n i n c l u d e s i n t e r c e p t i o n , i n f i l t r a t i o n and s u r f a c e storage o c c u r i n g before r u n o f f s t a r t s . T h i s r e l a t i o n s h i p may not be c o r r e c t under a l l circumstances, however, i t remains i n use u n t i l more comprehensive study i s accepted. The r a i n f a l l r u n o f f r e l a t i o n s h i p may a l s o be determined by r e f e r e n c e to f i g u r e 16. 0 50 100 150 200 ' 250 300 »» R; rainfall (mm) F i g u r e 16: Curve number graph f o r the con v e r s i o n of r a i n f a l l i n t o r u n o f f (Smedema and R y c r o f t 1983). The SCS method estimates d i r e c t r u n o f f only. The p r o p o r t i o n s of s u r f a c e r u n o f f and subsurface flow are ap p r a i s e d by means of 94 the r u n o f f curve number (CN): the l a r g e r the CN, the more l i k e l y t h a t the estimate i s of s u r f a c e r u n o f f , and the s m a l l e r the CN the more l i k e l y t h a t the estimate i s of subsurface r u n o f f (USDA 1 9 7 2 ) . The SCS curves were developed to p r e d i c t d i r e c t r u n o f f based on one or more storms o c c u r r i n g i n a calendar day ( s i n c e 24 hr r a i n f a l l t o t a l s are the most r e a d i l y a v a i l a b l e type of d a t a ) . For a storm which l a s t s more than one day, the storm can be t r e a t e d as a separate day a n a l y s i s or a s i n g l e event a n a l y s i s . The separate day a n a l y s i s c o n s i d e r s the storm as a s e r i e s of separate d a i l y storms, each having i t s own antecedent moisture c o n d i t i o n s based on what happened i n the p r e c e e d i n g f i v e days. The r u n o f f f o r each of the d a i l y storms i s added to give the t o t a l d i r e c t r u n o f f . The storm may a l s o be t r e a t e d as a s i n g l e event, although i t may l a s t f o r s e v e r a l days. The antecedent moisture c o n d i t i o n at the b e g i n n i n g of the storm i s used to determine the curve number to be used throughout the storm. For t h i s r e s e a r c h , data was c o l l e c t e d u s i n g a r e c o r d i n g raingauge, t h e r e f o r e r u n o f f was c a l c u l a t e d on an event b a s i s . Each storm p r o d u c i n g a d i s t i n c t response i n the stream hydrograph was analysed s e p a r a t e l y . I f s e v e r a l events occurred i n a row, a new antecedent moisture c o n d i t i o n was c a l c u l a t e d f o r each storm. T h i s allowed d i r e c t comparison with r u n o f f as c a l c u l a t e d from the stream hydrographs f o r each event. 95 F.2.e. model c a l i b r a t i o n F . 2 . e . i . s p r i n k l i n g i n f i l t r o m e t e r design A s p r i n k l i n g i n f i l t r o m e t e r was b u i l t f o r t h i s r e s e a r c h p a t t e r n e d a f t e r a model used by Lowrey (1980) at Oregon State U n i v e r s i t y (as adapted from Meeuwig (1971) and F r o e h l i c h and Hess (1 976)). The water chamber i s c o n s t r u c t e d of p l e x i g l a s s 1.27 cm (1/2 inch) t h i c k n e s s on the bottom, and 0.635 cm (1/4 inch) t h i c k n e s s f o r the top and s i d e s with i n s i d e dimensions of 60.96 by 60.96 by 25.4 cm (24 by 24 by 10 i n c h e s ) . A hose attachment on the box allows f o r r a p i d d r a i n i n g of the water, accompanied by a screw d r a i n p l u g i n the centre of the chamber. L e v e l l i n g bubbles are l o c a t e d on the top s u r f a c e at opposite corners of the chamber. A r u l e r on the i n s i d e f r o n t of the chamber allows r e g u l a t i o n of the head c o n t r o l l i n g the i n f i l t r a t i o n r a t e . A l a r g e l i d on the top a l s o p r o v i d e s access to the box ( f i g u r e 17). 96 F i g u r e 17: Diagram of I n f i l t r o m e t e r Chamber Simulated r a i n f a l l i s produced from 517 evenly spaced 21-gauge hypodermic needles ( i n s i d e bore diameter; 0.495 mm, o u t s i d e needle diameter; 0.813 mm). The p l a s t i c cup on the needles has been cut o f f , to prevent f o r m a t i o n of a i r bubbles. The needles are 25-4 mm (1 inch) l o n g , and p r o j e c t 12.7 mm (1/2 inch) below the i n f i l t r o m e t e r tank bottom. The s i d e w a l l s of the i n f i l t r o m e t e r extend 3-8 cm (1 1/2 inches) below the base to p r o t e c t the needles from b e i n g damaged, as w e l l as p r e v e n t i n g the operator from i n j u r i n g h i m s e l f on the needles ( f i g u r e 18). 97 F i g u r e 19: I n f i l t r o m e t e r stand The chamber i s supported by a stand c o n s t r u c t e d from angle 98 i r o n and p i p e . The stand i s supported by four a d j u s t a b l e l e g s , and s i t s on wood supports t o maintain a l e v e l chamber ( f i g u r e 19) . The base p i e c e , m i n i p l o t , i s c o n s t r u c t e d of 0.635 cm (1/4 inch) sheet metal w i t h t h r e e s i d e s 20.32 cm (8 inches) high, and one s i d e 10.16 cm (4 inches) high with a l i p welded on ( f i g u r e 20) . The m i n i p l o t i s pounded i n t o the ground 10.16 cm (4 inches) w i t h a sledge hammer, u n t i l the l i p i s at the ground s u r f a c e . A trough c o n s t r u c t e d of alluminum i s p l a c e d under the l i p on a slope l e a d i n g to a c o l l e c t i o n bucket. 2 0 . 3 2 cm sharpened e d g e s - ^ I0.I6 cm F i g u r e 20: M i n i p l o t (base) f o r i n f i l t r o m e t e r The water supply i s contained i n two 30 g a l l o n s t e e l drums t r a n s p o r t e d i n the back of a pick-up t r u c k . Garden hose i s used to siphon the water t o the i n f i l t r o m e t e r , and a flow c o n t r o l v a l v e allows the input r a t e to be c o n t r o l l e d . F i g u r e 21 below shows the f i e l d setup. 99 F i g u r e 21: F i e l d s e t up of the s p r i n k l i n g i n f i l t r o m e t e r apparatus. F . 2 . e . i i . s p r i n k l i n g i n f i l t r o m e t e r c a l i b r a t i o n procedures The i n f i l t r o m e t e r was c a l i b r a t e d u s i n g a range of 2 cm head to 20 cm head. This produced a simulated r a i n f a l l r a t e of 60 mm/hr to 425 mm/hour. The c a l i b r a t i o n curve i s i l l u s t r a t e d i n f i g u r e 22. Data f o r t h i s graph was generated by c o v e r i n g the bottom of the i n f i l t r o m e t e r with p l a s t i c , thereby c o l l e c t i n g the t o t a l p r e c i p i t a t i o n while o p e r a t i n g at d i f f e r e n t heads. SPRINKLING INFILTROMETER CALIBRATION R: =0.99 9 5 y = ? . 0 7 5 x + 2 . 5 2 0 1 9 1 8 1 7 1 6 1 5 1 4 1 3 1 2 11 1 0 9 8 7 6 5 4 3 2 H E A D ( c m ) c a l i b r a t i o n l i n e - l i n e a r r e g r e s s i o n 1 01 The simulated r a i n f a l l r a t e s produced are, once again, h i g h e r than the observed r a i n f a l l r a t e s i n the Lower Pr a s e r V a l l e y . Maximum i n t e n s i t i e s from the Aga s s i z IDP curve occur f o r a 5 minute d u r a t i o n g i v i n g a range of 30 to 70 mm/hr f o r the 2 - 1 0 0 year r e t u r n p e r i o d s . O r i g i n a l l y , s m a l l e r diameter needles (23 gauge needles -i n s i d e diameter, 0.318 mm; ou t s i d e diameter 0.635 mm) were used i n the i n f i l t r o m e t e r chamber. The c a l i b r a t i o n produced a range of r a i n f a l l i n t e n s i t y r anging from 4 mm/hr to 88 mm/hr. Th i s p r o v i d e d a very r e a l i s t i c r a i n f a l l i n t e n s i t y range, but problems wit h a i r - b u b b l e s and dust from the f i e l d b l o c k i n g some needles caused uneven r a i n f a l l i n t e n s i t y over the p l o t area. C a l i b r a t e d r a i n f a l l i n t e n s i t i e s could no longer be a p p l i e d . R e p l a c i n g the needles gave r e p e a t a b l e i n t e n s i t i e s at s p e c i f i e d heads, and the a i r bubble problem was e l i m i n a t e d . The i n f i l t r o m e t e r used at the U n i v e r s i t y of Oregon produced a p r e c i p i t a t i o n r a t e ranging from 27 to 185 mm/hr, although a l l i n f i l t r a t i o n measurements were conducted u s i n g a p r e c i p i t a t i o n r a t e of 71.8 mm/hr. Ther e f o r e , although a r e a l i s t i c r a i n f a l l i n t e n s i t y can be obtained u s i n g s m a l l e r diameter needles, o p e r a t i n g problems such as a i r - b u b b l e s and sediments c l o g g i n g the needles n e c e s s i t a t e going to a l a r g e r diameter needle, thereby i n c r e a s i n g the r a i n f a l l i n t e n s i t i e s . 102 F.5- Peak flow e s t i m a t i o n F.3-a. time of c o n c e n t r a t i o n d e t e r m i n a t i o n Time of c o n c e n t r a t i o n values were d e r i v e d u s i n g the t p o b s e r v a t i o n s from the stream hydrographs (t = 1.429t ). The c p h y d r a u l i c l e n g t h of the watershed was determined u s i n g the DEM and p r o f i l i n g program. The f o l l o w i n g time of c o n c e n t r a t i o n e s t i m a t i o n procedures were t e s t e d to determine which gave the most reasonable estimates as compared to the t obtained from the hydrograph a n a l y s i s : F . 3 - a . i . Nomograph F i g u r e 23 below p r o v i d e s an estimate of the time of c o n c e n t r a t i o n , assuming that the values of Manning's n and h y d r a u l i c r a d i u s p r e v a i l . The nomograph i s m o d i f i e d from K i r p i c h ' s equation: L1 .15 c 7700 H u ° a where: t = hours c L = l e n g t h of the watershed along the main stream from the watershed o u t l e t to the most d i s t a n t r i d g e i n f t ( h y d r a u l i c length) H = d i f f e r e n c e i n e l e v a t i o n between the watershed o u t l e t and the most d i s t a n t r i d g e i n f t . 103 6 0 , 0 0 0 -4 0 , 0 0 0 • 3 0 , 0 0 0 2 0 , 0 0 0 -10.000-8 , 0 0 0 -6 , 0 0 0 : 4 , 000 -3 . 0 0 0 -r 2 0 10 e - 6 - 4 a - 3 i — 2 -1 1,000-8 0 0 -6 0 0 : 4 0 0 -300-1 2 0 0 2 0 -10 r - 4 0 3 0 - 2 0 = 10 8 6 - 4 - 3 2 _ 0 = 0 8 = 0.6 0 4 0 3 h 0 . 2 2 . 0 0 0 - £ 6 - - 0 . 1 8 - 1 0 •20 - 3 0 - 4 0 60 - 8 0 - 1 0 0 - 2 0 0 - 3 0 0 - 4 0 0 : 6 0 0 - 8 0 0 1,000 - 2 , 0 0 0 F i g u r e 23: Nomograph f o r e s t i m a t i n g time of c o n c e n t r a t i o n (Chow 1964) F . 3 . a . i i . Kerhy formula The Kerhy formula was o r i g i n a l l y used i n c o n j u n c t i o n w i t h the r a t i o n a l formula. ,2.14 2 Ln rg-n-\ where: L = l e n g t h of flow i n f t . S = slope of the s u r f a c e n = Mannings roughness c o e f f i c i e n t . (Chow 1964) F . 3 . a . i i i . Flow V e l o c i t y Method ( a l s o c a l l e d the upland method) The V e l o c i t y method i n c o r p o r a t e s slope and l a n d use i n an i n t e r m e d i a t e step to estimate v e l o c i t y i n a given reach a l o n g the h y d r a u l i c flow l e n g t h . The time of c o n c e n t r a t i o n equals the r a t i o of the h y d r a u l i c flow l e n g t h to the v e l o c i t y : 104 t = - i - [68] c v L J where: 1 = t r a v e l l i n g d i s t a n c e ( f t or m) v = v e l o c i t y of o v e r l a n d f l o w ( f p s or m /s) When v e l o c i t y v a r i e s a l o n g t h e f l o w p a t h , t may he c c a l c u l a t e d as: * ^ [69] v. • I where 1^ and v^ r e s p e c t i v e l y r e p r e s e n t t h e t r a v e l l i n g d i s t a n c e and t h e v e l o c i t y of f l o w i n i n d i v i d u a l r e a c h e s . Nomographs such as i n f i g u r e 24 below a r e a v a i l a b l e f o r e s t i m a t i n g v e l o c i t i e s f o r t h e t h e u p l a n d method. 105 VELOCITY IN FEET PER (EC0NO F i g u r e 24: V e l o c i t i e s f o r upland method of e s t i m a t i n g T Q (McCuen 1982) F. 5 . a . i v . K i r p i c h formula The most accepted formula f o r s m a l l (A < 50 ha) a g r i c u l t u r a l b a s i n s r e l a t i n g t Q to the r e l e v a n t b a s i n c h a r a c t e r i s i t c s such as 106 b a s i n area, b a s i n shape, s l o p e , and s o i l c o n d i t i o n s i s the K i r p i c h formula (Smedema and R y c r o f t 1983 ; R a u d k i v i 1979). Once again, t h i s e m p i r i c a l formula deals with e s t i m a t i n g the time of overland flow: 1.15 V 0-38 tlO] G 3080 H ' where t = hours c L = maximum t r a v e l l i n g d i s t a n c e i n the b a s i n (m) H = the d i f f e r e n c e i n e l e v a t i o n over the above d i s t a n c e (m). F.5.a.v. Lag method The l a g method r e l a t e s the time l a g (L) which i s d e f i n e d as the time i n hours from the center of mass of r a i n f a l l excess to the peak d i s c h a r g e , to the slope Y i n percent, the h y d r a u l i c l e n g t h ( l ) i n f e e t , and the maximum r e t e n t i o n (S) (as c a l c u l a t e d u s i n g the SCS CN p r o c e d u r e s ) : L = J ^ l f 7 [ 7 1 ] 1900 Y u ° S - ^ - 10 [65] where: CN = Curve Number E m p i r i c a l evidence used i n d e v e l o p i n g the SCS methods r e s u l t e d i n the f o l l o w i n g r e l a t i o n s h i p between the time of c o n c e n t r a t i o n and the l a g : t c = J- L [72] where t i s measured i n hours, c By i n c o r p o r a t i n g the curve number i n the l a g method, the antecedent moisture c o n d i t i o n , s o i l h y d r o l o g i c c o n d i t i o n , and 107 la n d use and treatment c l a s s e s are a l l i n c l u d e d . Because the curve number v a r i e s with dormant and growing seasons, and the AMC c o n d i t i o n , the time of c o n c e n t r a t i o n must be c a l c u l a t e d f o r each storm. I n i t i a l comparison of the v a r i o u s t e s t i m a t i o n procedures l e d t o the s e l e c t i o n of the l a g method f o r use i n peak flow c a l c u l a t i o n s . 7.5'h. SCS u n i t hydrograph procedure The constant i n equation 73 may be a d j u s t e d to r e f l e c t the i n c r e a s e d area under the r i s i n g limb of the hydrograph i n a mountainous r e g i o n (McCuen 1982). * c T h i s assumes an i n c r e a s e i n overland flow response r e a c h i n g the stream i n a s h o r t e r p e r i o d of time (as i s o f t e n the case f o r Horton overland flow i n g r a s s l a n d catchments). The A g a s s i z Research Watershed d i d not r e f l e c t t h i s i n c r e a s e i n overland flow response time, t h e r e f o r e , a l l peak flow estimates used the formula as i l l u s t r a t e d above. There are two p o t e n t i a l sources of e r r o r i n the above equation; namely r e s u l t i n g from i n c o r r e c t estimates of e i t h e r r u n o f f (Q), or t . In order to i s o l a t e these terms, peak flow estimates were performed u s i n g the f o l l o w i n g combinations of v a l u e s : 1) t u s i n g the l a g method Q as estimated u s i n g the SCS CN method 2) t u s i n g estimate based on the observed t 1 08 Q as determined by measuring the area under the stream hydrographs. F.5»o» R a t i o n a l formula method The R a t i o n a l formula method i s based on the f o l l o w i n g r e l a t i o n s h i p : where: q. = peak discharge (m / s e c ) ( d e s i g n peak r u n o f f ) I = r a i n f a l l i n t e n s i t y i n mm per hour ( f o r the design r e c u r r e n c e i n t e r v a l and f o r the d u r a t i o n equal to the time of c o n c e n t r a t i o n of the watershed) A = watershed a r e a (ha) C = r u n o f f (discharge) c o e f f i c i e n t ( p r o p o r t i o n of r a i n f a l l d i s c h a r g i n g r a p i d l y as shallow flow) Peak flow d e t e r m i n a t i o n i n v o l v e d the f o l l o w i n g s t e p s : 1) Determination of s o i l t y p e ( s ) f o r the b a s i n (by r e f e r e n c e to p u b l i s h e d s o i l maps), and t h e i r e f f e c t on i n f i l t r a t i o n . 2) D etermination of the watershed area ( u s i n g the DEM). 3) D e l i n e a t i o n of the watershed i n t o d i f f e r e n t l a n d use types ($ by a r e a ) . 4) E v a l u a t i o n of the e f f e c t of land use on i n t e r c e p t i o n . 5) E s t i m a t i o n of the time of c o n c e n t r a t i o n f o r the b a s i n . 6) E s t i m a t i o n of the i n t e n s i t y or r a i n f a l l index (I) (the r a i n f a l l i n t e n s i t y f o r the time of c o n c e n t r a t i o n f o r each p a r t i c u l a r storm ). 7) E s t i m a t i o n of the r u n o f f (discharge) c o e f f i c i e n t . The 109 f o l l o w i n g t a b l e was used to determine the discharge c o e f f i c i e n t : I n f i l t r a b i l i t y of the s o i l High Medium Low Ara b l e l a n d slope < 5$ C = = 0. 30 C = 0.50 C = 0.60 5 - 10$ 0. 40 0.60 0.70 10 - 30$ 0. 50 0.70 0.80 Pasture slope < 5$ 0 = = 0. 10 C = 0.30 C = 0.40 5 - 10$ 0. 15 0.35 0.55 10 - 30$ 0. 20 0.40 0.60 F o r e s t s l o p e < 5$ C = = 0. 10 C = 0.30 C = 0.40 5 - 10$ 0. 25 0.35 0.50 10 - 30$ 0. 30 0.50 0.60 Table 6: G u i d e l i n e s f o r the d e t e r m i n a t i o n of the discharge c o e f f i c i e n t C i n the r a t i o n a l formula (USDA 1972) F.3»d. weir c a l i b r a t i o n The r e c t a n g u l a r weir i n s t a l l e d on s i t e has dimensions 1.524 meters (5 f e e t ) wide ac r o s s the c r e s t , and 0.762 meters (2.5 f e e t ) high above the c r e s t . F i e l d c a l i b r a t i o n r e s u l t e d i n the f o l l o w i n g formula f o r t r a n s l a t i n g recorded water t a b l e h e i g h t s to d i s c h a r g e : , Q = 1.77 L H 1 ' 5 [75] where: Q = m /s L = c r e s t width (m) H = head above the c r e s t (m) 110 G. RESULTS AND DISCUSSION  G.1. D i g i t a l E l e v a t i o n Model performance  G.1.a. data c o l l e c t i o n techniques The o r i g i n a l s t e r e o - p a i r used to s t e r e o p l o t the 1:5 000 base map was taken w i t h a 12 i n c h f o c a l l e n g t h at a f l y i n g height of 20 000 f e e t (1:20 000 s c a l e ) . The s t e r e o p l o t t e d map has a s c a l e of 1:5 000, w i t h a 10 meter i n t e r v a l +/- 50 $ (standard v a r i a n c e i n contour accuracy f o r a 1:5 000 map produced from 1:20 000 a i r p h o t o s ) . W i t h i n the f o r e s t e d r e g i o n of the watershed, the s t e r e o p l o t t e r operator must be a b l e to f i n d openings to the ground i n order to a c c u r a t e l y keep the f l o a t i n g p o i n t at s u r f a c e l e v e l . T h i s was not a s e r i o u s problem i n the Research watershed s i n c e adequate openings were a v a i l a b l e at rock outcrops or between c o n i f e r o u s t r e e s w i t h low cover d e n s i t y . One r e g i o n of cloud shadow i n the northwest corner of the watershed caused some d i f f i c u l t y i n v i e w i n g the ground. The d i g i t i z i n g of the 1:5 000 s t e r e o p l o t t e d map u s i n g the contour method proved to be an e f f i c i e n t procedure f o r manual entry of the e l e v a t i o n data. The procedure was f a r more operator f r i e n d l y than the g r i d system o r i g i n a l l y t e s t e d , r e s u l t i n g i n fewer e r r o r s due to operator f a t i g u e . S e t t i n g an i n t e r v a l of 2mm a long the X - a x i s and f o l l o w i n g t r a n s e c t s i n the Y - d i r e c t i o n (as was the case i n the g r i d system) can cause c o n s i d e r a b l e e y e s t r a i n , and easy l o s s of proper h o r i z o n t a l l o c a t i o n . G.1.b. DEM c r e a t i o n The DEM was c r e a t e d on the VAX by u s i n g the t r i a n g u l a t i o n 111 procedure, then c o n v e r t i n g the TIN to a g r i d ( b i n a r y f i l e ) . The g r i d f i l e was converted to an image f i l e , r e p r e s e n t i n g the e l e v a t i o n range of 790 m by 255 grey shades. T h i s gave a r e s o l u t i o n of 3 m e l e v a t i o n per grey l e v e l . The photograph below i s the raw image of the Agassiz Research watershed as seen on the r a s t e r t e c image d i s p l a y at the l a b f o r computational v i s i o n at UBC. The dark grey shades represent lower e l e v a t i o n s , and the l i g h t e r shades the higher e l e v a t i o n s . One can e a s i l y d i s t i n g u i s h between the lowland and upland components of the watershed. F i g u r e 25: Raw image 112 C r e a t i n g a s y n t h e t i c image from the raw image serves to r e f i n e the screen output. The f o l l o w i n g photograph i s a b l a c k and white s y n t h e t i c image of the watershed as would be viewed on February 7 at 12:00 noon. F i g u r e 26: S y n t h e t i c image of Research Watershed on February 7 at noon (azimuth 174°, e l e v a t i o n 25°). The r e l i e f can now be seen i n the image along w i t h r u n o f f channels i n the northeast uplands. The t r i a n g u l a r l i n e s at the SE edge of the lowland are a r t i f a c t s c r e a t e d by the l a c k of 113 d i g i t i z e d p o i n t s i n that r e g i o n (that r e g i o n i s beyond the study area - the southernmost cut o f f b e i n g the creek l e a d i n g from drained and undrained f i e l d s ) . To i l l u s t r a t e the a b i l i t y of s t u d y i n g an image at s p e c i f i e d times of day , the sun movement f o r May 1 can be charted as d e s c r i b e d i n the f o l l o w i n g t a b l e : DATE SUN AZIMUTH SUN ELEVATION TIME 79° 11 ° 7:00 102° 30° 9:00 133° 48° 1 1 :00 1 78° 56° 1 3:00 225° 49° 1 5:00 256° 32° 1 7:00 279° 12° 1 9:00 302° 3° 20:00 Table 7: Sun angles f o r the A g a s s i z Research Watershed The f o l l o w i n g photographs show the s y n t h e t i c images produced f o r the above sun angles on May 1 (note: the viewer angle i s 45° azimuth, and 30° e l e v a t i o n ) : F i g u r e 29: May 1 5:00 pm F i g u r e 30: May 1 7:00 pm 116 Contours can a l s o be d e r i v e d from the o r i g i n a l raw image f i l e and e i t h e r d i s p l a y e d on t h e i r own or o v e r l a i d on the s y n t h e t i c image. The f o l l o w i n g photograph shows the top h a l f of the r e s e a r c h watershed i n v a r i o u s contour i n t e r v a l s : from the top r i g h t 10m, 20 m, 40 m, and from the top l e f t 60 m, 80 m, and 100 m. F i g u r e 31: Contour maps f o r the top h a l f of the r e s e a r c h watershed i l l u s t r a t i n g v a r i o u s contour i n t e r v a l s . 11 7 The 40 and 100 meter contours have heen o v e r l a i d on the s y n t h e t i c images f o r February 7 at 12:00 noon as i l l u s t r a t e d i n the f o l l o w i n g two photographs. This a i d s the i n t e r p r e t a t i o n of the s y n t h e t i c image. F i g u r e 32: S y n t h e t i c image from Feb.7 40 meter contour i n t e r v a l 118 F i g u r e 33: S y n t h e t i c image from Feb.7 100 m contour i n t e r v a l . The next photograph i s a combination of the raw image ( b l u e ) , s y n t h e t i c image (red) and contour o v e r l a y f o r February 7 at noon. A d d i t i o n of the raw image (grey shades) helps to h i g h l i g h t r i d g e s i n the upland. 119 F i g u r e 34: S y n t h e t i c image f o r Feb.7 at noon combined with the raw image and a 100 m contour o v e r l a y . The f o l l o w i n g two photographs i l l u s t r a t e the p i x e l composition i n an image. The top h a l f of each photograph i s the northern s e c t i o n of the watershed. The bottom h a l f i s a fo u r and eig h t times enlargement r e s p e c t i v e l y of the top s e c t i o n . 1 20 1 21 The map output c r e a t e d u s i n g DISSPLA was a good r e p r e s e n t a t i o n of the o r i g i n a l map w i t h only minor d i s c r e p e n c i e s . DISSPLA proved to he d i f f i c u l t to run wit h such a l a r g e data base, and would only provide a minimum contour i n t e r v a l of 20 m. Contour maps c r e a t e d on the VAX were unable to be t r a n s f e r r e d to a p l o t t e r . The f e a s i b i l i t y of u s i n g the l a t e s t e d i t i o n of AUTOCAD was explored, but autocad does not p r o v i d e the software r e q u i r e d f o r c r e a t i n g the contours. There are companies f i l l i n g t h i s v o i d by marketing c o n t o u r i n g software f o r micro-computers, (not a c c e s s i b l e f o r t h i s r esearch.) G-.1 .C area comparisons The areas obtained u s i n g the c o n v e n t i o n a l approaches of p l a n i m e t e r i n g from the 1:50 000 NTS map sheet, p l u s p l a n i m e t e r i n g from the 1:5 000 s t e r e o p l o t t e d map were compared to those obtained by d i g i t i z i n g the r e s p e c t i v e boundaries of the sub-areas then u s i n g the area programs provided with the DEM. The r e s u l t s are presented i n the f o l l o w i n g t a b l e : 1 22 MAP SOURCE CALCULATED AREA (ha) NTS 1:5000 DEM TOTAL WATERSHED 330 303.6 474 LOWLAND 56.6 61 .76 PAN 18.4 18.9 UPLAND 228.4 41 2.2 DRAINED FIELD 1 .73 1 .78 UNDRAINED FIELD 1 .45 1 .38 Table 8: Area comparisons The area program gives the area i n square p i x e l s . The s c a l e of the o r i g i n a l map i s 1:5 000, the map represented by 300 rows and 168 columns of p i x e l s . Each p i x e l r e p r e s e n t s a ground o r e s o l u t i o n of 10 X 10 meters (2 mm X 2 mm on the map), 100 m . T h e r e f o r e , the t o t a l map area was represented as 47412.613716 sq. 2 p i x e l s , which t r a n s l a t e s to 4741261.3716 m , or 474 ha. As i l l u s t r a t e d i n the above t a b l e , the areas measured i n the lowland do not show s i g n i f i c a n t d i f f e r e n c e s i n t h e i r amount. This i s due to the f a c t t h a t f o r most regions i n the lowland there i s no s i g n i f i c a n t s l o p e . The areas obtained f o r the upland r e g i o n , which e x i b i t s extreme s l o p e s e s p e c i a l l y on the e a s t e r n s l o p e s of the upland, show a s i g n i f i c a n t d i f f e r e n c e between methods used. T h i s emphasizes the p o t e n t i a l u n d e r e s t i m a t i o n of areas measured from a p l a n i m e t r i c map f o r regions of extreme t e r r a i n . Watershed area 1 23 i s a key component of many r u n o f f and peak flow e s t i m a t i o n techniques, thereby a gross u n d e r e s t i m a t i o n of e r r o r may y i e l d m i s l e a d i n g r e s u l t s . The watershed boundaries drawn onto the NTS map sheet may cause gross e r r o r i n area measurement i f they are i n c o r r e c t l y p l a c e d . Due to the sm a l l s c a l e of the map, a change of l o c a t i o n of the boundary of only a few m i l i m e t e r s can cause dramatic o v e r e s t i m a t i o n or un d e r e s t i m a t i o n of area. I t appears that the boundaries were chosen w e l l , as the computed area does not s i g n i f i c a n t l y d i f f e r from that obtained u s i n g the l a r g e s c a l e map. G.1.d. p r o f i l i n g performance In the de t e r m i n a t i o n of the h y d r a u l i c l e n g t h of the watershed (as i n d i c a t e d on the map i n appendix B), the p r o f i l i n g program was used i n order to i n c l u d e the slope i n the l e n g t h c a l c u l a t i o n . A comparison of the l e n g t h measured from the p r o f i l e , to the pla n a r d i s t a n c e i s i l l u s t r a t e d below: GROUND DISTANCE PLANAR DISTANCE meters UPLAND 1 291 1 020 PAN" 422 410 LOWLAND 770 770 Table 9: Comparison of d i s t a n c e s along the h y d r a u l i c l e n g t h Once again, i n the lowland r e g i o n where there i s very l i t t l e 1 24 sl o p e , the i s no d i f f e r e n c e i n r e s u l t a n t d i s t a n c e s . The f a n s e c t i o n has a slope of 17-6$, and the p r o f i l e program takes t h i s i n t o account r e s u l t i n g i n a s l i g h t l y i n c r e a s e d d i s t a n c e over the plana r d i s t a n c e . The most dramatic d i f f e r e n c e between the two measurement procedures occurs i n the upland segment with a s l o p e Nof 54.2$. There i s an i n c r e a s e of 280 m i n the h y d r a u l i c l e n g t h as c a l c u l a t e d u s i n g the p r o f i l e program when i n c o r p o r a t i n g s l o p e . 1 25 G .2. Runoff comparisons  G.2.a. watershed curve numbers Curve numbers f o r a l l regions of the watershed were determined a c c o r d i n g to recommended procedures from the SCS and U.S. F o r e s t S e r v i c e (USDA 1972). The upland f o r e s t i s composed of approximately 50$ deciduous t r e e s ; thereby the cover d e n s i t y i s h i g h l y e f f e c t e d by season. The f o l l o w i n g t a b l e i l l u s t r a t e s the curve numbers d e r i v e d f o r the upland r e g i o n B, t a k i n g season i n t o account. UPLAND B ( 50/50 DECIDUOUS/CONIFEROUS) FOREST TYPE COVER CN AVE. CN GROWING- oak/aspen 80$ 32 SEASON c o n i f e r o u s ( p i n e ) 50$ 57 45 DORMANT oak/aspen 1 0$ 82 SEASON c o n i f e r o u s ( p i n e ) 50$ 57 70 Table 10 : Curve Numbers f o r the upland r e g i o n of the Agassiz Research Watershed. The graphs pr o v i d e d by the US F o r e s t S e r v i c e f o r the e s t i m a t i o n of CNs ( f i g u r e s 14 and 15) do not prov i d e estimates f o r S o i l h y d r o l o g i c c o n d i t i o n A. Therefore i n t e r p o l a t i n g from the graphs, the f o l l o w i n g curve numbers f o r the f o r e s t e d f a n A r e g i o n were obtained. 126 PAN A (70/30 DECIDUOUS/CONIFEROUS) FOREST TYPE COVER CN AVE. CN GROWING oak/aspen 80$ 25 SEASON c o n i f e r o u s ( p i n e ) 50$ 50 33 DORMANT oak/aspen 10$ 75 SEASON c o n i f e r o u s 50$ 50 68 Table 11: Curve Numbers f o r the Fan re g i o n of the Aga s s i z Research Watershed. I t i s important to note t h a t the f o r e s t types s i ; g n i f i e d i n the t a b l e s f o r the western U n i t e d S t a t e s are not the same s p e c i e s composition as found i n the Research Watershed (these were the only f o r e s t types f o r the western r e g i o n of the Uni t e d S t a t e s presented by the U.S. F o r e s t S e r v i c e f o r CN determination)(USDA 1972). The oak-aspen and j u n i p e r - g r a s s complexes were used f o r choosing curve numbers. The s p e c i e s i d e n t i f i e d i n these complexes i n c l u d e mountain brush mixtures of oak, aspen, mountain mahogany, b i t t e r brush, and maple, p l u s j u n i p e r or pinyon. Of the above s p e c i e s , only some maples (vine maple, and b i g l e a f maple), and bl a c k cottonwood (poplar) are found i n the Ag a s s i z Research watershed. The other s p e c i e s l i s t e d by the U.S. F o r e s t S e r v i c e are found i n the dryer oak woodlands and c h a p a r r a l r e g i o n s c o v e r i n g the f o o t h i l l s and lower mountain s l o p e s i n areas such as C a l i f o r n i a , southern A r i z o n a , and New Mexico. In areas 1 27 where the w i n t e r s are c o l d , such as the Great B a s i n and the Colorado P l a t e a u , woodlands are dominated by pinyons or j u n i p e r s r a t h e r than oaks. C h a p a r r a l c o e x i s t s w i t h a l l of these woodlands throughout much of t h e i r range (Whitney 1985). The A g a s s i z Research watershed i s p a r t of the P a c i f i c C o a s t a l Region, s u p p o r t i n g mainly s m a l l hemlock, douglas f i r , cedar, a l o n g w i t h hardwoods and shrubs such as giant b i g l e a f maples, red a l d e r s , cottonwoods, and vine maple. Nonetheless, use of the U.S. F o r e s t S e r v i c e g u i d e l i n e s seemed more a p p r o p r i a t e than u s i n g the woods c l a s s i f i c a t i o n i n t a b l e 2 (cover d e n s i t y f o r the d i f f e r e n t seasons could be taken i n t o account when determining curve numbers). The remaining l a n d use c a t e g o r i e s were a l s o evaluated to d e r i v e curve numbers, and the f o l l o w i n g t a b l e shows the a p p r o p r i a t e curve numbers f o r the complete watershed: 1 28 LAND USE HYDROLOGIC SOIL GROUP AREA CN DORMANT GROWING f o r e s t e d U/L B 83$ 70 45 f o r e s t e d f a n A 4$ 68 33 L/L scrub/marsh ( p a s t u r e or range) D 12.335$ 89 89 u n d r a i n e d f a l l o w D 0.29$ 94 94 d r a i n e d f a l l o w C 0.375$ 91 91 T a b l e 12: Curve Numbers f o r t h e A g a s s i z R e s e a r c h Watershed. G.2.b. r u n o f f e s t i m a t e s The curve numbers o u t l i n e d i n t a b l e 12 were used t o e s t i m a t e r u n o f f f o r each of the storms o u t l i n e d i n t a b l e 13 below. F o r computing t h e r u n o f f from complex h y d r o g r a p h s , a composite s t o r m r e c e s s i o n curve f o r the watershed was d e r i v e d from a n a l y s i n g s i x s i n g l e event s t o r m hydrographs (Appendix D). T h i s was used f o r e x t e n d i n g the r e c e s s i o n c u r v e s i n complex hydrographs f o r base f l o w s e p a r a t i o n . Hydrograph s e p a r a t i o n f o r a l l storms can be found i n Appendix E. Tab l e 13 below i s a summary of t h e r u n o f f e s t i m a t e s as c a l c u l a t e d u s i n g the SCS Curve Number approach, and as measured from t h e st r e a m h y d r o g r a p h s . DATE/ SEASON AMC SCS CN HYDROGRAPH STORM NO. (mm) (mm) Sept 4 - 8 1984 G I 2.87 15.2 Sept 4 - 8 1985 G I 1 -59 9.7 Sept 20 - 23 1984 G I 0.34 2.2 Oct 7 - 14 1984 1 G I 0.00 0.7 2 G I 0.00 1 .7 3 G I 1 .24 14.6 4 G I I I 0.85 — Oct 23 - 26 1984 G I 0.44 5.9 Oct 27 - 31 1984 1 G II 2.20 4.8 2 G II 0.07 1 .3 Nov 1 8 - 2 2 1984 1 D I 0.00 2.2 2 D I 0.00 3.3 3 D II 0.20 3-5 Dec 6 - 8 1984 D I 1 .87 14.6 Dec 8 - 1 7 1984 D II 1 5 .00 23-98 Mar 19 - 22 1985 1 G I 0.00 0.5 2 G I 0.00 1 .6 Mar 22 - 25 1985 G I 0.11 3-0 Mar28 - Apr 4 1985 1 G I 0.01 2.1 2 G I 0.13 4.0 4 G I I I 7-90 12.4 Apr 1 0 - 2 1 1 985 1 G I 0.04 5.2 2 G I 0.00 2.0 3 G II 0.01 1 .5 4 G I 0.00 1 .1 5 G I 0.00 2.6 Apr 22 - 26 1985 1 G I 0.00 2.4 2 G I 0.00 1 .5 Apr 26 - May 1 1985 G I 4.10 18 .9 May 4 - 7 1985 1 G I 0.00 2.0 2 G I 0.00 0.8 May 1 0 - 1 6 1985 1 G I 0.00 5.2 2 G I 0.01 4.0 1 30 RUNOFF cont. DATE/ SEASON AMC SCS CN HYDROGRAPH STORM NO. (mm) (mm) May 22 - Jun 1 1985 2 G I 0.01 3-2 Jun 6 - 17 1985 1 G I 0.80 7.5 2 G I 0.00 4.5 Table 13: Runoff estimates based, on the SCS Curve Number method and hydrograph a n a l y s i s The above r e s u l t s show that the SCS CN r u n o f f estimates f o r each of the storms s t u d i e d are l e s s than the r u n o f f measured from the stream hydrographs. In some storms, the SCS procedure p r e d i c t e d no r u n o f f at a l l . These r e s u l t s may be e x p l a i n e d i n v a r i o u s ways. F i r s t l y , the m a j o r i t y of the watershed (87$) i s f o r e s t e d . The curve numbers f o r the f o r e s t e d regions are very low, thereby r e f l e c t i n g h i g h storage p o t e n t i a l i n the s o i l . In order f o r r u n o f f to occur, the r a i n f a l l must be g r e a t e r than 0.2S (S be i n g the p o t e n t i a l maximum storage c a p a c i t y ) . There were only two storms, Dec 8 - 1 7 , 1985, and March 28 - A p r i l 4, 1985, where the p r e c i p i t a t i o n was great enough to f i l l the p o t e n t i a l storage c a p a c i t y (0.2S) i n the f o r e s t e d r e g i o n s , and cause r u n o f f . For the m a j o r i t y of the storms, r u n o f f was generated from the lowland scrub/marsh r e g i o n , drained, and undrained f i e l d s only. The curve numbers f o r these r e g i o n s were much higher than f o r the f o r e s t e d r e g i o n , thereby i n d i c a t i n g a s m a l l e r p o t e n t i a l storage c a p a c i t y i n the s o i l . On May 10 - 16, 1985, r u n o f f occurred from the d r a i n e d and undrained f i e l d s only. Some storms only 1 31 generated r u n o f f from the undrained f i e l d s i n c e a l l other r e g i o n s p r o v i d e d more p o t e n t i a l storage than the t o t a l p r e c i p i t a t i o n (Oct 7-14 1984 (2nd storm), A p r i l 10-21, 1985 (2nd storm), A p r i l 22-26, 1985 (1st storm), May 4-7, 1985, (1st storm)). The storms wi t h no p r e d i c t e d r u n o f f r e f l e c t adequate storage i n the e n t i r e watershed to accommodate a l l p r e c i p i t a t i o n . Review of r u n o f f r e s u l t s from the stream hydrographs i n d i c a t e s t h at a l l storms s t u d i e d d i d indeed produce r u n o f f as recorded at the b a s i n o u t l e t . T h i s i n d i c a t e s t h a t the SCS CN procedure i s not adequately r e f l e c t i n g r u n o f f processes o c c u r r i n g i n the watershed. The SCS procedure c o n s i d e r s each c h a r a c t e r i s t i c r e g i o n of the watershed independently. A curve number i s assigned to each r e g i o n then a weighted r u n o f f estimate i s made based on the r e l a t i v e area of each c h a r a c t e r i s t i c r e g i o n . This does not allow f o r one r e g i o n to i n f l u e n c e r u n o f f p r o d u c t i o n i n adjacent regions ( i . e . subsurface flow from the f o r e s t e d upland f i l l i n g the storage c a p a c i t y of the lowland s o i l s c a u s i n g the s a t u r a t e d r e g i o n to spread upslope - the v a r i a b l e c o n t r i b u t i n g area concept). Runoff as p r e d i c t e d u s i n g the SCS CN procedure i s almost e x c l u s i v e l y from the lowland regions (thereby assuming the only type of r u n o f f generated i n the Research Watershed i s overland flow and t h a t the upland r e g i o n does not c o n t r i b u t e to r u n o f f p r o d u c t i o n ) . T h i s i s c o n t r a r y to r e s e a r c h f i n d i n g s from other f o r e s t e d upland r e g i o n s where subsurface r u n o f f i s observed (Hewlett and H i b b e r t 1967). 1 32 The USDA (1972) p o i n t out that e r r o r s i n r u n o f f estimates are due to one or more of the f o l l o w i n g : empiricisms i n the antecedent moisture c l a s s i f i c a t i o n ( t a b l e 2), Curve Number g u i d e l i n e s ( t a b l e 4 and f i g u r e s 14 and 15), the r e l a t i o n between the AMC and Curve Numbers, the equation f o r i n i t i a l a b s t r a c t i o n ; and e r r o r s i n determinations of average watershed r a i n f a l l , s o i l groups, lan d use and treatment, and r e l a t e d computations. Consequently, i t i s i m p o s s i b l e to s t a t e a standard e r r o r of estimate f o r the r u n o f f equation [64]; comparisons of computed and a c t u a l r u n o f f s i n d i c a t e only the a l g e b r a i c sum of e r r o r s from v a r i o u s sources (USDA 1972). The Curve Number approach was f o r the most p a r t developed i n mid-western watersheds of the United S t a t e s , where storms are high i n t e n s i t y , s h o r t d u r a t i o n events as compared to the low i n t e n s i t y , l o n g d u r a t i o n storms i n the Lower Pr a s e r V a l l e y Region. The c l i m a t i c d i f f e r e n c e s between mid-western USA and the western c o a s t a l r e g i o n may a l s o i n t r o d u c e d i f f i c u l t i e s i n a s s i g n i n g Curve Numbers to catchments (not only due to d i f f e r e n t r a i n f a l l p a t t e r n s , but a l s o d i f f e r e n t topography, and v e g e t a t i o n ) . A study i n the Palouse area of Washington and Idaho, a r e g i o n a l s o e x p e r i e n c i n g a maritime c l i m a t e and low r a i n f a l l r a t e s , i n d i c a t e d d i f f i c u l t y i n e s t i m a t i n g the a p p r o p r i a t e Curve Number (Molnau et a l . 1983). The SCS model was o r i g i n a l l y intended f o r drainage areas of 2000 acres (8094 ha) or l e s s , with s l o p e s l i m i t e d to l e s s than 30 percent (Dickey e_t a l . 1 979). The Research Watershed e x i b i t s 133 s l o p e s over 50 percent i n the upland which composes 87 percent of the watershed area. The SCS procedures do not i n c l u d e slope as a parameter i n r u n o f f e s t i m a t i o n , i t i s only i n t r o d u c e d i n the time of c o n c e n t r a t i o n d e t e r m i n a t i o n and a p p l i e d i n peak flow e s t i m a t i o n . T h e r e f o r e , the e f f e c t s of upland r e g i o n s i n r u n o f f p r o d u c t i o n i s not adequately addressed i n the SCS CN procedures. Another p o t e n t i a l source of e r r o r may he the adjustments that are made to the CN a c c o r d i n g to the three c l a s s e s of antecedent moisture c o n d i t i o n (AMC). Problems with the approach f o l l o w e d by the SCS have been c r i t i c i s e d by Hope et a l . (1982) on the b a s i s of the f o l l o w i n g three p o i n t s : 1) The r e l a t i o n s h i p s between AMC and r a i n f a l l are shown as d i s c r e t e c l a s s e s , r a t h e r than b e i n g a continuum, thus i m p l y i n g sudden s h i f t s i n curve numbers and co r r e s p o n d i n g quantum jumps p o s s i b l e i n c a l c u l a t e d stormflow (Hawkins 1978). 2) The use of f i v e antecedent days' r a i n f a l l i s not based on p h y s i c a l r e a l i t y but i s , a c c o r d i n g to M i l l e r i n Hope e_t a l . (1982), based on s u b j e c t i v e judgement. 3) No c o n s i d e r a t i o n i s given to the d e p l e t i o n of catchment storages due to e v a p o t r a n s p i r a t i o n and drainage which may vary from r e g i o n to r e g i o n and w i t h i n a season. T h e r e f o r e , i t appears that the SCS CN method does not adequately r e p r e s e n t the r u n o f f processes o c c u r r i n g i n an upland f o r e s t e d watershed i n a humid c l i m a t e such as the A g a s s i z Research Watershed. Runoff estimates are c o n s i s t e n t l y underestimated. 134 G.3. TOPMODEL e v a l u a t i o n In the development of TOPMODEL, the need f o r a simple, p h y s i c a l l y - b a s e d h y d r o l o g i c a l f o r c a s t i n g model w i t h parameters that are d i r e c t l y measurable was emphasized. Review of v a r i o u s s t u d i e s by Beven and h i s a s s o c i a t e s over the past t en years i n d i c a t e d p r o m i s i n g r e s u l t s g i v i n g i n c e n t i v e to model a p p l i c a t i o n . However, when p l a n n i n g the f i e l d work and model c a l i b r a t i o n , i t became apparent t h a t p r a c t i c a l problems i n the model a p p l i c a t i o n s t i l l e x i s t e d . Therefore, the model procedures were evaluated, but not a p p l i e d i n t h i s r e s e a r c h . TOPMODEL has always been very much a r e s e a r c h t o o l and e x i s t e d i n many forms. The e s s e n t i a l s u n d e r l y i n g the use of a/tang d i s t r i b u t i o n s are very simple and the coding of the c a l c u l a t i o n s f o r one time step are very compact (Beven 1985). The model should not be used with very s h o r t time steps ( l e s s than 1 hour) or very f l a t h i l l s l o p e s because of the steady s t a t e assumptions that u n d e r l y the development of the theory. The model was a l s o intended f o r use i n u n f o r e s t e d watersheds i n humid-temperate c l i m a t e s (due to the problems of a c c o u n t i n g f o r e v a p o t r a n s p i r a t i o n ) . The l e a s t s a t i s f a c t o r y p a r t of TOPMODEL i s the "unsaturated zone" r o u t i n g . In the o r i g i n a l a p p l i c a t i o n s the S^, S c, i , OPV, and PC parameters were a l l constant w i t h i n each subcatchment, and were not measured i n a l l subcatchments but r a t h e r were determined on the b a s i s of v e g e t a t i o n / s o i l type combinations. The i was always so high that i t had l i t t l e e f f e c t on any unsatu r a t e d zone 135 delays, t h e r e f o r e three hour time steps were used. This i l l u s t r a t e d t h a t e s s e n t i a l l y the "unsaturated zone" had l i t t l e or no c o n t r o l over the form of the hydrograph. This may not be cons i d e r e d as r e a l i s t i c , the answer probably depending on the depth of the w a t e r t a b l e (Beven 1985). To allow more f l e x i b i l i t y , Beven presented the q. = S / t,S. [25] *v uz ' d I approach (Beven and Wood 1983), but t h i s has never been a p p l i e d with measured parameters. The t ^ parameter i s not r e a d i l y obtained from f i e l d measurements (a constant parameter which could be d i f f e r e n t f o r d i f f e r e n t sub-catchments). Inherent i n the de t e r m i n a t i o n of i n f i l t r a t i o n c h a r a c t e r i s t i c s of a watershed i s the problem of u s i n g s i n g l e p o i n t measurements. Beven recommends that at l e a s t one i n f i l t r a t i o n t e s t be performed per c h a r a c t e r i s t i c sub-area of the catchment. These t e s t s are then assumed to be r e p r e s e n t a t i v e of the e n t i r e sub-area. P r o v i d i n g t h a t the assumptions of s o i l p r o p e r t i e s changing e x p o n e n t i a l l y w i t h depth and of unsatu r a t e d flow being predominatly i n the v e r t i c a l plane are t r u e , the t h e o r e t i c a l b a s i s f o r e x t r a p o l a t i n g from p l o t to catchment s c a l e would appear to be capable of f u r t h e r development (Beven 1977). In p r a c t i c e , a f t e r s u b d i v i d i n g the watershed i n t o c h a r a c t e r i c t i c r e g i o ns a c c o r d i n g to landuse, s o i l type, and sl o p e , i t i s a very s u b j e c t i v e d e c i s i o n as to where the i n f i l t r o m e t e r measurements should be made. The d e c i s i o n becomes i n c r e a s i n g l y more d i f f i c u l t i n the upland where th e r e can be 136 extreme d i f f e r e n c e s i n r e l i e f and cover. In order to "be a b l e to c o l l e c t r u n o f f from the p l o t and c a l c u l a t e OFV, the p l o t must have some sl o p e towards the trough, and should not have l a r g e depressions which w i l l prevent the r u n o f f from r e a c h i n g the c o l l e c t i o n bucket. In order to achieve t h i s , one could c o n s i d e r that the r e s u l t s are b i a s e d by choosing p l o t s w i t h a r e l a t i v e l y smooth s o i l s u r f a c e , and r e p r e s e n t a t i v e ground cover, but the mechanics of the procedure d i c t a t e s t h i s . Ground cover can remain u n d i s t u r b e d , except f o r any trimming necessary to a l l o w the i n f i l t r o m e t e r to stand above the p l o t (the maximum extended height of the i n f i l t r o m e t e r i n the stand i s approximately 0.9 meters). Taking more than one t e s t per sub-region does not guarantee more confidence i n the r e s u l t s . Two p l o t s only a few meters apart can give very d i f f e r e n t r e s u l t s dependent upon the s o i l p r o f i l e and microtopography of the p l o t . The h y d r o l o g i s t must make a d e c i s i o n as to how he wishes to approach t h i s problem. In order to make the t e s t s s t a t i s t i c a l l y s i g n i f i c a n t , a s t a t i s t i c a l d esign adequately r e p r e s e n t i n g the v a r i a t i o n per sub-unit must be adapted g i v i n g a f i n a l e r r o r sum of squares with 30 degrees of freedom. In a watershed with 5 c h a r a c t e r i s t i c r e g i o ns such as the A g a s s i z Research Watershed ( d r a i n e d f i e l d , undrained f i e l d , lowland scrub, f o r e s t e d f a n r e g i o n ( i n c l u d i n g l o g g i n g s i t e ) , and f o r e s t e d uplands) a high number of t e s t s would be r e q u i r e d . The a d d i t i o n a l time and e f f o r t spent on these t e s t s may s t i l l not give more confidence to the r e s u l t s again due to the change i n 137 micro-topography , cover, s l o p e , and s o i l s f o r each s u b - p l o t . Since TOPMODEL i s a d e t e r m i n i s t i c model, a s t o c h a s t i c approach to i n f i l t r a t i o n d e t e r m i n a t i o n may not be r e q u i r e d . A s i n g l e p o i n t estimate per sub-region may be adequate and c o n s i s t e n t with the model design. In the c a l c u l a t i o n of q (the subsurface flow when S~ = 0) •^o 3 the moisture content of v a r i o u s s o i l samples taken from d i f f e r e n t p a r t s of the p r o f i l e i s i n v o l v e d . The s o i l moisture sampling i s a problem s i n c e i t i s a h i g h l y v a r i a b l e q u a n t i t y . T h i s was addressed by Beven i n the methodology by recommending p r o f i l e s be sampled down to the wa t e r t a b l e or impermeable l a y e r at at l e a s t 10 s i t e s i n a subcatchment. These should i d e a l l y have the same p r o b a b i l i t y of occurrence i n space as the a/tang values so that an approximately weighted average could be taken. Once again, as with the i n f i l t r o m e t e r t e s t s , the h y d r o l o g i s t must decide how he wishes to approach t h i s p o i n t sampling problem. E v a l u a t i o n of TOPMODEL as a p p l i e d i n Crimple Beck catchment i n England, and White Oak Run i n V i r g i n i a p r e d i c t e d c o n t r i b u t i n g areas f o r i n d i v i d u a l storms i n accordance w i t h observed s a t u r a t e d areas i n the f i e l d (Beven and Wood 1984). This was based on i n i t i a l s torage d e f i c i t s , a long with the p r e d i c t i o n of combined s u r f a c e and subsurface responses. Simple r e g r e s s i o n s were c a r r i e d out f o r comparison with the model, but the c o e f f i c i e n t of de t e r m i n a t i o n (R ) was below that obtained by TOPMODEL (Beven and Wood 1983). Beven et a l . (1984) r e p o r t r e s u l t s f o r three g r a s s l a n d 1 38 catchments i n B r i t a i n and Wales. These i l l u s t r a t e t h a t most of the storm flow i s d e r i v e d from quick response r u n o f f , and t h a t the l a c k of i n f i l t r a t i o n delay i s not very s i g n i f i c a n t . The model appeared to work best under wet c o n d i t i o n s . There i s concern t h a t the p o t e n t i a l e v a p o r a t i o n estimates used i n the model do not adequately represent the a c t u a l e v a p o t r a n s p i r a t i o n r a t e s d u r i n g the summer months. A comparison of model e f f i c i e n c e s however showed there was no seasonal v a r i a t i o n f o r these catchments (Beven et a l . 1984). This may not be the case f o r catchments wi t h l a r g e areas of woodland or crops such as the A g a s s i z Research Watershed, and a more s c i e n t i f i c approach f o r e s t i m a t i n g e v a p o t r a n s p i r a t i o n may be r e q u i r e d . TOPMODEL i n i t s present stage of development i s not ready to be used o p e r a t i o n a l l y f o r e s t i m a t i n g r u n o f f and peak flow f o r subsurface drainage design. S p e c i f i c problems a s s o c i a t e d w i t h a t t a i n i n g r e q u i r e d parameters, e v a p o t r a n s p i r a t i o n , and the e f f e c t of the i n f i l t r a t i o n storage on r u n o f f processes i n f o r e s t e d catchments must be addressed. However, i t s t i l l p r e s e n t s an i n t e r e s t i n g approach u t i l i z i n g p h y s i c a l l y based c h a r a c t e r i s t i c s of the catchment, and warrents f u r t h e r r e s e a r c h e f f o r t . 139 G.4. Peak flow comparisons G.4.a. time of c o n c e n t r a t i o n - h y d r a u l i c l e n g t h F i g u r e 37 below i l l u s t r a t e s a p r o f i l e c r e a t e d a l o n g the h y d r a u l i c l e n g t h of the watershed as o u t l i n e d on the map i n Appendix B. The p r o f i l e i s d i v i d e d i n t o three s e c t i o n s : upland, fan , and lowland, each having a c h a r a c t e r i s t i c s l o p e . i i Li 2 . 2 2 1.8 1.6 1.4 1.2 1 0 .8 0 . 6 0 . 4 0 . 2 0 T I M E O F C O N C E N T R A T I O N P R O F I L E TOTAL DISTANCE 1 21 anuuraumm umumnumii nimniminiw iHmiiiiMtnim[minimniniinfnniinm.uiuHp . 2 4 1 . 4 6 1 . 6 8 1 . 8 1 0 2 1 2 2 . 5 1 4 3 1 5 9 . 5 6 1 7 6 . 1 2 1 9 2 . 6 8 2 0 9 . 2 4 PLANAR DISTANCE ( x 1 0 m ) F i g u r e 37: P r o f i l e f o r h y d r a u l i c l e n g t h of A g a s s i z Research Watershed. 1 40 The le n g t h s and slope of each segment are measured as f o l l o w s : LENGTH SLOPE upland 1291 m (4236 f t . ) 0.532 fan 422 m ( 385 f t . ) 0.176 lowland 770 m (2526 f t . ) 0.0026 (note: the above lengths were c a l c u l a t e d u s i n g PROFILE.C and the DEM, thereby i n c o r p o r a t i n g s l o p e i n the c a l c u l a t i o n s ) . G.4.b. time of c o n c e n t r a t i o n The c a l c u l a t i o n of t u s i n g the f i r s t f o u r methods o u t l i n e d was s t r a i g h t forward. The h y d r a u l i c l e n g t h was d i v i d e d i n t o the three s e c t i o n s : upland, f a n , and lowland, and the i n d i v i d u a l t c estimates f o r each s e c t i o n were t o t a l e d to give the f i n a l t . ° c E s t i m a t i o n of t u s i n g the l a g method was somewhat more i n v o l v e d as the SCS CN i s one of the r e q u i r e d parameters. The h y d r a u l i c l e n g t h t r a v e r s e s f o u r of the f i v e h y d r o l o g i c complexes i d e n t i f i e d i n the SCS Runoff e s t i m a t i o n procedures: the f o r e s t e d upland segment, h y d r o l o g i c s o i l c o n d i t i o n B; the f o r e s t e d f a n segment, h y d r o l o g i c s o i l c o n d i t i o n A; the shrub/wet lowland s e c t i o n , h y d r o l o g i c s o i l c o n d i t i o n D; and a p o r t i o n of the drai n e d f i e l d , h y d r o l o g i c s o i l c o n d i t o n C. Since the CN s e l e c t e d f o r a r u n o f f event depends upon the season, and the moisture c o n d i t i o n (AMC), t a b l e 14 prov i d e s a summary of the CNs, and t , f o r the p o s s i b l e combinations of a v a i l a b l e moisture c l a s s and season f o r the three segments of the h y d r a u l i c l e n g t h : 141 CURVE NUMBERS GROWING SEASON DORMANT SEASON 1 AMC 2 3 1 AMC 2 3 UPLAND 27 45 65 43 63 81 .4 PAN 17.4 33 53 38 58 77.4 LOWLAND 76.4 89 97.8 76.4 89 97.8 T minutes UPLAND 60 35 21 c 37 22 13 PAN 62 35 20 30 18 11 LOWLAND146 96 63 146 96 63 TOTAL 268 166 104 MINUTES 21 3 136 87 4.47 2.77 1 .73 HOURS 3-55 2.27 1 .45 Table .14: Curve Numbers and t estimates u s i n g the Lag method c A summary of the f i v e time of c o n c e n t r a t i o n e s t i m a t i o n procedures s t u d i e d i s presented below: Method t c 1) Nomograph 46 min. 2) Kerby 53 min. 3) Plow v e l o c i t y 228 min. (3-8 hr) 4) K i r p i c h 41 min. 5) Lag method (as i n d i c a t e d i n t a b l e 14 ) Table 15". Time of c o n c e n t r a t i o n estimates 1 42 From the above t e s t i n g of the v a r i o u s t e s t i m a t i o n procedures, the wide range of r e s u l t s e a s i l y i l l u s t r a t e s the l a r g e degree of e r r o r which can be i n t r o d u c e d i n t o a r u n o f f model u s i n g t . The l a g method appeared to produce the most reasonable t estimates, t h e r e f o r e was chosen to use i n the peak flow c a l c u l a t i o n s . One must note though, that the t estimates from the l a g method s t i l l underestimate the observed t estimates from c the stream hydrographs ( t a b l e 16). T h i s problem may be e x p l a i n e d by the slower response time of subsurface flow as dominant i n f o r e s t e d watersheds compared to overland flow response. The procedures f o r e s t i m a t i n g t assume d i r e c t o v erland flow to be the r u n o f f g e n e r a t i n g process i n o p e r a t i o n . Th i s i s a major problem f o r f o r e s t e d watersheds l o c a t e d i n humid c l i m a t e s such as i n the Lower F r a s e r V a l l e y . The f o l l o w i n g t a b l e o u t l i n e s the t o b s e r v a t i o n s as obtained from the review of storm hydrographs i n appendix F, and the corre s p o n d i n g t (as c a l c u l a t e d by 1.43 t ). c p 143 DATE/ STREAM UNDRAINED FIELD DRAINED FIELD P STORM NO. T p T Q T p T Q T p T Q DURATION {hours) (hours) (hours) (hours) Sept4-8/84 12.0 17.1 ** 19.0 27. 0 25 Sept4-8/85 8.0 11 .4 6.0 8. 6 6.0 8. 6 9 Sept20-23/84 7.0 10.0 0.1 0. 14 11 .0 15. 7 4 0ct7-14/84 1 18.0 25-7 6.0 8. 6 ** 6 2 18.0 25-7 12.0 17. 1 ** 9 3 1 7.0 24-3 2.0 2. 9 #* 37 4 8.0 11 .4 5.0 7. 1 ** 16 0ct23-26/84 12.0 17.1 7.0 10. 0 14.0 20. 0 11 Oct27-31/84 1 18.0 25-7 1 7.0 24. 3 19.0 27. 1 19 2 8.0 11 .4 1 .0 1 . 4 5.0 7. 1 8 Nov18-22/84 1 6.0 8.6 f l o o d e d 4.0 5. 7 9 2 5-0 7.1 f l o o d e d 9.0 12. 9 7 3 10.0 14-3 f l o o d e d 4.5 6. 4 20 Dec6-8/84 31 .0 44.3 17.0 24. 3 32.0 45. 7 37 Dec8-17/84 1 6.0 8.6 2 2 17.0 24 .3 20 3 11.0 15-7 31 4 17.0 24 .3 19-0 27. 1 1 1 .0 15- 7 20 Marl 9-22/85 1 1 7.0 24 .3 12.0 1 7. 1 15 2 7.0 10.0 4.0 5. 7 7 Mar22-25/85 32.0 45.7 26.0 37. 1 39.0 55. 7 26 Mar28-Apr4/84 1 16.0 22.9 11.0 15. 7 21 .0 30. 0 18 2 14-0 20.0 11 .0 15. 7 1 6 3 11.0 15.7 9 4 20.0 28.6 20.0 28. 6 18.0 25. 7 22 Apr10-21/85 1 27-0 38.6 22.0 31 • 4 28.0 40. 0 31 2 18.0 25.7 6.0 8. 6 21 .0 30. 0 23 3 8.0 11 .4 0.0 0. 0 13.0 18. 6 14 4 8.0 11 .4 4.0 5. 7 8.0 11 . 4 7 5 5-0 7.1 0.0 0. 0 12.0 17. 1 5 Apr22-26/85 1 21 .0 30.0 17.0 24. 3 27.0 38. 6 21 2 8.0 1 1 .4 4.0 5. 7 12.0 17. 1 8 Apr26-May1/85 15-0 21 .4 2.0 2. 9 9.0 12. 9 31 May4-7/85 1 9-0 12 .9 4.0 5. 7 10.0 14. 3 9 2 8.0 11 .4 2.0 2. 9 8.0 11 . 4 8 May10-16/85 1 12.0 17.1 13-0 18. 6 25.0 35. 7 24 2 27.0 38.48 18.0 25- 7 32.0 45. 7 31 144 DATE/ STREAM UNDRAINED FIELD DRAINED FIELD P STORM NO. T p T Q T p T Q T p T Q DURATION {hours) (hours) (hours) (hours) May22-Jun1/85 1 18. ,0 25-.7 20 .0 28. ,6 20. .0 28. ,6 * 2 9. ,0 12. .9 3 .0 4. • 3 3. .0 4. .3 6 Jun6-17/85 1 17. .0 24. • 3 f l o o d e d 12, .0 17. ,1 22 2 35. .0 47. ,1 39 .0 55-,7 41 • .0 58. .6 1 2 * raingage problem ** r e c o r d e r problem, no ink Table 16: t and t Q as estimated from hydrograph a n a l y s i s Review and comparison of the time to peak f o r the stream, drained and undrained f i e l d s gave the f o l l o w i n g o b s e r v a t i o n s : 1) For the m a j o r i t y of storms the undrained f i e l d response was f a s t e r than the stream response, t h e r e f o r e p r e c i p i t a t i o n on the undrained f i e l d c o n t r i b u t e s to stream d i s c h a r g e . 2) For the m a j o r i t y of storms, the groundwater response to p r e c i p i t a t i o n i n the undrained f i e l d was f a s t e r than that i n the drained f i e l d . 3) For approximately 60$ of the storms s t u d i e d , the response of the drained f i e l d to p r e c i p i t a t i o n was slower than the stream response. 4) For almost a l l storm events the groundwater l e v e l was near the s u r f a c e at the begi n n i n g of the storm i n the undrained f i e l d , i n d i c a t i n g very poor n a t u r a l drainage c o n d i t i o n s . G.4.c. peakflow estimates Peak discharge estimates u s i n g the r a t i o n a l formula r e q u i r e d an estimate of C ( d i s c h a r g e c o e f f i c i e n t ) . A weighted value of C 145 was c a l c u l a t e d as o u t l i n e d i n t a b l e 17: Area Slope I n f i l t r a t i o n C FOREST 0.87 >30$ HIGH 0.30 PASTURE 0.12335 10 - 30$' LOW 0.60 LOWLAND 0.00665 <5$ MEDIUM 0.50 Table 17: E s t i m a t i o n of the r u n o f f c o e f f i c i e n t C f o r the A g a s s i z Research Watershed. Th e r e f o r e , the weighted value of C equals 0.31. The f o l l o w i n g t a b l e p r o v i d e s a summary of peak flow estimates as determined u s i n g the weir c a l i b r a t i o n , SCS U n i t Hydrograph method, and the R a t i o n a l formula. The f o l l o w i n g combinations of t and r u n o f f (Q) estimates were used to o b t a i n these r e s u l t s : 1) SCS U n i t Hydrograph Method 1 - t as estimated by the l a g method, and Q ( r u n o f f ) as estimated u s i n g SCS CN method. 2 - t as estimated from hydrograph o b s e r v a t i o n of t , c p and Q as measured from the stream hydrograph. 2) R a t i o n a l Formula 1 - r a i n f a l l i n t e n s i t y (I) determined f o r t as estimated by the l a g method. 2 - r a i n f a l l i n t e n s i t y (I) determined f o r t as estimated from hydrograph o b s e r v a t i o n of t . P 3) R a i n f a l l I n t e n s i t y values - I determined f o r t as estimated by the l a g method - I determined f o r t as estimated from hydrograph o b s e r v a t i o n of t . P WEIR SCS RATIONAL INTENSITY DATE/ 1 2 1 2 1 2 STORM NO. Sept4-8/84 1T25 0795 1T32 IT54 1T55 3745 3750" Sept4-8/85 0.77 0.52 1.26 2.20 1.74 4-91 3-88 Sept20-23/84 0.32 0.11 0.33 0.64 1.31 1-43 2.92 0ct7-14/84 1 0.05 0.00 0.04 0.55 0.12 1.23 0.27 2 0.13 0.00 0.10 0.10 0.18 0.22 0.40 3 1.07 0.41 0.89 0.68 0.77 1-53 1-72 4 0.33 0.73 - 0.57 0.45 1.27 1.00 0ct23-26/84 0.68 0.14 0.51 O.56 0.87 1.25 1-94 Oct27-31/84 1 0.46 1.18 0.28 0.95 0.68 2.13 1.51 2 0.14 0.04 0.17 0.66 0.41 1.48 0.91 Nov18-22/84 1 0.29 0.00 0.38 0.83 0.45 1.86 1.00 2 0.39 0.00 0.69 0.39 0.55 0.87 1.23 3 0.44 0.13 0.36 0.20 0.33 0.45 0.73 Dec6-8/84 0.86 0.78 0.49 0.32 0.57 0.72 1.23 Dec8-17/84 2.17 9-79 1.46 0.43 1-39 0.97 3-10 Marl 9-22/85 1 0.08 0.00 0.03 0.34 0.12 0.77 0.28 2 0.18 0.00 0.24 0.89 0.47 1.99 1.05 Mar22-25/85 0.46 0.04 0.10 0.90 0.29 2.01 0.64 Mar28-Apr4/85 1 0.22 0.00 0.14 0.68 0.33 1-52 0.73 2 0.52 0.04 0.30 0.21 0.55 0.47 1.22 4 0.93 6.76 0.64 0.43 0.76 0.97 1.70 Apr10-21/85 1 0.53 0.01 0.20 0.28 0.24 0.63 0.53 2 0.22 0.00 0.12 0.29 0.18 0.65 0.41 3 0.18 0.00 0.20 0.73 0.28 1.62 0.62 4 0.16 0.00 0.14 0.24 0.15 0.54 0.33 5 0.31 0.00 0.54 0.56 0.35 1.25 0.79 Apr22-26/85 1 0.26 0.00 0.12 0.10 0.16 0.22 0.36 2 0.26 0.00 0.20 0.42 0.28 0.94 0.63 Apr26-May1/85 1.12 1.36 1.31 0.99 1.17 2.22 2.62 May4-7/85 1 0.38 0.00 0.23 0.39 0.38 0.87 0.85 2 0.28 0.00 0.10 0.39 0.20 0.87 0.45 May10-1 6/85 1 0.57 0.00 0.45 0.57 0.35 1.28 0.79 2 0.51 0.00 0.15 0.29 0.20 0.64 0.44 148 DATE/ 1 2 1 2 1 2 STORM NO. May22-Jun1 / 85 • 2 2.79 0.00 0.37 0.63 0.46 1.41 1.02 Jun6-17/85 1 2.18 0.27 0.46 0.64 0.68 1.42 1.53 2 0.61 0.00 0.14 0.05 0.07 0.11 0.15 Table 18: Peak flow estimates A l l peak flow estimates were compared, to the peak discharge as recorded at the weir. Peak flow r e s u l t s u s i n g the r u n o f f (Q) and time of c o n c e n t r a t i o n (t ) as estimated u s i n g the SCS CN procedures present v a r i o u s problems. For many of the storm events, the SCS CN procedure p r e d i c t e d no r u n o f f from the watershed. This t r a n s l a t e d i n t o a zero value f o r peak flow. When r u n o f f was estimated from a l l regions of the watershed, an unreasonably high peak flow was generated (Dec 3-17 1984, and Mar 28-Apr4 1985, storm 4). For the remaining storms with r u n o f f c o n t r i b u t i o n s only from the lowland, the m a j o r i t y of peak flow estimates were underest imated. The SCS u n i t hydrograph approach u s i n g t , and Q as observed c from the stream hydrographs, produces estimates of peak flow that are reasonable but underestimated f o r the m a j o r i t y of storms. The watershed appears to respond slower than the SCS procedures are designed f o r , perhaps i n d i c a t i n g t h a t the u n i t hydrograph approach i s more a p p l i c a b l e i n watersheds g e n e r a t i n g overland flow. A c c o r d i n g to the average SCS dimensionless u n i t hydrograph developed, 3/8 of the t o t a l volume of flow occurs b e f o r e the time to peak. In a watershed e x p e r i e n c i n g subsurface flow, the time 149 to peak may be delayed due to the slower response time of subsurface flow from the f o r e s t e d r e g i o n as compared to the expected response time from an e q u i v a l e n t area g e n e r a t i n g overland flow, and a g r e a t e r p r o p o r t i o n of the t o t a l flow may reach the o u t l e t before peak flow i s a t t a i n e d . The r e s u l t s f o r the peak flow estimates u s i n g the R a t i o n a l Formula p r o v i d e good estimates of peak flow, both u s i n g the t as estimated from the SCS l a g method, and observed from the stream hydrograph. The t from the hydrograph was always longer than the t from the l a g method, t h e r e f o r e c a u s i n g a change i n r a i n f a l l i n t e n s i t y input ( I ) . The r a i n f a l l i n t e n s i t y depends on the d i s t r i b u t i o n of r a i n f a l l i n the storm. For some events, the time of c o n c e n t r a t i o n observed from the hydrograph was longer than the r a i n f a l l event, t h e r e f o r e a reduced r a i n f a l l i n t e n s i t y value (I) was used i n the r a t i o n a l formula c a l c u l a t i o n s . The o b j e c t i v e of u s i n g e i t h e r the SCS u n i t hydrograph approach, or the R a t i o n a l Formula was to be able to apply the methods to ungauged catchments. Therefore, e x c l u d i n g the c a l c u l a t i o n s u s i n g r u n o f f and time of c o n c e n t r a t i o n from the hydrograph r e c o r d s , the R a t i o n a l Formula p r o v i d e s the best estimates of peak flow. 150 H. CONCLUSIONS One of the o b j e c t i v e s of t h i s r e s e a r c h was to evaluate the o p e r a t i o n a l p o t e n t i a l of u s i n g a d i g i t a l e l e v a t i o n model based on an IBM-PC f o r o b t a i n i n g watershed i n f o r m a t i o n as r e q u i r e d by a drainage engineer, or h y d r o l o g i s t . Since most people i n the p o s i t i o n of p r e p a r i n g drainage designs have access to a micro-computer, t h i s could become a r e a l i s t i c component of the design procedures. T h i s r e s e a r c h i n d i c a t e d t h a t the use of d i g i t a l e l e v a t i o n models (DEMs) i n the f i e l d of a g r i c u l t u r a l hydrology has d e f i n i t e p o t e n t i a l b e n e f i t s . The DEM p r o v i d e s a much more accurate r e p r e s e n t a t i o n of the t e r r a i n than do standard NTS 1:50 000 topographic maps. Not only can areas and p r o f i l e s be computed r e t a i n i n g ground t r u t h , but the watershed can be d i s p l a y e d as an image on an image a n a l y s i s system or p l o t t e d as a contour map f o r f u r t h e r a n a l y s i s . The process of c r e a t i n g a DEM f o r a s p e c i f i c watershed by s t e r e o p l o t t i n g then d i g i t i z i n g the r e s u l t a n t map works w e l l . A l e s s labour i n t e n s i v e approach would be to o b t a i n d i r e c t d i g i t a l output from the s t e r e o p l o t t i n g p rocess. Recent trends w i t h i n the mapping agencies of the F e d e r a l government, as w e l l as the P r o v i n c i a l governments of B r i t i s h Columbia and A l b e r t a , suggest t h a t d i g i t a l data w i l l become a v a i l a b l e through data banks. T h i s w i l l e l i m i n a t e the data c o l l e c t i o n process f o r most users (unless l a r g e r s c a l e coverage i s r e q u i r e d than t h a t p r o v i d e d ) , and allow an o p e r a t i o n a l system to be based around an IBM-PC and the software capable of e x t r a c t i n g the s p e c i f i c resource i n f o r m a t i o n . 151 At the present time, the use of a d i g i t a l e l e v a t i o n model f o r on-farm drainage design procedures i s s t i l l a f e a s i b l e approach. S t e r e o p l o t t e r operators are l o c a l l y t r a i n e d at the B r i t i s h Columbia I n s t i t u t e of Technology (BCIT), and s m a l l c o n t r a c t o r s p r o v i d e good work at a reasonable c o s t . D i g i t i z i n g procedures are s t r a i g h t f o r w a r d , and pr o v i d e an a l t e r n a t i v e approach i f l a r g e s c a l e maps a l r e a d y e x i s t f o r the drainage s i t e . The c r e a t i o n of the g r i d data base i n t h i s r e s e a r c h was done on a VAX minicomputer system, but there are microcomputer-based image a n a l y s i s systems a v a i l a b l e at reasonable c o s t s . The computation of a rea and p r o f i l e s anywhere w i t h i n the DEM are e a s i l y performed on the micro-computer. The p o t e n t i a l f o r the a p p l i c a t i o n and f u r t h e r development of d i g i t a l e l e v a t i o n m o d e l l i n g , e s p e c i a l l y i n c o n j u n c t i o n w i t h complete geographic i n f o r m a t i o n systems, i s c e r t a i n l y a f e a s i b l e approach only l i m i t e d by budget r e s t r i c t i o n s and user i m a g i n a t i o n . The SCS CN approach f o r e s t i m a t i n g r u n o f f does not adequately rep r e s e n t the p o t e n t i a l subsurface r u n o f f from f o r e s t e d r e g i o n s . Due to the low r a i n f a l l i n t e n s i t i e s common i n the Ag a s s i z Research Watershed (and consequent low p r e c i p i t a t i o n t o t a l s ) , many storms were p r e d i c t e d to produce no r u n o f f at a l l (assuming t h a t once the i n i t i a l demands of i n t e r c e p t i o n , i n f i l t r a t i o n , and s u r f a c e storage have been s a t i s f i e d ( i n i t i a l a b s t r a c t i o n ) , there i s no r a i n f a l l a v a i l a b l e f o r r u n o f f ) . For the storms s a t i s f y i n g the i n i t i a l a b s t r a c t i o n , r u n o f f was g e n e r a l l y only produced from 1 52 the lowland regions (overland flow) . When extending c o n c l u s i o n s i n t o the r e g i o n , i t should he noted t h a t t h i s r e s e a r c h i s based on 1.5 years of stream di s c h a r g e data. Since the s t a t i s t i c a l approach to r u n o f f e s t i m a t i o n , i . e . r e g r e s s i o n a n a l y s i s , was not evaluated, t h i s r e l a t i v e l y s h o r t data c o l l e c t i o n p e r i o d should not cast doubt on the r e s u l t s . Approximately f o r t y storm events were evaluated d u r i n g the study p e r i o d . I d e a l l y , a longer study p e r i o d a l l o w i n g f o r l a r g e r event storms to occur, p l u s a l l o w i n g a p e r i o d of l o c a l c a l i b r a t i o n then subsequent model t e s t i n g would be i d e a l . The R a t i o n a l Formula appears to be the p r e f e r r e d approach f o r c a l c u l a t i n g peak flows i n t h i s r e s e a r c h . The SCS u n i t hydrograph approach runs i n t o problems when u s i n g the underestimated r u n o f f values from the SCS CN approach. U s i n g r u n o f f and time of c o n c e n t r a t i o n c a l c u l a t e d from the stream hydrographs, the SCS u n i t hydrograph estimates are s t i l l underestimated f o r the m a j o r i t y of storms. This may be due to the procedure b e i n g t a i l o r e d to overland flow g e n e r a t i o n , r a t h e r than subsurface flow as occurs i n f o r e s t e d upland r e g i o n s . A common problem i n peak flow e s t i m a t i o n i s the time of c o n c e n t r a t i o n v a r i a b l e . A l l e s t i m a t i o n procedures evaluated underestimated the time of c o n c e n t r a t i o n as compared to the r e s u l t s from the stream hydrograph a n a l y s i s . U l t i m a t e l y , a s t o c h a s t i c approach u s i n g r e g r e s s i o n r e l a t i o n s h i p s w i t h s i m i l a r watersheds i n the r e g i o n , or a m o d e l l i n g approach which accounts f o r the p h y s i c a l watershed c h a r a c t e r i s t i c s may pro v i d e a more 153 f e a s i b l e approach to both r u n o f f and peak flow e s t i m a t i o n . Review of a p h y s i c a l l y - b a s e d d e t e r m i n i s t i c h y d r o l o g i c model, TOPMODEL, developed by Beven i n d i c a t e d t hat i n i t s present stage, i t i s not y e t i n an o p e r a t i o n a l s t a t e f o r use i n drainage design. Problems i n the treatment of the i n f i l t r a t i o n s t o r e , plus c o n f u s i o n i n parameter d e t e r m i n a t i o n must f i r s t be addressed. P h y s i c a l l y based models, such as TOPMODEL, do however present a a t t r a c t i v e a l t e r n a t i v e to c o n v e n t i o n a l methods of r u n o f f and peak flow e s t i m a t i o n i n theory s i n c e topographic f e a t u r e s of the watershed are a key component. V a r i a b l e source areas can be modelled, an important f e a t u r e i n a f o r e s t e d catchment. Nonetheless, complex, expensive models do not always p r o v i d e b e t t e r r e s u l t s . As a recent study by Loague and Freeze (1985) i n d i c a t e s , s i m p l e r and l e s s data i n t e n s i v e models provide as good or b e t t e r p r e d i c t i o n s than a p h y s i c a l l y based model. I f p h y s i c a l l y based models become l e s s data i n t e n s i v e and more s t r a i g h t forward to use, they may have a f u t u r e p l a c e i n drainage design procedures. The q u e s t i o n of d e a l i n g w i t h r u n o f f from the upland, or seepage i n subsurface drainage design must s t i l l be addressed. An underestimate of r u n o f f used i n subsurface drainage design may r e s u l t i n an underdesigned system. In subsurface drainage design, i t i s a d v i s a b l e to d e a l w i t h any upland r u n o f f input b e f o r e i t reaches the main drainage system. T h i s could be accomplished through i n t e r c e p t i o n of the r u n o f f by e i t h e r a s u r f a c e d i t c h , or an i n t e r c e p t o r d r a i n when s u r f a c e d i t c h i n g would cause an 154 inconvenience i n farming o p e r a t i o n s . An important c o n s i d e r a t i o n i n making d e c i s i o n s r e g a r d i n g subsurface drainage design i n the Lower F r a s e r V a l l e y , i s the r e g i o n a l drainage i n f r a s t r u c t u r e one must work w i t h i n . U l t i m a t e l y , most r e g i o n a l drainage systems handle upland r u n o f f , e s p e c i a l l y d u r i n g the s p r i n g f r e s h e t . But, as a g r i c u l t u r e spreads i n t o the f r i n g e s of the lowland, and i n t o p a r t s of the upland, many farms are not p r o t e c t e d by the r e g i o n a l drainage system, and are s u b j e c t to the l o c a l e f f e c t s of the adjacent uplands. Such subsurface p r o j e c t s must ensure t h a t adequate o u t l e t s e x i s t , e i t h e r v i a the n a t u r a l drainage system or m u n i c i p a l d i t c h e s nearby. Accurate upland r u n o f f estimates are c r u c i a l f o r s u c c e s s f u l subsurface drainage design f o r lowland a g r i c u l t u r e adjacent to upland r e g i o n s . 155 I. REFERENCES Allam, M.M. 1982. A c q u i s i t i o n of d i g i t a l t o pographic data and the need f o r a s t a n d a r d i z e d d i g i t a l data base. Proc. I n t . Soc. f o r Photogrammetry and Remote Sensing, Commission 4, C r y s t a l C i t y , Va, Aug. 22-28, 1982, pp. 1-12. A l l d e r , W.R., V.M. Caruso, R.A. P e a r s a l l , and M.I. Troup. 1982. Proc. Auto-Carto 5, Int.' Symp. on Computer-Assisted Cartography, C r y s t a l C i t y , Va., Aug. 22-28, 1982,pp. 23-52. Baehr, B.E. 1980. Drainage System Design and Implementation i n Southwestern B r i t i s h Columbia. In: Proceedings of the 1980 S p e c i a l t y Conference I r r i g a t i o n and Drainage Todays Challenges. J u l y 22-25, 1980. Boise Idaho. American S o c i e t y of C i v i l Engineers. pp. 244-279-Bertrand , R.A. and Wood, R.C. 1983. S o i l Management Handbook f o r the F r a s e r V a l l e y . S o i l s Branch B.C. M i n i s t r y of A g r i c u l t u r e and Food. 94p. Betson, R.P. 1964- What i s watershed r u n o f f ? : J . Geophys. Res., 69(8): 1541-1552. Beven, K.J., and M.J. K i r k b y . 1976. Towards a simple, p h y s i c a l l y - b a s e d , v a r i a b l e c o n t r i b u t i n g area model of catchment hydrology. School Geog., Univ. Leeds, Leeds, work. Pap. No. 154-Beven K. 1977. TOPMODEL - A P h y s i c a l l y - B a s e d V a r i a b l e C o n t r i b u t i n g Area H y d r o l o g i c m o d e l l i n g program. School Geog., Univ. Leeds, Leeds, Work. Pap. No. 183-Beven, K.J. and M.J. K i r k b y . 1979- A p h y s i c a l l y based, v a r i a b l e c o n t r i b u t i n g area model of b a s i n hydrology. H y d r o l o g i c a l Sciences B u l l e t i n , 24(1):43-69. Beven, K.J., and E.F. Wood. 1983- Catchment Geomorphology and the dynamics of r u n o f f c o n t r i b u t i n g areas. J o u r n a l of Hydrology, 65:139-158. Beven, K.J., M.J. K i r k b y , N. S c h o f i e l d , and A.F. Tagg. 1984-T e s t i n g a p h y s i c a l l y - b a s e d f l o o d f o r e c a s t i n g model (TOPMODEL) f o r three U.K. catchments. J o u r n a l of Hydrology, 69:119-143. Beven, K. 1985. Runoff p r o d u c t i o n and f l o o d frequency i n catchments of order n: an a l t e r n a t i v e approach. Submitted to J o u r n a l of Hydrology f o r p u b l i c a t i o n . 1 56 B o n d e l i d , T.R., McCuen, R.H., and Jackson, T.J. 1982. S e n s i t i v i t y of SCS Models to Curve Number V a r i a t i o n . Water Resources B u l l e t i n 1 8 ( 1 ) : 1 1 1 - 1 1 6 . Chow, V.T. 1964- Handbook of A p p l i e d Hydrology. New York: McGraw-Hill Book Co. C o l l i n s , S.H. 1975- T e r r a i n Parameters D i r e c t l y From a D i g i t a l T e r r a i n Model. Le Geometre Canadien. 29(5):507-518. C o l l i n s , S.H. 1979. R e s e r v o i r Areas and C a p a c i t i e s from D i g i t a l E l e v a t i o n Models. Proc. ASP. Ann. Meet., 45th, Washington, DC, Mar. 18-24, 1979, V o l . 1, pp. 311-520. Dickey, E.C., M i t c h e l l , J.K., and Scarborough, J.N. 1979- The C a l i b r a t i o n and o p t i m i z a t i o n of H y d r o l o g i c Models on s m a l l watersheds having mi l d topography. Proc. ASAE and CSAE summer meeting, June 24-27, 1979, U n i v e r s i t y of Manitoba, Winnipeg, Manitoba, 19p. Dunne, T., Moore, T.R., and T a y l o r , C.H. 1975- R e c o g n i t i o n and P r e d i c t i o n of Runoff-Producing zones i n Humid areas. H y d r o l o g i c a l Sciences B u l l e t i n 20(3):305-327. Ebner, H., and R e i s s , P. 1984. Experience w i t h Height I n t e r p o l a t i o n by F i n i t e Elements. Photogrammetric E n g i n e e r i n g & Remote Sensing. 50(2), pp. 177-182. Engman, E.T. and Rogowski, A.S. 1974- A p a r t i a l area model f o r storm flow s y n t h e s i s . Wat. Resour. Res. 10(3), pp. 464-472. F a r l e y , D.W. 1985- Hydrodynamic M o d e l l i n g of R i v e r s with T e r r a i n Data. Workshop on T e r r a i n Mapping, V i c t o r i a , B.C., November 1-2, 1985, 25p. F r o e h l i c h , H.A., and V.S. Hess. 1976. Oregon S t a t e U n i v e r s i t y i n f i l t r o m e t e r users manual. School of F o r e s t r y , Oregon S t a t e U n i v e r s i t y , C o r v a l l i s , Oregon. Hawkins, R. 1980. I n f i l t r a t i o n and Curve Numbers: Some Pragmatic and T h e o r e t i c R e l a t i o n s h i p s . Proc. Symposium on Watershed Management, J u l y 21-23, 1980, B o i s i , Idaho, pp. 925-951. Hedgey, F. 1986. Pe r s o n a l Communication. B r i t i s h Columbia M i n i s t r y of F o r e s t s , P l a n n i n g and Inventory Branch. V i c t o r i a , B r i t i s h Columbia. 157 Hewlett, J.D. 1961. S o i l moisture as a source of base flow from steep mountain watersheds. Southeast F o r e s t Expt. Sta., Paper 152, 11 pp. Hewlett, J.D., and A.R. H i b b e r t . 1967. F a c t o r s a f f e c t i n g the response of s m a l l watersheds to p r e c i p i t a t i o n i n Humid areas. In: W.E. Sooper and H.W. L i l l ( E d i t o r s ) , I n t e r n a t i o n a l Symposium on F o r e s t Hydrology. Pergamon, Oxford, pp. 275 290. Hope, A., and Schulze, R. 1982. Improved Estimates of Stormflow Volume U s i n g the SCS Curve Number method. In: (V.P. Singh, E d i t o r ) , R a i n f a l l Runoff R e l a t i o n s h i p Proc. I n t e r n a t i o n a l Symposium on R a i n f a l l - R u n o f f Modeling, May 18-21, 1981, M i s s i s s i p p i S tate U n i v e r s i t y , M i s s i s s i p p i S t a t e , Water Resources P u b l i c a t i o n s , Colorado, pp. 419-428. Hornberger, G.M., K.J. Beven, B.J. Cosby, D.E. Sappington. 1985. C a l i b r a t i o n of TOPMODEL to White Oak Run. V i r g i n i a . Submitted to Water Resources Research f o r p u b l i c a t i o n . Horton, R.E. 1933- The r o l e of i n f i l t r a t i o n i n the h y d r o l o g i c a l c y c l e . Trans. Am. Geophys. Union. 14, pp. 446-460. H u e g l i , P., S t e i d l e r , F., and Zumofen, G. 1984. A Program f o r I n t e r p o l a t i o n and P l o t t i n g of D i g i t a l Height Models. Proc. ASP-ACSN Ann. Meet., 50th, Washington, D C , Mar. 11-16, 1984, pp. 662-671. K i r k b y , M.J. 1976. Hydrograph m o d e l l i n g s t r a t e g i e s . In: R. P e e l , M. Chisholm and P. Haggett ( E d i t o r s ) , Processes i n P h y s i c a l and Human Geography. Academic Press, London, pp. 9-90. Kerr, J . 1979. Geographic Data Bases. Proc. The Seminar on D i g i t a l T e r r a i n Models, U n i v e r s i t y of Guelph, School of E n g i n e e r i n g , Guelph, Ont, Oct 5 - 7 , 1979, pp. 5 2 - 5 5 . Langford, G. 1986. P e r s o n a l Communication. A l b e r t a Department of Energy and N a t u r a l Resources. Resource E v a l u a t i o n and P l a n n i n g D i v i s i o n . Edmonton, A l b e r t a . L i n s l e y , R.K. J r . , Kohler, M.A., and Paulhus, J.L. 1958. Hydrology f o r Engineers. New York: McGraw-Hill Book Company Inc., 340p. L i n s l e y , R.K. J r . , Kohler, M.A., and Paulhus,J.L. 1982. Hydrology f o r Engineers, T h i r d E d i t i o n . New York: McGraw-H i l l Book Company Inc., 508 p. 1 58 Loague, K.M., and Freeze, R.A. 1985. A Comparison of R a i n f a l l - R u n o f f Modeling Techniques on Small Upland Catchments. Water Resources Research, 21 (2):229-248. Lowrey B. 1980. H y d r o l o g i c a l Parameters A f f e c t i n g Overland Flow i n an A g r i c u l t u r a l Watershed. Ph.D. T h e s i s . Oregon S t a t e U n i v e r s i t y - C o r v a l l i s . Univ. M i c r o f i l m s i n t . , Ann Arbor, Mich. ( D i s s . Abstr 41:2401-B) L u t h i n , J . 1978. Drainage E n g i n e e r i n g . New York: Robert.E. K r i e g e r P u b l i s h i n g Co., 281 p. Luttmerding, H.A., and Sprout, P.N. 1967. S o i l Survey of Aga s s i z Area, P r e l i m i n a r y Report No. 8. Kelowna, B.C., B r i t i s h Columbia Department of A g r i c u l t u r e , 112p. McCuen, R.H. 1982. A Guide to H y d r o l o g i c A n a l y s i s u s i n g SCS methods. Englewood C l i f f s ; P r e n t i c e H a l l Inc., 145p. Meeuwig, R.O. 1971. I n f i l t r a t i o n and water r e p e l l i n g i n g r a n i t i c s o i l s . USDA F o r e s t S e r v i c e , Research Paper INT-I I I , I n t e r n a t i o n a l F o r e s t and Range Exp. St a . , Ogden, Utah. M i l l e r , N. 1979- Un i t e d States Department of A g r i c u l t u r e , S o i l C o n s e r v a t i o n S e r v i c e , Lanha, Maryland. Molnau, M., and Mesu, F.P. 1983. Hydrographs f o r a Winter Runoff Regime Watershed. Proc. ASAE PNP Annual Meeting, 0ct12-14, 1983, V i c t o r i a , B r i t i s h Columbia, 17p. R a u d k i v i , A.J. 1979. Hydrology An Advanced I n t r o d u c t i o n to H y d r o l o g i c a l Processes and M o d e l l i n g . New York: Pergamon Press, 479p. R o s s m i l l e r , R. 1982. R a t i o n a l Formula R e v i s i t e d . Proc. Conference on Stormwater D e t e n t i o n F a c i l i t i e s . New York: American S o c i e t y of C i v i l E ngineers, pp. 146-162. Sawayama, G. 1985. Per s o n a l Communication. Computerized T e r r a i n Mapping f o r B.C. An Industry/Government I n i t i a t i v e . Workshop on T e r r a i n Mapping, V i c t o r i a , B.C., Nov 1-2, 1985. Smedema, L., and R y c r o f t , D. 1983. Land Drainage: P l a n n i n g and Design of A g r i c u l t u r a l Drainage Systems. New York: C o r n e l l U n i v e r s i t y Press, 376 p. Smith, R.E. 1976. Approximations f o r V e r t i c a l I n f i l t r a t i o n Rate P a t t e r n s . Trans. Am. Soc. AG. Eng. 19(3):505-509. Sondheim, M. 1986. Per s o n a l Communication. B.C. M i n i s t r y of Environment, Surveys and Resource Mapping Branch. 159 USDA, S o i l C o n s e r v a t i o n S e r v i c e . 1972. N a t i o n a l E n g i n e e r i n g Handbook, S e c t i o n 4, Hydrology. USGPO Washington, D.C.. White, D.L. 1981. USGS D i g i t a l E l e v a t i o n Model Data Base. I n t r o d u c t i o n to D i g i t a l Image A n a l y s i s of Remotely Sensed Data f o r Bureau of Land Management. Sioux P a l l s : U.S. G e o l o g i c a l Survey, Eros Data Center, pp. 1-5-Whitney, S. 1985. Western F o r e s t s . New York: A l f r e d A Knopf Inc.. 671 p. Wong, C. 1985. Personnal Communication. Data C o l l e c t i o n f o r DEMs. Workshop on T e r r a i n Mapping, V i c t o r i a , B.C., Nov 1-2, 1985. APPENDICIES 161 APPENDIX A 1 62 1 64 APPENDIX B 166 APPENDIX C PROGRAMS FOR CALCULATING AREA •include <stdio.h> POLY.C Idefine COL 1 char gridCMAXROU][MAXCOL]; •ain(argc,argv) int argc; char largvCl; int rlast, dast, r, c, r l , cl, rint, cint; /* initialize the grid XI for (r = 0; r < HAXROU; r++) for (c = 0: c < MAXCOL; c+t) gridCr][c] = 0; It read the interior point tl scanfCXd Xd",fcrint,fccint); It read the first point */ scanfCXd Id'.lrl.lcDj rlast = rl ; dast = cl; It read nev (r c) points and draw the edges tl while(l){ scanfCZd ",ir); if(r == -1) break: scanfCZd',k); line(rlast,clast,r,c,2); rlast = r; dast = c; fprintf(stderr, "Working . . . relax\n'); It join the last point to the first point tl line(rlast,clast,rl,cl,2); /{ f i l l the interior with ones tl fill(rint,cint,2); /* write the grid */ for (r = 0; r < HAXROU; r++) for (c = 0: c < NAXC0L: ctt) putc(grid[r][cJ,stdout); exit(0); Iine(rl,cl,r2,c2,colour) int rl,cl,r2,c2,colour; double rinc, cine, length, tlen, r, c; int i; It Based on the sinple DDA froa Neumann and Sproull tl length = r2 - r l ; if (length < 0.0) length *= -1.0; tlen = c2 - d ; if (tlen < 0.0) tlen t= -1.0; if (tlen > length) length = tlen; i f (length != 0.0) { rinc = (r2 - rl)/length; cine = (c2 - cl)/length; r = r1; c = cI; for (i = 0; i < length; i++) { gnd((int)r][(int)c] = colour; r += rinc; c •= cine; } } \ f i lUrseed, cseed, colour) int rseed, cseed, colour; { static int nevgyrom = (3,0,1,2,3,0,1); static int i n c H J M i m = It LEFT FRONT RI6HT BACK */ { { (O . - l l , (-1,0), (0, 1), (1, <)•}>}, It NORTH 1/ { {-1,0}, (0, 1), (1, 0), (0.-1) ), /* EAST */ { (0, 1), (1, 0), (0.-1), {-1,0} ), /* SOUTH */ { (1, 0), {0,-11, {-1,0}, (0, 1} }); It WEST tl struct coord (int r, c;} current, new; int gyro, idx, turn; while(!gridCrseed](cseed]) It aove left to periaeter tl cseed—; cseed++; gyro = NORTH; /* start pointing NORTH tl current.r = rseed; current.c = cseed; vhile(l){ if(!grid[current.r3[current.c]) for(idx=current.c : idx < MAXCOL; idx*+) It l i t line tl if(gridfcurrent.rlf.idx]) break; else gridfcurrent.rHidx] = 1; for(turn=0;;turn++){ new.r = current.r + inctgyroHturnlfROW]; new.c = current.c + incCgyrolCturnKCOLl; if(gridCnew.rlfnew.c] != colour) break; current.r = new.r; current.c = new.c; if(current.r == rseed i i current.c == cseed) break; gyro = newgyrofgyro + turnl; } mtttmtttttttntttttttttttttntmttttttttttttttttmtttttttmmmm r e i - Brignal oy^riarlt Hajka A R E A , a e 191 -Additions and adaptation to DeSaet C by Francois Ouioulin purpose: To coapute the area within a polygon, usage: area aask -c cosi [-help] C-nr rows] [-nc c o l s ] options: - a aask naie of task f i l e - c cosi naae of cosi f i l e -help help aessage -nr rows nuaber of rows -nc c o l s nuaber of colunns ttmttttmttttttttttttttttttttttttttttttttnttmttntttnttttttttttttttt ti • i n c l u d e <stdio.h> tdefine GETARS(X) getarg(X,argc,argv) i d e f i n e HAXROU 300 Idefine MAXCOL 168 s t a t i c char PR06NANEC] = " a r e a " , USA6EH = "Usage: area - a aask - c cosi [-help] C-nr rows] [-nc c o l s ] \ n " ; aain(argc,argv) i n t argc; char * a r g v U ; FILE * c f p , * a f p , I fopenO; int row, c o l , argn, aaxrow = MAXROW, aaxcol = HAKCOL; double area, c o s i , i , aask; It parsing the cosaand l i n e tl i f (GETARGChelp")) Bessout("Xs\n", USAGE); i f (argn = 6ETARG('nr")) aaxrow = atoi(argv[++argn]); i f (argn = GETARGCnc")) aaxcol = atoi(argv[++argnl); i f (argn = GETARG(V)) afp = fopen(argv[++argnl,"r"); else aessoutCno aask f i l e s p e c i f i e d ! \ n X s \ n " , USAGE); i f (afp == NULL) aessout( 'can't open aask f i l e ! \ n " ) ; i f (argn = 6ETAR6("c")) cfp = fopen(argv[++argn] ,V) ; else cfp = s t d i n ; i f (cfp == NULL) aessout("can't open cosi f i l e ! \ n " ) ; It the job tl for (row = 0, area = 0.0 : row < oaxrow : row++) for (col = 0 ; col < uaxcol ; coin) { eask = (unsigned) fgetc(nfp); cosi = (unsigned) fgetc(cfp); i f (task) area += 255.0 / (cosi t task): } printf("area = Xlf\n",area); exit(0); It function getarg: get arguments on coamand line tl getarg(desig,argc,argv) int argc; char loesig, targvf.1; int argn; char nnus[2), lookfor[12]; strcpyCtsinus,"-"); strcpydookfor,sinus); strcaulookfor,desig); for (argn = 1; argn < argc; argn++) i f (!strcip(argv[argn],lookror)) return(argn); return (0); /* function lessout: error aessages tl •essout (isg, pari, par2, par3, par4) char lasg, {pari, Ipar2, Ipar3, Ipar4; { fprintf(stderr, "Xs: PR06NAME); fprintf(stderr, isg, pari, par2, par3, par4); fprintf(stderr, "Vn'); ex i t ( l ) ; } /I end of function nessout tl PROGRAM FOR CALCULATING PROFILES 173 /mtmtmmmtmmmmtmmmmmmmmmw IX Copyright (c) 1985 tl. IX Marc S. Najka - UBC Laboratory for Coaputational Vision tj IX Permission is hereby granted to copy a l l or any part of 1/ IX this prograa for non-coaaercial use. The author's name 1/ It and this copyright notice lust be included in any copy, tl mtxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxtxxtxtxtxttxxttxxxttnttxtx/ IX /t profile - construct an intensity profile of an iaage */ It synopsis: profile IX options: - i i f f (Xs) IX (input image f i l e , default = stdin) /* -r n (Xd) IX (nuiber of rows) IX -c n (Xd) It (nuiber of columns) /* -p r l c l r2 c2 (Xd Xd Xd Xd) It (start and end points) IX -s n (Xd) IX (nuaber of steps) /* -d f (XIf) It (step size. Ignored i f -s given) /I -help It (print options suanary and exit) /{ compile: cc -o profile profile.c - l a IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXtXXXXXXXXXXXI •include <stdio.h> •include <aath.h> •define MAXIM 1024 •define GETARG(X) getarg(X,argc,argv) •ain(argc,argv) int argc; char largvL]; FILE *ifp, tfopenO; int i , j . argn, r l , c l , r2, c2, reverse, step, nstep, a, b; int rowxl, rowx2, nrows, ncols; long iline[2][MAXIM], pix, vOO, vOl, vlO, v l l : double rc, cc, dist. i va l , theta, dr. dc, scale, ssize; double sqrO, sqrtO, interpO, s inO, cost), acosO; unsigned getpixi); i f (GETARGChelp")) { fprintf(stderr,"useage: profile [-i i f f ] t - r n] I- c n) C-p r l c l r2 c2] f -s nl [-d f)\n"); fprintf(stderr," - i i f f = input iaage file\n")( fprintf(stderr," -r n = nunber of rows in iaage t300)\n"); fprintf(stderr," -c n = nuaber of coluans in iaage C2003\n"); fprintf(stderr," -p r l c l = start point\n"); fprintf(stderr," r2 c2 = end point\n"); fprintf(stderr," -5 fprintf(stderr," -d exit(0); n = nuaber of steps\n"); f = step size (float)\n l); i f (argn = 6ETAR6("i")) ifp = fopen(argv[++argn),"r"); else ifp = stdin; i f (ifp == NULL) { fprintf(stderr,"profile: can't open input iaage\n"); exit ( l ) ; i f (argn = GETAR6("r")) nrows = atoi(argvl++argn]); else nrows = 300; i f (argn = 6ETAR6(V)) ncols = atoi(argv[++argnJ); else ncols = 200; i f (argn = GETARG("p")) { r l = atoi(argvC+*argn]); c l = atoi(argv[+*argn]); r2 = atoi(argv[++argn]); c2 = atoi(argvf>+argn]); else { fpr in t f (s tderr ,"s tar t ing row and column: ° ) ; scanfCXd Z d " , i r l , f c c l ) ; fpr intf (s tderr ," ending row and column: " ) ; scanfCXd X d " , i r 2 , k 2 ) ; i f (argn = GETARGCs")) nstep = atoi(argv[++argn]); else i f (argn = GETARGCd")) { sscanf(argv[++argn3,'Xlf",&ssize); dist = sgrt(sqr((double)(r2 - r l ) ) + sqr((double)(c2 - d ) ) ) ; nstep = 0.5 + dist / ss ize; } else { . fprintf(stderr,"nuaber of steps: " ) ; scanfCXd",nstep); li sort the points so that r l i s less than r2 XI reverse = 0; i f ( r l > r2) { fp r in t f t s tder r , "prof i l e : can't scan froa (Xd Xd) to (Xd Xd)\n", r l , d , r 2 , c 2 ) ; fpr int f (s tderr ," p ro f i l e w i l l be (Xd Xd) to (Xd Xd)\n", r 2 , c 2 , r l , c l ) ; reverse = 1 ; i = r l ; r l = r2; r2 = i ; i = c l ; c l = c2; c2 = i ; It love down to start ing row tl for ( i = 0; i < r l ; i++) for (j = 0; j < ncols; j++) pix = getpix( i fp) ; It i n i t i a l i z e tl rc = r l : cc = c l ; a = 0; b = 1; rowxl = r l ; rowx2 = r l + 1; t . . It read the next two rows tl for ( i = 0; i < ncols; i++) i l i n e C a l C i J = getpix( i fp) ; for ( i = 0; i < ncols; i++) i l i n e C b l C i l = getpix( i fp) ; /{ calculate distance and angle between the two points tl dis t = sqrt(sqr((double)(r2 - r l ) ) t sqr((double)(c2 - d ) ) ) ; theta = acos((double)(r2 - r l ) / d i s t ) ; /{ find delta r and delta c steps tl dr = cos(theta) t dist / Tdouble)(nstep - 1); dc = sin(theta) I dist / (double)(nstep - 1); i f ( c l > c2) dc t= -1.0; It f i r s t point (easy) tl i v a l = i l i n e C a l t c l l ; pr intf("X8.2f X8.2f Z 8 . 2 f \ n " , r c , c c , i v a l ) ; rc += dr; cc += dc; /{ now step by delta r and delta c along the prof i l e tl for (step = 1; step I nstep; step<-+) { It decide i f lore rows Bust be read tl while (rc > (double)rowx2) { rowxl++; rowx2++; a = !a; b = !b; for ( i = 0; i < ncols; i++) i l i n e t b l t i ] = getpix( i fp) ; } } It get the 4 neighbouring pixels and interpolate at (rc cc) XI vOO = ilineCa][(Fnt)cc]; vol = ilineCaH(int)(cc + 1.0)1; vlO = iline[b][(int)cc]; v l l = ilinefb][(int)(cc + 1.0)]; ival = interp((double)(rc - (int)rc).(double)(cc - (int)cc), vO0,vOl,vl0,vll); ' printf('I8.2.f I8.'2f X8.2f\n',rc,cc,ival); rc += dr; cc += dc; fclose(ifp); exit(O); double interp(r,c,v00,v01,vl0,vll) double r, c; long v00,v01,vl0,vll; It bilinear interpolation tl double a, b, v; a = (vlO - vOO) t r + vOO: b = (vll - vOl) t r * vOt; v = (b - a) t c + a; return(v); double sqr(x) double x; { j return(xtx); unsigned getpix (fp) FILE tfp; It reads 8 bits (1 pixel) froa a f i le tl return((unsigned)getc(fp)); getarg(desig,argc,argv) int argc; char loesig, largv[]; int argn; char iinusr.21, lookfor[12]; 5trcpy(Binus,"-"); strcpy(lookfor,ainus); strcat(1ookfor,desig); for (argn = 1; argn < argc; argn+t) i f (!strc»p(argv[argn],lookfor)) return(argn); return (0); 176 APPENDIX D COMPOSITE TOTAL STORM RECESSION CURVE w Lul CO a: < i o t o Q u. O (J) o 0 . 5 0 - 0 . 5 - 1 •1 .5 - 2 . 5 • 3 . 5 • — r SEPT 4 - 8 1984 HYDROGRAPH R E C E S S I O N A N A L Y S I S / T T T ~ i n i n I I I i n i i i i n I I i i n I I I T T T T T I I I I I I I I I I I I I I I I I I t i l I I I I I I 1 9 2 3 3 7 11 1 5 1 9 2 3 3 7 11 1 5 1 9 2 3 3 7 11 1 5 1 9 2 3 3 7 TIME (hours) SEPT 4 - 8 1985 HYDROGRAPH R E C E S S I O N A N A L Y S I S 21 3 9 1 5 21 3 9 1 5 21 3 9 1 5 21 3 9 1 5 TIME ( h o u r s ) SEPT 16 - 19 1985 HYDROGRAPH R E C E S S I O N A N A L Y S I S OCTOBER 23 - 26 1984 HYDROGRAPH R E C E S S I O N A N A L Y S I S O c t 2 3 1 4 2 0 2 8 1 4 2 0 2 8 1 4 2 0 2 8 1 4 2 0 TIME ( h o u r s ) OCTOBER 27 - 31. 1984 HYDROGRAPH R E C E S S I O N A N A L Y S I S 0 . 5 - i 1 1 j r j 1 1 1 1 r - j - | — | T 0 1 4 2 0 2 8 1 4 2 0 2 8 1 4 2 0 2 8 1 4 2 0 2 8 1 4 2 0 TIME ( h o u r s ) CO UJ CD DC < I O (/) Q U. O o o 0 . 5 o - 0 . 5 -1 - 1 . 5 - 2 - 2 . 5 , - 3 • 3 . 5 DEC 6 - DEC 9 1984 HYDROGRAPH R E C E S S I O N A N A L Y S I S 1 1 1 1 1 M i l l T T T I I I I M i l l I I I I I I I I I I I I I I I I I 1 0 1 6 2 2 4 1 0 1 6 2 2 4 1 0 1 6 2 2 4 1 0 1 6 TIME ( h o u r s ) CO 184 APPENDIX E SEPT 4- 81985 HYDROGRAPH 0 . 8 S e p t 4 S e p t 5 8 1 2 1 6 S e p t 6 8 1 2 1 6 S e p t 7 8 1 2 1 6 S e p t 8 8 1 2 1 6 TIME ( h o u r s ) SEPT 20 - 231984 HYDROGRAPH 188 NOVEMBER 18-221984 HYDROGRAPH 0 . 5 - | 1 1 1 1 1 r 1 1 — r - ] 1 1 r 0 . 4 5 1 N o v 1 8 6 1 2 1 8 N o v 1 9 6 1 2 1 8 N o v 2 0 6 1 2 1 8 N o v 2 1 6 1 2 1 8 N o v 2 2 TIME ( h o u r s ) 1 92 DEC 9 - DEC 17 1984 HYDROGRAPH 2 . 2 D e c 9 D e c l O 1 2 D e c 1 1 1 2 D e c 1 2 1 2 D e c 1 3 1 2 D e c 1 4 1 2 D e c 1 5 1 2 D e c 1 6 1 2 D e c 1 7 TIME ( h o u r s ) ^ 195 ( S / U J ) B o a v H O S i a MARCH 28 - APRIL 5 1985 HYDROGRAPH UJ O a: < o 00 Q 0 . 9 0 . 8 0 . 7 0 . 6 0 . 5 0 . 4 0 . 3 0 . 2 0.1 M a r 2 8 M a r 2 9 1 2 M a r 3 0 1 2 M a r 3 1 1 2 A p r 1 1 2 A p r 2 1 2 A p r 3 1 2 A p r 4 1 2 A p r 5 TIME ( h o u r s ) APRIL 10- 211985 HYDROGRAPH 0 . 5 5 A p r i l A p r 1 2 A p r 1 3 A p r U A p r 1 5 A p r 1 6 A p r 1 7 A p r 1 8 A p r 1 9 A p r 2 0 A p r 2 1 TIME ( h o u r s ) ^ D I S C H A R G E ( m / ' s ) APRIL 26-MAY11985 HYDROGRAPH A p r 2 6 1 6 A p r 2 7 8 1 6 A p r 2 8 8 1 6 A p r 2 9 8 1 6 A p r 3 0 8 1 6 M a y 1 8 1 6 TIME ( h r s ) MAY 4 - 7 1985 HYDROGRAPH M a y 4 6 1 2 1 8 M a y 5 6 1 2 1 8 M a y 6 6 1 2 1 8 M a y ? TIME ( h o u r s ) IV) o o MAY 10 -161985 HYDROGRAPH V) Ul O OH < X o Q 0 . 6 0 . 5 5 0 . 5 0 . 4 5 0 . 4 0 . 3 5 0 . 3 0 . 2 5 0 . 2 M a y 1 0 1 2 M a y 1 1 1 2 M a y 1 2 1 2 M a y 1 3 1 2 M a y 1 4 1 2 M a y 1 5 1 2 M a y 1 6 TIME ( h o u r s ) O ( s v £ J J ) 3 o y v H o s i a 203 204 APPENDIX E SEPT 4 . - 8 1984- H Y D R O G R A P H A N A L Y S I S 205 H Y E T O O R A P H e a s«pt4 s«pts a 1 2 1 o s«pte a 1 2 1 e s«pt7 a T I M E C h e u r s ) S E P T 4 — 8 1 9 8 4 H Y D R O G R A P H 1 2 i s s * p t a 1.3 1.2 1.1 1 0 . 8 0 . 8 0 . 7 0 . 6 O.S 0.4 0.3 0.2 O.I O r \ L / \ / \ j • v \ \ / \ / / / , -/ SapM- SoptS 8 12 16 Sapt6 8 12 16 TIME (houre) Sspt7 8 12 16 SoptS IO O -IO -20 -30 .4.0 -SO -60 -70 -ao - 9 0 W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS L NDR MNE 0 / / / / / / J / f r T T-I 'J- 1 1 I 1 1 1 1 T t 1" •t r r T I T ' 1 "t T~ 1 TT Sspt4 SoptS 8 12 16 Sept6 8 12 16 Sept7 TIME (hours) a 1 2 16 Septa a S E P T A- — 8 1 9 8 5 H Y D R O G R A P H A N A L Y S I S H Y E T O O R A P H 206 1 3 1 2 1 1 1 0 e A. 12 1 a s*pts a 12 1 e S E P T 4 — 8 1 9 8 5 H Y D R O G R A P H 0.8 0.7 0.6 O.O 0.4 0.3 0.2 0.1 - J O Sspt4 SsptS B 12 16 Sapt6 8 12 16 Sopt7 8 12 16 Septa 8 12 16 T I M E (houna) W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S '. S E P T ZO — 2 3 1 9 8 4 H Y D R O G R A P H A N A L Y S I S 207 H Y E T O G R A P H 7 e 3 2 S « p t 2 0 1 2 1 0 S * p t 2 1 a 1 2 1 6 S s p t 2 2 T I M E ( h s j m ) a 1 2 i a s«pt23 a 1 2 S E P T 2 0 - 2 3 1 9 8 4 - H Y D R O G R A P H "1= 0 . 3 4 0 . 3 2 0 . 3 0 . 2 8 0 . 2 6 0 . 2 4 0 . 2 2 0 . 2 0 . 1 8 O.I 6 0 . 1 4 0 . 1 2 0.1 o.oa o.oe 0 . 0 4 0 . 0 2 o A / -> S e p t 2 0 1 2 1 6 S e p t 2 1 8 1 2 1 6 S e p t 2 2 T I M E ( h o u r s ) 8 1 2 1 6 S o p t 2 3 8 1 2 O 8 1 0 o - 1 0 - 2 0 - 3 0 - 4 0 - 5 0 - B O -70 - B O - B O W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S D R A I h E D S « p t 2 0 1 2 1 6 S e p t 2 1 1 2 1 6 S o p t 2 2 T I M E ( h o u r s ) 8 1 2 1 6 S a p t 2 3 8 1 2 O C T O B E R 7 — U 1984- H Y D R O G R A P H A N A L Y S I S 208 HYETO O RAP H 1 1 i - "**• L IIIM i X 1 IL J Oot712 OotS 12 OotS 12 Oot IO 12 Oot1 1 12 Oot12 12 Oot13 12 Os t14 T I M E C^oura) O C T O B E R 7 - 1 4 1 9 8 4 - H Y D R O G R A P H 1.1 1 0 . 9 o.a 0 . 7 o.a o.s 0 .4 -0 . 3 0 . 2 0.1 o A / \ . \ \ / \ / \ \ \ \ > f J I / O o t " 7 1 2 O o t S 1 2 O c t 9 1 2 O o t I O 1 2 O o t 1 1 1 2 O c t 1 2 1 2 O o t 1 3 1 2 O o t 1 4 T I M E ( . h o u r s ) W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S <T., — . A I r*0 fee ' V V I j J / / / / — TTTTT TTTTT TTTTT TTTTT TTTTT u m TTTTT TTTTT TTTTT TTTTT M i l l TTTTT 2 O — 2 — 4 - 8 — 8 — 1 0 - 1 2 — 1 4 - 1 6 - 1 8 - 2 0 - 2 2 - 2 4 — 2 6 - 2 8 — 3 0 O c t 7 1 2 O o t S 1 2 O c t 9 1 2 O c t I O 1 2 O c t 1 1 1 2 O o t 1 2 1 2 Oot13 1 2 O o t 1 4 T I M E ( h o u r s ) O C T 2 3 — O C T 2 6 1 9 8 4 H Y D R O G R A P H A N A L Y S I S 209 H V E T O O R A P H H Oatu i e O a U 4 a i 2 1 a Ooua a 1 2 1 0 Ootza a T I M E C h o u i n a ) O C T O B E R 2 3 - 2 6 1 9 8 4 - H Y D R O G R A P H 1 2 I S O o U 7 0 . 7 o . s 0 . 3 0 . 4 0 . 3 O.Z 0.1 O o t 2 3 1 6 O c t 2 4 8 1 2 1 6 O c t 2 5 8 1 2 1 6 O c t 2 6 8 1 2 1 6 O c t 2 7 TIMET ( h o u r s ) IO o 1 0 2 0 3 0 4 0 SO a o 7 0 a o W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S U N I IRAII J E D y — tAINI : D • 1 1 1 1 11" • • • . . . • • . • " ' . ' ' . . • . . . O c t 2 3 1 6 O c t 2 4 8 1 2 1 6 O c t 2 S 8 1 2 1 6 O c t 2 6 T I M E ( h o u r s ) 8 1 2 1 6 O c t 2 7 O C T 2 7 — 31 1984- H Y D R O G R A P H A N A L Y S I S 210 H Y E T O O R A P H o e U 7 o o t 2 a a 12 i e o o u a a 12 10 o o t s o a 12 i e o s t a i a 12 1a 20 T I M E ( h o u m ) O C T O B E R 2 7 — 3 1 1 9 8 4 - H Y D R O G R A P H ro; a Oot27 OctZB 8 12 16 Oct29 8 12 16 Oct30 TIME (hours) 8 12 16 OctJI 8 12 16 20 z g (3 s o —5 - 1 0 -15 -20 -23 -30 -35 -40 —45 W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS y L MDI F P RAII JED / / f 11 T *' * 1 . . ' ' ' • • . ' ' ' ' ' ' ' ' ' Oot27 Oct28 8 12 16 Oot29 8 12 16 0ot30 B 12 18 Oot31 TIME (hours) 8 12 18 20 N O V E M B E R 18—22 1984- H Y D R O G R A P H A N A L Y S I S 211 H Y C T O O R A P H -I ill 2.S 2 1.S Novia a 1 2 i s Novie e 12 i a N O V 2 0 e 12 10 N O V 2 1 S 12 1a N o v 2 2 T I M E ( H o u r * } N O V E M B E R 1 8 - 2 2 1 9 8 4 H Y D R O G R A P H W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S N o v 1 8 6 1 0.9 O.S 0.7 o . e O.S 0.3 0.2 D E C e — D E C 9 1 9 8 4 - H Y D R O G R A P H A N A L Y S I S H Y E T O G R A P H 21 2 D E C 6 — D E C 9 1 9 8 4 - H Y D R O G R A P H o . i i o Doc6 16 D«c7 8 12 16 DocB 8 12 16 Qsc9 8 12 1< TIME (hours) W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS JND CD s L5RA NED 7 / / * • • ' ' * • • • • • • • . « > . . • • . • • • • • • IO 20 30 •40 SO e o Doc6 16 Doc7 8 12 16 DecS 8 12 16 TIME (hours) Doc9 8 12 16 D E C 9 — D E C 17 1 9 8 4 H Y D R O G R A P H A N A I _ Y S I S 2 1 3 H Y E T O O R A P H D E C 9 — D E C 1 7 1 9 8 4 H Y D R O G R A P H 2 . 2 2 . 1 2 1 .9 1 . 8 1 . 7 1 . 8 1 . 5 1 . 4 1 . 3 1 . 2 1.1 1 0 . 9 O . S 0 . 7 O . S O . S 0 . 4 0 . 3 W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S M A R C H 19 — 2 2 1 9 8 5 H Y D R O G R A P H A N A L Y S I S 214 H Y E T O O R A P H 1 II I ill 1. J J I l l " idlU 3 .S 3 2 . S 2 1 .a 1 o.a M a r i s 18 2 0 Mar20 4 12 1B 2 0 Mar21 -4-T I M E (hours) a 12 1 a 2 0 Mar22 4 a 12 M A R C H 1 9 — 2 2 1 9 8 5 H Y D R O G R A P H 0 . 1 9 0 . 1 S 0 . 1 7 0 . 1 6 0 . 1 5 0 . 1 4 0 . 1 J 0 . 1 2 0 . 1 1 0 . 1 O . O S o.oa 0 . 0 7 o.oe 0 . 0 5 0 . 0 4 / \ / V \ \ \ V V / \ / \ \ / / 1—1—T~ ~l—1—T— T ' 1 • • T" T—J— 1 I" T-f™ M o r 1 9 1 6 2 0 M a r 2 0 4 1 2 1 6 2 0 M o r 2 1 4 a T I M E ( h o u r s ) 1 2 1 6 2 0 M o i - 2 2 4 8 1 2 O - 1 0 - 2 0 - 3 0 — 4 0 - S O — 6 0 - 7 0 —ao — 9 0 W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S ^ A T N T D " M o r 1 9 1 6 2 0 M a r 2 0 4 8 1 2 1 6 2 0 M a r 2 1 4 T I M E ( h o u r s ) 8 1 2 1 6 2 0 M a r 2 2 4 8 1 2 M A R C H 2 2 — 2 5 1 9 8 5 H Y D R O G R A P H A N A L Y S I S 215 H Y E T O O R A P H •+-° -n 1 1 1 1 1 1 1 1 1 1 1— Mor22 12 IO M a r U O 12 I B Mor24 O 12 1B Mar2S 8 12 T I M E ( h o u n ) M A R C H 2 2 - 2 5 1 9 8 5 H Y D R O G R A P H O . S - i 1 1 1 1 1 1 1 1 1 1 1 r - ^ 1 1 1 E U J S3 M o r 2 2 1 2 1 6 M a r 2 3 I O O - 1 0 - 2 0 - 3 0 -AO -SO - 6 0 - 7 0 - S O - S O S 1 2 1 6 M a r 2 4 TIMET ( h o u r s ) 8 1 2 W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S U N j R A i r I E D «A1NI : D / • • • • • • 1 "?-T~ 1 • • M a r 2 2 1 2 1 6 M o r 2 3 8 1 2 1 6 M o r 2 4 T I M E ( h o u r s ) 8 1 2 1 6 M o r 2 5 8 1 2 M A R 2 8 — A P R 5 1 9 8 5 H Y D R O G R A P H A N A L Y S I S 216 H Y E T O O R A P H M a r 2 B M o r 2 9 1 2 M a r 3 0 1 2 M a r 3 1 1 2 A p i - 1 1 2 A p r 2 1 2 A p r 3 1 2 A p r * 1 2 A p r s T I M E ( h o u r s ) M A R C H 2 8 — A P R I L 5 1 9 8 5 H Y D R O G R A P H U l 3 O 5 1 O.B 0.8 0.7 0.6 O.S 0.4 0.3 0.2 0.1 O j \ / \ \ \ \ f I \ ( —' \ / I O ^ —10 —20 -30 Mar2BMor29 12 Mor30 12 Mar31 12 Apr1 12 Apr2 12 Apr3 12 Apr4 12 AprS TIME (hours) W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS -40 —SO - S O -70 -Km TT TTT TTT TTT UIJCR/Jh El) TTT TTT TTT T D R Al i ^ t / Mor28Mar29 12 MorSO 12 Mor31 12 Apr1 12 Apr2 12 Apr3 12 Apr* 12 AprS TIME (hours) g 2.a 2 . e 2 . 4 2.2 2 L O 1 .a 1 .•* 1.2 1 o.a o.e o.* o.a o A P R I L 10 —,21 1 9 8 5 H Y D R O G R A P H A N A L Y S I S 217 H Y E T O O R A P H A p r i l A p r 1 2 A p r 1 3 A p r 1 4 A p r l O A p r 1 O A p r l "7 A p r l B A p r 1 S A p r 2 0 A p r i l T I M E ( h o u r s ) A P R I L 1 0 — 2 1 1 9 8 5 H Y D R O G R A P H Q 0 . 5 5 O.S 0 . 4 5 0 . 4 0 . 3 5 0 . 3 0 . 2 S 0 . 2 0 . 1 S 0.1 O.OS A \ J f L J \ / / / AJ / r 1 A p r l 1 A p r 1 2 A p r 1 3 . A p r 1 4 A p r l 5 A p r l 6 A p r l 7 A p r l 8 A p r l 9 A p r 2 0 A p r 2 1 T I M E ( h o u r s ) I O W A T E R T A B L E F L U C T U A T I O N S D R A I N E D A N D U N D R A I N E D F I E L D S E o 9 I z § ( 3 — 2 0 - 3 0 — 4 0 - S O - B O - 7 0 A p r l 1 1 2 A p r 1 2 1 2 A p r l 3 1 2 A p r l 4 1 2 A p r 1 5 1 2 A p r l 6 1 2 A p r 1 7 1 2 A p r l 8 1 2 A p r l 9 1 2 A p r 2 0 1 2 A p r 2 1 T I M E ( h o u r s ) April 22 — 26 1 9SS HYDROGRAPH ANALYSIS H Y E T O O R A P H 218 • EI A p r 2 2 1 2 1 8 A p r 2 3 1 2 18 A p r 2 4 e 1 2 18 A f > r 2 S 8 1 2 1 8 A p i - 2 8 T I M E Cr.no) A p r i l 2 2 — 2 6 1 9 8 5 H Y D R O G R A P H 0.26 0.25 0.24 0.23 0.22 0.21 0.2 0.10 0.1s O.I 7 O.I 6 0.13 0.14 0.13 0.12 0.1 1 0.1 0.09 o.oa 0.07 \ \ \ \ \ \ j \ / v / A, v N J \ I / _J • Apr22 12 18 Apr23 6 12 18 Apr24 6 12 TIME (hrs) 18 Apr25 6 12 18 Apr26 10 W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS —10 —20 —30 —40 -SO UND iAINEtl DRAINED — SO — I I I l l i i i i i j i i i ri | i i i i i | i i i—I I I I i i i I I I I I I I I T Apr22 12 18 Apr23 8 12 18 Apr24 6 12 18 Apr23 6 12 18 Apr26 TIME (hrs) A P R I L 2 6 — M A Y 1 1 9 8 5 H Y D R O G R A P H A N A L Y S I S H Y E T O O R A P H 219 I in t II I A p r - 2 6 1 e A p r 2 7 8 1 8 A p r 2 8 8 1 8 A p r i B 8 I B A p r l O T I M E C h n » ) 1 8 M o y l 8 1 8 A P R I L 2 6 — M A Y 1 1 9 8 5 H Y D R O G R A P H 1.3 1.2 1.1 1 O.Q o.a 0.7 o.a o . s o.+ 0.3 0.2 0.1 O a o - o i o i s 20 25 30 35 •+0 AS AprZa 10 Apr27 a 16 Apr28 8 16 Apr20 8 16 Apr30 8 16 May1 8 18 TIME ihrmi W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS / U l I D F (All J E I 1 \ I )R> .INI : D I — / TTT TTT TTT TTT • • • ''' • • • i n u i i n 111 111 111 i n i n i n Apr26 16 Apr27 8 18 Apr28 8 16 Apr29 8 16 Apr30 8 16 Moyl 8 18 TIME (hra) M A Y A- — 7 1 9 S 5 H Y D R O G R A P H A N A L Y S I S 220 H Y E T O O R A P H 3 2 . 0 2 . S SL.A 2.2 May* L I M a y s 1 2 1 8 T I M E ( h a u r « ) M o y S M a y 7 M A Y A 7 1 9 8 5 H Y D R O G R A P H May A 1 2 1 8 . M o y 5 6 1 2 1 8 M a y B 6 1 2 1 8 M a y 7 T I M E ( h o u r s ) 10 W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS — S O | j i i i i i I | i i i i i I i i i i i | i i i i i | I i i i i i | i i i i i | i i i i i | i i i i i | I i i i M a y * 6 1 2 1 8 M o y S 6 1 2 1 8 M a y B 6 1 2 1 8 M a y 7 T I M E ( h o u r s ) M A Y 1 O — 2.1 2 1.0 1 .a 1.7 1 .e 1 .a 1.4 1.3 1.2 1.1 1 o.a o.a 0.7 o.a o.a o.-* 0.3 0.2 0.1 o 16 1 9 8 5 H Y D R O G R A P H A N A L Y S I S H Y E T O O R A P H 221 1 1 1 H i IBH IBB 1 I H i IHi IHB 1 H i IHI IHB 1 H i IH « H 1 H i IH IHH 1 • IH IHI 1 H i IH IHH H i IH IBH H i IH H i H i IH ' HH H i III ' MM* IHi 111 • H • "<.• H 1 • 1 H ; • > • H ' : • . ••• •> m •:: 1 • . 1 1 . H1.;SV- 1 • 1 ->••,.>* Si |...waw.w. 1 M o y 1 O 1 2 M a y l l 1 2 M a y 1 2 1 2 M a y 1 3 1 2 M a y ! 4 1 2 M a y 1 0 1 2 M a y T I M E ( h o u r . ) M A Y 1 0 — 1 6 1 9 8 5 H Y D R O G R A P H o.e o.ss o.s 0 . 4 5 0 . 4 0.3S 0.3 0 . 2 5 0 . 2 10 -10 — 2 0 -30 — 4 0 - S O - 6 0 W A T E R T A B L E F L U C T U A T I O N S D R A I N E D . A N D U N D R A I N E D F I E L D S U N D R A N E C T - 7 0 M a y 1 0 1 2 M a y l 1 1 2 M o y 1 2 1 2 M a y 1 3 1 2 M a y 1 4 1 2 M o y 1 5 1 2 M o y • T I M E ( h o u r s ) M A Y 2 2 J U N E 1 1 9 8 5 H Y D R O G R A P H A N A L Y S I S H Y E T O O R A P H 222 -£ 1 M s y i a M a y U M a y 2 4 J o y J O M a y 2 « M o y 2 7 M a y 2 a T I M E ( h o u r s ) rfoy29 M a y J O M a y 3 1 Jun* 1 M A Y 2 2 - J U N E 1 1 9 8 5 H Y D R O G R A P H 2 . 8 2 . 8 2 . 4 2 . 2 1 . 8 1 . 8 1 . 4 1 . 2 1 O .S 0 . 6 0 . 4 L 0 . 2 -M a y 2 2 M a y 2 3 M o y 2 4 M a y 2 5 M a y 2 6 M a y 2 7 M a y 2 8 M a y 2 9 M a y 3 0 M a y 3 1 J u n s l T I M E ( h o u r s ) 1 0 W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS M a y 2 2 M a y 2 3 M a y 2 4 M a y 2 5 M a y 2 8 M o y 2 7 M a y 2 8 M a y 2 9 M o y 3 0 M o y 3 1 uun«1 T I M E ( h o u r o ) ; J U N E 6 — 1 7 1 9 8 5 H Y D R O G R A P H A N A L Y S I S 223 H Y E T O C S R A P H q Jun7 JunO JunS JunIO Jun11 Jun 12 0un13 J j n U J u n l S J u n i e Jun17 T I M E ( h s j r a ) J U N E 6 - 1 7 1 9 8 5 H Y D R O G R A P H a I z 1 0 - 1 0 —20 -30 -40 -SO -60 Jun7 W A T E R T A B L E F L U C T U A T I O N S DRAINED AND UNDRAINED FIELDS 

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