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Infiltration and surface ponding on a sand-based sportsfield Murrie, W. Trevor 1987

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INFILTRATION AND SURFACE PONDING ON A SAND-BASED SPORTSFIELD by W. TREVOR MURRIE B.A.(Geog-) U n i v e r s i t y o f B r i t i s h Columbia, 1975 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF SOIL SCIENCE We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA AUGUST, 1987 Cop y r i g h t ; W. TREVOR MURRIE, 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of *~^>o\L- ^ c i g p g - E . The University of British Columbia 1956 Main Mal l Vancouver, Canada V6T 1Y3 Date ABSTRACT The t h e s i s addresses the problem o f ponding as i t p e r t a i n s t o sand-based s p o r t s f i e l d s . The Lower Premier S p o r t s f i e l d , i n the D i s t r i c t o f North Vancouver, was s p e c i f i c a l l y s t u d i e d . I t i s l o c a t e d i n a h i g h r a i n f a l l l o c a t i o n . The hypothesis i s t h a t a 'surface l a y e r ' at the top o f the s o i l p r o f i l e was d i r e c t l y r e s p o n s i b l e f o r the reduced s u r f a c e i n f i l t r a t i o n necessary f o r the ponding observed. The accumulation and compaction o f d e t r i t a l o r g a n i c matter w i t h i n the pore space o f t h i s l a y e r was assumed to be the source o f the ponding problem. Pond depth hydrographs were d e r i v e d from f i e l d measurements to i l l u s t r a t e the behaviour o f the pond i n response t o v a r i o u s r a i n f a l l c o n d i t i o n s . Furthermore, a s e m i - e m p i r i c a l model was d e v i s e d to determine the water balance o f the pond f o r an i n c i d e n t r a i n f a l l event. R e s u l t s from the model show t h a t o v e r l a n d flow from the area c o n c e n t r i c a l l y a djacent t o the pond c o n t r i b u t e d approximately f o u r times as much water to the pond as was c o n t r i b u t e d d i r e c t l y by r a i n f a l l . From the a n a l y s i s , i t was determined t h a t a low 'surface l a y e r ' s a t u r a t e d h y d r a u l i c — 8 — 1 c o n d u c t i v i t y , o f the order o f 10 m.s was necessary f o r t h i s t o occur. Recommendations emphasize p r e v e n t a t i v e management t h a t l i m i t s the accumulation o f d e t r i t a l p l a n t matter and the employment of groundskeeping techniques to c o n t r o l the formation o f the h y d r o l o g i c a l l y r e s t r i c t i v e 'surface l a y e r ' . Furthermore, to avoid the c o n c e n t r a t i o n o f s u r f a c e r u n o f f , i t i s e s s e n t i a l t h a t s u r f a c e d e p r e s s i o n s not be allowed to form i n the f i e l d s u r f a c e . i i Table o f Contents ABSTRACT i i i LIST OF TABLES v i LIST OF FIGURES v i i LIST OF SYMBOLS i x ACKNOWLEDGEMENTS x i i i 1. INTRODUCTION 1 1.1 S p o r t s f i e l d s i n a S o i l and Water Management Context 1 1.2 S p o r t s f i e l d s 3 1.2.1 General 3 1.2.2 S a n d f i e l d s 7 1.2.3 The Lower Premier S p o r t s f i e l d 15 1.3 F i e l d Observations 20 1.4 Cl i m a t e 23 1.5 Research O b j e c t i v e s and Hypothesis 27 1.5.1 Research o b j e c t i v e s 27 1.5.2 Hypothesis 31 2. MATERIALS AND METHODS 32 2.1 General 3 2 2.2 S o i l s 32 2.2.1 S o i l p h y s i c a l t e s t s 32 2.2.1.1 P a r t i c l e s i z e f r a c t i o n a t i o n 34 2.2.1.2 P a r t i c l e s i z e a n a l y s i s by s i e v i n g .. 36 2.2.1.3 D e n s i t y o f s o l i d s (p ) 38 2.2.1.4 Bulk d e n s i t y (p^) 3 9 2.2.1.5 P o r o s i t y 40 2.2.2 H y d r o l o g i c a l t e s t s and analyses 42 i i i 2.2.2.1 Sa t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( V 4 2 2.2.2.2 P a r t i a l water r e t e n t i o n c h a r a c t e r i s t i c s 51 2.2.2.3 Determination o f the K(\J> ) c h a r a c t e r i s t i c curve f o r ^ t h e 'North Van 1 sand 54 2.3 F i e l d Measurement Methods 58 2.3.1 S o i l probe core sampling 58 2.3.2 Pond measurement 59 2.3.3 Depth to the w a t e r t a b l e measurements 62 2.4 R a i n f a l l P r e c i p i t a t i o n Data 62 3. RESULTS, ANALYSES, AND DISCUSSION 65 3.1 R e s u l t s from the S o i l P h y s i c a l and H y d r o l o g i c a l T e s t s made on the 'Fraser R i v e r ' and 'North Van' Sands ... 65 3.2 Ponding 75 3.3 The 'Cone' Dimensioned Pond Water Balance Model .... 78 3.3.1 Pond r i s e and r e c e s s i o n 78 3.3.2 S u r f a c e area expansion o f the pond w i t h pond r i s e 85 3.3.3 The pond water balance 87 3.4 The A p p l i c a t i o n o f the Pond Water Balance Model .... 9 3 3.5 The Determination o f the 'Surface Layer' S a t u r a t e d H y d r a u l i c C o n d u c t i v i t y ( K i p ) f o r the Ponded Case ... 97 3.6 Overland flow 109 3.7 The Determination o f the 'Surface Layer' Saturated H y d r a u l i c C o n d u c t i v i t y ( K 1 U ) f o r the Unponded Case 118 4. SUMMARY, CONCLUSIONS, AND MANAGEMENT RECOMMENDATIONS ... 121 4.1 Summary and Co n c l u s i o n s 121 4.2 Recommendations 126 4.2.1 Management recommendations 126 i v 4.2.2 Research recommendations 5. REFERENCES AND BIBLIOGRAPHY 128 130 L i s t o f Tables T a b l e I; 'Topmix' Sand P a r t i c l e S i z e S p e c i f i c a t i o n s .. 17 T a b l e I I ; ' P i t r u n ' Sand P a r t i c l e S i z e S p e c i f i c a t i o n s .. 17 Tab l e I I I ; S o i l Separate S i z e C l a s s i f i c a t i o n 37 Tab l e IV; Sand Separate S i z e , C l a s s Upper L i m i t s (U.S.D.A. C l a s s i f i c a t i o n System) and Corresponding, Wire Mesh S i e v e S i z e s 37 Tab l e V; U.S.D.A. S o i l T e x t u r a l C l a s s i f i c a t i o n o f 'Sand' (U.S.D.A., 1951) 66 Tab l e VI; Sawdust P a r t i c l e S i z e S p e c i f i c a t i o n s 66 Tab l e V I I ; P a r t i c l e S i z e F r a c t i o n a t i o n , S o i l P h y s i c a l P r o p e r t i e s , and H y d r a u l i c C o n d u c t i v i t i e s o f 'Eraser R i v e r ' Sand 70 Tab l e V I I I ; P a r t i c l e S i z e F r a c t i o n a t i o n , S o i l P h y s i c a l P r o p e r t i e s , and H y d r a u l i c C o n d u c t i v i t i e s o f 'North Van' Sand 71 Tab l e IX; Standpipe Readings 7 9 T a b l e X; The Coordinates o f the Pond at Three D i s c r e e t Times 79 T a b l e XI; S o l u t i o n s t o the Volume Terms i n the Water Balance Equation from t 0 t o t , 94 v L i s t o f F i g u r e s F i g u r e 1; Schematic r e p r e s e n t a t i o n o f grass s p o r t s f i e l d c o n s t r u c t i o n s as g i v e n i n l i t e r a t u r e (van Wijk, 1980) 14 F i g u r e 2; Short D u r a t i o n R a i n f a l l , I n t e n s i t y , D u r a t i o n , Frequency Data f o r North Vancouver, Lynn Creek (1964-1983, 19 years) . 19 F i g u r e 3; The Lower Premier S p o r t s f i e l d Depth P r o f i l e . 22 F i g u r e 4; 'Mean Annual P r e c i p i t a t i o n ' i n G r e a t e r Vancouver, (Hay, J . and Oke, T., 1976) 24 F i g u r e 5; Long Term, Mean Monthly Average R a i n f a l l f o r Lynn Creek, North Vancouver 26 F i g u r e 6; S o i l Core Sampling Plan 41 F i g u r e 7; ' F a l l i n g Head' Apparatus f o r D e t e r m i n a t i o n o f Saturated H y d r a u l i c C o n d u c t i v i t y (K ) o f the 'Fraser R i v e r ' Sand 44 F i g u r e 8; 'Constant Head' Apparatus f o r Determination o f H y d r a u l i c C o n d u c t i v i t y (K) o f the •North Van' Sand 4 7 F i g u r e 9; P r e p a r a t i o n o f the Brass Core Ring Permeameter 48 F i g u r e 10; Vacuum S a t u r a t i o n o f the Brass Core Ring Permeameter 50 F i g u r e 11; Hanging Water Column Apparatus 52 F i g u r e 12; I n f i l t r a t i o n Column Apparatus f o r Determining K(v|»p) 56 F i g u r e 13; Standpipe L o c a t i o n s 60 F i g u r e 14; Pond R i s e and R e c e s s i o n Measurement Apparatus 61 F i g u r e 15; Recording Rain Gauge D a i l y Charts f o r Lynn Creek, North Vancouver (82-04-14 and 82-04-16) 64 F i g u r e 16; Cumulative P a r t i c l e S i z e D i s t r i b u t i o n o f the 'Fraser R i v e r ' Sand 67 F i g u r e 17; Cumulative P a r t i c l e S i z e D i s t r i b u t i o n o f the 'North Van' Sand 68 v i F i g u r e 18; P a r t i a l Water R e t e n t i o n Curves; 9(\J> ) 73 F i g u r e 19; P a r t i a l Unsaturated H y d r a u l i c C o n d u c t i v i t y , K(^p)/ C h a r a c t e r i s t i c Curves f o r 'North Van' Sand (<2.00 mm f r a c t i o n ) 74 F i g u r e 20; Pond Depth Hydrograph (82-04-14) and Depth to the Water Tab l e 76 F i g u r e 21; Pond Depth Hydrograph (82-04-16) 77 F i g u r e 22; Pond Dimensions (82-04-14) 80 F i g u r e 23; Pond Depths (82-04-16) 82 F i g u r e 24; A vs H p f o r the 'Cone' Dimensioned Pond 88 F i g u r e 25; Volume (Q) vs Slope; (9) 89 F i g u r e 26; The Pond Water Balance 91 F i g u r e 27; Water P o t e n t i a l P r o f i l e s (\|> , \|) , and \|> ) versus Depth (z) ?...? 101 F i g u r e 28; L o c i o f S o l u t i o n s f o r the H y d r a u l i c C o n d u c t i v i t i e s , K i p and K 2 p , i n the Composite 'Top Layer' Under the Pond 107 F i g u r e 29; I n f i l t r a t i o n Rate (q i rj) i n the Unponded Area vs the R a i n f a l l P a r t i t i o n i n g C o e f f i c i e n t (v) 110 F i g u r e 30; The I m p l i c i t F u n c t i o n Q Q ( A T 0 T , v) 112 F i g u r e 31; A T Q T vs Slope; (9) 114 F i g u r e 32; AQ/At vs q p 117 v i i LIST OF SYMBOLS c r o s s - s e c t i o n a l area o f the permeameter (m ) ' e f f e c t i v e ' pond area r e p r e s e n t i n g the b a s a l area i n the cone dimensioned ponding model (m ) 2 t o t a l catchment area (m ) c r o s s - s e c t i o n a l area o f the sta n d - p i p e used i n the F a l l i n g Head Permeameter T e s t Apparatus (m ) exponent used i n the s e m i - e m p i r i c a l model developed by Campbell (1974) f o r i n f e r r i n g the p a r t i a l u n s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y curve, K(\Jjp), f o r a s o i l from i t s p a r t i a l water r e t e n t i o n curve [9(\|jp)] (dimensionless) c o e f f i c i e n t o f c u r v a t u r e as used i n the U n i f i e d S o i l C l a s s i f i c a t i o n (USC) System (dimensionless) c o e f f i c i e n t o f u n i f o r m i t y as used i n the U n i f i e d S o i l C l a s s i f i c a t i o n (USC) System (dimensionless) p a r t i c l e diameter (mm) p a r t i c l e diameter at which a percentage f r a c t i o n (x %) on the Cumulative P a r t i c l e S i z e D i s t r i b u t i o n Curve i s s m a l l e r (mm) 3 - 3 t o t a l p o r o s i t y (m m ) i ) h y d r a u l i c head i n the S a t u r a t e d H y d r a u l i c C o n d u c t i v i t y T e s t s (m) i i ) h e i g h t o f the water t a b l e above the t i l e d r a i n s , as used i n the 'Hooghoudt Equation' (m) i i i ) pond depth, as measured a t the p o i n t e r p o s i t i o n (m) estimated depth o f the pond a t the p o i n t e r p o s i t i o n ; taken from the r e g r e s s i o n l i n e f o r the pond r i s e over time p e r i o d (C) on the A p r i l 14, Pond Depth Hydrograph (m) ' i n i t i a l ' pond depth; the depth o f water a t the c e n t r e o f the pond when the depth o f water at the p o i n t e r p o s i t i o n i s 0 (m) pond depth at the c e n t r e o f the pond (m) estimated pond depth at the c e n t r e o f the pond t h a t corresponds w i t h the depth o f the pond a t the p o i n t e r p o s i t i o n ; taken as the o r d i n a t e i n t e r c e p t o f the r e g r e s s i o n l i n e f o r the pond r i s e over time p e r i o d (C) on the A p r i l 14, Pond Depth Hydrograph (m) depth o f the pond a t the p o i n t e r p o s i t i o n t h a t i s i n d i c a t e d by the o r d i n a t e i n t e r c e p t o f the r e g r e s s i o n l i n e f o r the pond r i s e over time p e r i o d (C) on the A p r i l 14, Pond Depth Hydrograph (m) h y d r a u l i c head c o r r e s p o n d i n g t o times o f measurement (m) time (hour) i n s i d e diameter o f the permeameter column (m) h y d r a u l i c c o n d u c t i v i t y (m.s - 1) s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (m.s - 1) h y d r a u l i c c o n d u c t i v i t y o f the composite 'Top Layer' (m.s - 1) s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 'surface l a y e r ' (m.s - 1) s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 'surface l a y e r ' under the pond (m.s - 1) s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 'surface l a y e r ' i n the unponded p a r t o f the f i e l d (m.s - 1) h y d r a u l i c c o n d u c t i v i t y o f the 'sand/sawdust' mixed l a y e r u n d e r l y i n g the 's u r f a c e l a y e r ' under the pond (m.s - 1) i ) l e n g t h o f the sand sample i n the permeameter column (m) i i ) l e n g t h o f s l o p e i n K i r p i c h ' s e m p i r i c a l l y d e r i v e d formula f o r det e r m i n i n g the time of c o n c e n t r a t i o n f o r ov e r l a n d flow (m) i i i ) t h i c k n e s s o f the composite 'Top Layer' (m) t h i c k n e s s o f the 'surface l a y e r ' (m) i x t h i c k n e s s o f the 'sand/sawdust' mixed l a y e r underneath the 'surface l a y e r ' (m) l e n g t h (metre) volume ( m i l l i l i t r e ) 3 volume (m ) 3 volume o f water i n f i l t r a t e d under the pond (m ) volume o f water c o n t r i b u t e d t o the pond from 3 o v e r l a n d flow (m ) volume o f water c o n t r i b u t e d t o the pond from 3 r a i n f a l l (m ) 3 volume o f water s t o r e d i n the pond (m ) f l u x d e n s i t y (m.s - 1) f l u x d e n s i t y under the pond (m.s - 1) r a i n f a l l r a t e (m.s - 1) f l u x d e n s i t y i n the unponded p a r t o f the f i e l d (m.s - 1) f l u x d e n s i t y through the 's u r f a c e l a y e r ' under the pond (m.s - 1) f l u x d e n s i t y through the 'surface l a y e r ' i n the unponded p a r t o f the f i e l d (m.s - 1) ' e f f e c t i v e ' pond r a d i u s r e p r e s e n t i n g the b a s a l r a d i u s i n the cone dimensioned model (m) ' i n i t i a l ' pond r a d i u s r e p r e s e n t i n g the d i s t a n c e from the c e n t r e o f the pond t o the p o i n t e r , or measurement, p o s i t i o n (m) t o t a l catchment r a d i u s (m) i ) p a r a l l e l d r a i n s p a c i n g as used i n the 'Hooghoudt Equation' (m) i i ) s l o p e r a t i o i n K i r p i c h ' s e m p i r i c a l l y d e r i v e d formula f o r dete r m i n i n g the time of c o n c e n t r a t i o n f o r o v e r l a n d flow (m) time (second) x time (s and h) time o f c o n c e n t r a t i o n i n K i r p i c h ' s e m p i r i c a l l y d e r i v e d formula f o r dete r m i n i n g the time o f c o n c e n t r a t i o n f o r ov e r l a n d flow (s) times o f measurement (s and h) pond volumes corre s p o n d i n g t o times o f 3 measurement (m ) depth o f s o i l (m) s o i l depth increments c a l c u l a t e d u s i n g the f i n i t e d i f f e r e n c e method, as proposed by C h i l d s (1969) (m) change i n a v a r i a b l e 3 - 3 i ) v o l u m e t r i c water content (m m ) i i ) pond s l o p e angle (dimensionless) i ) v o l u m e t r i c water content at s a t u r a t i o n 3 - 3 (nTm ° ) i i ) measured ' w a t e r - f i l l e d ' p o r o s i t y at 3 - 3 s a t u r a t i o n (m m ) p a r t i t i o n i n g , or r u n o f f , c o e f f i c i e n t (dimensionless) _ 3 bulk d e n s i t y (kgm ) d e n s i t y o f s o l i d s (kgm ) _ 3 d e n s i t y o f water (kgm ) ' a i r e n t r y value' p r e s s u r e p o t e n t i a l (m) g r a v i t y p o t e n t i a l (m) p r e s s u r e p o t e n t i a l (m) p r e s s u r e p o t e n t i a l increments used i n the f i n i t e d i f f e r e n c e method to estimate \}i ( z ) , as proposed by C h i l d s (1969) (m) p p r e s s u r e p o t e n t i a l s at s o i l l a y e r i n t e r f a c e s (m) t o t a l p o t e n t i a l (m) x i ACKNOWLEDGEMENTS For t h e i r p a t i e n c e and c a r i n g , I express by deep a p p r e c i a t i o n t o my mother and grandmother. Without t h e i r support the work would not have been completed. I g r a t e f u l l y acknowledge the a s s i s t a n c e g i v e n by Dr. Jan d e V r i e s , my t h e s i s s u p e r v i s o r , as w e l l as by Drs. M i c h a e l Novak and A r t h u r Bomke. Thanks must a l s o be g i v e n t o the D i s t r i c t o f North Vancouver and e s p e c i a l l y t o D i r k O o s t i n d i e , the Superintendent o f Parks, f o r . a l l o w i n g the f i e l d work on the Lower Premier S p o r t s f i e l d . To Dr. Les L a v k u l i c h , the Department Head, and a l l others i n the S o i l S c i e n c e Department t o whom I have b e f r i e n d e d over the yea r s , thanks i s g i v e n f o r t h e i r a s s i s t a n c e and unending kindness. To the s o i l p h y s i c s group o f Ev e l y n T i s c h e r , John Heinonen, Dr. Mensah Bonsu, and Karim Abbaspour, I g i v e a r o u s i n g hurrah! Thanks are expressed t o the U n i v e r s i t y o f . B r i t i s h Columbia f o r the award o f a graduate f e l l o w s h i p and the B r i t i s h Columbia S c i e n c e C o u n c i l and the D i s t r i c t o f North Vancouver f o r t h e i r GREAT Award. x i i 1 1. INTRODUCTION; 1 . l S p o r t s f i e l d s In a S o l i and Water Management Context A d i v e r s i t y o f t o p i c s i s covered under the broad heading ' S o i l and Water Management'. One t o p i c i n p a r t i c u l a r focuses on the s o i l and hydrology of t u r f g r a s s e d s p o r t s f i e l d s . Fundamentally, i t d e a l s w i t h the p r o v i s i o n and management of good q u a l i t y f i e l d s u r f a c e s s u i t a b l e f o r p l a y i n g s p o r t s . The impetus f o r r e s e a r c h on t h i s t o p i c stems from the evergrowing p o p u l a r i t y o f f i e l d s p o r t s and the need f o r more and b e t t e r q u a l i t y f i e l d s . The ' S o i l and Water Management' i s s u e r a i s e d i n the t h e s i s d e a l s s p e c i f i c a l l y w i t h the ponding o f s p o r t s f i e l d s b u i l t w i t h sand. The study h o p e f u l l y i l l u s t r a t e s and p r o v i d e s q u a n t i f i c a t i o n o f some o f the p h y s i c a l c h a r a c t e r i s t i c s o f these f i e l d s . Although emphasis i s p l a c e d on the t h e o r e t i c a l e n quiry, a c u r s o r y d e s c r i p t i v e background i s a l s o g i v e n t o some o f the p e c u l i a r i t i e s o f ' s a n d f i e l d s ' , t h e i r ' s o i l s ' , and the i n f l u e n c e o f c l i m a t e upon them. The i n v e s t i g a t i o n i s d i r e c t e d towards the 'ponding' problem as i t p e r t a i n s s p e c i f i c a l l y t o one p a r t i c u l a r s p o r t s f i e l d i n a h i g h r a i n f a l l l o c a t i o n . The t h e s i s concludes by d i s c u s s i n g the i m p l i c a t i o n s o f ponding t o f i e l d management. The t h e s i s i s based on a f i e l d study made d u r i n g the w i n t e r and s p r i n g o f 1982. The s p o r t s f i e l d o f i n t e r e s t i s the Lower Premier S p o r t s f i e l d i n the D i s t r i c t o f North Vancouver, a l o c a t i o n noted f o r i t s c o o l and wet c l i m a t i c c o n d i t i o n s . T h i s sand-based f i e l d i s managed by the D i s t r i c t 'Parks Department'. In response to heavy r a i n f a l l d u r i n g the study p e r i o d the 2 s u r f a c e o f the f i e l d remained predominantly wet and u n p l a y a b l e . F r e q u e n t l y i t showed f r e e s t a n d i n g water on i t s p l a y i n g s u r f a c e . These problems occu r r e d even though an adequate drainage system was i n p l a c e . L i n e d r a i n s were i n s t a l l e d at the time o f c o n s t r u c t i o n and were l a i d down a c c o r d i n g to a p r o f e s s i o n a l l y planned drainage scheme.* The p r e s c r i b e d d r a i n depth was approximately 0.6 m, at spacings o f approximately 6.1 m (20 f e e t ) . I t i s a l s o known t h a t d u r i n g i t s f i r s t f i v e years of use the f i e l d showed few i f any s e r i o u s problems.* To account f o r the wetness o f the f i e l d , i t i s c o n j e c t u r e d t h a t i n some way the p h y s i c a l p r o p e r t i e s o f i t s s o i l had a l t e r e d s i n c e c o n s t r u c t i o n , hence a f f e c t i n g the h y d r o l o g i c behaviour at i t s s u r f a c e . Furthermore, i t i s shown t h a t the f r e e water p r e s e n t on the f i e l d s u r f a c e was ponded and not the r e s u l t o f f l o o d i n g . F l o o d i n g r e q u i r e s t h a t the water t a b l e r i s e above the s o i l s u r f a c e and t h i s was not observed. A l t e r n a t i v e l y , 'ponding' r e p r e s e n t s an i n f i l t r a t i o n problem, not one o f inadequate sub-s u r f a c e s o i l d r a i n a g e . From a ' S o i l and Water Management' p e r s p e c t i v e the broadest c h a l l e n g e i n r e l a t i o n t o s p o r t s f i e l d s i s to determine the r o l e o f the s o i l i n the performance o f d i f f e r e n t f i e l d s . For s p e c i f i c cases t h i s means f i n d i n g e x p l a n a t i o n s f o r the way i n which the p r o p e r t i e s and c h a r a c t e r i s t i c s o f a p a r t i c u l a r s o i l c o n t r i b u t e t o , or d e t r a c t from, i t s s u i t a b i l i t y f o r s p o r t s f i e l d use. I t a l s o means determining the p h y s i c a l p rocesses t h a t change i n i t i a l l y f a v o u r a b l e s o i l c o n d i t i o n s i n t o those t h a t * P e r s o n a l communication w i t h the D i s t r i c t Park's Superintendent. 3 l e a v e the f i e l d s u n p l a y a b l e . The s o i l s r e s e a r c h e r t r i e s t o come up w i t h u s e f u l f i e l d management recommendations to enhance the d u r a b i l i t y o f s p o r t s f i e l d s u r f a c e s , and thus l e a v e them more e n j o y a b l e f o r p l a y . Towards meeting these goals t h e r e i s d e f i n i t e l y a need f o r f u r t h e r r e s e a r c h i n t o u n derstanding the s o i l p h y s i c a l and h y d r o l o g i c a l processes i n v o l v e d . T h i s i s e x e m p l i f i e d by r e f e r e n c e to a r e p o r t e n t i t l e d 'Current T u r f Research i n Canada' ( T a y l o r , 1984) i n which e l e v e n a c t i v e r e s e a r c h programs were l i s t e d . Of the f i f t y - e i g h t r e s e a r c h t o p i c s c i t e d only two were s o i l p h y s i c a l l y or h y d r o l o g i c a l l y r e l a t e d , o n l y one was d i r e c t e d towards s p o r t s f i e l d s . I t i s hoped t h a t t h i s t h e s i s makes a s a t i s f a c t o r y and u s e f u l r e s e a r c h c o n t r i b u t i o n . 1.2 S p o r t s f i e l d s 1.2.1 General S p o r t s f i e l d s are expansive areas o f ground, o f v a r i o u s dimensions, s u i t a b l e f o r p l a y i n g f i e l d s p o r t s . They are b u i l t t o f a c i l i t a t e the h e a l t h f u l a c t i v i t i e s o f those i n c r e a s i n g l y concerned w i t h p h y s i c a l f i t n e s s and r e c r e a t i o n . They are g e n e r a l l y p r o v i d e d out o f p u b l i c funds and seen to be important investments towards our s o c i e t a l w e l l - b e i n g . C o n s i d e r a b l e time and money i s spent i n terms o f f i e l d c o n s t r u c t i o n and maintenance. Thus, t o reduce c o s t s and o p t i m i z e b e n e f i t s t h e r e i s a v e s t e d i n t e r e s t i n p r o v i d i n g good s p o r t s f i e l d d e s i g n and e f f e c t i v e f i e l d management p r a c t i c e s . Foremost, one r e a l i z e s t h a t s p o r t s f i e l d s r e p r e s e n t a 4 c o n t r i v e d grass growing environment. T h i s i s i n c o n t r a s t to n a t u r a l g r a s s l a n d s and most forage s e t t i n g s . S p o r t s f i e l d s r e q u i r e t u r f g r a s s e d s u r f a c e s t h a t are s t r o n g , even, and c o mfortable t o p l a y on. The key c o n s i d e r a t i o n f o r s p o r t s f i e l d s i s t h a t they must be ' p l a y a b l e ' . I t r e q u i r e s t h a t t h e i r s o i l s be s u f f i c i e n t l y s t r o n g to withstand the p h y s i c a l p r e s s u r e s u n i q u e l y a s s o c i a t e d w i t h p l a y e r and equipment t r a f f i c (Canaway, 1980). I t i s v i t a l l y important t h a t f i e l d managers take the necessary steps t o minimize the d e g r a d a t i v e e f f e c t s these p r e s s u r e s , or s t r e s s e s , have on the p h y s i c a l s t a t e o f the s o i l . T h i s i s e s p e c i a l l y t r u e under wet c o n d i t i o n s (van Wijk, 1980). I f l e f t unchecked, the consequences r e s u l t i n d e l e t e r i o u s e f f e c t s on the performance of the p l a y i n g s u r f a c e . I f wet and muddy the f i e l d s u r f a c e s are e s s e n t i a l l y u n p l a y a b l e and, consequently, unacceptable. I t i s important, t h e r e f o r e , t h a t s p o r t s f i e l d s o i l s a llow r a i n , or i r r i g a t i o n water, to i n f i l t r a t e and d r a i n f r e e l y . At the very l e a s t they should be expected to cope w i t h 'frequent' i n c i d e n t r a i n f a l l r a t e s . T h i s r e q u i r e s t h a t i n f i l t r a t i o n and drainage c r i t e r i a be t i e d t o the p r e v a i l i n g c l i m a t i c c o n d i t i o n s experienced at the s i t e . The a b i l i t y t o c o n s t r u c t , and then s u s t a i n , good p l a y i n g s u r f a c e s i s not a simple t a s k . In f a c t , o l d s u r f a c e s are f r e q u e n t l y r e p l a c e d or, through p a r t i a l s o i l m o d i f i c a t i o n , r e c e i v e major ren o v a t i o n s (Adams, 1986). New f i e l d s are c o n s t r u c t e d to s o l v e what o f t e n appear to be insurmountable problems. These are d r a s t i c and expensive s o l u t i o n s . N e v e r t h e l e s s , by r e s o r t i n g to the r e c o n s t r u c t i o n o f new f i e l d s u r f a c e s , e i t h e r i n whole or i n p a r t , f a v o u r a b l e r e s u l t s are u s u a l l y produced, o f t e n d e s p i t e the s o i l s chosen. S t i l l , the 5 b e n e f i t s d e r i v e d from c o n s t r u c t i n g new f i e l d s are not immediate. S u f f i c i e n t time must be allowed to ensure t h a t the new t u r f g r a s s e d s u r f a c e e s t a b l i s h e s i t s e l f , w i t h p l a y g e n e r a l l y p r o h i b i t e d f o r up to a year or more. Over t h a t p e r i o d , provided i t s n u t r i e n t , energy, and moisture requirements are s a t i s f a c t o r i l y met, good p l a n t cover and r o o t development are expected. Thus, g i v e n s u f f i c i e n t time t o e s t a b l i s h , the new t u r f g r a s s produces an e x t e n s i v e , i n t e r t w i n e d , r o o t system t h a t makes the p l a y i n g s u r f a c e s t r o n g and r e s i l i e n t t o t r a f f i c . S p e c i f i c a l l y , t h i s s t r e n g t h prevents the p h y s i c a l compaction and 'shearing' o f the s o i l under s t r e s s (van Wijk, 1980). Furthermore, the s o i l s o f new s p o r t s f i e l d s are not y e t i n f l u e n c e d by m a t e r i a l a d d i t i o n s and a l t e r a t i o n s t h a t r e s u l t i n changes to the p h y s i c a l p r o p e r t i e s o f the s o i l (Adams, 1986). Assuming t h a t the c o n s i s t e n c y o f the s o i l i s reasonable, t h a t i s ' n o n - p l a s t i c ' when wet and ' f i r m ' or harder when moist, the b e n e f i t s d e r i v e d from new s p o r t s f i e l d s o f t e n seem i n s e n s i t i v e to the t e x t u r e and s t r u c t u r e o f the s o i l s used and more a f u n c t i o n o f t h e i r newly e s t a b l i s h e d t u r f g r a s s e d s u r f a c e s . T h i s at l e a s t appears t o be the case over the s h o r t term. New s p o r t s f i e l d s , t h e r e f o r e , do r e p r e s e n t a temporary remedy i f not a l o n g term s o l u t i o n . E v e n t u a l l y , though, t h e i r newness, and the r e l i a n c e p l a c e d on the b e n e f i t s from the t u r f g r a s s alone, succumbs to the e f f e c t s from l o n g p e r i o d s o f use. I n v a r i a b l y , t h e i r s o i l s change i n response t o a v a r i e t y of s o i l a l t e r i n g p r o c e s s e s , whether from a d d i t i o n s , l o s s e s , t r a n s f o r m a t i o n s , or t r a n s l o c a t i o n s , r e g a r d l e s s o f how c a r e f u l l y designed and c o n s t r u c t e d the s p o r t s f i e l d may be. Besides making 6 the c o r r e c t c h o i c e o f s o i l m a t e r i a l s , the q u e s t i o n a l s o a r i s e s , how does one manage the processes r e s p o n s i b l e f o r these changes i n order t o o p t i m i z e the b e n e f i t s d e s i r e d ? Over the l o n g term, the success of a s p o r t s f i e l d depends not o n l y on the type of s o i l but a l s o upon how w e l l the s p o r t s f i e l d i s c o n s t r u c t e d and managed. When faced w i t h heavy use, the d u r a b i l i t y of the f i e l d depends to a l a r g e extent on the s o i l m a t e r i a l s used, the placement s p e c i f i c a t i o n s f o l l o w e d , and the drainage and i r r i g a t i o n systems i n s t a l l e d . However, a p p r o p r i a t e f i e l d management must be f o l l o w e d to o p t i m i z e t h e i r b e n e f i t s . Management methods must g i v e f u l l a t t e n t i o n to the c o n t i n u a l agronomic needs o f the t u r f g r a s s , the changing p h y s i c a l c o n d i t i o n s o f the s o i l , and the amount and type o f use the f i e l d endures. A l l o f these f a c t o r s have to be c o n s i d e r e d i n l i g h t o f p r e v a i l i n g c l i m a t i c c o n d i t i o n s . In terms o f s o i l m a t e r i a l s f o r s p o r t s f i e l d use, the p h y s i c a l s u i t a b i l i t y o f a g i v e n s o i l can be t e s t e d u s i n g w e l l -e s t a b l i s h e d s o i l s c i e n t i f i c methods. V a r i o u s parameters, i n c l u d i n g p a r t i c l e s i z e d i s t r i b u t i o n , s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ), and p e n e t r a t i o n r e s i s t a n c e are commonly used as s o i l p h y s i c a l and h y d r o l o g i c a l c r i t e r i a . In the l i t e r a t u r e , c r i t e r i a are drawn from work and r e s e a r c h c a r r i e d out a l l over the world (Beard, 1973). Adopted i n the d e s i g n stage these c r i t e r i a are u s u a l l y l a i d out i n the f i e l d ' s s o i l s p e c i f i c a t i o n s p r i o r t o c o n s t r u c t i o n . C o n s i d e r i n g the d i v e r s i t y o f o p i n i o n s h e l d , however, i t i s c l e a r t h a t f u l l y r a t i o n a l assessments of the m a t e r i a l s and methods are not always made, nor are the c r i t e r i a always w e l l - d e f i n e d or a p p r o p r i a t e f o r d i f f e r e n t l o c a l i t i e s and c l i m a t e s . 7 There i s l i t t l e doubt t h a t a f u r t h e r emphasis s t i l l needs t o be p l a c e d upon the b a s i c p h y s i c a l p r o p e r t i e s o f s p o r t s f i e l d s o i l s . Yet, p o s s i b l y o f g r e a t e r need, i s t o understand the p h y s i c a l processes t h a t are c o n t i n u a l l y at work a l t e r i n g the s o i l . The consequences o f many o f these processes s e r i o u s l y a f f e c t s p o r t s f i e l d performance. For example, r e g a r d l e s s o f how w e l l a s p o r t s f i e l d i s prepared or managed, i t s s o i l i s c o n t i n u a l l y s u b j e c t e d to the compactive p r e s s u r e s from p l a y and the accumulation o f t u r f g r a s s - d e r i v e d o r g a n i c matter. These processes have s e r i o u s i m p l i c a t i o n s , r e l a t e d t o both the hydrology and t r a f f i c a b i l i t y o f the f i e l d s u r f a c e . One assumes t h a t w i t h those s o i l s t h a t are u n s u i t a b l e , and w i t h those t h a t are p o o r l y managed, d e t e r i o r a t i o n occurs e a r l i e r and the e f f e c t s prove more s e r i o u s . 1.2.2 S a n d f i e l d s Sand-based s p o r t s f i e l d s , or ' s a n d f i e l d s ' , r e p r e s e n t an i n n o v a t i v e approach to s p o r t s f i e l d d e s i g n . A l l s a n d f i e l d s use sand, e i t h e r by i t s e l f or amended wit h other m a t e r i a l s . P h y s i c a l l y , 'sands' are c o a r s e - t e x t u r e d and d i s t i n c t from other s o i l f r a c t i o n s , i n response t o m a n i p u l a t i o n , the g r a n u l a r , though o f t e n angular, shape o f sand g r a i n s r e s u l t i n a r o l l i n g , or s h i f t i n g , o f p a r t i c l e s r e l a t i v e t o each o t h e r . With on l y p o i n t c o n t a c t between p a r t i c l e s , s u r f a c e i n t e r a c t i o n i s minimized. T h i s , p l u s t h e i r r e l a t i v e l y i n e r t mineralogy l e a v e s the sands c o h e s i o n l e s s . However, when c l o s e l y packed they are i n c o m p r e s s i b l e . In t h i s s t a t e , under s l i g h t l y moist c o n d i t i o n s , they are h i g h l y t r a f f i c a b l e . When completely dry or under 8 p o s i t i v e h y d r a u l i c p r e s s u r e s , however, t h e i r shear s t r e n g t h i s reduced ( C r a i g , 1973). Sands have a p o r o s i t y t h a t f a l l s w i t h i n the range o f 30 t o 40 %, depending upon t h e i r packing arrangement and sortedness (Adams et a l . , 1971). Moreover, u n l e s s clogged by m a t e r i a l from extraneous sources, t h e i r pore space remains open and permeable to the flow o f water. By v i r t u e o f t h e i r p h y s i c a l c h a r a c t e r i s t i c s , sands are u s u a l l y w e l l - d r a i n e d . Given good management, sands can a l s o support h e a l t h y t u r f g r a s s and p r o v i d e s p o r t s f i e l d s a g e n e r a l r e s i l i e n c e to p l a y e r use, even under wet c l i m a t i c c o n d i t i o n s . A c c o r d i n g l y , sands are g e n e r a l l y acknowledged t o be w e l l - s u i t e d f o r s p o r t s f i e l d s s i t u a t e d i n humid l o c a t i o n s . In comparison, f i n e - t e x t u r e d s o i l s may have s i m i l a r or h i g h e r p o r o s i t i e s than sands, even without the c o n t r i b u t i o n from pore space r e l a t e d to s o i l s t r u c t u r e . When manipulated under wet c o n d i t i o n s , the c l a y p a r t i c l e s w i t h t h e i r l a m e l l a t e - s h a p e s l i d e p a s t each other and a l i g n themselves i n a p a r a l l e l f a s h i o n , c r e a t i n g an extremely t o r t u o u s path o f s m a l l c o n s t r i c t e d pores. As a r e s u l t these types o f s o i l s have much lower s a t u r a t e d h y d r a u l i c c o n d u c t i v i t i e s (K ). As w e l l , under these same wet c o n d i t i o n s the f i n e - t e x t u r e d s o i l s are e s p e c i a l l y s u s c e p t i b l e t o compaction. Consequently, i n wet s p o r t s f i e l d s i t u a t i o n s , these s o i l s are commonly i n a degraded, ' p l a s t i c ' s t a t e t h a t i s s e v e r e l y r e s t r i c t i v e t o the i n f i l t r a t i o n o f water and hence t o p l a y . The chemical and p h y s i c a l s t a b i l i t y o f sand i s l a r g e l y a t t r i b u t a b l e to i t s r e l a t i v e l y i n e r t quartz mineralogy. With a low s p e c i f i c s u r f a c e area, and low e l e c t r o s t a t i c s u r f a c e charge, 9 t h e r e i s cause f o r onl y minimal p a r t i c l e i n t e r a c t i o n ( H i l l e l , 1971). 'Sands', thus, are not s u s c e p t i b l e t o the same s o i l b e h a v i o u r a l processes as are the f i n e r s o i l t e x t u r e s . The consequence o f t h i s i s t h a t the r a t e s o f t r a n s f o r m a t i o n i n the sandy environment are slow. In the Canadian S o i l C l a s s i f i c a t i o n System (Canada S o i l Survey Committee, 1978), 'Sands' are t y p i f i e d as " S t r u c t u r e l e s s : (with) no ob s e r v a b l e a g g r e g a t i o n or no d e f i n i t e o r d e r l y arrangement around n a t u r a l l i n e s o f weakness." They have " s i n g l e g r a i n s t r u c t u r e : ( r e p r e s e n t i n g a) l o o s e i n c o h e r e n t mass o f i n d i v i d u a l p a r t i c l e s . . . " . S i n c e sands do not compact beyond c l o s e packing t h e i r m a t r i x remains open and maintains r e l a t i v e l y h i g h s a t u r a t e d h y d r a u l i c c o n d u c t i v i t i e s (K ). The openness o f the sand a l s o favours good s o i l a e r a t i o n and r o o t p e n e t r a t i o n . Given adequate i r r i g a t i o n , t h i s openness i s seen t o be an important b e n e f i t towards the development o f good r o o t i n g systems. The added shear s t r e n g t h p r o v i d e d by the r o o t s has been shown to be an important a s s e t towards the maintenance o f s t r o n g p l a y i n g s u r f a c e s , (van Wijk, 1980). When the sand g r a i n s are c l o s e l y packed, sands have an i n h e r e n t shear s t r e n g t h t h a t r e q u i r e s a c o n s i d e r a b l e a p p l i c a t i o n o f f o r c e b e f o r e t h e i r p a r t i c l e s s h i f t ( C r a i g , 1973). T h i s depends upon the t h e i r p a r t i c l e s i z e d i s t r i b u t i o n , p a cking arrangement, p a r t i c l e shape, water t e n s i o n and co r r e s p o n d i n g water content, a l l o f which are determinant f a c t o r s i n j u s t how much f o r c e i s r e q u i r e d . The d i s r u p t i v e shear f o r c e s are determinable, however, and, g i v e n t y p i c a l f i e l d m oisture c o n d i t i o n s , are shown t o be much g r e a t e r f o r sands than f o r f i n e r t e x t u r e d s o i l s (van Wijk and Beuving, 1978). The a b i l i t y o f the s p o r t s f i e l d s o i l t o r a p i d l y conduct 10 water t o the drainage system i s an e s s e n t i a l c o n d i t i o n . In p a r t t h i s r e q u i r e s a h i g h h y d r a u l i c c o n d u c t i v i t y (K ), which i s dependent p r i m a r i l y upon the p h y s i c a l p r o p e r t i e s and h y d r o l o g i c c h a r a c t e r i s t i c s o f the s o i l . To s a t i s f y the i n f i l t r a t i o n requirement o f the s p o r t s f i e l d the i n f i l t r a b i l i t y o f i t s s u r f a c e must meet a n t i c i p a t e d r a i n f a l l i n t e n s i t i e s . The l i m i t a t i o n s t o t h i s i n f i l t r a b i l i t y depend l a r g e l y upon the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the s o i l . C h a r a c t e r i s t i c a l l y , sands have a r e l a t i v e l y h i g h e r s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) than f i n e r , and p o o r l y s o r t e d , s o i l m a t e r i a l s . Measured (K ) value s s — 3 —1 f o r w e l l - s o r t e d sands commonly range between 5x10 m.s to -5 - l 10 m.s (Adams, 1986). P o o r l y s o r t e d sands may have lower (K ) v a l u e s . In c o n t r a s t , f i n e r s o i l - t e x t u r a l groups, h i g h i n s i l t s and c l a y s , may have very low (K ) v a l u e s , although these are s t r o n g l y dependent upon s o i l s t r u c t u r e and past m a n i p u l a t i o n . I f the f i n e r t e x t u r e d s o i l s are d i s p e r s e d or 'puddled 1, t h e i r (K ) value s may be i n the order o f 10~ 8 m.s - 1, or l e s s . * Because the f i n e r t e x t u r e d s o i l s are h i g h l y i n f l u e n c e d b e h a v i o u r a l l y , t h e i r s t r u c t u r e , and consequently t h e i r hydrology, are c h a r a c t e r i s t i c a l l y u n s t a b l e . As a r e s u l t t h e r e i s a l i t a n y o f s o i l h y d r o l o g i c problems a s s o c i a t e d w i t h s p o r t s f i e l d s b u i l t w i t h these types o f s o i l s . T h e i r s o i l c o n s i s t e n c e and behaviour under wet c o n d i t i o n s i s r e p e a t e d l y shown t o be u n s u i t a b l e f o r s p o r t s f i e l d a p p l i c a t i o n s . Sands on the other hand g e n e r a l l y p r o v i d e a p h y s i c a l l y s t a b l e s o i l m a t r i x . * P e r s o n a l communication w i t h Dr. J . d e V r i e s , S o i l S c i e n c e Department, U.B.C. 11 Throughout much o f the year Vancouver and i t s s u r r o unding m u n i c i p a l i t i e s experience the c o o l and r a i n y weather t y p i c a l o f temperate, maritime c l i m a t e s . In an attempt t o cope w i t h the l o n g p e r i o d s of heavy r a i n f a l l , s a n d f i e l d s were i n t r o d u c e d i n the e a r l y n i n e t e e n - s e v e n t i e s . To most f i e l d managers they represented a new, i f not r a d i c a l , approach to s p o r t s f i e l d s . The e a r l y sand-based f i e l d s performed w e l l , and f o r many became p r e f e r a b l e over other types o f s p o r t s f i e l d s . However, s e r i o u s r e s e r v a t i o n s were h e l d by o t h e r s . The doubts t h a t p e r s i s t e d were d i r e c t e d mostly towards the agronomic problems a s s o c i a t e d w i t h growing t u r f g r a s s on sand, t h a t i s , towards t h e i r d r o u g h t i n e s s and low s o i l f e r t i l i t y . D e s p i t e the s k e p t i c i s m s a n d f i e l d s were b u i l t . In due course improved drainage and i r r i g a t i o n systems helped make the agronomic problems more managable. As w e l l , the advent o f c o n t r o l l e d r e l e a s e forms o f f e r t i l i z e r s proved t o be h i g h l y b e n e f i c i a l towards t h e i r acceptance. I t i s c l e a r t h a t a l l t u r f g r a s s e d p l a y i n g s u r f a c e s , whether on sand or other types o f s o i l , f a c e a c e r t a i n amount of d e t e r i o r a t i o n w i t h use. i n t e n s i v e l y played areas show the most damage, e s p e c i a l l y around c e n t r e - f i e l d and the g o a l mouths (van Wijk, 1980). Compared to other p a r t s o f the f i e l d these areas show the sparse and patchy p l a n t cover t y p i c a l l y a s s o c i a t e d with e x c e s s i v e wear. The h e a v i l y worn t u r f g r a s s i s g e n e r a l l y r i p p e d and d i v o t e d . A f t e r heavy r a i n f a l l the d e t e r i o r a t e d s u r f a c e remains wet and spongy. Although s a n d f i e l d s do not show the muddiness o f s p o r t s f i e l d s b u i l t w i t h f i n e r - t e x t u r e d s o i l s , the soggy s u r f a c e s s t i l l e x i s t . Under i n t e n s e r a i n f a l l , the more s e r i o u s l y a f f e c t e d s a n d f i e l d s even c o l l e c t water on t h e i r 12 s u r f a c e s . When t h i s happens the f u n c t i o n a l c a p a b i l i t y o f the f i e l d i s l o s t , g e n e r a l l y r e q u i r i n g l o n g , dry p e r i o d s to r e t u r n t o a p l a y a b l e s t a t e . Because s a n d f i e l d s were adopted p r e c i s e l y t o a v o i d such h y d r o l o g i c problems, these occurrences r e p r e s e n t a p a r t i c u l a r l y a g g r a v a t i n g s p o r t s f i e l d management problem. From o b s e r v a t i o n s , some s a n d f i e l d s f u n c t i o n b e t t e r than o t h e r s . To e x p l a i n t h i s one must f i r s t r e a l i z e t h a t i n h e r e n t d i f f e r e n c e s are b u i l t i n t o every s a n d f i e l d . They are c o n s t r u c t e d t o d i f f e r e n t s p e c i f i c a t i o n s , s u b j e c t e d t o d i f f e r e n t l e v e l s o f use, and experience d i f f e r e n t l o c a l c l i m a t i c c o n d i t i o n s . Moreover, d i f f e r e n t sands d i f f e r g r e a t l y i n t h e i r p h y s i c a l c h a r a c t e r and composition. They have d i f f e r e n t p a r t i c l e s i z e d i s t r i b u t i o n s , p a r t i c l e shapes, and p acking arrangements (Spomer, 1980; Gupta and Larson, 1979; Bingaman and Kohnke, 1970; C h i l d s , 1969; Stakman, 1969; Bodman and C o n s t a n t i n , 1965). F u r t h e r c o n t r i b u t i n g t o the n o n - s p e c i f i c i t y of s a n d f i e l d s i s t h a t no c l e a r l y e s t a b l i s h e d r u l e s e x i s t f o r or a g a i n s t amending the sands w i t h other m a t e r i a l s , even though mixing amendments i n t o the sands i s commonly p r a c t i c e d ( T a y l o r and Blake, 1981; Blake, 1980; Spomer, 1980; Thornton, 1973; Adams et a l . , 1971; Bingaman and Kohnke, 1970; Paul e t a l . , 1970; Juncker and Madison, 1967; Morgan e t a l . , 1966, 1965). Adding amendments i s done p r i m a r i l y f o r agronomic reasons, to enhance both the sand's n u t r i e n t and moisture r e t e n t i o n c a p a b i l i t i e s . I t u s u a l l y i n v o l v e s mixing, on a volume b a s i s , some form o f o r g a n i c matter i n t o the sand. Sawdust i s commonly used i n the G r e a t e r Vancouver area although peat has been used as w e l l . F i n a l l y , and probably more i m p o r t a n t l y , once 13 s a n d f i e l d s are i n p l a c e and s u b j e c t e d t o p l a y e r use t h e r e are no c l e a r g u i d e l i n e s a v a i l a b l e on how t o manage them c o r r e c t l y to prevent l a t e r problems. I n c o n s i s t e n c i e s i n t h e i r performance are expected. N e v e r t h e l e s s , b a s i c s o i l p h y s i c a l p r o p e r t i e s and processes p r o v i d e c l u e s as to p r e c i s e l y why some problems e x i s t . With only minor r e s e r v a t i o n s h e l d w i t h regards t o t h e i r use, the i n t e r e s t i n s a n d f i e l d s i s widespread. Schematic r e p r e s e n t a t i o n s o f v a r i o u s s p o r t s f i e l d c o n s t r u c t i o n s are g i v e n i n F i g u r e 1 (van Wijk, 1980). The d i f f e r e n t d e s i g n c r i t e r i a t h a t are a s s o c i a t e d w i t h these c o n s t r u c t i o n s are f u r t h e r d i s c u s s e d , both by van Wijk (1980) and Beard (1973). The d e s i r a b i l i t y of u s i n g sands f o r s p o r t s f i e l d s i s r a t i o n a l l y based on the u nderstanding t h a t sand r e p r e s e n t s both a p h y s i c a l l y and c h e m i c a l l y s t a b l e s o i l . A d i r e c t consequence from a f i e l d management p o i n t o f view i s t h a t t h e i r hydrology i s more p r e d i c t a b l e . Thus, from an i n i t i a l examination s a n d f i e l d s c e r t a i n l y appear to have the p o t e n t i a l f o r s t a y i n g dry and t r a f f i c a b l e under adverse wet c o n d i t i o n s . As i s shown i n t h i s study, however, t h i s i s not always the case. S a n d f i e l d s do d e t e r i o r a t e over time, as evidenced by the s t a n d i n g f r e e water on the Lower Premier S p o r t s f i e l d . The d i r e c t i o n taken here towards un d e r s t a n d i n g such problems i s to emphasize the s o i l p h y s i c a l processes t a k i n g p l a c e , p a r t i c u l a r l y those which change the p h y s i c a l p r o p e r t i e s o f the sand and a f f e c t the h y d r o l o g i c behaviour o f the f i e l d . 14 F i g u r e 1; Schematic r e p r e s e n t a t i o n o f grass s p o r t s f i e l d c o n s t r u c t i o n s as g i v e n i n l i t e r a t u r e (van Wijk, 1980). I. 2. 0 20 40 P I 60 80 W/////I/M fine send sand soil mixture original subsoil •oil or coarse sand backfilled trench drain interval 5 -10 m medium coarse granu-lar materials drainage lave*-: coarse sand or grave* drain original subsoil sandy loam tnd peat amended coarse sand original subsoil: coarse sand drought susceptible coarse sand peat clay mixture coarse sand or gravel backfilled trench original clayey subsoil SO. 'S/S/SSSA 7///////// ///A sand (0.61 peat (0.4) sand (200 400 urn) coarse gravel backfilled trenches dram interval 4 m original subsoil sand peat (soil) mixture fine sand adjustable watenabte dram network plastic sheet barrier original subsoil 3. 0 20 40 60 80 4. 0 20 40 60 80 sand eggregated-clay peat mixture sand aggregated-clay mixture drain interval 3*4. 5 m original subsoil sand org. matter soil $ m mixture coarse sand gravel drain interval 4 - 6 m original subsoil sandy loam or coarse sand peat clay mixture coarse sand gravel backfilled trench drain interval 3 • 4.5 m original clayey subsoil fine sand coarse sand backfilled drain interval 4 • 6 m poorly permeable subsoil Legend: Source 1. Deutscher Normenausschuss (1974). 2. Deutscher Normenausschuss (1974). 3. Beard (1973), 'Cal i fornia Method'. 4. Beard (1973), 'USGA Green Section Method'. 5. Beard (1973). 6. Beard (1973). 7. Beard (1973). 8. Moesch (1975), ' C e l l System 1. Langvad (1968), 'Wiegrass Method'. 9. 10 Daniel et a l . (1974), 'Prescription Athle t ic Turf (PAT) System'. Part iculars -For K s of the subsoil >10~5 m . s - 1 . -For K g of the subsoil <10~5 m . s - 1 . -For perched water table above the gravel . -Part ia l modification of sandy s o i l s . -Part ia l modification of clay s o i l s , where monies are l imi ted . -Complete modification of clay s o i l s . -Patented 'sandfield' system. -For construction of foot-b a l l grounds in grass. -Patented 'sandfield' system. 15 1.2.3 The Lower Premier S p o r t s f i e l d The Lower Premier S p o r t s f i e l d was c o n s t r u c t e d i n 1975 and was the f i r s t s p o r t s f i e l d c o n s t r u c t e d on the 'Premier S t r e e t S a n i t a r y L a n d f i l l ' s i t e . The ' L a n d f i l l ' s i t e i s l o c a t e d i n the D i s t r i c t o f North Vancouver and was developed and managed by the 'Parks Department' i n the D i s t r i c t . I t was planned as a l o n g term l a n d r e c l a m a t i o n p r o j e c t , d e s t i n e d t o become the home o f a v a s t , outdoor r e c r e a t i o n a l complex. S i n c e the s p o r t s f i e l d was b u i l t on a hodgepodge of r e f u s e , i t was necessary t o e l e v a t e i t above the u n d e s i r a b l e m a t e r i a l below. T h i s r e q u i r e d t h a t new s o i l m a t e r i a l be obtained from elsewhere. Sand was c o n s i d e r e d t o be a v i a b l e o p t i o n f o r such an a p p l i c a t i o n . At the time s a n d f i e l d s were being i n t r o d u c e d i n t o the r e g i o n and were i n c r e a s i n g l y r e f e r r e d t o i n the l i t e r a t u r e (Moesch, 1975; D a n i e l e t a l . , 1974; Beard, 1973; Langvad,1968). A l s o , i n favour o f choosing s a n d f i e l d s over other types o f s p o r t s f i e l d s was a ready supply o f l o c a l l y a v a i l a b l e r i v e r and beach d e p o s i t sands. i n accordance w i t h ' S p o r t s f i e l d S p e c i f i c a t i o n s ' t h a t were s p e c i f i c a l l y s e t out f o r the c o n s t r u c t i o n o f s p o r t s f i e l d s i n the D i s t r i c t o f North Vancouver, two d i f f e r e n t sands, and sand p r e p a r a t i o n s , were used i n the c o n s t r u c t i o n o f the Lower Premier S p o r t s f i e l d . * These sands were put down and graded as two d i s t i n c t l a y e r s . The lower ' p i t r u n ' l a y e r was comprised o f a sand r e f e r r e d t o as the 'North Van' sand, w h i l e the upper 'topmix' l a y e r , r e f e r r e d t o as the 'Top Layer' i n the t h e s i s , * The ' S p o r t s f i e l d S p e c i f i c a t i o n s ' were p r o v i d e d by the Superintendent o f Parks, D i s t r i c t o f North Vancouver. 16 was comprised o f a 'Fraser R i v e r 1 sand mixed w i t h sawdust t o a 3:1 volume r a t i o . Both sands were r i v e r - d r e d g e d and met r e s p e c t i v e 'sand p a r t i c l e s i z e s p e c i f i c a t i o n s ' as p r e s c r i b e d f o r the two l a y e r s ; see Tables I and I I . Hence, the 'Fraser R i v e r 1 sand was l a i d down as a 'Top Layer' over the u n d e r l y i n g ' p i t r u n ' l a y e r o f 'North Van' sand. The 'Top Layer' was s p e c i f i e d t o be o f uniform s e t t l e d t h i c k n e s s (L = 0.15 m) and the ' p i t r u n ' l a y e r t o be 0.5 m t h i c k . S p e c i a l c a r e was t o be taken so as not to mix the two l a y e r s d u r i n g the placement o f the sand. As w e l l the f i e l d was designed t o be f l a t . Presumably, r a i n f a l l i n f i l t r a t i o n problems were unforseen and crowning the s u r f a c e f o r o v e r l a n d s u r f a c e d r a inage was c o n s i d e r e d unnecessary. A l s o , p r i o r t o the placement o f the sand a p o l y e t h y l e n e p l a s t i c sheet was l a i d down t o i s o l a t e the f i e l d from r i s i n g gases g i v e n o f f by the decomposing garbage. The p l a s t i c sheet a l s o i s o l a t e d the f i e l d from adverse r e g i o n a l groundwater e f f e c t s . A l s o , p r i o r t o the placement o f the sands, a t i l e d r a i n a ge system was i n s t a l l e d . U n d e r l a i n by the p l a s t i c l i n e r and surrounded by a pea g r a v e l f i l t e r , 0.10 m diameter drainage p i p e s were l a i d i n 0.25 m wide trenches to a 1 % s l o p e . L a t e r a l d r a i n s p a c i n g was 6.1 m. An a p p l i c a t i o n o f 'Hooghoudt's Equ a t i o n ' (Eq. 1.1) shows t h a t the depth and s p a c i n g o f the t i l e d r a i n s produce a drainage c a p a b i l i t y t h a t s a t i s f i e s a l a r g e — 5 —1 r a i n f a l l r a t e (q = 1.4x10 m.s ). The 'Hooghoudt' a n a l y s i s was performed as d e s c r i b e d by H i l l e l (1980); see Eq. 1.1. T h i s S 2 = 4K sH(H + 2 d A ) / q (1.1) 17 Tabl e I; 'Topmix' Sand P a r t i c l e S i z e S p e c i f i c a t i o n s * S i e v e % P a s s i n q 4 i n c h (102 mm) 100 3/8 i n c h (9.72 mm) 100 No. 16 (1.18 mm) 85-100 No. 80 (0.180 mm) 0-10 No. 200 (0.074 mm) 0 * Taken from the ' S p o r t s f i e l d S p e c i f i c a t i o n s ' d r a f t e d by the Parks Department o f the D i s t r i c t o f North Vancouver. Tab l e I I ; ' P i t r u n ' Sand P a r t i c l e S i z e S p e c i f i c a t i o n s * S i e v e % P a s s i n q No. 3 (76.2 mm) 100 No. 4 (4.76 mm) 85-100 No. 8 (2.38 mm) 0-90 No. 100 (0.149 mm) 0-10 No. 200 (0.074 mm) 0-2** * Taken from the ' S p o r t s f i e l d S p e c i f i c a t i o n s ' d r a f t e d by the Parks Department o f the D i s t r i c t o f North Vancouver. ** The m a t e r i a l s u p p l i e d cannot c o n t a i n more than 2 perc e n t t o t a l s i l t and c l a y by weight. 18 Given: S = the p a r a l l e l d r a i n s p a c i n g (6.1 m) K g = the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the s o i l ( 3 x l 0 ~ 4 m.s - 1) H = the h e i g h t o f the p h r e a t i c s u r f a c e (water t a b l e ) above the t i l e d r a i n s (0.65 m) d A = the h e i g h t o f the t i l e d r a i n s above an 'impervious' l a y e r (0 m) q = water supply, or recharge, from r a i n f a l l or i r r i g a t i o n at a constant f l u x d e n s i t y (m.s~ By s e t t i n g d A = 0 m, and r e a r r a n g i n g Eq. 2.1: and, S = 2 H ( K s / q ) 0 * 5 (1.2) q = 4K H 2/S 2 (1.3) By s u b s t i t u t i n g i n r e s p e c t i v e v a l u e s f o r K , H, and S: q = 4 ( 3 x l 0 " 4 m.s _ 1 )(0.65 m) 2/(6.1 m) 2 (1.3a) q = 1. 4 x l 0 ~ 5 m.s - 1 (~ 50 mrn.h"1) (1.3b) v a l u e f o r q i n d i c a t e s t h a t a recharge f l u x d e n s i t y equal t o -5 -1 1.4x10 m.s would be r e q u i r e d t o r a i s e the water t a b l e t o the s u r f a c e o f the f i e l d . To the c r e d i t o f the f i e l d d rainage d e s i g n , g i v e n i t s i n i t i a l m a t e r i a l s and c o n s t r u c t i o n , t h e r e i s a low p r o b a b i l i t y o f f l o o d i n g on the Lower Premier S p o r t s f i e l d . The approximate p r o b a b i l i t i e s o f such a r a i n f a l l i n t e n s i t y o c c u r r i n g i s once i n 25 years f o r a 720 s (12 minute) event, once i n 10 years f o r a 480 s (8 minute) event, and once i n 5 years f o r a 360 (6 min.) event; see F i g . 2. Through the use o f the 'Hooghoudt Equa t i o n ' , a r a t i o n a l l y based drainage s p a c i n g c r i t e r i o n i s i n c o r p o r a t e d i n t o the drainage d e s i g n p r o c e s s . A f t e r c o n s t r u c t i o n the f l a t sand/sawdust f i e l d s u r f a c e Figure 2; Short Duration Rainfall, Intensity, Duration, Frequency Data for  North Vancouver, Lynn Creek (1964-1983, 19 years); Prepared by Atmospheric Environment Service, Environment Canada. loo I — — — 1 a. JO i s 20 30 60 z 6 »a * f M I N U T E S Hooftc, D U R A T I O N 20 was ready f o r seed-bed p r e p a r a t i o n and seeding. P r e p a r a t i o n s i n v o l v e d the a p p l i c a t i o n o f 'lime' and chemical f e r t i l i z e r s o f s p e c i f i c a l l y p r e s c r i b e d a n a l y s e s . Subsequently, a 1:1 mixture o f 'Bluegrass' and 'Red Fescue' was sown on the s u r f a c e o f the sand/sawdust 'Top Layer'. I n i t i a l maintenance i n c l u d e d r o l l i n g , w a t e ring, and l i g h t mowing p r a c t i c e s . Once seeded, a f u l l year was r e q u i r e d to e s t a b l i s h the t u r f g r a s s e d p l a y i n g s u r f a c e . Play a c t u a l l y began i n 1977. A c c o r d i n g to the managers o f the f i e l d the t u r f g r a s s cover had good c o l o u r , s t r o n g stems and good r o o t d i s t r i b u t i o n . Moreover, the Lower Premier S p o r t s f i e l d performed f a v o u r a b l y f o r about f i v e years a f t e r w a r d . * Two concerns, though, e v e n t u a l l y came to the a t t e n t i o n o f the f i e l d managers. F i r s t , subsidence, which was due t o c o n s o l i d a t i o n o f the u n d e r l y i n g l a n d f i l l m a t e r i a l , was v i s i b l e i n the middle o f the f i e l d and, second, the p l a y i n g s u r f a c e remained i n c r e a s i n g l y wet d u r i n g the wetter seasons. By the w i n t e r o f 1982 d e t e r i o r a t i o n o f the f i e l d reached the p o i n t where f r e e water c o l l e c t e d on the p l a y i n g s u r f a c e i n response to heavy r a i n f a l l . Changes had o c c u r r e d i n the o v e r a l l performance o f the s p o r t s f i e l d s i n c e c o n s t r u c t i o n t h a t were presumably the consequences o f changes i n the p h y s i c a l and h y d r o l o g i c a l c h a r a c t e r i s t i c s o f the s o i l . 1.3 F i e l d Observations The f i e l d and i t s s o i l p r o f i l e were observed d u r i n g the * P e r s o n a l communication w i t h the Superintendent o f Parks, i n the D i s t r i c t o f North Vancouver. 21 w i n t e r months o f 1982. During t h i s time the f i e l d g e n e r a l l y appeared soggy and u n t r a f f i c a b l e . A l s o , a f t e r heavy r a i n f a l l , f r e e water as deep as 0.10 m t h a t covered a s u r f a c e area o f diameter i n excess o f 10 m c o l l e c t e d on the f i e l d s u r f a c e . By m o n i t o r i n g the depth t o the water t a b l e , the s u r f a c e water was confirmed t o be ponded. C o n f i r m a t i o n was p r o v i d e d by o b s e r v i n g t h a t the f r e e water remained on the s u r f a c e w h i l e the water t a b l e was at depth. Importantly, t h i s a l s o i n d i c a t e d t h a t the h y d r o l o g i c problems, at l e a s t i n p a r t , were i n f i l t r a t i o n problems. C o n v e r s e l y , i f the problem had been caused by f l o o d i n g , due to inadequate sub- s u r f a c e s o i l d r a i nage, the f r e e water would have been p a r t o f a water t a b l e t h a t i n t e r c e p t s the f i e l d s u r f a c e . T h i s was not the case. An examination o f the s o i l p r o f i l e a l s o p r o v i d e d important i n f o r m a t i o n ; see F i g . 3. D i f f e r e n c e s between the l a y e r s c o u l d be seen, wi t h a d i s t i n c t boundary e x i s t i n g between the 'Top Layer' and ' p i t r u n ' l a y e r s . A pronounced 'surface l a y e r ' a l s o showed up at the s o i l s u r f a c e , j u s t below the t h a t c h , i t was apparent t h a t a d e f i n i t e c o m p o s i t i o n a l change had o c c u r r e d i n the 1 sand/sawdust' mixed 'Top Layer". The ' s u r f a c e l a y e r ' was e n r i c h e d w i t h p a r t i a l l y decomposed o r g a n i c matter. The l a y e r was approximately 0.01 m to 0.02 m i n t h i c k n e s s , and was n o t a b l y darker i n c o l o u r than the sandy m a t e r i a l s below i t . The i n t e r f a c e between the 'surface l a y e r ' and the 'sand/sawdust' mixture, t h e r e f o r e , was seen as a d i s t i n c t t r a n s i t i o n from a compact, dark brownish, sandy s o i l , h i g h i n d i s i n t e g r a t e d , but o n l y p a r t i a l l y decomposed, o r g a n i c matter, to a l o o s e r , p a l e r and g r e y i s h c o l o u r e d , sandy s o i l , which was i n t e r s p e r s e d w i t h sawdust t h a t remained r e l a t i v e l y 22 F i g u r e 3; The Lower Premier S p o r t s f i e l d Depth P r o f i l e 23 i n t a c t . Moreover, i t was noted t h a t a l a y e r of 'thatch' was p r e s e n t over most o f the f i e l d , although i n p l a c e s e x t e n s i v e p a t c h i n e s s and t h i n n i n g o f the p l a n t cover was e v i d e n t , e s p e c i a l l y near c e n t r e - f i e l d . Presumably the d i s r u p t e d s u r f a c e was caused by e x c e s s i v e wear. Here, both the grass 'sward' and 'thatch' are i n c l u d e d i n the p l a n t cover d e s c r i p t i o n , the 'sward' being the top growth and the t h a t c h the combination of r o o t s , rhizomes, and p l a n t d e t r i t u s l y i n g on top o f the s o i l . 1.4 C l i m a t e C l i m a t e and weather are fundamental concerns i n almost any d i s c u s s i o n i n v o l v i n g s o i l hydrology. The weather experienced i n the D i s t r i c t o f North Vancouver i s t y p i c a l l y c o o l and wet, although t h e r e i s c o n s i d e r a b l e v a r i a b i l i t y throughout the r e g i o n . T h i s humid, temperate c l i m a t e i s c h a r a c t e r i s t i c o f the southern c o a s t o f B r i t i s h Columbia. The c l o s e p r o x i m i t y o f the P a c i f i c Ocean p r o v i d e s an enormous r e s e r v o i r o f heat energy and moisture t o moderate a i r temperatures and m a i n t a i n humid c l i m a t i c c o n d i t i o n s . The i s o h y e t map o f 'Mean Annual P r e c i p i t a t i o n i n Greater Vancouver' (Hay and Oke, 1976), shows the D i s t r i c t o f North Vancouver r e c e i v i n g a range i n mean annual r a i n f a l l between approximately 1800 mm and 2500 mm; see F i g . 4. A l s o , the map shows the v a r i a b i l i t y o f mean annual r a i n f a l l r e c e i v e d over the r e g i o n , from v a l u e s l e s s than 1000 mm to over 3000 mm. The wetter months o f the year, which were taken to be those r e c e i v i n g g r e a t e r than 150 mm .of r a i n f a l l measured at the Lynn F i g u r e 4; 'Mean Annual P r e c i p i t a t i o n ' i n Greater Vancouver - (Hay, J . and Oke, T., 1976). 25 Creek weather s t a t i o n , produce a r a i n y season from September through t o A p r i l ; see F i g . 5. 'Short d u r a t i o n , ' I n t e n s i t y , D u r a t i o n , Frequency'' r a i n f a l l i n f o r m a t i o n f o r the 19 year p e r i o d from 1964 to 1983 f o r the Lynn Creek weather s t a t i o n i s a l s o a v a i l a b l e ; see F i g . 2. These graphs show the p r o b a b i l i t y o f occurrence o f i n t e n s e , s h o r t d u r a t i o n r a i n f a l l events r e t u r n p e r i o d s o f 2, 5, 10, 25, 50, and 100 y e a r s . Low i n t e n s i t y and s h o r t e r d u r a t i o n r a i n f a l l events occur w i t h g r e a t e r frequency. The causes behind t h i s weather are f r o n t a l low p r e s s u r e systems generated out over the P a c i f i c Ocean. These storms move onshore w i t h both seasonal and s u c c e s s i o n a l r e g u l a r i t y . T h e i r a i r masses become moisture l a d e n i n the p r o c e s s . Although Vancouver I s l a n d and the Olympic Mountains p r o v i d e the area l i m i t e d p r o t e c t i o n from these c y c l o n i c d i s t u r b a n c e s , c o n d i t i o n s s t i l l e x i s t f o r abundant r a i n f a l l i n the Greater Vancouver Region. On t h e i r eastward t r a c k the a i r masses pass over the Coast Range Mountains, i n v o l v i n g a r i s e i n e l e v a t i o n o f over 1000 m. Orographic c o o l i n g subsequently takes p l a c e . Once the atmosphere can no l o n g e r r e t a i n i t s moisture, p r e c i p i t a t i o n i s r e l e a s e d . The D i s t r i c t o f North Vancouver and the Lower Premier S p o r t s f i e l d are s i t u a t e d at the f o o t , and on the windward s i d e , o f t h i s mountain range. C o n s i d e r a b l e r a i n f a l l p r e c i p i t a t i o n i s t y p i c a l l y r e c e i v e d . In the D i s t r i c t o f North Vancouver the l o c a l topography a l s o has an i n f l u e n c e on the amount of p r e c i p i t a t i o n r e c e i v e d at p a r t i c u l a r s i t e s . As the low p r e s s u r e d i s t u r b a n c e s move o f f the ocean and onto the c o a s t , p a r c e l s o f moist a i r s e l e c t i v e l y f u n n e l up the v a l l e y s and draws between the mountains. T h i s F i g u r e 5 ; Long Term, Mean Monthly Average R a i n f a l l f o r Lynn Creek, North  Vancouver; Prepared by Atmospheric Environment S e r v i c e , Environment Canada. > -i •x h •2 o 1 i AO o 3 SO < u. Z 5 0 1 Ul Zoo < UJ < I SO loo 3o6 AA, A/X •AA //X A A Y/\ YY, L o w e T e R n , MEAKJ A U U U A L A V E R A G E R ^ I U F A L U = 2.580 mm V'/ A / A A /A \/A Y: <A V/ '// ' V / '/ '••'A ICG A - ,-1 lo8 T -_/ ,-> 73.2. / 7 A A A Ito'b * /" A 3 o ^ • // A / . S A V,-YA A '-VV 3^1 A A s i J M O K J T H S r4 388 V, YA •' --' •-1 • .-' • >v '/A\ A / A / s Y/ ^ A YY to 27 r e s u l t s i n enhanced c l o u d formation and i n c r e a s e d l o c a l p r e c i p i t a t i o n (Hay and Oke, 1976). The Lower Premier S p o r t s f i e l d , s i t u a t e d on the outwash p l a i n o f Lynn V a l l e y , i s e s p e c i a l l y v u l n e r a b l e t o t h i s l o c a l i z e d e f f e c t . On a m i c r o c l i m a t i c s c a l e the s i t e i s w e l l shaded by surrounding steep, f o r e s t e d h i l l s l o p e s . T h i s undoubtedly c o n t r i b u t e s t o the s i t e being g e n e r a l l y c o o l and damp. F i e l d wetness i s p a r t i c u l a r l y a problem throughout the r a i n y months from October through A p r i l . The r a i n f a l l i n f o r m a t i o n used i n the study was c o l l e c t e d at the North Vancouver, Lynn Creek weather s t a t i o n . The s t a t i o n i s a d m i n i s t e r e d by Environment Canada, Atmospheric Environment S e r v i c e and i s l o c a t e d approximately 4.8 km due n o r t h o f the Lower Premier S p o r t s f i e l d , a t an e l e v a t i o n o f 191 m above mean sea l e v e l . The s p o r t s f i e l d i s a t an e l e v a t i o n o f approximately 23 m. 1.5 Research O b j e c t i v e s and Hypothesis 1.5.1 Research o b j e c t i v e s 'Ponding' i s a h y d r o l o g i c a l c o n d i t i o n where f r e e s t a n d i n g water has accumulated due to the " p r e v a l e n t i n f i l t r a t i o n c a p a c i t i e s (or i n f i l t r a b i l i t i e s ) b e i n g exceeded by the r a t e o f water supply t o (the) s o i l s u r f a c e " (Rubin and S t e i n h a r d t , 1964). I t re p r e s e n t s a s e r i o u s p l a y a b i l i t y problem f o r s a n d f i e l d s . Indeed, the main reason f o r u s i n g sands at a l l i s t o p r o v i d e a porous, w e l l d r a i n e d s o i l medium, f r e e from such h y d r o l o g i c o c c u r r e n c e s . So the q u e s t i o n a r i s e s , how do these 28 p r o b l e m s d e v e l o p ? I t s e e m s t h e i n i t i a l b e n e f i t s d e r i v e d f r o m s a n d a r e n o t a s p e r s i s t e n t a s o n e w o u l d h o p e . A l i k e l y a n s w e r l i e s i n t h e s o i l - a l t e r i n g p h y s i c a l p r o c e s s e s , w h i c h w h e n g i v e n s u f f i c i e n t t i m e m a k e t h e i r m a r k o n a l l s o i l s . U n d o u b t e d l y , t h e s o i l s u r f a c e e n v i r o n m e n t o f t h e s p o r t s f i e l d i s a l t e r e d c o n t i n u a l l y i n r e s p o n s e t o p l a y e r u s e , m a n a g e m e n t p r a c t i c e s , c h a n g e s i n w a t e r c o n t e n t , f e r t i l i z e r a p p l i c a t i o n s , a n d r h i z o s p h e r e a c t i v i t y . T o i s o l a t e a l l t h e s e i n t e r d e p e n d e n t v a r i a b l e s a n d t h e n t r y t o u n d e r s t a n d a l l t h e i r i n t e r a c t i o n s o v e r t i m e w o u l d b e a n a r d u o u s c h a l l e n g e . F r o m a p r e l i m i n a r y a s s e s s m e n t i t s e e m s l i k e l y t h a t a c h a n g e o f t h e p h y s i c a l c o m p o s i t i o n o f t h e s o i l w o u l d c o n t r i b u t e t o t h e r e d u c e d s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) . I n s p e c t i o n o f t h e s o i l p r o f i l e o f t h e L o w e r P r e m i e r S p o r t s f i e l d s h o w e d t h a t c h a n g e s h a d o c c u r r e d , p r o d u c i n g a d e f i n i t e l a y e r j u s t b e l o w t h e p l a n t c o v e r ; s e e F i g . 3 . S u c h a ' s u r f a c e l a y e r ' c o u l d o n l y h a v e d e v e l o p e d f r o m e i t h e r t h e s a n d b e i n g s u p p l i e d w i t h m a t e r i a l a d d i t i o n s o r b e i n g p h y s i c a l l y t r a n s f o r m e d . G i v e n t h e i n e r t a n d s t a b l e p r o p e r t i e s o f s a n d s t h e o b s e r v e d c h a n g e w a s l i k e l y c a u s e d b y a d d i t i o n s . T h e a c c u m u l a t i o n o f p l a n t d e t r i t a l m a t t e r r e p r e s e n t e d t h e o n l y s i g n i f i c a n t i n p u t o f m a t e r i a l . P a r t i a l l y d e c o m p o s e d i n t o a p u l p y f o r m , t h i s m a t e r i a l p r e s u m a b l y w o r k e d i t s w a y i n t o t h e s a n d , c l o g g i n g t h e p o r e s b e t w e e n t h e s a n d p a r t i c l e s . T h e c l o g g i n g p r o c e s s w o u l d b e f u r t h e r a c c e l e r a t e d b y i n t e n s i v e t u r f g r a s s p r o d u c t i o n a n d b y s u b s e q u e n t c o m p a c t i o n f r o m p l a y a n d e q u i p m e n t t r a f f i c . I t s e e m s l i k e l y t h a t t h e p o r e c l o g g i n g o f t h e ' s u r f a c e l a y e r ' p r e s e n t e d t h e m a j o r b a r r i e r t o t h e i n f i l t r a t i o n o f w a t e r . 29 A simple p r o o f o f the hyp o t h e s i s was not c o n s i d e r e d f e a s i b l e . I t would have r e q u i r e d a f i e l d i n f i l t r a t i o n study where runs would be made both w i t h and without the 'surface l a y e r ' i n p l a c e . The methods i n v o l v e d would i n c l u d e i n s i t u i n f i l t r o m e t r y and/or the sampling o f u n d i s t u r b e d cores t o be run i n the l a b o r a t o r y . The l o g i s t i c s o f s e t t i n g up t h i s type o f study were c o n s i d e r e d f o r m i d a b l e . The main concern was the problem o f p e e l i n g o f f the 'surface l a y e r ' without d i s t u r b i n g the s o i l . Because o f the v a r i a b i l i t y t o be expected over the s u r f a c e o f the f i e l d , i t would a l s o have r e q u i r e d a g r e a t many samples f o r the data t o be u s e f u l . I t i s b e l i e v e d t h a t t h i s v a r i a b i l i t y would have s e r i o u s l y confounded the r e s u l t s as t o whether they t r u l y represented the i n f i l t r a t i o n p r o c e s s , or pr o c e s s e s , t h a t were o c c u r r i n g on the f i e l d . A l s o , s i n c e the s p o r t s f i e l d was h e a v i l y used the d i s r u p t i o n from such f i e l d sampling would have been unacceptable. With r e s p e c t t o the causes o f the ponding phenomenon, the mechanisms and processes i n v o l v e d , and the management problems a s s o c i a t e d w i t h i t , i t was decided t h a t a s t a t i s t i c a l approach would r e v e a l fewer i n s i g h t s than would a model-based approach t h a t addressed w h o l i s t i c a l l y the hydrology o f the ponding problem. I t i s r e a l i z e d t h a t i n choosing the model approach the q u e s t i o n as t o whether the hypothesis i s c o r r e c t or not, can only be answered on the b a s i s o f how c r e d i b l e the model i s and on how good the i n p u t s i n t o the model are. A d m i t t e d l y , s i m p l i f y i n g assumptions have t o be made to d e s c r i b e the p h y s i c a l dimensions o f the pond, the l a y e r depths, and the h y d r o l o g i c p r o c e s s e s at work. I t i s f e l t , however, t h a t the s e m i - e m p i r i c a l model presented does r e f l e c t a s a t i s f a c t o r y p h y s i c a l 30 i n t e r p r e t a t i o n o f the ponding phenomenon. The approach taken was t o t r e a t the e n t i r e f i e l d as one l a r g e i n f i l t r o m e t e r . Instead o f r e l y i n g on numerous p o i n t - s p e c i f i c measurements, the s e m i - e m p i r i c a l model was developed to c h a r a c t e r i z e the ponding process as i t appeared on the f i e l d . Thus, the l i m i t a t i o n s o f the r e s e a r c h are not r e l a t e d to a s t a t i s t i c a l a n a l y s i s o f the r e s u l t s but i n s t e a d to the v a l i d i t y o f the s i m p l i f y i n g assumptions made i n the model. The main o b j e c t i v e o f the study was t o c o n t r i b u t e t o the u n d e r s t a n d i n g o f the s o i l p h y s i c a l processes and mechanisms a f f e c t i n g the i n f i l t r a b i l i t y o f s a n d f i e l d s . The h y d r o l o g i c behaviour t h a t i s observed on the Lower Premier S p o r t s f i e l d i s u l t i m a t e l y the consequence of i t s s o i l p r o p e r t i e s and s o i l h y d r o l o g i c c h a r a c t e r i s t i c s i n response t o the r a i n f a l l , or i r r i g a t i o n , r e c e i v e d . T h e r e f o r e , by f i r s t a s s e s s i n g how the f i e l d was c o n s t r u c t e d , and by a n a l y z i n g the p h y s i c a l p r o p e r t i e s and h y d r o l o g i c c h a r a c t e r i s t i c s o f i t s s o i l m a t e r i a l s , a r a t i o n a l b a s i s i s p r o v i d e d from which t o address the h y d r o l o g i c problems f a c e d . H o p e f u l l y , the t h e s i s l e a v e s those r e s p o n s i b l e f o r s p o r t s f i e l d management b e t t e r informed and more reassured about what consequences to a n t i c i p a t e from t h e i r s p o r t s f i e l d designs and f i e l d maintenance programs, p a r t i c u l a r l y as they r e l a t e to the i n f i l t r a t i o n and ponding o f t h e i r p l a y i n g s u r f a c e s . W i t h i n the c o n t e x t o f the h y p o t h e s i s the t h e s i s o b j e c t i v e s were as f o l l o w s : I) To e s t a b l i s h the cause o f the accumulation o f f r e e s t a n d i n g water on the Lower Premier S p o r t s f i e l d . I I ) To c h a r a c t e r i z e the f r e e s t a n d i n g water i n terms o f i t s r i s e and r e c e s s i o n over time. 31 I I I ) To d e s c r i b e the water balance a s s o c i a t e d w i t h the f r e e s t a n d i n g water and q u a n t i f y i t s c o n s t i t u e n t i n p u t , output, and change i n sto r a g e terms. IV) To c h a r a c t e r i z e the 's u r f a c e l a y e r ' i n terms o f i t s s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y . V) To expound upon the management i m p l i c a t i o n s o f the 'su r f a c e l a y e r ' and make p r a c t i c a l management recommendations. 1.5.2 Hypothes i s The h y p o t h e s i s i s t h a t a s o i l ' s u r f a c e l a y e r ' o f low s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K 1) i s p r i m a r i l y r e s p o n s i b l e f o r ponding on the Lower Premier S p o r t s f i e l d . Furthermore, through a pond water balance a n a l y s i s , a narrow range o f p o s s i b l e v a l u e s f o r K i s i n f e r r e d . 32 2. MATERIALS AND METHODS 2.1 General Most o f the s o i l t e s t s r e q u i r e d t h a t d i r e c t sampling o f the sands from the s p o r t s f i e l d be avoided so as not t o d i s r u p t the p l a y i n g s u r f a c e . Instead, ' s i m i l a r ' sands were analyzed. Assurances were made t h a t the sands t e s t e d came from the same sources as those used i n the c o n s t r u c t i o n o f the f i e l d . * The methods employed i n the a n a l y s i s i n c l u d e those t h a t g i v e a comprehensive d e s c r i p t i o n o f the p h y s i c a l and h y d r o l o g i c a l p r o p e r t i e s o f the sand as w e l l as a s o i l p r o f i l e d e s c r i p t i o n from s o i l probe samples taken i n the f i e l d . Most o f the t e s t s i n v o l v e d l a b o r a t o r y analyses although important f i e l d measurements, p a r t i c u l a r l y o f the ponding p r o c e s s , were a l s o made. 2.2 S o i l s 2.2.1 S o i l P h y s i c a l T e s t s The bulk 'Fraser R i v e r ' sand sample came from the s i t e o f a new s p o r t s f i e l d , which was being c o n s t r u c t e d i n the D i s t r i c t o f North Vancouver. The bulk sampling procedure i n v o l v e d s h o v e l l i n g a 'b a g f u l ' o f sand w h i l e the new f i e l d was prepared f o r f i n a l grade. T h i s was done p r i o r t o the sand being * P e r s o n a l communication w i t h the Superintendent o f Parks, D i s t r i c t o f North Vancouver. amended w i t h sawdust. Approximately 0.01 m of sand was c o l l e c t e d . The 'North Van' sand was sampled from a t r u c k l o a d dumped o f f s i t e . Bulk sampling o f the 'North Van' sand was c a r r i e d out u s i n g the 'Coning and Q u a r t e r i n g Method' as d e s c r i b e d i n the Manual on T e s t S i e v i n g Methods, (1972 E d i t i o n ) , ASTM Committee E-29. The sampling method i n v o l v e d s h o v e l l i n g sand from the c e n t r e o f the dumped p i l e i n t o a cone on a (1.2 x 1.4 m) sheet o f plywood. S p e c i a l c a r e was taken not t o sample from the s u r f a c e o f the dumped p i l e , p a r t i c u l a r l y near i t s base. The 3 s i z e o f the cone, approximately 0.004 m , was d i c t a t e d by how much c o u l d be p r a c t i c a b l y 'coned and q u a r t e r e d ' on the plywood. Ten cones were s h o v e l l e d and each cone was q u a r t e r e d t w i c e . Each o f the t e n bulk samples p r o v i d e d approximately 0.001 m of sand. The sand was c o l l e c t e d i n numbered p l a s t i c bags. The ten 'North Van' sand samples p r o v i d e d approximately 0.01 m o f bulk sampled sand f o r l a t e r a n a l y s e s . The s o i l p h y s i c a l t e s t s used to c h a r a c t e r i z e the 'Fraser R i v e r ' and 'North Van' sands are: 1) P a r t i c l e s i z e f r a c t i o n a t i o n ( i n c l u d i n g o r g a n i c matter and m i n e r a l matter content d e t e r m i n a t i o n s ) . 2) P a r t i c l e s i z e a n a l y s i s by s i e v i n g 3) P a r t i c l e d e n s i t y (p ) 4) Bulk d e n s i t y (P^) 5) P o r o s i t y Again, r e f e r e n c e was made t o the Manual on T e s t S i e v i n g  Methods (ASTM Committee E-29) f o r the F r a c t i o n a t i o n and P a r t i c l e S i z e A n a l y s e s . Bulk samples were a i r d r i e d and reduced to a subsample, or ' s p l i t ' sample, mass t h a t ranged between 0.10 kg 34 and 0.40 kg. T h i s r e q u i r e d r e d u c i n g each bulk sample t h r e e times. A commercially a v a i l a b l e 'Sample S p l i t t e r ' was used. Because the width o f the passages i n the ' S p l i t t e r ' i s 13 mm, and t h e r e were concerns about i t c l o g g i n g w i t h o v e r s i z e d p a r t i c l e s , a 10 mm x 10 mm, g a l v a n i z e d , s t e e l mesh s c r e e n was p l a c e d over top o f the 'Sample S p l i t t e r ' t o remove the l a r g e r p a r t i c l e s . The 10 mm diameter, t h e r e f o r e , became the upper p a r t i c l e s i z e l i m i t f o r the analyses t h a t f o l l o w e d . 2.2.1.1 ' P a r t i c l e s i z e f r a c t i o n a t i o n ' As d e s c r i b e d , the sample s p l i t t i n g process i n c l u d e d s c r e e n i n g o f f p a r t i c l e s >10.0 mm i n diameter. T h i s removed any l a r g e r twigs, r o c k s , and lumps o f c l a y from the samples t o be l a t e r t e s t e d and analysed. In the dumped p i l e o f 'North Van' sand, however, l a r g e amorphous lumps o f c l a y , up to 0.4 m i n l e n g t h , were observed. Presumably, these lumps came from c l a y l e n s e s e x i s t i n g i n the r i v e r d e p o s i t which was dredged. As a g e n e r a l p r a c t i c e , these lumps o f c l a y are removed when the sand i s p l a c e d and graded d u r i n g f i e l d c o n s t r u c t i o n . * Only a few i n d i v i d u a l p a r t i c l e s remained on the 10.0 mm x 10.0 mm s c r e e n . I t i s assumed t h a t t h i s l a r g e r p a r t i c l e s i z e f r a c t i o n has an i n s i g n i f i c a n t e f f e c t on the s p o r t s f i e l d as a whole. The f i n e e a r t h f r a c t i o n , t h a t i s m a t e r i a l <2.00 mm diameter p a r t i c l e s i z e , was then separated from the ' s p l i t ' samples t h a t had passed through the s c r e e n . The p a r t i c l e s i z e * P e r s o n a l communication wi t h the Superintendent o f Parks, D i s t r i c t o f North Vancouver. 35 f r a c t i o n a t i o n procedure was as f o l l o w s : i ) A i r - d r y ' s p l i t ' samples were passed through a 2.00 mm wire mesh s i e v e . The m a t e r i a l p a s s i n g through the s i e v e was c o l l e c t e d i n a s i e v i n g pan o f known weight. Along w i t h the >2.00 mm diameter s i z e p a r t i c l e s , some 'sandy' aggregates a l s o remained on the s i e v e . With s l i g h t p r e s s u r e between one's f i n g e r s , however, these aggregates crumbled i n t o f i n e e a r t h s i z e d s o i l p a r t i c l e s , which a l s o passed through the 2.00 mm s i e v e . i i ) The >2.00 mm f r a c t i o n t h a t remained on the s i e v e was c o l l e c t e d and weighed i n a t a r e d weighing boat. i i i ) The o r g a n i c matter fragments i n the >2.00 mm f r a c t i o n were v i s i b l y r e c o g n i z a b l e and removed by hand. The remaining m i n e r a l matter was again weighed and the mass o f the o r g a n i c matter determined by d i f f e r e n c e . The o r g a n i c matter and m i n e r a l matter contents i n the >2.00 mm f r a c t i o n were c a l c u l a t e d on a mass b a s i s . i v ) The f i n e e a r t h (<2.00 mm diameter s i z e ) f r a c t i o n t h a t was c o l l e c t e d i n the s i e v i n g pan was weighed and subsequently oven d r i e d o v e r n i g h t at 105 °C. v) The oven d r i e d s o i l and s i e v i n g pan were weighed. The ' a i r dry' water content (w Q^) o f the s o i l was determined u s i n g the d i f f e r e n c e i n mass. v i ) The oven-dried, <2.00 mm diameter s i z e f r a c t i o n was t r a n s f e r r e d i n t o a c r u c i b l e o f known mass. Together they were weighed. They were then p l a c e d i n a m u f f l e furnace f o r a minimum o f 5 h r s . at 550 °C. The o r g a n i c matter was removed on i g n i t i o n . The remaining m i n e r a l ash was c o n s i d e r e d n e g l i g i b l e r e l a t i v e t o the mass o f the m i n e r a l f r a c t i o n . 36 v i i ) The 'muffled' sample was removed from the furnace and c o o l e d i n a d e s i c c a t o r . Once c o o l e d , the sample was weighed to determine the o r g a n i c matter l o s s . The o r g a n i c matter and m i n e r a l matter contents f o r the <2.00 mm d i a m e t e r - s i z e f r a c t i o n , on a mass b a s i s , were c a l c u l a t e d by d i f f e r e n c e . 2.2.1.2 ' P a r t i c l e s i z e a n a l y s i s by s i e v i n g ' A p a r t i c l e s i z e a n a l y s i s was c a r r i e d out on the sands, the purpose o f which was to determine the d i s t r i b u t i o n o f s o i l s e p a r a t e s on a mass b a s i s . The s i z e groupings o f the s o i l s e p a r a t e s are g i v e n i n the United S t a t e s Department o f A g r i c u l t u r e , ' S o i l Separate S i z e C l a s s i f i c a t i o n ' system; see T a b l e I I I . The system i s d e s c r i b e d i n the S o i l Survey Manual, U.S.D.A. Handbook No. 18, pp. 206-207. The method employed was the 'Mechanical S i e v e Shaker Method', as d e s c r i b e d i n the Manual  on T e s t S i e v i n g Methods (1972 e d i t i o n ) , A.S.T.M. Committee (E-29). The method r e q u i r e s a nest o f stacked p r e c i s i o n wire mesh s i e v e s , each s i e v e c o r r e s p o n d i n g , or being c l o s e , t o a sand s e p a r a t e s i z e c l a s s l i m i t ; see T a b l e IV. T e s t s were performed on the p r e v i o u s l y 'muffled', <2.00 mm p a r t i c l e diameter s i z e f r a c t i o n . Each sample was a i r dry. The samples were s i e v e d f o r 900 s (15 minutes) on a mechanical ('Rotap') s i e v e shaker. Three 'Fraser R i v e r ' sand samples and n i n e 'North Van' sand samples were s i e v e d . The sand s i z e d s e p arates were s e q u e n t i a l l y added to the t a r e d s i e v i n g pan and weighed. The cumulative percentage mass amounts o f the sand separates are r e p r e s e n t e d as 'Cumulative P a r t i c l e S i z e D i s t r i b u t i o n ' curves; see F i g u r e 16 i n S e c t i o n 3.1. P a r t i c l e s i z e i s represented i n 37 Ta b l e I I I ; S o i l Separate S i z e C l a s s i f i c a t i o n * 12.7 mm** > GRAVEL > 2.00 mm SANDS: 2 .00 mm > very coarse > 1 .00 mm 1 .00 mm > coarse > 0. 500 mm 0. 500 mm > medium > 0. 250 mm 0. 250 mm > f i n e > 0. 100 mm 0. 100 mm > very f i n e > 0. 050 mm 0. 050 mm > SILT > 0.002 mm 0. 002 mm > CLAY * U.S. Department o f A g r i c u l t u r e c l a s s i f i c a t i o n o f s o i l f r a c t i o n s a c c o r d i n g t o p a r t i c l e diameter ranges. ** The upper bound f o r the g r a v e l s i z e f r a c t i o n used i n the study was 10.0 mm r a t h e r than 12.7 mm (1/2 i n c h ) . T a b l e IV; Sand Separate S i z e , C l a s s Upper L i m i t s (U.S.D.A. C l a s s i f i c a t i o n System) and Corresponding, Wire Mesh Si e v e S i z e s S o i l Separate S i z e C l a s s L i m i t s S i e v e S i z e s Upon Which S o i l Separates C o l l e c t * G r a v e l : > 2.00 mm 2.00 mm Very Coarse Sand: 1.00 - 2.00 mm 1.00 mm Coarse Sand: 0.50 - 1.00 mm 0.50 mm Medium Sand: 0.25 - 0.50 mm 0.25 mm F i n e Sand: 0.100 - 0.25 mm 0.104 mm Very F i n e Sand: 0 .050 - 0.100 mm 0.053 mm S i l t and C l a y : < 0.050 mm S i e v i n g pan * T h i s sequence o f s i e v e s i z e s r e p r e s e n t s the s t a c k i n g order i n the 'nest' o f s i e v e s used i n the p a r t i c l e s i z e a n a l y s i s . 38 terms o f p a r t i c l e diameter (D). S i g n i f i e d w i t h the s u b s c r i p t ( x ) , D r e p r e s e n t s the p a r t i c l e diameter a t which a percentage f r a c t i o n (x) on the 'Cumulative P a r t i c l e S i z e D i s t r i b u t i o n ' curve i s s m a l l e r . Furthermore, the ' U n i f i e d S o i l C l a s s i f i c a t i o n (U.S.C) System' w i t h i t s ' C o e f f i c i e n t o f U n i f o r m i t y ( C y ) ' and ' C o e f f i c i e n t o f Curvature (C^)' was used t o c h a r a c t e r i z e the sands. Using t h i s system, both the 'Fraser R i v e r ' and 'North Van' sands are c h a r a c t e r i z e d as being p o o r l y graded. The 'U.S.C. System' i n c o r p o r a t e s the c o e f f i c i e n t s Cy and C c t o i n t e r p r e t the 'Cumulative P a r t i c l e S i z e D i s t r i b u t i o n 1 c u r v e s . These ' C o e f f i c i e n t s ' c h a r a c t e r i z e the g e n e r a l s l o p e and shape o f the cu r v e s . They are d e f i n e d as f o l l o w s ( C r a i g , 1983). C o e f f i c i e n t o f U n i f o r m i t y (C„) = D--/D..-U b U 1U C o e f f i c i e n t o f Curvature (C c) = D 3 o 2 / D 6 0 D 1 0 Using the 'U.S.C. System', the sand i s c h a r a c t e r i z e d as being e i t h e r 'well graded' or 'poorly graded'. 'Well graded (SW)' sands r e q u i r e 0-5 % f i n e s (<0.075 mm p a r t i c l e diameter s i z e ) w i t h ( C u > 6) and (1 < C c < 3). 'Poorly graded (SP) 1 sands, although they a l s o r e q u i r e 0-5 % f i n e s , do not s a t i s f y the SW ' C o e f f i c i e n t ' requirements. The term 'graded', i n s t e a d o f • s o r t e d ' , i s used i n the 'U.S.C. System' because o f i t s e n g i n e e r i n g b i a s . A 'poorly graded' sand and a 'well graded' sand are g e n e r a l l y r e f e r r e d t o as being 'well s o r t e d ' and 'poorly s o r t e d ' , r e s p e c t i v e l y , i n the s o i l s c i e n c e l i t e r a t u r e . 2.2.1.3 D e n s i t y of s o l i d s (p ) 39 The d e n s i t y of s o l i d s o f the 'North Van' sand was determined u s i n g the pycnometry d e s c r i b e d by G.R. Blake i n Methods o f S o i l A n a l y s i s , P a r t I [Black, C.A.(ed.)], Agronomy No.9, 1965; pp. 371-373. The method u t i l i z e s d i s t i l l e d water. S i x sub-samples, o f approximately, 0.025 kg mass, were taken from the ' s p l i t ' samples. The d e n s i t y of water (P w) at the o p e r a t i n g temperature i s taken from the T a b l e : 'Absolute Density of Water 1 i n the Handbook o f Chemistry and P h y s i c s , ( 4 — E d . ) , The Chemical Rubber Co., 1964. The p a r t i c l e d e n s i t y o f the 'Fraser R i v e r ' sand was assumed t o equal t h a t of the 'North Van' sand. The p a r t i c l e d e n s i t y o f the sawdust was not o b t a i n e d . 2.2.1.4 'Bulk d e n s i t y ( P b ) ' The bulk d e n s i t i e s o f both the <10.0 mm and the <2.00 mm f r a c t i o n s f o r both sands were determined. The sands were r e c o n s t i t u t e d and c l o s e l y packed i n the l a b o r a t o r y i n such a manner as t o s i m u l a t e c o n d i t i o n s i n the f i e l d . Ten 'Fraser R i v e r " sand samples and n i n e 'North Van' sand samples were analyzed. The p b o f the <10.0 mm f r a c t i o n was c a l c u l a t e d d i r e c t l y from mass and volume measurements. The p^ f o r the <2.00 mm f r a c t i o n was c a l c u l a t e d by c o r r e c t i n g f o r the mass and volume c o n t r i b u t i o n o f the 2.00 t o 10.0 mm g r a v e l s i z e f r a c t i o n . The g r a v e l was separated by s i e v i n g from the ' s p l i t ' sample and by weighing. The volume of the g r a v e l was c a l c u l a t e d by d i v i d i n g i t s mass by the p a r t i c l e d e n s i t y t h a t was determined f o r the 'North Van' sand. The q u o t i e n t of the d i f f e r e n c e i n mass d i v i d e d by the d i f f e r e n c e i n volume gave the p, f o r the 40 <2.00 mm f r a c t i o n . I t i s assumed t h a t the g r a v e l - s i z e d p a r t i c l e s were i n d i v i d u a l l y i s o l a t e d w i t h i n the sand m a t r i x . To measure the <10.0 mm sample volumes, a t a r e d , 50 mL, p l a s t i c , graduated c y l i n d e r was used. An a i r - d r i e d sample was f i r s t poured i n t o the c y l i n d e r t o approximately the 50 mL g r a d a t i o n . I t was then tapped w i t h the handle o f a s c r e w d r i v e r u n t i l no f u r t h e r s e t t l i n g was observed. The s e t t l e d volume was recorded and the c y l i n d e r and i t s content weighed. The mass o f the sand sample was c a l c u l a t e d by s u b t r a c t i n g the mass o f the c y l i n d e r . From p r i o r d e t e r m i n a t i o n s the water contents (w a (j) o f the a i r d r i e d sand accounted f o r approximately 0.5 % o f i t s mass. The mass c o n t r i b u t i o n o f water was, t h e r e f o r e , c o n s i d e r e d n e g l i g i b l e . The bulk d e n s i t y o f the 'Fraser R i v e r ' sand mixed with sawdust was measured from u n d i s t u r b e d s o i l core samples taken from the 'Top Layer' o f the s p o r t s f i e l d . E i g h t s o i l core samples were taken below the 'surface l a y e r ' a c c o r d i n g t o the sampling p l a n g i v e n i n F i g . 6. The s o i l cores were approximately 3 . 0 x l 0 ~ 4 m3 and oven dry-weighings were taken. 2.2.1.5 ' P o r o s i t y ' T o t a l p o r o s i t y ( f) and ' w a t e r - f i l l e d ' ( 9 g ) p o r o s i t y were determined f o r both sands. T o t a l p o r o s i t y ( f) i s c a l c u l a t e d u s i n g the equ a t i o n f = l - (P^/Pg) <• which i n c o r p o r a t e s both c a l c u l a t e d and p g v a l u e s . I t was determined f o r both the <10.0 mm and <2.00 mm f r a c t i o n s . The ' w a t e r - f i l l e d ' p o r o s i t y was determined on the <10.0 mm f r a c t i o n . T h i s was done by f i r s t summing the cumulative 41 F i g u r e 6 ; S o i l Core Sampling P l a n * * Four r e p l i c a t e subsamples were taken a t each o f the 8 (I-V I I I ) sampling s i t e s . S i t e s I-IV were p u r p o s e f u l l y chosen t o be w i t h i n the ponded area (A). S i t e s V-VIII were w i t h i n the t o t a l catchment area (A n ) but o u t s i d e (A). 42 outflow o f water from the 'Hanging water column t e s t ' (see S e c t i o n 2.2.2.2) t o the moisture remaining i n the sample at the end o f the t e s t . Both amounts were determined g r a v i m e t i c a l l y but were converted t o volumes by d i v i d i n g the t o t a l mass o f 3 - 3 water by the d e n s i t y o f water ( P w ) / taken as 1.0x10 kgm . The c a l c u l a t e d t o t a l volume o f water was then d i v i d e d by the volume o f the sample to determine the ' w a t e r - f i l l e d ' p o r o s i t y o f the s o i l . 2.2.2 H y d r o l o g i c a l T e s t s and Analyses "An important s o i l p r o p e r t y i n v o l v e d i n the behaviour of s o i l water flow systems i s the c o n d u c t i v i t y o f the s o i l t o water. Q u a l i t a t i v e l y , the c o n d u c t i v i t y i s the a b i l i t y o f the s o i l t o t r a n s m i t water ( K l u t e , 1965)". Two d i f f e r e n t methods were used f o r determining the 'saturated h y d r a u l i c c o n d u c t i v i t y (K g) o f the two sands. For both methods i t i s assumed t h a t i s o t h e r m a l and laminar flow c o n d i t i o n s p r e v a i l , and t h a t Darcy's Law i s v a l i d . Darcy's Law s t a t e s : q = -K(AH/L) (2.1) Given, q = f l u x d e n s i t y (m.s - 1) K = h y d r a u l i c c o n d u c t i v i t y (m.s ) AH = change i n h y d r a u l i c head (or t o t a l p o t e n t i a l ) (m) L = l e n g t h (or t h i c k n e s s ) o f s o i l (m). F i v e 'Fraser R i v e r ' sand samples and s i x 'North Van' sand samples were e v a l u a t e d . 2.2.2.1 Sat u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) 43 i ) ' F a l l i n g Head' Permeameter Method The s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) o f the 'Fraser R i v e r ' sand was determined u s i n g the ' F a l l i n g Head' Permeameter Method. The apparatus used i n c l u d e d f i v e , 0.37 m x [0.051 m ( i . d . ) ] , c l e a r , a c r y l i c p l a s t i c tubes, s e t up v e r t i c a l l y as permeameter columns; see F i g . 7. A No. 11 stopper was i n s e r t e d i n the bottom o f each column. The stoppers were bored and f i t t e d w i t h a 0.05 m x [0.0095 m ( i . d . ) ] , c l e a r , a c r y l i c p l a s t i c tube o u t l e t . L a i d on top of the stopper was a l . 0 m m x l . 2 m m mesh, p l a s t i c s c r e e n f o l l o w e d by a 0.02 m t h i c k g r a v e l l a y e r f i l t e r . At the top o f the g r a v e l a piezometer was i n s e r t e d through the w a l l o f the column. The piezometer c o n s i s t e d o f a f o l d e d , b r a s s , mesh scre e n f i t t e d i n t o a bored No. 00 rubber stopper. An upper piezometer was i n s t a l l e d 0.20 m above t h i s lower piezometer. S i n c e t h i s second piezometer was above the s u r f a c e o f the s o i l the wire mesh s c r e e n was not r e q u i r e d , hence a l l o w i n g the use o f a 0.03 m x 0.003 m ( i . d . ) , c l e a r , a c r y l i c p l a s t i c tube f o r the purpose. The columns were p a r t i a l l y f i l l e d w i t h a i r - d r i e d sand to approximately 0.01 m below the upper piezometer. T h i s gave a sample l e n g t h between 0.18 m and 0.19 m. P a r t o f the f i l l i n g p r o cess was to tap the columns twenty times w i t h the handle o f a s c r e w d r i v e r w h i l e the sand was being poured i n t o the column. T h i s was done t o ensure c l o s e packing. Before s a t u r a t i n g , a i r was f i r s t evacuated by a p p l y i n g s u c t i o n from a vacuum a s p i r a t o r t o the top o f each permeameter column f o r 1200 s (20 minutes). A l l vents t o the atmosphere were c l o s e d . The a i r - e v a c u a t e d F i g u r e 7; ' F a l l i n g Head' Apparatus f o r Determination o f S a t u r a t e d H y d r a u l i c  C o n d u c t i v i t y (K ) o f the 'Fraser R i v e r ' Sand MAklOMETBB. &OAPX> Cou&TAMT ttCAD OU T F L O W U K I I T T o MArJOHRTER, i|l F R O M P K R M E A M B T B R Ptw\£AMETHB.: +- D-3 L - o.y* m PlEZoMSTERS. "To MAlOOHETBR, BoAB-D 0/„ Tb C o p f t T A U X M E A D O O T P L O W O U I T <S) SpRijJ^  CLAMP I I 1 DASHED LiWBS RepRESES>T R U B B E R . T U B I N > < % 45 columns were then wetted s l o w l y from below w i t h d i s t i l l e d water, which was at room temperature. To avoid ' b o i l i n g ' the water, which would cause d i s r u p t i o n o f the samples, the s u c t i o n r e q u i r e d t o siphon water i n t o the column was decreased t o an optimum l e v e l . The water l e v e l was allowed t o r i s e above the s u r f a c e o f the sand. At t h i s time the s u c t i o n was removed. Again, the column was tapped u n t i l no s e t t l i n g o f the sand was observed. T h i s was done at l e a s t one hundred times. At t h i s stage s a t u r a t i o n and c l o s e packing was assumed. P r i o r t o running the columns, i t was noted t h a t a t h i n l a y e r o f ' f i n e s ' had s e t t l e d on the sand s u r f a c e as a r e s u l t o f the p r e p a r a t o r y p r o c e s s . Water was made to flow downwards through the permeameter by p r o d u c i n g a p o s i t i v e h y d r a u l i c p o t e n t i a l d i f f e r e n c e across the l e n g t h o f the sample, w i t h the h y d r a u l i c p o t e n t i a l or ' t o t a l head' a t the top o f the sample g r e a t e r than t h a t at the bottom. The p i e z o m e t r i c measurements were made on a manometer board. H 1 and H 2 are the t o t a l head d i f f e r e n c e s between l o c a t i o n s 1 and 2 a t times t 1 and t 2 , r e s p e c t i v e l y ; see F i g . 7. Using the ' F a l l i n g Head' method the h y d r a u l i c head d i f f e r e n c e decreases over a recorded p e r i o d o f time. The r a t e o f decrease o f h y d r a u l i c p o t e n t i a l d i f f e r e n c e a c r o s s the sample, H, i s determined. The equation f o r c a l c u l a t i n g K g u s i n g the f a l l i n g head method, as presented by K l u t e and D i r k s e n ( K l u t e , 1986), i s : K g = [ a L / A ( t 2 - t 1 ) ] l n ^ / H j (2.2) Given: K = s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (m.s 1 ) 46 l e n g t h o f the s o i l sample (m) the c r o s s - s e c t i o n a l area o f the tube (stand-pipe) 2 extending above the sand sample (m ) 2 the c r o s s - s e c t i o n a l area o f the sand sample (m ) time ' i n i t i a l ' f o r a run (s) time a t the end o f a run (s) the h y d r a u l i c p o t e n t i a l d i f f e r e n c e across the sample at times t 1 and t^, r e s p e c t i v e l y . The range i n c a l c u l a t e d K g values i n c l u d e d those measured both w i t h and without the l a y e r o f ' f i n e s ' . F i v e runs were made wit h the ' f i n e s ' i n p l a c e and then f i v e more a f t e r the ' f i n e s ' were siphoned o f f . i n t e r e s t i n g l y , both the upper and lower l i m i t s of the range were measured i n the s e t where the f i n e s remained i n p l a c e . Consequently, the i n f l u e n c e o f the l a y e r o f f i n e s was assumed n e g l i g i b l e . i i ) 'Constant Head' Permeameter Method The s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) o f the 'North Van' sand was determined u s i n g the 'Constant Head' Permeameter Method. S i x 'Buchner f u n n e l ' ( t a b l e type, f i x e d p l a t e , p o r c e l a i n ) set-ups were c o n s t r u c t e d t o run s i m u l t a n e o u s l y . The 'Buchner f u n n e l s ' f a c i l i t a t e d u s i n g the brass core r i n g permeameters to h o l d the sand samples; see F i g . 8. The assembly o f the brass core r i n g permeameter i n v o l v e d t a p i n g two brass r i n g s and a brass r i n g 'bottom s e c t i o n ' i n t o a s i n g l e , segmented c y l i n d e r ; see F i g . 9. The 'top' r i n g and s i d e w a l l o f the 'bottom s e c t i o n ' were 0.012 m x 0.07 3 m ( i . d . ) , L = a = A = H 1 and H 2 = F i g u r e 8; 'Constant Head' Apparatus f o r Determination o f S a t u r a t e d H y d r a u l i c C o n d u c t i v i t y ( K ^ o f the 'North Van' Sand M l O O M E T g R &OABO G©»W,TAUT • J M E A D Dorr ' • OUTFLOW UwtT" T O H A p O K V H T H V l US - J U M C T i O K j I I I I I 11 -T- v 48 F i g u r e 9 ; P r e p a r a t i o n o f the Brass Core Ring Permeameter 2. CftPSS-SECTIONAL V^eVJ C P P R E P A R E D PteRMEAMETEg. 49 brass r i n g s . The 'bottom s e c t i o n ' was f i t t e d w i t h a p l a s t i c d i s c , which was cemented i n p l a c e . The permeameter 'body' was a 0.038 m x [0.073 m ( i . d . ) , brass r i n g . The brass c o r e r i n g permeameter was subsequently f i l l e d w i t h 'North Van' sand. To ensure c l o s e packing o f the sand the permeameter was tapped w i t h the handle o f a s c r e w d r i v e r u n t i l no f u r t h e r s e t t l e m e n t was observed. The 'top' r i n g was then removed and the sand l e v e l l e d . A f o u r p l y p i e c e o f c h e e s e c l o t h was p l a c e d over top o f the c y l i n d e r and secured w i t h a rubber band. The e n t i r e c y l i n d e r was i n v e r t e d and the 'bottom s e c t i o n ' removed. Again the sand was l e v e l l e d . With t h i s s t e p completed, the sand sample dimensions equal the i n s i d e dimensions o f the brass core r i n g c y l i n d e r . A new 'top' r i n g was then taped t o the top o f the i n v e r t e d permeameter. Next, the prepared 'permeameter' was p l a c e d on the 'Buchner f u n n e l ' . A 10.0 mm x 10.0 mm wire mesh s c r e e n was p l a c e d on the p e r f o r a t e d p a r t i t i o n i n the 'funnel' so as not t o r e s t r i c t l a t e r a l flow t o the p e r f o r a t i o n s . Once assembled, the sand w i t h i n the permeameter was s a t u r a t e d . T h i s i n v o l v e d the e v a c u a t i o n o f a i r through use o f a vacuum a s p i r a t o r ; see P i g . 10. A s l i g h t vacuum was a p p l i e d f o r at l e a s t ten minutes. Under a n e g a t i v e p r e s s u r e , d i s t i l l e d water was siphoned from a two l i t r e f l a s k i n t o the 'Buchner f u n n e l 1 below the s a n d - f i l l e d permeameter. The water l e v e l was s l o w l y r a i s e d i n the sand sample u n t i l s a t u r a t i o n was achieved. The 'Buchner f u n n e l ' was subsequently f i t t e d t o the outflow u n i t , the c o n s t a n t head u n i t and the manometer board. A h y d r a u l i c g r a d i e n t was e s t a b l i s h e d over i t s l e n g t h (L = 0.0 38 m) by l o w e r i n g the outflow u n i t , making sure t h a t the water t a b l e 50 F i g u r e 10; vacuum S a t u r a t i o n o f the Brass Core Ring Permeameter T o & U C . H U E K . F U U O E U X n u e x Jl II T o \ A c U t » K AsP'BAToR V*vCuo^> A - r r A c H M g U ROBBER, RIQ6, BucHMER. VEWT V r -F L A S K . (^) - rluH\BOI_T CLAKP±> 51 d i d not drop below the bottom o f the permeameter. The outflow o f water was c o l l e c t e d over time and i t s mass converted to a 3 - 3 volume by d i v i d i n g by p w = 1.0x10 kgm . By a p p l y i n g Darcy's Law (Eq. 2.1) the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) o f the sand was c a l c u l a t e d . The h y d r a u l i c r e s i s t a n c e produced by the c h e e s e c l o t h , the wire mesh, and the f u n n e l , i n c l u d i n g the t u b i n g and connectors, was assumed to be n e g l i g i b l e . 2.2.2.2 P a r t i a l water r e t e n t i o n c h a r a c t e r i s t i c s To determine the p a r t i a l water r e t e n t i o n c h a r a c t e r i s t i c s o f the sands the 'hanging water column t e s t ' was a p p l i e d d i r e c t l y t o the 's a t u r a t e d ' sand samples t h a t had p r e v i o u s l y undergone s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y t e s t s . The sand samples were a l r e a d y prepared i n the brass core r i n g c y l i n d e r s . S i x 'North Van' sand samples were t e s t e d . The t e s t s r e q u i r e d the removal o f the cores from the 'Buchner f u n n e l s ' and p l a c i n g them onto the prepared Hanging Water Column Apparatus. Care was taken t o work q u i c k l y and e f f i c i e n t l y so as t o avoid d e s a t u r a t i o n . The Hanging Water Column Apparatus was assembled as shown i n F i g . 11. A ' c i r c l e ' o f f i l t e r paper, w i t h an ' a i r e n t r y ( ^ A E V ) ' p r e s s u r e p o t e n t i a l o f approximately -0.80 m o f water, was used as a t e n s i o n p l a t e . The cumulative outflow of water was c o l l e c t e d i n p l a s t i c b o t t l e s . The t e s t was c a r r i e d out over a range of i n c r e m e n t a l drops i n p r e s s u r e p o t e n t i a l , from \|> = -0.10 m t o \|> = -0.50 m P P o f water, where the datum, or measurement r e f e r e n c e l e v e l f o r the outflow u n i t , was s e t at a h e i g h t c o r r e s p o n d i n g to the middle of the brass core r i n g . With each drop i n \|) water was 52 F i g u r e 1 1 ; Hanging Water Column Apparatus 1. E X P L O D E D V I E W O F  tUd&iKiGi W A T Eft, £ o L U r » \ > J T H R E A P E D S R A S S S C R E W S R U S H E R . G A S K E T „ * • FiLTgB. PAPER TEQ6IOP Pl-ATe. F I U L £ Q V J I T H ^>OIL- SAHPLg. ^tj H o M B o i - T C L A M P • S e & T i o i J S I —4- F A B R I C A T E D vurrw C L E A R , A C R Y L I C . P L A S T I C S E C T I O I J S Z, 3, A*>D 4- W E R E CEneuTEO T O G E T H E R , TO FORM A £ l k > £ , L E U U I T , Vp in m VtwT Tb CLEAR AlR Suasi-g£> A S S E M B L E D A A U G » - > < S I V O A T E R C O L U M O W I T H B R A S ^ > Ceg.e.  RitJca io P L A C E . S E P R S S B U T R U B B E R Ti»e>ir^G» M A T E R I A L , * K C . U A S S » U \ & O » J C A R 6 ' O E Poiooew., M A Y e>E ^ D D B D T> KCT A S A TGOi'oO P L - A T E . TvUi rr-|A-rt?R\AV- irAPRev/ES TnE S O R P A C E (jjoTAcf toiTH T H E SfthPLE. "TfetTEO. 53 c o l l e c t e d u n t i l no f u t h e r outflow was observed. An e q u i l i b r a t i o n time o f at l e a s t 24 hours was observed. The water was weighed and, subsequently, converted to a volume by d i v i d i n g 3 - 3 i t s mass by the d e n s i t y o f water, taken at 1.0x10 kgm . The water remaining i n the sand sample a t \b = -0.50 m o f water was d r i v e n o f f by oven d r y i n g and i t s mass determined g r a v i m e t r i c a l l y . T h i s mass o f water was a l s o converted to a volume b a s i s and added t o the volume o f cumulative outflow c o l l e c t e d . The t o t a l volume o f water was d i v i d e d by the sand sample volume to determine the water content at s a t u r a t i o n (or 'water f i l l e d ' p o r o s i t y ) (G ). s The water content (9) at a g i v e n p r e s s u r e p o t e n t i a l (\Jjp) was c a l c u l a t e d by s u b t r a c t i n g the cumulative outflow volume o f water, t h a t desorbed i n response t o the decrease i n \|> , from the t o t a l volume o f water and then d i v i d i n g the d i f f e r e n c e by the volume of the sand sample. The ' p a r t i a l water r e t e n t i o n c h a r a c t e r i s t i c curve (6(vp ) ) ' f o r the s a t u r a t e d 'North Van' sand was d e r i v e d by p l o t t i n g c a l c u l a t e d water content (9) a g a i n s t p r e s s u r e p o t e n t i a l (^p); see F i g u r e 18 i n S e c t i o n 3.1. E i g h t , sawdust-amended, 'Fraser R i v e r ' sand samples were a l s o t e s t e d . Undisturbed core samples were removed u s i n g the brass r i n g core sampler. The sampling p l a n i s g i v e n i n F i g u r e 6, w i t h the sampling l o c a t i o n s numbered from I t o V I I I . P r i o r t o the sampling, the p l a n t cover and ' s u r f a c e l a y e r ' were c a r e f u l l y removed from the f i e l d . Care was taken not t o sample below the 0.15 m depth o f the 'Top Layer'. These samples were re t u r n e d t o the l a b o r a t o r y f o r t e s t s . As d e s c r i b e d above, the cores were p l a c e d onto the Hanging Water Column Apparatus (see F i g . 10). U n l i k e the t e s t s 54 f o r the 'North Van' sand, t h e r e was no c h e e s e c l o t h below the brass r i n g s . A l a y e r o f s a t u r a t e d s i l i c o n c a r b i d e powder (240 g r i t ) was p l a c e d on top o f the f i l t e r paper as an a d d i t i o n a l t e n s i o n p l a t e m a t e r i a l , t o improve s u r f a c e c o n t a c t w i t h the s o i l sample and to lower the ' a i r e n t r y ( ^ A E V ) ' p r e s s u r e p o t e n t i a l t o approximately -1.0 m o f water. The sand samples were wetted s l o w l y from below. Once s a t u r a t e d , the e x t r a c t i o n o f water was i n i t i a t e d . Again, the datum was taken to be the c e n t r e o f the sample. Incremental drops i n \|) were made to -0.80 m. Weighings o f outflow water were c a r r i e d out a f t e r a minimum of e i g h t hours o f e q u i l i b r a t i o n time. The measured mass o f the c o l l e c t e d water was converted t o volume by d i v i d i n g by the 3 — 3 d e n s i t y o f water ( P w ) , taken a t 1.0x10 kgm . The 6(^p) c h a r a c t e r i s t i c curve f o r the sawdust amended 'Fraser R i v e r ' sand was d e r i v e d i n the same manner as d e s c r i b e d above. 2.2.2.3 Determination o f the K(\|) ) c h a r a c t e r i s t i c curve f o r the 'North Van' sand p P a r t i a l K(^_) c h a r a c t e r i s t i c curves were determined f o r IT the 'North Van' sand ( C h i l d s and C o l l i s - G e o r g e , 1950); see F i g u r e 19 i n S e c t i o n 3.1. In a uniform s o i l , where the i n f i l t r a t i o n r a t e i s f l u x - c o n t r o l l e d under steady s t a t e c o n d i t i o n s , and where ^ ( z ) i s c o n s t a n t w i t h depth, the constant f l u x d e n s i t y (q) i s equal to the h y d r a u l i c c o n d u c t i v i t y , K(\}) ), P o f the s o i l . The h y d r a u l i c c o n d u c t i v i t y (K) i s thus represented as a f u n c t i o n o f the p r e s s u r e p o t e n t i a l (\|)p) o f the water i n the s o i l . I t i m p l i e s t h a t i f q i s constant through the t e s t s e c t i o n o f s o i l , and no change i n storage i s o c c u r r i n g , \|) i s constant 55 (A\|) /Az = 0) and g r a v i t y i s the only c o n t r i b u t o r t o the ' d r i v i n g 3? f o r c e ' . Thus, under these c o n d i t i o n s , a ' u n i t y ' h y d r a u l i c g r a d i e n t [A\|>T/Az = (A\J> /Az + A\)J /Az) = 1] moves the water v e r t i c a l l y downwards through the s o i l ; \|)T i s the t o t a l p o t e n t i a l and \|)g i s the g r a v i t y p o t e n t i a l . The K(\J>p) c h a r a c t e r i s t i c o f the 'North Van' sand was determined f o r both w e t t i n g and d r y i n g runs, which were r e g u l a t e d by the i n f l o w o f water i n f i l t r a t i n g through the s u r f a c e o f the sand column. The 'wetting curve' was determined by s t a r t i n g from an i n i t i a l l y dry c o n d i t i o n and the 'drying curve' from a s a t u r a t e d c o n d i t i o n . S u f f i c i e n t time was l e f t between subsequent readings f o r steady s t a t e t o be achieved, t h a t i s u n t i l water n e i t h e r entered nor l e f t s t o r a g e . Steady s t a t e was achieved when the outflow r a t e remained co n s t a n t and a c o n s t a n t \|> was sensed by the tensiometers i n the t e s t s e c t i o n o f sand. The t e s t s e c t i o n was t h a t s e c t i o n o f sand between the upper and lower t e n s i o m e t e r s . A 0.79 m l o n g ' i n f i l t r a t i o n column' was s e t up; see F i g . 12. The column was c o n s t r u c t e d from a 0.85 m x 0.026 m ( i . d . ) , c l e a r , a c r y l i c p l a s t i c tube. The bottom o f the tube was f i t t e d w i t h a bored No. 5 stopper, i n s e r t e d w i t h a 0.05 m x 0.0095 m ( i . d . ) , c l e a r , a c r y l i c p l a s t i c tube o u t l e t . On the stopper was l a i d a 1.0 mm x 1.2 ram mesh, p l a s t i c s c r e e n , f o l l o w e d by a 0.02 m t h i c k g r a v e l l a y e r f i l t e r . Near the top o f the column, t h r e e t e n s i o m e t e r s were i n s t a l l e d . They were l o c a t e d at depths z 1 = -0.10 m, z 2 = -0.20 m, and = -0.30 m, r e s p e c t i v e l y . The s o i l s u r f a c e was taken as the datum l e v e l (z = 0 m). The tensiometer cups c o n s i s t e d o f f r i t t e d g l a s s beads. They had a s u f f i c i e n t l y low a i r e n t r y p r e s s u r e p o t e n t i a l v a l u e (v|) a w) t h a t d e s a t u r a t i o n 56 Figure 12; In f i l t r a t i o n Column Apparatus for Determining K(\l>^). , DCPTH F R O M f PERI4TM-TIC PU>MP Twee. P R E S S U R E F»TelJTlAt_£vr>p,) 7 f X t J S E R T * - C L O S e - y P O P T E O S l O H t T E R I7v I" * % I^BgWALL 1 Oo.oo S T O P P E R  ftAfflnc Tuae i o « o FRITTED GJLA&S -BEAD OElOSlQMETER I V A R I A B L E Speeo  pe ^ \ S T A U T i c P O M P FROM C«»J«rXMTyy "To C o u v T A v r r VAEAD P u r r O.O SL m ~ ~ 7 f — 0 I. I - O.I O rr, -O.IO "1 5E E Xo-,esrr 11 • • i ® <S>« i To P U M P 'II ( H ) I^OMBOLT C L A M P T o Coi-1-EC.TlOw) BOTTLE To T E I ^ St o WC.TER6 57 o f the tensiom e t e r s would not occur f o r \|> £ -0.50 m o f water. Each tensiometer was i n s t a l l e d through the column. They were connected t o the manometer board w i t h f l e x i b l e 0.00476 m ( i . d . ) , p l a s t i c t u b i n g . A i r dry 'North Van* sand was poured i n t o the column u n t i l i t was f u l l . The sand was c o n t i n u o u s l y poured, d u r i n g which i t was v i b r a t e d w i t h a p n e u m a t i c a l l y - d r i v e n v i b r a t o r . The v i b r a t i o n was a p p l i e d t o minimize any t r a n s i t i o n a l d i f f e r e n c e s caused by l a y e r i n g , and to encourage c l o s e p a c k i n g . F o l l o w i n g the a d d i t i o n o f sand, the column was tapped a t l e a s t twenty times w i t h the handle o f a s c r e w d r i v e r , to f u r t h e r ensure t h a t c l o s e packing was achieved. Constant i n f l o w r a t e s (q) were r e g u l a t e d by a v a r i a b l e speed p e r i s t a l t i c pump, which drew water from a con s t a n t head r e s e r v o i r . For the 'wetting' run, which began from a dry s t a t e , water was s l o w l y d r i p p e d onto the sand s u r f a c e . Outflow over a p e r i o d o f f o u r hundred seconds was c o l l e c t e d and weighed at each s e t t i n g . Four r e p l i c a t e weighings were made f o r each flow r a t e ( q ) . Between s e t t i n g s s u f f i c i e n t time was allowed t o r e - e s t a b l i s h steady s t a t e c o n d i t i o n s and a cons t a n t \|) d i s t r i b u t i o n w i t h depth (\p - s t r a i g h t ) w i t h i n the t e s t s e c t i o n , as d e s c r i b e d above. S p e c i f i c time p e r i o d s were not a l l o t t e d . At the end o f the 'wetting' run, wit h a t e s t s e c t i o n p r e s s u r e p o t e n t i a l v a l u e o f \j> = -0.04 m, the column was s a t i a t e d w i t h a i r entrappment p r e v e n t i n g t o t a l s a t u r a t i o n . From the K(\|» ) curve the s a t i a t e d c o n d i t i o n f o r the 'North Van' sand corresponds w i t h a h y d r a u l i c c o n d u c t i v i t y t h a t was lower than the measured s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y , 7 x l 0 - 5 m.s - 1 -4 -1 versus 3x10 m.s 58 Beginning from the s a t i a t e d s t a t e , the same procedure was f o l l o w e d f o r the 'drying' run, except t h a t step-wise decreases, r a t h e r than i n c r e a s e s , i n the flow r a t e (q) were made. With very low flow r a t e s (q ^  I O - 6 m.s - 1) problems i n m a i n t a i n i n g a constant d r i p i n f l o w , as w e l l as steady s t a t e c o n d i t i o n s w i t h i n the sand column, were encountered. These problems were i n d i c a t e d by v a r i a b l e and i n c o n s i s t e n t tensiometer r e a d i n g s . The val u e q = 1 0 - 6 m.s - 1, t h e r e f o r e , became the lower l i m i t f o r the K(\J)p) d e t e r m i n a t i o n , and was obtained o n l y f o r the 'drying' run. 2.3 F i e l d Measurement Methods 2.3.1 S o i l probe core sampling The depths o f the 'Top Layer' and ' p i t r u n ' l a y e r s , which were r e q u i r e d i n the a n a l y s i s were taken from the ' S p o r t s f i e l d S p e c i f i c a t i o n s ' . I t was assumed t h a t the ' S p e c i f i c a t i o n s ' were met d u r i n g the c o n s t r u c t i o n o f the f i e l d . Moreover, except w i t h r e s p e c t t o the 'surface l a y e r ' i t was assumed t h a t the s o i l l a y e r s r e t a i n e d t h e i r p h y s i c a l p r o p e r t i e s over time. Using an ' O a k f i e l d ' s o i l probe, samples were taken t o i n v e s t i g a t e the formation o f the 'surface l a y e r ' . The s o i l probe samples were e x t r a c t e d a c c o r d i n g t o the same f i e l d sampling p l a n used f o r removing the u n d i s t u r b e d 'Top Layer' s o i l c o r e s ; see F i g . 6. The sampling scheme was designed s p e c i f i c a l l y t o sample the f i e l d area under the pond as w e l l as the s u r r o u n d i n g catchment area. At each o f the e i g h t l o c a t i o n s chosen, f o u r r e p l i c a t e subsamples were taken. Each sample was 59 taken t o a depth o f approximately 0.08 m. A r u l e r w i t h 1 mm increments was used to determine the t h i c k n e s s o f the 'surface l a y e r 1 . Because o f the t r a n s i t i o n a l nature of the i n t e r f a c e , and the i m p r e c i s i o n of the t h i c k n e s s measurements, measurement _3 e r r o r was taken to be ± 2.5x10 m. Any compaction o f the s o i l sample, caused e i t h e r by the sampler or the technique employed, was n e g l e c t e d . 2.3.2 Pond measurement To o b t a i n pond measurements, ponding was induced on the p l a y i n g s u r f a c e o f the Lower Premier S p o r t s f i e l d through use o f i t s 'pop-up' s p r i n k l e r system. Two l a t e r a l i r r i g a t i o n l i n e s were employed, each w i t h f o u r s p i n k l e r heads i n s e r i e s . The l i n e s were spaced at 6.1 m. The 'wetting-up' process took approximately f o u r hours. Pond s i z e was measured i n the h o r i z o n t a l and v e r t i c a l dimensions. H o r i z o n t a l , or l a t e r a l , d i s t a n c e measurements were made i n the North-South and East-West d i r e c t i o n s . These d i s t a n c e s were measured w i t h a metre tape from the ' p o i n t e r p o s i t i o n ' t o the perimeter o f the pond along p r e s e t c o o r d i n a t e axes. Although the p o i n t e r was intended to be c e n t r a l l y p o s i t i o n e d i n the pond, subsequent measurements showed i t t o be o f f c e n t r e ; see F i g . 13. Changes i n the v e r t i c a l dimension, r e p r e s e n t i n g e i t h e r pond r i s e or r e c e s s i o n , were a l s o measured at the ' p o i n t e r p o s i t i o n ' . The a c t u a l r i s e and r e c e s s i o n of the pond s u r f a c e was measured w i t h a p o i n t e r apparatus; see F i g . 14. The apparatus was c o n s t r u c t e d w i t h two, f i n e threaded, equal l e n g t h brass rods, a body s e c t i o n , and an anchor rod. The two rods were each 60 F i g u r e 13; Standpipe L o c a t i o n s 61 F i g u r e 14; Pond R i s e and Re c e s s i o n Measurement Apparatus 62 sharpened to a p o i n t at one end. A l i g n e d v e r t i c a l l y , the rods were r a i s e d or lowered independently by t u r n i n g them counter c l o c k w i s e or c l o c k w i s e , r e s p e c t i v e l y . One rod was s e t a t the h e i g h t o f the s o i l s u r f a c e and the other at the h e i g h t o f the pond s u r f a c e . The d i f f e r e n c e i n h e i g h t between the two rods was measured and taken to be the pond depth (H). 2.3.3 Depth to the water t a b l e measurements Depths t o the water t a b l e were measured w i t h t h r e e standpipes i n s t a l l e d at d i f f e r e n t l o c a t i o n s j u s t beyond the p e r i m e t e r o f the pond; see F i g . 13. The standpipes were c o n s t r u c t e d from g a l v a n i z e d metal tubes, 1 m i n l e n g t h and 0.039 m ( i . d . ) . The bottom end o f each tube was pinched c l o s e d w h i l e the top end remained open. A t e s t s e c t i o n o f d i a g o n a l s l i t s was cu t i n t o the c l o s e d end of the tube and extended approximately 0.10 m up from the bottom. Each standpipe was i n s t a l l e d v e r t i c a l l y , w i t h the t e s t s e c t i o n l o c a t e d a t a depth o f 0.65 m. Placement i n v o l v e d making a s l i g h t l y o v e r s i z e d auger h o l e and then i n s e r t i n g the standpipe. Measurements were made wit h a metre s t i c k lowered i n t o the standpipes. The d i s t a n c e from the f r e e water s u r f a c e t o the top o f the standpipe was measured. The h e i g h t d i f f e r e n c e t o the f i e l d s u r f a c e was s u b t r a c t e d to determine the depth to the water t a b l e . 2.4 R a i n f a l l P r e c i p i t a t i o n Data R a i n f a l l data, c o l l e c t e d from a r e c o r d i n g r a i n gauge, i s a v a i l a b l e from the Atmospheric Environment S e r v i c e , Environment 63 Canada, c o v e r i n g the p e r i o d from 1964-1983. Copies o f the recorded r a i n gauge data, t h a t correspond to the two p e r t i n e n t days o f the study, A p r i l 14 and 16, 1982, are g i v e n i n F i g u r e 15. For the A p r i l 14 data, a l a g to peak o f approximately 0.5 h was a t t r i b u t e d t o the rounding o f f to the n e a r e s t hour (0800 h) f o r the changing o f the Recorded Rain Gauge Chart; see F i g . 15. The weather s t a t i o n was l o c a t e d 4.8 km due n o r t h o f the Lower Premier S p o r t s f i e l d at an e l e v a t i o n o f 191 m (168 m above t h a t of the f i e l d ) . The d i s t a n c e o f the Recorded Rain Gauge from the f i e l d was d e f i n i t e l y a concern. S t i l l , i t was l i k e l y t h a t the h i g h e r l o c a t i o n r e c e i v e d a t l e a s t those amounts t h a t f e l l on the s p o r t s f i e l d . 64 F i g u r e 15; Rec o r d i n g R a i n Gauge D a i l y Charts f o r Lynn Creek, North  Vancouver (82-04-14 and 82-04-16); Prepared by Atmospheric Environment S e r v i c e , Environment Canada. D A Y !6 J O U R iZ M O N T H _ A ^ R U -N O R M A L T I M E O F C H A R T C H A N G E (nearest h o u r * T E M P S N O R M A L O E P O S E D E L A F E U I L L E (heure la p lu 5 0'OChe) R E C O R D I N G R A I N G A U G E D A I L Y C H A R T 99 F E U I L L E J O U R N A L I E R E P L U V I O M E T R E E N R E G I S T R E U R ( S I ) S T A T I O N ^S.i'-^^'^ccJC PROV R E C O R D E D E ' I B E C I S T R E E C C f i B E C T E D C O R R I G E E M O N T H ~ ' MOIS . 0? N O R M A L T IME OF C H . \ R T C H A N C E (rnj.WBSI h o u r l 1 L M P S N O R M A L 06 P O S E DE L A f EU.L.L.E (heure I.* p l u * p roeh- ) 5 T ( TIME Z O N E ) ' ( F U S t A O HOR AIRE ) 73.t, ™ H A NDARO G A U G E T O T A L mm T O T A L P L U V I O M E T R E S T A N D A R D R E C O R D I N G R A I N G A U G E D A I L Y C H A R T 9 9 F E U I L L E J O U R N A L I E R E P L U V I O M E T R E E N R E G I S T R E U R ( S I ) -65 3. RESULTS, ANALYSES and DISCUSSION 3.1 R e s u l t s from the S o i l P h y s i c a l and Hydro-logical T e s t s made  on the 'Fraser R i v e r ' and 'North Van' Sands As s t a t e d i n S e c t i o n 1.2.3, the Lower Premier S p o r t s f i e l d was constructed' w i t h two l a y e r s o f d i f f e r e n t sand; see F i g . 3. The o v e r l y i n g 'Top Layer' was comprised o f a ' g r a v e l l y , coarse sand', r e f e r r e d to as the 'Fraser R i v e r ' sand, mixed w i t h sawdust to a 3:1 r a t i o . The sand was c l a s s i f i e d a c c o r d i n g to the United S t a t e s Department o f A g r i c u l t u r e (U.S.D.A.) ' S o i l T e x t u r a l C l a s s i f i c a t i o n System' ( S o i l Survey S t a f f , 1962); see T a b l e V. The ' g r a v e l l y * m o d i f i e r was used because i t had a h i g h g r a v e l content i n the g r e a t e r than 2.0 mm but l e s s than 10.0 mm diameter s i z e f r a c t i o n , 22 % by mass (approximately 15 % by volume). A l s o , i n i t s f i n a l p r e p a r a t i o n the 'Fraser R i v e r ' sand was mixed 25 % by volume w i t h ' F i r ' and/or 'Hemlock' sawdust, the s i e v e s p e c i f i c a t i o n s f o r which were a l s o g i v e n by the Parks Department; see T a b l e VI. The mixing was done by ' R o t o t i l l i n g ' the sawdust i n t o the 'Fraser R i v e r * sand. The mixture was l a i d down as a d i s t i n c t l a y e r on top o f the sand below. The sand i n the lower l a y e r was r e f e r r e d to as a ' c o n s t r u c t i o n ' sand and f e l l w i t h i n the 'sand' s o i l t e x t u r a l c l a s s d e f i n e d i n the U.S.D.A. system. I t had a 5 % g r a v e l content by mass (approximately 3 % by volume). T h i s l a y e r was a ' p i t r u n l a y e r ' and as such l i t t l e a t t e n t i o n was g i v e n to i t s s c r e e n i n g . In the study t h i s sand was c a l l e d the 'North Van' sand. F i g u r e s 16 and 17 show the cumulative p a r t i c l e s i z e 66 T a b l e V; U.S.D.A. S o i l T e x t u r a l C l a s s i f i c a t i o n o f 'Sand' (U.S.D.A., 1951) T e x t u r a l C l a s s Sub-class D e f i n i t i o n s (percentages on a mass b a s i s ) Sands S o i l m a t e r i a l t h a t c o n t a i n s 85 percent or more o f sand; percentage o f s i l t , p l u s 1.5 times the percentage o f c l a y s h a l l not exceed 15 % Coarse Sand 25 percent or more very coarse and co a r s e sand, and l e s s than 50 p e r c e n t any other one grade o f sand. Sand 25 percent or more, very c o a r s e , c o a r s e , and medium sand, and l e s s than 50 % f i n e or very f i n e sand. F i n e Sand 50 % or more f i n e sand (or) l e s s than 25 per c e n t very coarse, coarse, and medium sand and l e s s than 50 % very f i n e sand. Very F i n e Sand 50 % or more very f i n e sand Tab l e VI; Sawdust P a r t i c l e S i z e S p e c i f i c a t i o n s * S i e v e % P a s s i n q 1 i n c h (25.4 mm) 100 3/8 i n c h (9 .52 mm) 90-100 No. 8 (2.38 mm) 0-10 * Taken from the ' S p o r t s f i e l d S p e c i f i c a t i o n s ' d r a f t e d by the Parks Department o f the D i s t r i c t o f North Vancouver. F i g u r e 16; Cumulative P a r t i c l e S i z e D i s t r i b u t i o n o f the 'Fraser R i v e r ' Sand / oo 40 3 0 20 o O . O l A—j> o / / / / / / / / 1 / I / / / 6 ' r n / u/ / / i 1 i / / / / / / J3 a < 10.0 mm F r a c t i o n / / o < 2.00 mm F r a c t i o n f / / A 'Topmix' S p e c i f i c a t i o n s ; / see T a b l e IV / > / / / 0 1 1 1 For the < 2.00 mm F r a c t i o n 1 1 I D 5 Q - 0.52 mm pi / / C U " D 6 0 / D 1 0 " 3 ' 3 /V C C - D 3 0 2 / D 6 0 D 1 0 ' 1 ' 0 0 // £> 1 1 1 i O.IO •»5o IO lOO IOOO PARTICLE DIAMETER (D) IN METRES (xlO 3 ) F i g u r e 17; Cumulative P a r t i c l e S i z e D i s t r i b u t i o n o f the 'North Van 1 Sand m -H in (0 XX Ui Ui ftf e — a <*> o w w > o w < H E-" CO S5 H K U O « D W O Z EH O H O En 55 <: H 2 CO 2 CO D < CO loo =10 8 o 50 4-o 30 10 — — & 1 / s // // // // // // // /' •< 10.0 mm F r a c t i o n [ o < 2.00 mm F r a c t i o n A ' P i t r u n ' S p e c i f i c a t i o n s ; : see TABLE V j For the < 2.00 mm F r a c t i o n / D 5 Q = 0.31 mm / C U - D 6 0 / D 1 0 = 2 ' 1 i i C C = D 3 0 2 / D 6 0 D 1 0 = 1 ' 0 5 1 1 i o O.OI O.IO I . O 10 I O O O PARTICLE DIAMETER (D) IN METRES (XlO 3 ) 69 d i s t r i b u t i o n s produced from s i e v e analyses o f both the 'Fraser R i v e r ' and 'North Van' sands, r e s p e c t i v e l y . They a l s o i n c l u d e the 'sand p a r t i c l e s i z e s p e c i f i c a t i o n s ' f o r both the 'topmix' and ' p i t r u n ' sands, which were g i v e n i n the ' S p o r t s f i e l d S p e c i f i c a t i o n s ' ; see Tables I and I I . F u r t h e r p a r t i c l e f r a c t i o n a t i o n data, as w e l l as some s o i l p h y s i c a l and h y d r o l o g i c p r o p e r t i e s o f the sands are g i v e n i n Tables VII and V I I I . The 'Fraser R i v e r ' sand had a median p a r t i c l e diameter ( D 5 Q = 0.52 mm); see F i g . 16. With a C o e f f i c i e n t o f U n i f o r m i t y (C y) o f 3.0 and a C o e f f i c i e n t o f Curvature (C c) o f 1.0 the sand was c l a s s i f i e d as a 'Poorly-graded sand (SP)' a c c o r d i n g t o the ' U n i f i e d S o i l C l a s s i f i c a t i o n System' ( C r a i g , 1983). T h i s meant t h a t the 'Fraser R i v e r ' sand d i d not s a t i s f y the c r i t e r i a o f a well-graded sand. The 'North Van' sand had a D..-. = 0.31 mm bU and was c l a s s i f i e d a l s o as a 'Poorly-graded sand (SP)'. I t s and C c were 2.1 and 1.0 r e s p e c t i v e l y ; see F i g . 17. A comparison o f the bulk d e n s i t i e s ( p ^ ) o f the two sands 3 showed the bulk d e n s i t y o f the 'Fraser R i v e r ' sand ( p ^ = 1.9x10 _3 kgm ) to be h i g h e r than t h a t f o r the 'North Van' sand ( p ^ = 3 -3 1.7x10 kgm ); see Tables VII and V I I I . The reason the p b v a l u e s were so h i g h i s t h a t they represented the l e s s than 10.0 mm diameter s i z e f r a c t i o n , which i n c l u d e d g r a v e l s i z e d p a r t i c l e s . When mixed w i t h sawdust, however, the p ^ f o r the 3 — 3 'Fraser R i v e r ' sand dropped to a p ^ = 1.4x10 kgm . Due to i n c o n s i s t e n t mixing, the range o f p ^ i n c r e a s e d from being _ 3 i n s i g n i f i c a n t t o 0.7 kgm . The p a r t i c l e d e n s i t y ( p ) o f the _3 'North Van' sand was ( p = 2700 kgm ). Using t h i s v a l u e , t o t a l p o r o s i t i e s (f) f o r both the 'North Van' sand and the 'Fraser R i v e r ' sand were c a l c u l a t e d . 70 T a b l e V I I ; P a r t i c l e S i z e F r a c t i o n a t i o n , S o i l P h y s i c a l P r o p e r t i e s and H y d r a u l i c C o n d u c t i v i t i e s o f 'Fraser R i v e r ' Sand. P a r t i c l e S i z e F r a c t i o n a t i o n Mean No. o f Samples Range S p l i t Sample (<10.0 mm f r a c t i o n ) Organic Matter Content by mass 1.0 % 0.97-1.03 M i n e r a l Content by mass - >2.00 mm - <2.00 mm S o i l Sample (<2.00 mm f r a c t i o n ) Organic Matter Content F i n e M i n e r a l Content (<0.053 mm) 22.0 % 77.0 % assumed 1.0 % 0.4 % 3 20.9-23.2 % 75.8-78.1 % - 0.4 % -2. S o i l P h y s i c a l P r o p e r t i e s S o i l T e x t u r a l C l a s s (USDA) - 'GRAVELLY, COARSE SAND' Median P a r t i c l e Diameter (D,-^) 0.52 mm 3 0.51-0.54 mm b u C o e f f i c i e n t of U n i f o r m i t y (C..); < D60 / D10> C o e f f i c i e n t _ o f Curvature (Cr); ( D 3 0 / D « n ° i n > 3.0 1.0 3.0-3.1 0.93-1.11 60 10 ' U n i f i e d S o i l C l a s s i f i c a t i o n System' group - SP P a r t i c l e D e n s i t y (p ) i n H 90 - assumed 2700 kgm Bulk D e n s i t y (P b) - <2.00 mm -3 - <io.0 mm - <10.0 mm (mixed w i t h sawdust) T o t a l P o r o s i t y ( f ) ; f = [ l - p , / p ] - <2.00 mm - <10.0 mm - <10.0 mm (mixed w i t h sawdust) W a t e r - f i l l e d P o r o s i t y at S a t u r a t i o n (9 ); - <10.0 mm (mixed w i t h sawdust) S o i l H y d r a u l i c C o n d u c t i v i t i e s S a t u r a t e d H y d r a u l i c C o n d u c t i v i t y (K ) 1.8x10" kgm _ 1.9x10; kgm _ l .4x10:: kgm 3 -3 0.35 m_m__ 0.30 m^ m_^  0.48 mJm 0.43 m3m 3 Geometric Mean 3.5x10 m.s -4 -1 10 --1.8x10 - = kgm 10 —1.9x10 - = kgm~ 8 1.0-1.7xl0_ 3 kgm 3 -3 -0.35 m_m__--0.30 mm -10 10 8 0.63 -0.37 m3m 3 0.55 -0.36 mm 3.2-3.7x10 m.s" -4 71 Ta b l e V I I I ; P a r t i c l e S i z e F r a c t i o n a t i o n , S o i l P h y s i c a l P r o p e r t i e s and H y d r a u l i c C o n d u c t i v i t i e s o f 'North Van' Sand. No. o f Mean Samples Range 1. P a r t i c l e S i z e F r a c t i o n a t i o n S p l i t Sample (<10.0 mm f r a c t i o n ) Organic Matter Content by mass - >2.00 mm - <2.00 mm M i n e r a l Content by mass - >2.00 mm - <2.00 mm S o i l Sample (<2.00 mm f r a c t i o n ) Organic Matter Content F i n e M i n e r a l Content (<0.053 mm) 2. S o i l P h y s i c a l P r o p e r t i e s S o i l T e x t u r a l C l a s s (USDA) - 'SAND' Median P a r t i c l e Diameter ( D 5 Q ) C o e f f i c i e n t o f U n i f o r m i t y (C..); < D60 / D10> C o e f f i c i e n t o f Curvature ( C - ) ; <D30 / D60 D10> ' U n i f i e d S o i l C l a s s i f i c a t i o n System' group - SP P a r t i c l e D e n s i t y ( p g ) i n H 20 2700 kgm" 3 6 2690-27l0_ 3 0.3 % 6 0.1-0.6 % 1.1 % 6 1.0-1.2 % 4.7 % 6 2.3-6.5 % 93.9 % 6 91.9-96.4 % 1.2 % 6 1.1-1.2 % 1.0 % 9 0.6-1.8 % 0.31 mm 9 0.29-0.33 mm 2.1 9 1.9-2.3 1.0 9 0.92-1.30 Bulk D e n s i t y (p,) - <2.00 mm 1.6xl0_ 3 9 — 1 . 6 x l O J - = 3 kgm ,3 kgm_ kgm_ - <10.0 mm 1.7x10 9 1.6-1.7xl0__ kgm kgm T o t a l P o r o s i t y ( f ) ; .3-3 f = [ l - p h / p _ ] ; - <2.00 mm 0.40 mm 6 0.42 - , , D s ^ , 0.40 mJm J - <10.0 mm 0.37 mm 6 0.37 -0.39 mJm J W a t e r - f i l l e d P o r o s i t y at S a t u r a t i o n (0 ); - <10.0 mm 0.34 mm 6 0.40 -0.31 nTm S o i l H y d r a u l i c C o n d u c t i v i t i e s S a t u r a t e d H y d r a u l i c Geometric Mean C o n d u c t i v i t y (K ) 3.4x10 5 6 2.3-4.2x10 f J s' - l - l m.s m.s 72 H y d r o l o g i c c h a r a c t e r i s t i c s o f the s o i l m a t e r i a l s were a l s o examined. The p a r t i a l water r e t e n t i o n curves f o r the two sands are presented together f o r comparison; see F i g . 1 8 . Taken from i t s p a r t i a l water r e t e n t i o n curve, the s a t u r a t e d water 3 - 3 content (9 ) o f the sand/sawdust mixture (9 = 0 . 4 3 m m ) was 3 - 3 h i g h e r than t h a t o f the 'North Van' sand (9 = 0 . 3 4 mm ); see Tables VII and V I I I . These val u e s correspond w i t h t h e i r water-f i l l e d p o r o s i t i e s a t s a t u r a t i o n . I t i s noteworthy t h a t the 'Fraser R i v e r ' sand/sawdust mixture r e l e a s e s i t s m a t r i x - h e l d water more r e a d i l y than does the 'North Van' sand. The a i r e n t r y v a l u e (^ A E V) o f the mixture i s a l s o more p o o r l y d e f i n e d . C o n v e r s e l y , the 'North Van' sand has a more d i s t i n c t ^ A E V / at approximately \|) = - 0 . 2 0 m o f water. The 'Fraser R i v e r ' sand/sawdust mixture a l s o r e t a i n s more water at \1> v a l u e s lower P than - 0 . 3 0 m o f water. At \|> = - 0 . 5 0 m, the mixture had a 3 - 3 v o l u m e t r i c water content 9 = 0 . 2 1 mm , whereas 9 f o r the 3 — 3 'North Van' sand had dropped t o 9 = 0 . 0 8 mm . Another important c o n s i d e r a t i o n i s t h a t w i t h f u r t h e r d r y i n g a f t e r ' a i r i n t r u s i o n ' (taken t o be the i n f l e c t i o n p o i n t at approximately \J> = - 0 . 3 4 m on the 9(\J) ) graph) the 'North Van' sand r e l e a s e s i t s moisture a t a more r a p i d r a t e , e v i d e n t from both the stee p e r curve and divergence of the two graphs. F i g u r e 19 shows the p a r t i a l u n s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c f o r the 'North Van' sand. The d r y i n g 'envelope' curve i n F i g u r e 19 i s e s p e c i a l l y important f o r i t r e p r e s e n t s the steady s t a t e u n s a t u r a t e d c o n d i t i o n s i n c u r r e d w i t h d e c r e a s i n g flow r a t e s . A s s o c i a t e d w i t h decreases i n water content ( 9 ) , and c o r r e s p o n d i n g l y vp^, the 'drying envelope' K(\|>p) r e l a t i o n s h i p represented c o n d i t i o n s t h a t c o u l d be a p p r o p r i a t e l y 7 3 F i g u r e 18; P a r t i a l Water R e t e n t i o n Curves; 9(\1)^ _) o.so • * F R A S E R . R I V E Q / S A U O y S A W O O S T M I X T U R E . O ' f J o R T H V A K / S A p D rp t« m F i g u r e 19; P a r t i a l Unsaturated H y d r a u l i c C o n d u c t i v i t y , K(\|) ) ,  C h a r a c t e r i s t i c Curves f o r the 'North Van' Sand p (<2.00 mm f r a c t i o n ) 75 used t o d e s c r i b e u n s a t u r a t e d flow c o n d i t i o n i n the 'North Van' sand i n the f i e l d , as occurs when the water t a b l e drops w i t h i n the ' p i t r u n l a y e r ' . 3.2 Ponding On A p r i l 14 and A p r i l 16, 1982, ponding experiments were c a r r i e d out on the Lower Premier S p o r t s f i e l d . In the A p r i l 14 experiment, a f t e r c r e a t i n g the pond w i t h the s p r i n k l e r system, the s p r i n k l e r s were turned o f f at t 1 = 14400 s (4.00 h ) , causing the pond t o recede; see P i g . 20. The r e c e s s i o n was i n t e r r u p t e d by r a i n f a l l , however, a t t 2 = 20700 s (5.75 h ) , which caused the pond to r i s e a gain. The c o i n c i d i n g ' r i s i n g limb (C)' on the A p r i l 14 Pond Depth Hydrograph appears as a d i r e c t response to the r a i n f a l l . The r a i n f a l l event i t s e l f i s e v i d e n t on the c o r r e s p o n d i n g hyetograph, which was produced w i t h r e c o r d i n g r a i n gauge measurements taken at the Lynn Creek Weather s t a t i o n ; see F i g . 20. Pond r i s e continued u n t i l t 3 = 28800 s (8.00 h) , over the time i n t e r v a l At = 8100 s (2.25 h ) . In the a n a l y s i s t h i s h y d r o g raphic response proves to be p a r t i c u l a r l y b e n e f i c i a l f o r s o r t i n g out the terms i n the pond water balance; see S e c t i o n 3.3. R e g r e t t a b l y , the ' A p r i l 16 Pond Depth Hydrograph' i s confounded by i n t e r m i t t e n t r a i n f a l l ; see F i g . 21. As a consequence, the A p r i l 14 experiment i s the source o f more u s e f u l i n f o r m a t i o n and i s used e x c l u s i v e l y i n the a n a l y s i s t h a t f o l l o w s . By m o n i t o r i n g the depths t o the water t a b l e , i t was e s t a b l i s h e d t h a t the ' f r e e ' water observed on the f i e l d was not the r e s u l t o f f l o o d i n g but o f ponding i n s t e a d . The d i f f e r e n c e 76 Figure 20; Pond Depth Hydrograph (82-04-14) and Depth to the Water Table 77 F i g u r e 21; Pond Depth Hydrograph (82-04-16) 78 between ponding and f l o o d i n g i s t h a t f l o o d i n g occurs when the water t a b l e r i s e s above the f i e l d s u r f a c e , w h i l e ponding occurs w i t h the water t a b l e at depth. In response t o the i n i t i a l 'wetting up', cor r e s p o n d i n g w i t h the ' r i s i n g limb (A)' on the A p r i l 14 Pond Depth Hydrograph, the water t a b l e rose t o w i t h i n 0.1 m o f the f i e l d s u r f a c e ; see Table IX. When the s p r i n k l e r s were turned o f f , the water t a b l e subsequently dropped, w i t h i n 15 minutes, t o a depth o f 0.65 m. Never, d u r i n g the experiments, was t h e r e evidence o f the water t a b l e i n t e r c e p t i n g the f i e l d s u r f a c e . T h i s water t a b l e behaviour v e r i f i e s the ponded c o n d i t i o n . 3.3 The 'Cone' Dimensioned Pond Water Balance Model 3.3.1 Pond r i s e and r e c e s s i o n The d e t e r m i n a t i o n o f the A p r i l 14 and A p r i l 16 Pond Depth Hydrographs was an i n t e g r a l p a r t o f the i n f i l t r a t i o n experiments; see F i g u r e s 20 and 21. The hydrographs r e p r e s e n t pond depth as a f u n c t i o n o f time (H(t)) and t h e i r s l o p e s (dH/dt) r e p r e s e n t e i t h e r pond r i s e or r e c e s s i o n r a t e s . Corresponding to the A p r i l 14 hydrograph, l a t e r a l dimensions o f the pond were measured as w e l l . These measurements were made along two superimposed axes across the d e p r e s s i o n i n the f i e l d ; see Table X, F i g u r e s 13 and 22. They p r o v i d e , however, on l y a rough i n d i c a t i o n o f the a c t u a l s i z e and shape o f the pond, g i v e n t h a t i r r e g u l a r i t i e s i n i t s shape r e s u l t from even s m a l l changes i n the s l o p e o f the f i e l d s u r f a c e . To s a t i s f a c t o r i l y d e a l w i t h the c o m p l i c a t i o n s these i r r e g u l a r i t i e s i n t r o d u c e , major assumptions 79 Tab l e IX; Standpipe Readings Standpipe No. 1 2 3 Time i n s (h) Depth t o water t a b l e i n m 1.44xl0 4 (4.0) -0.10 -0.14 -0.22 1.53x107 (4.25) -0.52 - n i l 1.71x107 (4.75) -0 .52 -0.66 n i l 1.98X10T (5.5) -0.61 -0.66 n i l 2. 34x10* (6.5) -0.60 - -2.79x10* (7.75) -0.61 - -3.24x10 (9.0) n i l n i l n i l T a b l e X; The Coordinates of the Pond at Three D i s c r e e t Times Times c o r r e s p o n d i n g t o A p r i l 14 hydrograph i n s (h) 1 1.08X10 4 (3.0) 2 1.53X10 4 (4.25) 3 1.91X10 4 (5.25) Pond Depth (H) at p o i n t e r 0.062 m 0.067 m 0.057 m Measured Coo r d i n a t e s (a,b) from F i g u r e 22 N S E W (0,4.0 m) (0,-4.0 m) (2.7 m,0) (-7.9 m,0) (0,4.4 m) (0,-4.0 m) (3.4 m,0) (-7.8 m,0) (0,4.0 m) (0,-3.7 m) (2.4 m,0) (-7.8 m,0) E l l i p t i c a l Area 76 m2 81 m2 72 m2 ' E f f e c t i v e * Pond Radius 4.9 m 5.1 m 4.8m 80 F i g u r e 22; Pond Dimensions (82-04-14) L E C E M P ; ( R E F E R T O T A B L E X ) L A T E R A L M E A S U R E M E N T S a AT -fc, o A T ± z • AT t 3 III \ P<*WTWR. I j j S C A L E : 81 are necessary f o r d e v e l o p i n g the model. How w e l l the model s i m u l a t e s the a c t u a l s p o r t s f i e l d ponding phenomenon u l t i m a t e l y depends upon how reasonable these assumptions are. From o b s e r v a t i o n s and the l a t e r a l measurements o f the pond, i t was apparent the shape o f the s u r f a c e o f the pond was e l l i p t i c a l , elongated s l i g h t l y along the east-west major a x i s ; see F i g u r e s 13 and 22. Measurements t o the edge o f the pond were made from the 'p o i n t e r p o s i t i o n ' , which corresponds w i t h the o r i g i n , or i n t e r s e c t i o n , o f the two axes 'a' and 'b'; see Table X. The axes were a l i g n e d i n the c a r d i n a l d i r e c t i o n s , n o r t h t o south and east t o west, r e s p e c t i v e l y . Although i t s l o c a t i o n was chosen t o be as c e n t r a l l y p o s i t i o n e d as p o s s i b l e , i t was c a l c u l a t e d t h a t the 'p o i n t e r p o s i t i o n ' was approximately 2.5 m t o the e a s t o f the c e n t r e o f the pond. A l s o , from F i g u r e 22 i t i s e v i d e n t t h a t the c e n t r e o f the pond wandered s l i g h t l y as the pond expanded. The perimeter o f the pond co u l d not be d e l i n e a t e d p r e c i s e l y on the t u r f g r a s s e d s u r f a c e . E f f o r t s were made, n e v e r t h e l e s s , t o keep the d i s t a n c e measurements t o the edge o f the pond w i t h i n a measurement e r r o r o f ± 5%. T h i s r e q u i r e d w a i t i n g u n t i l the perimeter o f the pond was at l e a s t 2 m from the o r i g i n and on making measurements t h a t were a c c u r a t e t o w i t h i n ± 0.05 m. Three separate s e t s o f pond measurements were ob t a i n e d , one s e t d u r i n g pond r i s e , 3 h a f t e r the i r r i g a t i o n was turned on, and two s e t s d u r i n g i t s subsequent r e c e s s i o n , 0.25 h and 1.25 h a f t e r the i r r i g a t i o n was turned o f f . I t i s a l s o worth n o t i n g t h a t i n the v i c i n i t y o f the o r i g i n o f the two axes, the f i e l d s u r f a c e was u n d u l a t i n g w i t h two d i s t i n c t d e p r e s s i o n s ; see F i g . 23. Beyond a r a d i a l d i s t a n c e o f 2 m from the 'po i n t e r 82 F i g u r e 23; Pond Depths (82-04-16) - depths i n metres (xlO ) - A the ' p o i n t e r p o s i t i o n ' 8 3 p o s i t i o n ' , though, the f i e l d s u r f a c e appeared more even. Given the i m p r e c i s i o n i n v o l v e d , a s i m p l i f i e d pond geometry was c o n s i d e r e d d e s i r a b l e . Thus, a major assumption i n the 'cone' dimensioned pond water balance model t h a t was formulated, i s t h a t the pond and the d e p r e s s i o n i n which i t formed takes the shape o f an i n v e r t e d , shallow r i g h t cone. I t i s assumed t h a t the c i r c u l a r area o f the cone base and the c o n s t a n t s l o p e o f the cone s i d e s , i n a l l d i r e c t i o n s , duly approximate the dimensional and s u r f a c e c h a r a c t e r i s t i c s o f the f i e l d d e p r e s s i o n h o l d i n g the pond. The ' r i g h t cone' analogy p r o v i d e s a simple, but i n t u i t i v e l y p l a u s i b l e , t h r e e dimensional shape f o r the pond water balance model. E l l i p t i c a l pond areas were f i r s t c a l c u l a t e d from the f i e l d measurements; see Table X . These areas were subsequently assumed t o be the c i r c u l a r , ' e f f e c t i v e ' , pond areas ( A ) , used to r e p r e s e n t the cone base i n the model. ' E f f e c t i v e ' pond r a d i i (r) were a l s o c a l c u l a t e d ; see Eq. 3 . 1 . The ' e f f e c t i v e ' pond r = ( A / I T ) 0 , 5 ( 3 . 1 ) r a d i i (r) correspond w i t h pond depth measurements (H) made at the ' p o i n t e r p o s i t i o n ' ; see Table X . S i n c e the ' p o i n t e r p o s i t i o n ' was o f f c e n t r e , an ' i n i t i a l ' pond r a d i u s ( r i ) accounts f o r the d i s t a n c e from the c e n t r e of the pond to the ' p o i n t e r p o s i t i o n ' . The ' i n i t i a l ' pond r a d i u s ( r i ) was c a l c u l a t e d t o be 2.5 m. By det e r m i n i n g the ' e f f e c t i v e ' pond r a d i i (r) and t h e i r c o r r e s p o n d i n g pond depths (H), at t h r e e d i f f e r e n t times, a s u r f a c e s l o p e r a t i o o f [H/(r - r^) = 1 : 4 0 ] was estimated f o r the d e p r e s s i o n on the Lower Premier S p o r t s f i e l d . 84 Adopting the c o n i c a l geometry, the pond water balance model i s a p p l i e d t o the hydrographic data represented on the A p r i l 14 Pond Depth Hydrograph; see F i g . 20. Of p a r t i c u l a r importance i s the pond r i s e behaviour over time p e r i o d (C), from t 2 t o t 3 - As s t a t e d i n S e c t i o n 3.2, t h i s r i s e was i n response t o a d i s t i n c t r a i n f a l l event. The r a t e o f r i s e (dH c/dt) i s gi v e n by the s l o p e o f the r e g r e s s i o n l i n e r e p r e s e n t i n g the ' r i s i n g limb (C)'; see Eq. 3.2. H c ( t ) = H Q + ( d H c / d t ) t (3.2) The r e g r e s s i o n e q u a t i o n was s o l v e d , y i e l d i n g Eq. 3.3, u s i n g measured pond depth values (H), or i n t h i s case H c, taken at the ' p o i n t e r p o s i t i o n ' d u r i n g p e r i o d (C) from t 2 = 2.07xl0 4 s (5.75 h) t o t 3 = 2 . 8 8 X 1 0 4 s (8.00 h ) ; At = 8100 s (2.25 h ) . The s l o p e o f the r e g r e s s i o n l i n e (dH c/dt) and the pond depth r e p r e s e n t i n g the o r d i n a t e i n t e r c e p t c o r r e s p o n d i n g w i t h t = 0 s ( H Q ) were c a l c u l a t e d ; dH c/dt = l . 5 x l 0 ~ 6 m.s - 1 and H Q = 0.024 m. H c ( t ) = 0.024 + ( 1 . 5 x l 0 ~ 6 ) t (3.3) Si n c e the 'p o i n t e r p o s i t i o n ' was o f f c e n t e r , an ' i n i t i a l ' pond depth ( H ^ has t o be added t o value s o f H to c a l c u l a t e the h e i g h t o f the pond a t i t s c e n t r e ( H p ) ; see Eq. 3.4. The ' i n i t i a l ' pond depth (H i) i s taken t o be the depth o f Hp = H + H. (3.4) water at the c e n t r e o f the pond when the r a d i u s o f the pond 85 equals ( r ^ ) , as d e f i n e d above; see Eq. 3.5. For a 1:40 s l o p e , H i = r i / ( c o t e ) (3.5) where = 2 . 5 m, = 0 . 0 6 2 m. Adding the two cons t a n t s H.^  and H Q , H p Q = 0 . 0 8 6 m. Thus, w i t h H p ( t ) taken t o be the depth o f water a t the c e n t r e o f the pond at time ( t ) , from Eq. 3 . 2 : H p ( t ) = H p Q + ( d H c / d t ) t ( 3 . 6 ) S u b s t i t u t i n g i n value s f o r H p 0 and dH c/dt: H p ( t ) = 0.086 + (1.5x10 6 ) t (3.6a) 3.3.2 S u r f a c e area expansion o f the pond w i t h pond r i s e By det e r m i n i n g how the s u r f a c e o f the pond expands d u r i n g pond ' r i s e ' , the v a r i o u s volume components i n the pond water balance can be determined. However, t h i s r e q u i r e s . a n e x p r e s s i o n f o r the r e l a t i o n s h i p o f how the pond s u r f a c e area grows w i t h r e s p e c t t o time. The e x p r e s s i o n f o r the expansion o f the pond area, d u r i n g the pond r i s e from t 2 to t 3 , i s 13 J ^ 2 A ( t ) d t . P h y s i c a l l y , i n terms o f the pond water balance, t h i s i n t e g r a l i s important because i n c r e a s e s i n A p r o v i d e a g r e a t e r s u r f a c e area t o r e c e i v e r a i n f a l l d i r e c t l y and under which i n f i l t r a t i o n can occur, while p r o v i d i n g l e s s a v a i l a b l e f i e l d s u r f a c e area t o c o n t r i b u t e o v e r l a n d flow. Moreover, i n c r e a s e s i n A are an obvious i n d i c a t i o n o f water going i n t o pond s t o r a g e . S o l v i n g f o r the growth o f the pond area i s 86 achieved by u s i n g the geometry o f the r i g h t cone, and the v a r i a b l e s o f pond depth (H p) and ' e f f e c t i v e ' pond r a d i u s (r) which were d e r i v e d from measurements taken i n the f i e l d . Once formulated, these terms are i n t e g r a t e d over the time i n t e r v a l At, from t o t 2 , to c a l c u l a t e the volumes o f water i n v o l v e d i n 13 the pond water balance. Thus, the e x p r e s s i o n f o r J ^ 2 A ( t ) d t i s d e r i v e d . Given, the formula f o r the base o f a r i g h t cone, equal t o the area o f a c i r c l e : A = n r 2 (3.7) Given, an e q u a t i o n f o r the pond r a d i u s (r) i n terms o f s l o p e angle (G) and pond h e i g h t ( H p ) : r = H p ( c o t 9) (3.8) S u b s t i t u t i n g Eq. 3.8 i n t o Eq. 3.7 p r o v i d e s an e x p r e s s i o n f o r A as a f u n c t i o n o f H p (see P i g . 24): A = T r[H p(cot 9 ) ] 2 (3.9) S u b s t i t u t i n g Eq. 3.6 i n t o Eq. 3.9 and r e a r r a n g i n g : A ( t ) = ir(cot 0 ) 2 [ H p o + ( d H c / d t ) t ] 2 (3.10) Given the s u r f a c e s l o p e 1:40 (9 = 1.43°) and s u b s t i t u t i n g Eq. 3.6a i n t o Eq. 3.10: A ( t ) = [(37) + ( 1 . 3 x l 0 ~ 3 ) t + ( 1 . l x l 0 ~ 8 ) t 2 ] (3.11) I n t e g r a t e d over the time i n t e r v a l At from t = 2.07xl0 4 s to t = 2.88X10 4 s: J t 2 t 3 A ( t ) d t = J t 2 t 3 [ ( 3 7 ) + ( 1 . 3 x l 0 " 3 ) t + ( l . l x l 0 " 8 ) t 2 ] d t (3.12) J t 2 t 3 ( t ) d t = 37(2.88 - 2 . 0 7 ) x l 0 4 + 1.3x10 3 ( 2 . 8 8 2 - 2 . 0 7 2 ) x l 0 8 / 2 + l . l x l 0 ~ 8 ( 2 . 8 8 3 - 2 . 0 7 3 ) x l 0 1 2 / 3 (3.12a) 87 J t 2 t 3 A ( t ) d t = 3.0X10 5 + 2 . 6 x l 0 5 + 5.5X10 4 (3.12b) J t 2 t 3 A ( t ) d t = 6.2X10 5 m2S (3.12c) I t i s a l s o apparent t h a t the r e l a t i o n s h i p between A and Hp d i f f e r s f o r v a r i o u s s l o p e angles 9 as shown i n F i g . 24. Thus, i f one assumes the ponded d e p r e s s i o n takes the shape of a shallow r i g h t cone the volume terms i n the pond water balance are, i n p a r t , a l s o r e l a t e d t o s u r f a c e s l o p e ; see F i g . 25. S u r f a c e s l o p e may be represented as the s l o p e r a t i o o f pond h e i g h t to r a d i u s or as the cotangent o f the s u r f a c e s l o p e angle (9 = 1.43°). The equations f o r Q_, Q_, Q T, and AQ^, t h a t are hi U 1 S shown i n F i g . 25, are d e r i v e d i n S e c t i o n 3.4. 3.3.3 The pond water balance I f 'steady s t a t e ' flow c o n d i t i o n s e x i s t soon a f t e r the water t a b l e drops, which assumes t h a t water i s n e i t h e r being removed from, or going i n t o , s torage i n the s o i l , a balanced e q u a t i o n o f h y d r o l o g i c i n p u t , output, and change i n s t o r a g e terms e x i s t s t o s a t i s f y the c o n s e r v a t i o n o f mass f o r those c o n d i t i o n s . The g e n e r a l water balance equation i s : Inputs = Outputs + Change i n Storage (3.13) For the induced ponds the only sources o f water were r a i n f a l l and i r r i g a t i o n . R a i n f a l l alone, however, was r e s p o n s i b l e f o r the r i s e d u r i n g i n t e r v a l C from t 2 t o t 3 on the A p r i l 14 Pond Depth Hydrograph; see F i g . 20. The t o t a l i n p u t of water i n t o the pond, t h e r e f o r e , was the volume o f p r e c i p i t a t i o n 88 F i g u r e 24; A vs H f o r the 'Cone' Dimensioned Pond ) o o .o i © 0 4 . ook o.oft 0 . 1 0 0 . 1 1 . 0 . 1 A 89 F i g u r e 25; Volume (Q) vs Slope; (9) VEXT>CA,I_ r . i o l : A O irc /cof©^[apCO']a« s(.+ i :SO < I.IS*) 90 (Q„) r e c e i v e d d i r e c t l y a t the s u r f a c e o f the pond and water t h a t may have been c o n t r i b u t e d i n d i r e c t l y through 'Horton' overland flow (Q Q); see F i g . 26. The l a t t e r c o n t r i b u t i o n r e p r e s e n t s the p a r t i t i o n e d f r a c t i o n o f p r e c i p i t a t i o n t h a t was r e c e i v e d over the p e r i p h e r a l unponded p a r t o f the catchment area ( A T 0 T - A ) / where A T Q T i s the t o t a l catchment area represented i n the model. 'Horton' o v e r l a n d flow i s d e s c r i b e d s p e c i f i c a l l y as t h a t water which, " . . . s p i l l s over ( a f t e r the d e p r e s s i o n s t o r a g e c a p a c i t y on a s l o p e i s exhausted) t o run downslope as an i r r e g u l a r s h e e t . . . ( a n d ) . . . o c c u r s anywhere r a i n f a l l i n t e n s i t y exceeds the i n f i l t r a t i o n c a p a c i t y (or i n f i l t r a b i l i t y ) o f the s o i l (Dunne & Leopold, 19 78)." Runoff f l o w i n g i n t o the pond would be r e c e i v e d at a con s t a n t r a t e a f t e r the t r a n s i e n t decay o f the r a i n f a l l i n f i l t r a t i o n r a t e t o the steady s t a t e i n f i l t r a b i l i t y o f the f i e l d s u r f a c e (Rubin and S t e i n h a r d t , 1963), Groundwater seepage and s u b s u r f a c e flow, as other p o s s i b l e i n p u t s , were n e i t h e r e v i d e n t nor expected, l a r g e l y because the p l a s t i c sheet u n d e r l y i n g the s p o r t s f i e l d p r o t e c t e d i t from such r e g i o n a l groundwater i n f l u e n c e s . On the other s i d e o f the equation the only s i g n i f i c a n t output term from the pond i s the volume o f water (Q ) t h a t i n f i l t r a t e s the f i e l d s u r f a c e under the pond. Presumably, no r u n o f f flowed away from the pond, even though d i s c o n t i n u o u s f r e e water was e v i d e n t i n p l a c e s . Water l o s s due to e v a p o t r a n s p i r a t i o n i s presumed n e g l i g i b l e d u r i n g the c o o l , cloudy, and humid, A p r i l a f t e r n o o n . The onl y change i n storage term (AQ ) represented i n the equation i s the volume o f water c o l l e c t e d i n the pond i t s e l f . Although some d e p r e s s i o n storage accumulated over the m i c r o - r e l i e f o f the p l a y i n g s u r f a c e , most 91 F i g u r e 26; The Pond Water Balance INPUT TERMS 3 Cumulative R a i n f a l l Volume (Q_) i n m 3 Cumulative Overland Volume (Q Q) i n m OUTPUT CHANGE IN STORAGE TERMS Cumulative I n f i l t r a t i o n Volume (Q ) i n m3 3 Change i n Storage Volume (AQ ) i n m 9 = s l o p e angle c o r r e s p o n d i n g t o s u r f a c e s l o p e 92 was taken up by the a r e a l expansion o f the pond. Any d i s c o n t i n u o u s , f r e e water on the p e r i p h e r a l catchment area, t h e r e f o r e , i s assumed to be p a r t o f the ov e r l a n d flow component making i t s way t o the pond. In i t s f i n a l form the water balance i s formulated i n the f o l l o w i n g equation: Q R + Q 0 = Q T + AQ S (3.14) The volume terms Q D, Q_., Q T and ACL i n the pond water K U J. S balance are a f u n c t i o n o f pond growth and, t h e r e f o r e , o f the geometry o f the pond. C l e a r l y , w i t h pond r i s e t h e r e i s an i n c r e a s e i n pond volume, i n d i c a t i n g a change i n s t o r a g e . S i n c e the pond was always i n a s t a t e o f expansion or c o n t r a c t i o n , the terms i n the pond water balance have to be s o l v e d as a f u n c t i o n o f time. The assumptions made i n the 'cone dimensioned' pond water balance model are as f o l l o w s : 1) The dimensions of the pond are d u l y represented by a shallow, i n v e r t e d , r i g h t c o n i c a l shape o f con s t a n t s l o p e . 2) The pond water balance equation (Eq. 3.14) accounts f o r a l l the i n p u t s , outputs, and change i n storage terms i n the pond system. 3) The Recorded Rain Gauge data, g i v e n i n F i g . 15, a c c u r a t e l y r e p r e s e n t the r a i n f a l l r e c e i v e d on the s p o r t s f i e l d . 93 3.4 The A p p l i c a t i o n o f the Pond Water Balance Model As s t a t e d , the r i s e i n pond depth, noted by the ' r i s i n g arm (C)' on the A p r i l 14 hydrograph, was caused by a d i s t i n c t r a i n f a l l event; see F i g . 20. I t i s assumed t h a t t h i s r a i n f a l l corresponded w i t h the near simultaneous r i s e shown on the hyetograph o f recorded r a i n gauge data; see F i g u r e s 15 and 20. -7 -1 T h i s r a i n f a l l a t t a i n e d an average r a t e , q n = 6.7x10 m.s From the A p r i l 14 f i e l d data, i n t e g r a t e d over the d e f i n i t e i n t e g r a l from t 2 = 2.07xl0 4 s (5.75 h) to t 3 = 2.88xl0 4 s (8.00 h ) , the f o l l o w i n g water balance i s determined. The s o l u t i o n s t o the volume terms i n the water balance equation (Eq. 3.14) are summarized i n Tab l e XI. 1. The volume o f r a i n f a l l , Q R, t h a t f e l l onto the pond s u r f a c e over the time i n t e r v a l t 2 = 2.07xl0 4 s to t 3 = 2.88xl0 4 s: i ) Q R = q R J t 2 t 3 ( t ) d t (3.15) i i ) S u b s t i t u t i n g Eq. 3.12c i n t o Eq. 3.15 and u s i n g the — 7 — 1 r a i n f a l l r a t e (q^ = 6.7x10 m.s ): Q_ = ( 6 . 7 X 1 0 " 7 ) ( 6 . 2 x l 0 5 ) (3.15a) Q R = 0.41 m3 (3.15b) The volume o f water t h a t i n f i l t r a t e d through the f i e l d s u r f a c e beneath the pond (Q-j.), over the time i n t e r v a l t 2 to V i ) Q T = q l p J t 2 t 3 A ( t ) d t (3.16) i i ) S u b s t i t u t i n g Eq. 3.12c i n t o Eq. 3.16 and u s i n g the — 6 — 1 i n f i l t r a t i o n r a t e ( q i p = 1.7x10 m.s ) i n f e r r e d from the pond r e c e s s i o n over time p e r i o d 'D' on the A p r i l 14 94 T a b l e XI: S o l u t i o n s t o the Volume Terms i n the Water Balance E q u a t i o n from t0 to t». WATER BALANCE TERMS VOLUME VOLUME RATIOS Inputs: R a i n f a l l (Q R) 0.4 m3 0.27 Overland Flow (Q Q) 1.5 m3 0.73 Outputs p l u s Change i n Storage: I n f i l t r a t i o n (Q ) Change i n Storage (AQ g) 1.0 m3 0.9 m3 0.53 0 .47 95 pond depth hydrograph: Qx = ( 1 . 7 x l 0 ~ 6 ) ( 6 . 2 X 1 0 5 ) (3.16a) QT = 1.04 m3 (3.16b) 3. The volume o f water c o l l e c t e d i n the pond as s t o r a g e , AQ , over the time i n t e r v a l t 2 to t 3 : i ) AQ S = (V 3 - V 2 ) (3.17) i i ) AQ S = J t 2 t 3 ( c o t 6 ) 2 [ H p ( t ) ] 2 d H p (3.18) i i i ) S u b s t i t u t i n g Eq. 3.6a i n t o Eq. 3.18 and s o l v i n g ; g i v e n 6 = 1.43 0 AQ = 0.9 m3 (3.18a) rO 4. Q Q was obtained by d i f f e r e n c e by s u b s t i t u t i n g the val u e s f o r Q R, Q-j-, and AQ S i n Eq. 3.14, and r e a r r a n g i n g . The volume o f water c o n t r i b u t e d t o the pond through o v e r l a n d flow, Q Q, over the time i n t e r v a l t 2 t o t 3 - . i ) Q Q = (Q I + AQ S) - Q R (3.19) Q = (1.0 m3 + 0.9 m3) - 0.4 m3 (3.19a) Q Q = 1.5 m3 (3.19b) A l l o f the terms i n the pond water balance are dependent upon the growth o f the pond. The r a i n f a l l and i n f i l t r a t i o n volume r a t e s , and the i n c r e a s e d volume r a t e o f water going i n t o s t o r a g e a l l i n c r e a s e as the pond expands. Only the ov e r l a n d flow volume r a t e decreases as the ' e f f e c t i v e ' pond area (A) i n c r e a s e s . From the water balance i t was determined t h a t the o v e r l a n d flow volume c o n t r i b u t i o n t o the pond was s l i g h t l y l e s s than f o u r times the volume o f r a i n f a l l r e c e i v e d d i r e c t l y at the 3 2 0 = 1.5 m compared t o Q R 3 3 pond s u r f a c e , Q = 1.5 m compared t o Q p = 0.4 m , r e s p e c t i v e l y ; 96 see T a b l e XI. As was s t a t e d i n S e c t i o n 3.3.2, an important parameter a f f e c t i n g the growth o f the pond i s the s u r f a c e s l o p e r a d i a t i n g out from the c e n t r e o f the pond. A 1:40 s l o p e , w i t h a s l o p e angle (G = 1.43°), was determined from f i e l d measurements. T h i s s l o p e was used i n the water balance presented above. Volumes (Q) were a l s o c a l c u l a t e d f o r 1:30 and 1:50 s l o p e s ; see F i g . 25. The volumes (Q) i n c r e a s e by over 1/2 by d e c r e a s i n g the s l o p e from 1:30 to 1:50. I n t e r e s t i n g l y , w i t h m a n i p u l a t i o n o f s l o p e the r a t i o s between the volume terms do not vary. T h i s can be seen from the e x p r e s s i o n s f o r Q_, Q_, and A(D i n F i g . 25, where K J. S 2 (cot 9) drops out o f the r a t i o o f any p a i r o f Q. The most important f a c t o r s r e s p o n s i b l e f o r ponding and the outcome o f the water balance, however, are the p h y s i c a l and h y d r o l o g i c p r o p e r t i e s o f the s o i l l a y e r s , both a t and below the f i e l d s u r f a c e . These p r o p e r t i e s had a d i r e c t e f f e c t upon the i n f i l t r a t i o n r a t e d u r i n g r a i n f a l l . Furthermore, i t i s s i g n i f i c a n t t h a t the s o i l p r o f i l e i s comprised o f t h r e e d i s t i n c t l a y e r s , these being the 'surface l a y e r ' , the 'Fraser R i v e r ' sand/sawdust mixed l a y e r , and the ' p i t r u n ' l a y e r o f 'North Van' sand; see F i g . 3. In a d d i t i o n , the h y d r o l o g i c c h a r a c t e r i s t i c s o f the d i f f e r e n t l a y e r m a t e r i a l s are o f i n t e r e s t . They are the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 'surface l a y e r 1 (K 1) and the s o i l h y d r o l o g i c c h a r a c t e r i s t i c s , (6(\|) )) and K(\|) ), o f the P P two s u b - l a y e r s . The r a i n f a l l r a t e ( q R ) , the depth t o the water t a b l e , and the above s o i l - r e l a t e d f a c t o r s t o g e t h e r d i c t a t e d the h y d r o l o g i c c o n d i t i o n s t h a t r e s u l t e d i n the ponding o f the Lower Premier S p o r t s f i e l d . As w e l l , i t i s important to d i s t i n g u i s h between the i n f i l t r a t i o n process t h a t o c c u r r e d under the pond 97 and t h a t t h a t o c c u r r e d through the s u r f a c e o f the p e r i p h e r a l area beyond the pond. Consequently, two d i f f e r e n t i n f i l t r a t i o n systems must be c o n s i d e r e d . 3.5 The Determination o f the 'Surface Layer' S a t u r a t e d  H y d r a u l i c C o n d u c t i v i t y ( K l p ) f o r the Ponded Case The s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K l p ) of the 'sur f a c e l a y e r ' under the pond was not measured d i r e c t l y . I n s t e a d , i t was determined through an a n a l y s i s based on f i e l d -c o l l e c t e d data s p e c i f i c t o the ponding observed and a l s o on laboratory-measured s o i l h y d r o l o g i c c h a r a c t e r i s t i c s o f the 'sand/sawdust' and ' p i t r u n ' l a y e r m a t e r i a l s . In theory, by knowing the f l u x d e n s i t y ( q p ) , and the ' d r i v i n g f o r c e ' (A\p T/Az), Darcy's Law (Eq. 2.1) can be a p p l i e d i n the form o f Eq. 3.20 to c a l c u l a t e K l p . K 1 P = -qp/(A\|>T/Az) (3.20) s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 'surface l a y e r ' below the pond; m.s - 1. i n f i l t r a t i o n r a t e or f l u x d e n s i t y ; m.s - 1. ' d r i v i n g f o r c e ' or h y d r a u l i c g r a d i e n t ; d i m e n s i o n l e s s . In the a n a l y s i s , the t h i c k n e s s (Az) o f the 'surface l a y e r ' and the h y d r a u l i c g r a d i e n t (A\J>T/Az) are both p o s i t i v e . The f l u x d e n s i t y ( q p ) i n a downward d i r e c t i o n i s n e g a t i v e . The r e f e r e n c e datum (z = 0 m) i s taken t o be the water t a b l e , which was K IP M1P (Ai^/Az) = 98 measured to be 0.65 m below the f i e l d s u r f a c e . A l s o , d r y i n g was i n d i c a t e d by the drop o f the water t a b l e . T h i s meant t h a t the s o i l was vented to the atmosphere e i t h e r through the drainage l i n e s i n the f i e l d or the s u r f a c e beyond the f i e l d d e p r e s s i o n . The f l u x d e n s i t y ( q p ) , equal t o the i n f i l t r a t i o n r a t e -7 -1 ( q l p = -1.7x10 m.s ) under the pond, was i n f e r r e d from the s l o p e of the r e g r e s s i o n l i n e (dH D/dt) r e p r e s e n t i n g pond r e c e s s i o n 'D' on the A p r i l 14, pond depth hydrograph; see F i g . 20. Moreover, the constancy o f the s l o p e of the recession.arm 'D' i n d i c a t e s the e x i s t e n c e o f steady s t a t e i n f i l t r a t i o n . Given downward v e r t i c a l flow under these c o n d i t i o n s the ' d r i v i n g f o r c e ' , or h y d r a u l i c g r a d i e n t (A\|>T/Az) may a l s o be w r i t t e n as the sum o f the p r e s s u r e and g r a v i t y p o t e n t i a l g r a d i e n t s , where the l a t t e r i s equal to one; see Eq. 3.21. A\pT/Az = (Ai|)p/Az + 1) (3.21) Consequently, Eq. 3.20 may be w r i t t e n : K 1 P = - q p / ( A ^ p / A z + 1); q p < 0 (3.22) By r e a r r a n g i n g Eq. 3.22: Az = - A\|»p/(1 + q l p / K l p ) (3.23) From Eq. 3.22, i t i s apparent t h a t the h y d r a u l i c g r a d i e n t (A\J) /Az + 1) i s dependent on l y upon the p r e s s u r e p o t e n t i a l g r a d i e n t (A\|)p/Az). By s e t t i n g \p^0 and \|> as the p r e s s u r e p o t e n t i a l s a t the s u r f a c e and lower i n t e r f a c e o f the 99 ' s u r f a c e l a y e r ' , r e s p e c t i v e l y , the p r e s s u r e p o t e n t i a l g r a d i e n t can be w r i t t e n : A\|)p/Az = (xp p Q - Y- p l)/Az (3.24) Thus, i f q l p i s g i v e n and the median ' s u r f a c e l a y e r ' t h i c k n e s s (Az) f o r the range o f t h i c k n e s s e s (0.01 m ^ Az ^ 0.02 m) i s chosen, the d e t e r m i n a t i o n o f K l p only r e q u i r e s t h a t the drop i n pr e s s u r e p o t e n t i a l (A\J>p = \|) p 0 - be known. The p r e s s u r e p o t e n t i a l (Y^Q) f e l t at the f i e l d s u r f a c e below the pond i s equal t o the ponding depth. T h e r e f o r e , the median ponding depth ( H p = 0.06 m) t h a t was determined f o r the pond r i s e from t 2 to t 3 corresponds w i t h an equ a l , average, p r e s s u r e p o t e n t i a l (^ p 0 = 0.06 m) f o r t h a t same time p e r i o d . Moreover, t h i s v a l u e f o r \J) p Q was assumed t o equal the p r e s s u r e p o t e n t i a l a t the s u r f a c e under the pond f o r the e n t i r e pond r i s e p e r i o d . Only by determining the pr e s s u r e p o t e n t i a l d i s t r i b u t i o n (\j) (z)) w i t h i n the s o i l p r o f i l e , however, c o u l d a va l u e f o r \J) be determined. The d e t e r m i n a t i o n o f the e x i s t e n t ^ p ( z ) p r o f i l e r e q u i r e d a le n g t h y a n a l y s i s o f c o n d i t i o n s p e c u l i a r t o the ponding under study. To begin w i t h , i t was assumed t h a t below the ' s u r f a c e l a y e r ' u n s a t u r a t e d flow c o n d i t i o n s e x i s t e d . The assumption i s p h y s i c a l l y based, g i v e n the low i n f i l t r a t i o n r a t e , or f l u x d e n s i t y , ( q i p = q p = - l . 7 x l 0 ~ 6 m.s - 1) and the r e l a t i v e l y h i g h s a t u r a t e d h y d r a u l i c c o n d u c t i v i t i e s (K ) of the 'sand/sawdust' and ' p i t r u n ' l a y e r m a t e r i a l s , both o f which are i n the order o f 1 0 - 4 m.s - 1. The unsatur a t e d c o n d i t i o n s , however, made i t d i f f i c u l t t o c h a r a c t e r i z e the p r e s s u r e 100 p o t e n t i a l p r o f i l e (\|> (z ) ) . P r i m a r i l y , t h i s i s because w i t h u n s a t u r a t e d flow the d i s t r i b u t i o n o f p r e s s u r e p o t e n t i a l s i s f l u x (q)-dependent. Furthermore, one c o u l d not assume t h a t the p r e s s u r e p o t e n t i a l d i s t r i b u t i o n over any depth i n t e r v a l (Az) i n the u n s a t u r a t e d s u b - l a y e r s was independent o f the e f f e c t s o f the water t a b l e . For such a c o n d i t i o n i t r e q u i r e s t h a t A\|)p/Az = 0 and K(\J)p) = q, w i t h the ' u n i t y ' g r a v i t y p o t e n t i a l g r a d i e n t remaining as the s o l e determinant ' d r i v i n g f o r c e ' . Consequently, ^ - ( z ) f o r the g i v e n f l u x d e n s i t y (q ) was determined from which the p r e s s u r e p o t e n t i a l s (^p) a t g i v e n depths (z^) i n the u n s a t u r a t e d p a r t o f the s o i l p r o f i l e were ob t a i n e d ; see F i g . 27. T h i s a n a l y s i s r e q u i r e d knowledge o f the s o i l h y d r o l o g i c c h a r a c t e r i s t i c K(\|)p) o f both the 'sand/sawdust' and ' p i t r u n ' l a y e r m a t e r i a l s . Layer depths w i t h i n the s o i l p r o f i l e and the f l u x d e n s i t y ( q p ) were g i v e n . The s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ) and the 0(\|) ) and K(\p ) s p p c h a r a c t e r i s t i c curves o f the 'North Van' sand, which comprised the ' p i t r u n ' l a y e r , were measured. Only the K and the 9(\)J ) s p c h a r a c t e r i s t i c curve o f the 'Fraser R i v e r ' sand/sawdust mixture were measured, however. S i n c e the 'Fraser R i v e r ' sand/sawdust mixture K(\J>p) c h a r a c t e r i s t i c curve was not measured, i t s d e t e r m i n a t i o n r e l i e d on an i n d i r e c t method t h a t i n c l u d e d knowledge o f i t s K s and 6(\|)p) f u n c t i o n . The method used to d e s c r i b e the u n s a t u r a t e d m oisture c o n d i t i o n s w i t h i n the l a y e r was based on the model developed by Campbell (1974). The model p r o v i d e s a p h y s i c a l l y based, s e m i - e m p i r i c a l r e l a t i o n s h i p o f the form vp = a6 ( H i l l e l , 1969); see Eq. 3.25. F i g u r e 27; Water P o t e n t i a l P r o f i l e s : v|) , \|> , & \|> Versus Depth (z). - For a composite l a y e r steady s t a t e flow system under ponded c o n d i t i o n s . T 1 1 r -o.(o - o . s -oA •o.'b -o.x -o. | rn 102 Drawing from the measured p a r t i a l water r e t e n t i o n (9(\|> )) c h a r a c t e r i s t i c curve f o r the sand/sawdust mixed s o i l (see F i g . 18), the f o l l o w i n g constants were i n f e r r e d : ^AEV = ~ 0 * 1 5 m ; *-he a^- r e n t r y p r e s s u r e p o t e n t i a l . 3 -3 9 g = 0.43 m m ; the s a t u r a t i o n v o l u m e t r i c water content. The c o n s t a n t 'b' i n the exponent i s c a l c u l a t e d as the s l o p e of the l e a s t square l i n e drawn through the p l o t o f log(\|> A E V/\Jj p) vs l o g (9/9 ). By r e a r r a n g i n g Eq. 3.25: b = [ l o g ( x | ) A E V / v T p ) ] / [ l o g ( 9 / 9 s ) 3 (3.26) = 1.4533 (3.26a) The d e t e r m i n a t i o n o f 'b' allows f o r the f u r t h e r e x p r e s s i o n o f K(\JJ ), as put forward by Campbell (1974), a c c o r d i n g to Eq. 3.27: K = v w v ( 2 + 3 / b ) ( 3 - 2 7 ) I t i s assumed t h a t K i n Eq. 3.27 r e p r e s e n t s a homogeneous l a y e r m a t e r i a l , and i s equal t o , or g r e a t e r than, the l a b o r a t o r y -determined s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 'Fraser R i v e r ' sand alone ( i e . , K = 3 . 5 x l 0 ~ 4 m . s - 1 ) . T h i s i s j u s t i f i e d by the o b s e r v a t i o n t h a t l i t t l e i n f i l l i n g o c c u r r e d below the 103 ' s u r f a c e l a y e r ' and t h a t the sawdust w i t h i n the 'Top Layer' remained mostly i n t a c t , i n a ' f i b r i c ' stage o f decomposition. I t was assumed the sawdust e x i s t e d as r e l a t i v e l y l a r g e p a r t i c l e s w i t h i n the sand m a t r i x . Thus, the p r e d i c t e d r e l a t i o n s h i p f o r K(\|) ) o f the sand/sawdust l a y e r was determined. The method t h a t was used subsequently to c a l c u l a t e the p r e s s u r e p o t e n t i a l p r o f i l e (z)) from the K(\J) ) c h a r a c t e r i s t i c hr hr curve r e l i e d on the i n t e g r a t i v e approach o f Bybordi (1968) and the f i n i t e d i f f e r e n c e method presented by C h i l d s (1969). The \J> (z) p r o f i l e was f i r s t c a l c u l a t e d from the water t a b l e to the hr ' p i t r u n l a y e r ' i n t e r f a c e , and then continued upwards t o the ' s u r f a c e l a y e r ' i n t e r f a c e . The ^ D ( z ) p r o f i l e was produced by hr i n t e g r a t i n g over depth the steady s t a t e flow e q u a t i o n (Eq. 3.23) f o r the c o n s t a n t f l u x d e n s i t y ( q p ) . From Bybordi (1968): Az - - [ J ^ d ^ / d + q p / K l ) ] + ... + ^ p ( n _ 1 ) * p n d V < 1 + (3.28) From C h i l d s (1969), the f i n i t e d i f f e r e n c e e quation f o r each i n c r e m e n t a l depth term ( z ^ ; 0 £ z^ £ z ): Z l " - A V t 2 q P / ( K ( Y p l ) + K ^ p l + A1.p)> + 1 ] ; q < ° ( 3 ' 2 9 > By i n t e g r a t i n g , ^ _ ( z ) i n the ' p i t r u n ' l a y e r was hr determined and the p r e s s u r e p o t e n t i a l (\pp2 = -0-31 m) a t the top o f the ' p i t r u n ' l a y e r was c a l c u l a t e d . F u r t h e r i n t e g r a t i o n , u s i n g the c a l c u l a t e d K(v|>) r e l a t i o n s h i p o f the 'Fraser R i v e r ' sand/sawdust mixture extended ^p(z) t o the top of the 'sand/sawdust' l a y e r , which p r o v i d e d the estimated p r e s s u r e 104 p o t e n t i a l \|>^  = -0.415 m at the 'surface l a y e r ' i n t e r f a c e . By s u b s t i t u t i n g the p r e d i c t e d e s timate o f i n t o Eq. 3.24, g i v e n -7 -1 q p = -1.7x10 m.s and m) ^ = 0.06 m, and u s i n g the median 's u r f a c e l a y e r ' t h i c k n e s s (Az = 0.015 m), Eq. 3.22 was s o l v e d , y i e l d i n g an e s t i m a t e o f K l p ; see Eq. 3.22b. K l p = -(-1.7xl0~ 6)/(0.475/0.015 + 1) (3.22a) = 5 . 2 x l 0 ~ 8 m.s - 1 (3.22b) By a p p l y i n g i n d u c t i v e reasoning a range o f estimates f o r K l p was a l s o determined without r e l y i n g on the e x t e n t i o n o f \|)p(z) above the ' p i t r u n ' l a y e r . T h i s negates having to c a l c u l a t e K(\|i ) from the 'sand/sawdust' l a y e r 9(\|) ) curve, P P through the a p p l i c a t i o n o f Campbell's (1974) model. Instead, an a n a l y t i c a l approach was adapted from the a n a l y s i s o f H i l l e l and Gardner (1969). S i m i l a r l y , the approach r e q u i r e d t h a t the d i f f e r e n t l a y e r s be represented as h y d r a u l i c r e s i s t a n c e s , where ' h y d r a u l i c r e s i s t a n c e ' i s d e f i n e d as the r a t i o o f the l a y e r t h i c k n e s s (L) to the h y d r a u l i c c o n d u c t i v i t y (K) o f the s o i l (R = L/K), ( H i l l e l and Gardner, 1969). The h y d r a u l i c r e s i s t a n c e s of the ' s u r f a c e ' and 'sand/sawdust' l a y e r s , are l 1 / K l p and 1 2/K 2 p, r e s p e c t i v e l y . The h y d r a u l i c r e s i s t a n c e o f the composite 'Top Layer' ( L / K e f f ) i s represented i n terms o f an ' e f f e c t i v e ' h y d r a u l i c c o n d u c t i v i t y ( K e f f ) • Moreover, s i n c e h y d r a u l i c r e s i s t a n c e s are a d d i t i v e and the 'Top Layer' r e p r e s e n t s a composite two-layer system, the h y d r a u l i c r e s i s t a n c e ( L / , K e f f ) i s equal to the sum o f the h y d r a u l i c r e s i s t a n c e s o f i t s two component l a y e r s ; see Eq. 3.30. 105 L / K e f f " V K 1 P + V K 2 P ( 3 ' 3 0 ) KQff = the ' e f f e c t i v e ' h y d r a u l i c c o n d u c t i v i t y o f the composite 'Top Layer' (m.s - 1) K i p = the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the ' s u r f a c e l a y e r ' K 2 p = the ' e f f e c t i v e ' h y d r a u l i c c o n d u c t i v i t y o f the sand/sawdust l a y e r (m.s - 1) L = the t h i c k n e s s o f the composite 'Top Layer' (m) 1^ = the t h i c k n e s s o f the 'surface l a y e r ' (m) 1- = the t h i c k n e s s o f the 'sand/sawdust' l a y e r (m) With the d e t e r m i n a t i o n o f ty^2 = -0.31 m, the p r e s s u r e p o t e n t i a l drop across the 'Top Layer' (Atyp = typQ - ^ p 2 = 0.37 m) was c a l c u l a t e d . Given, the steady s t a t e , f l u x d e n s i t y ( q p = — 6 — 1 -1.7x10 m.s ) and the t h i c k n e s s o f the 'Top Layer' (L = 0.15 m), as was s p e c i f i e d i n the s p o r t s f i e l d d e s i g n s p e c i f i c a t i o n s , a l l the terms r e q u i r e d to determine the ' e f f e c t i v e ' h y d r a u l i c c o n d u c t i v i t y ( K e f f ) f ° r the 'Top Layer' were p r o v i d e d . By a p p l y i n g Darcy's Law, i n the form o f Eq. 3.31: K e f f = -q p/(A^ p/Az + 1) (3.31) = - ( - 1 . 7 x l 0 - 6 ) / ( 0 . 3 7 / 0 . 1 5 + 1) (3.31a) = 4 . 9 X 1 0 - 7 m.s - 1 (3.31b) I t must be emphasized t h a t K g^^ i s an ' e f f e c t i v e ' h y d r a u l i c c o n d u c t i v i t y f o r the composite 'Top Layer', one t h a t r e p r e s e n t s i t s h e t e r o g e n e i t y . I t does not r e f l e c t the p h y s i c a l or h y d r o l o g i c p r o p e r t i e s o f e i t h e r the ' s u r f a c e l a y e r ' or the 106 sand/sawdust mixed m a t e r i a l s . I n d i v i d u a l l y , the 'surface l a y e r ' i s r e p resented by a s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K i p ) while the u n d e r l y i n g 'sand/sawdust' l a y e r i s represented by an ' e f f e c t i v e ' h y d r a u l i c c o n d u c t i v i t y ( K 2 p ) t h a t r e f l e c t s u n s a t u r a t e d , f l u x d e n s i t y (q)-dependent c o n d i t i o n s . The h y d r a u l i c c o n d u c t i v i t y ( K 2 p ) °f the 'sand/sawdust' l a y e r r e p r e s e n t s an unsatu r a t e d h y d r a u l i c c o n d u c t i v i t y t h a t i s v a r i a b l e over depth. A l s o , i f steady s t a t e i s not achieved, i t i s v a r i a b l e over time as w e l l . However, by knowing ( K e f f ) o f the composite 'Top Layer', and the d i f f e r e n t l a y e r t h i c k n e s s e s , a l o c i o f s o l u t i o n s ( K l p , K 2 p} e x i s t s . T h i s i s made apparent by r e a r r a n g i n g Eq. 3.30 i n t o Eq. 3.32: K 1 P " 1 l K e f f K 2 P / ( L K 2 P " 1 2 K e f f ) (3.32) S i n c e a range of 'surface l a y e r ' t h i c k n e s s e s (0.01 £ 1 1 £ 0.02 m) i s c o n s i d e r e d , two values f o r K l p correspond t o these upper and lower t h i c k n e s s l i m i t s . The l i m i t s are based on p r o f i l e o b s e r v a t i o n s and measurements made i n the f i e l d . The range o f t h i c k n e s s e s f o r the sand/sawdust mixed l a y e r corresponds w i t h the d i f f e r e n c e s between L and 1^, such t h a t [0.13 ^  ( 1 2 = L - 1±) £ 0.14 m]. For a l l cases, K f f = 4 . 9 x l 0 - 7 m.s - 1 and L = 0.15 m. The two bounding s o l u t i o n s e t s ( K i p , K 2 p ) are represented by Equations 3.32a and 3.32b; see F i g . 28. For 1 1 = 0.01 m; K l p = (0.01 m)(4.9xl0~ 7 m.s - 1) K 2 p / [(0.15 m)K 2 - (0.14 m ) ( 4 . 9 x l 0 - 7 m . s - 1 ) ] (3.32a) F i g u r e 28; L o c i o f S o l u t i o n s f o r the H y d r a u l i c C o n d u c t i v i t i e s , 1^ and K 2 p j  i n the Composite 'Top Layer' Under the Pond. ~-3 IO 5 x -i s S U R F A C E L A Y E E " THidCKjcss E F F E C T I V E . ' H Y O R A U U C C O ^ D U C T I V I T V O F T « K C o W o t a s . 'Top L A Y E R , ' ; l ,>x IO m . S I O -s —I— 5" S U R F A C E . L A yee, K ip ; n m.s" 1 108 For 1 = 0.02 m; K l p = (0.02 m)(4.9xl0~ 7 m.s - 1) K 2 p / [(0.15 m)K 2 - (0.13 m ) ( 4 . 9 x l 0 - 7 m . s - 1 ) ] (3.32b) Given the 'Top Layer' t h i c k n e s s (L = 0.15 m) and the range o f 'su r f a c e l a y e r ' t h i c k n e s s e s (0.01 ^  1 1 ^ 0.02 m), i t i s apparent from F i g . 28 t h a t a wide range o f value s f o r K 2 p correspond t o a narrow range f o r K 1 P ' The lower l i m i t f o r K l p — 8 — 1 a s y m t o t i c a l l y approaches 3.3x10 m.s . I t i s a l s o apparent t h a t t h i s lower l i m i t tends t o be cons t a n t f o r K 2 p v a l u e s g r e a t e r than K 2 p = 5 x l 0 - ^ m.s - 1. However, i t i s u n l i k e l y t h a t K 2 p > 5 x l 0 - 6 m.s - 1 s i n c e K 2 p r e p r e s e n t s an un s a t u r a t e d s o i l l a y e r . Thus, the range f o r K l p , determined from t h i s a n a l y s i s , — 8 —1 — 7 —1 was 3.3x10 m.s < K l p ^ 4.9x10 m.s . I t i s important t o note t h a t the 'surface l a y e r ' s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y — 8 -1 ( K i p = 5.2x10 m.s ) obtained i n the e a r l i e r a n a l y s i s f a l l s w i t h i n t h i s range. I t was a l s o assumed t h a t the t h a t c h l a y e r had a very low h y d r a u l i c r e s i s t a n c e and, t h e r e f o r e , d i d not a f f e c t the i n f i l t r a t i o n r a t e ( T a y l o r and Blake, 1982). For t h i s reason the t h a t c h l a y e r was not i n c l u d e d i n the a n a l y s i s . The r e s u l t s o f T a y l o r and Blake (1982) i n d i c a t e d t h a t the "Pore s i z e s i n the t h a t c h were s u f f i c i e n t l y l a r g e , even a f t e r packing, t o conduct water as f a s t as the conductance o f the packed sand below would all o w . " A l s o , "At s i x f i e l d l o c a t i o n s removal o f the t h a t c h l a y e r d i d not s i g n i f i c a n t l y change the i n f i l t r a t i o n r a t e , (and) at t h r e e others removal o f the s u r f a c e s i g n i f i c a n t l y decreased the measured i n f i l t r a t i o n r a t e s ( T a y l o r and Blake, 1982; pp. 618 and 619)." Based on t h i s work, the h y d r a u l i c r e s i s t a n c e from the t h a t c h l a y e r was assumed n e g l i g i b l e and was not i n c l u d e d i n 109 the above computations, 3.6 Overland Flow Obv i o u s l y , the p e r i p h e r a l catchment area beyond the pond ( A T Q T - A ( t ) ) r e c e i v e d r a i n f a l l . When the r a i n f a l l i n t e n s i t y exceeds the i n f i l t r a b i l i t y o f the s o i l only a f r a c t i o n o f the p r e c i p i t a t i o n i n f i l t r a t e s the s u r f a c e . The remainder runs o f f 3 as o v e r l a n d flow. Indeed, the water balance shows t h a t 1.5 m , or 7 3 p e r c e n t o f the t o t a l i n p u t , a r r i v e d a t the pond as s u r f a c e r u n o f f . Runoff, a c c o r d i n g t o 'Hortonian o v e r l a n d flow theory', r e q u i r e s t h a t the i n f i l t r a t i o n r a t e (q l r j) i n the unponded p a r t o f the f i e l d be l e s s than the r a i n f a l l r a t e (q„) (Horton, 1933). The i n f i l t r a t i o n r a t e ( q - ^ ) , can be w r i t t e n as a f r a c t i o n o f the r a i n f a l l r a t e , w i t h v r e p r e s e n t i n g a r a i n f a l l p a r t i t i o n i n g c o e f f i c i e n t ; see Eq. 3.33 and F i g . 29. q l U = q R ( 1 " v ) 3 > 3 3 > By r e a r r a n g i n g Eq. 3.33, v - 1 " qir/qR (3.34) The v a l u e f o r the r a i n f a l l p a r t i t i o n i n g c o e f f i c i e n t v f a l l s w i t h i n the range 0 £ v < 1. When v = 0, t h e r e i s no r u n o f f and a l l the r a i n f a l l i n f i l t r a t e s , t h a t i s the i n f i l t r a t i o n r a t e equals the r a i n f a l l r a t e (q.^ = q R) . H y p o t h e t i c a l l y , i f v = 1 complete r u n o f f occurs and q i y = 0. 110 F i g u r e 29; I n f i l t r a t i o n Rate (c^ u * 1 i n the Unponded Area vs the R a i n f a l l  P a r t i t i o n i n g C o e f f i c i e n t ( v ) . 1 ?.o A o 0,x oA o.t* o.8 l.o I l l S i n c e n e i t h e r the i n f i l t r a t i o n r a t e f o r the unponded case (q l r j ) nor the o v e r l a n d flow r a t e were measured, an e v a l u a t i o n o f the p a r t i t i o n i n g process t h a t r e s u l t e d i n r u n o f f depends upon an assessment o f the h y d r o l o g i c and s o i l - r e l a t e d c o n d i t i o n s i n the f i e l d . These i n c l u d e the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K ^ ) o f the 'surface l a y e r ' f o r the unponded case and the ' d r i v i n g f o r c e ' moving water through t h a t 'surface l a y e r 1 . The volume c o n t r i b u t i o n o f water t o the pond from o v e r l a n d flow (Q Q) i s a f u n c t i o n o f the r a i n f a l l r a t e ( q R ) , the i n f i l t r a t i o n r a t e ( q l u ) , and the p e r i p h e r a l catchment area ( A p 0 T - A ( t ) ) , over which ov e r l a n d flow o c c u r r e d . From Eq. 3.33, the i n f i l t r a t i o n r a t e (q, r T) must f a l l between 0 m.s - 1 and q^. The t o t a l catchment area ( A T 0 T ) i s p h y s i c a l l y bound by the perimeter of the d e p r e s s i o n . Although an unknown i n the a n a l y s i s , i t i s assumed t h a t A T Q T i s f i n i t e and a constant parameter. Thus, the p e r i p h e r a l catchment area ( A T 0 T - A ( t ) ) decreases i f the pond area, A ( t ) , i n c r e a s e s w i t h time. Moreover, A T 0 T i s i m p l i c i t l y r e l a t e d t o v, a c c o r d i n g t o Equations 3.35 and 3.36; see F i g . 30. Q 0 = v q R f [ A T 0 T - A ( t ) ] d t (3.35) Rearranged, = [Q n/vq„ + j A ( t ) d t ] / A t (3.36) 3 The o v e r l a n d flow volume (Q Q = 1.5 m ) was determined from the pond water balance, the r a i n f a l l r a t e (q„ = 6.7x10 m.s 1 ) was taken from the r e s p e c t i v e hyetograph, and A ( t ) was 2TT 113 d e r i v e d from the ' c o n i c a l ' model, see Eq. 3.10. As v i n c r e a s e s , s m a l l e r A T 0 T v a l u e s are c a l c u l a t e d w i t h Eq. 3.36, t h a t i m p l i c i t l y s a t i s f y Eq. 3.35. As v approaches 1, however, i t i s d i f f i c u l t t o o f f e r a p h y s i c a l l y - b a s e d e x p l a n a t i o n f o r the p e r m e a b i l i t y o f the f i e l d s u r f a c e t h a t would produce the extremely low i n f i l t r a t i o n r a t e s (<51U) necessary f o r near t o t a l r u n o f f . Conversely, as v decreases, a l a r g e r A T Q T must e x i s t t o s a t i s f y the o v e r l a n d flow equation (Eq. 3.35). T h e o r e t i c a l l y , as v approaches 0, A T 0 T approaches i n f i n i t y . By s u b s t i t u t i n g Equations 3.6 and 3.10 i n t o Eq. 3.36, A T Q T i s a l s o c a l c u l a b l e f o r d i f f e r e n t s u r f a c e s l o p e v a l u e s 8; see F i g . 31. A T Q T = [ Q Q / v q R + 7T(cot 9 ) 2 J t 2 t 3 [ H p ( t ) ] 2 d t ] / A t (3.37) Although an indeterminate s o l u t i o n s e t { A T Q T , V} e x i s t s f o r d i f f e r e n t v a l u e s o f Q Q, p h y s i c a l l y , only one unique s o l u t i o n ( A T Q T , v) i s c o r r e c t f o r the Q Q computed. I t s uniqueness i s governed by the p a r t i t i o n i n g o f r a i n f a l l , as expressed i n the r e l a t i o n s h i p o f v w i t h q (see Eq. 3.34), w h i l e r e c o g n i z i n g t h a t v and q l t J are d i c t a t e d by the p h y s i c a l and h y d r o l o g i c a l c o n d i t i o n s p r e s e n t i n the f i e l d . The s o l u t i o n i s a l s o a f u n c t i o n o f the t o t a l catchment area ( A T 0 T ) , although an unknown i n the a n a l y s i s . S u r f a c e s l o p e a l s o has i t s e f f e c t a c c o r d i n g to Eq. 3.37. As the s u r f a c e s l o p e decreases f o r s e t v a l u e s of v, c o r r e s p o n d i n g A T 0 T v a l u e s must be l a r g e r t o p r o v i d e a s o l u t i o n . The o p p o s i t e holds as the s u r f a c e s l o p e i s i n c r e a s e d . P h y s i c a l c o n s t r a i n t s to the s o l u t i o n s e t { A T 0 T , v} were imposed. One was the extent o f the catchment b a s i n area ( A T 0 T ) , which was u l t i m a t e l y c o n s t r a i n e d by the area o f the s p o r t s f i e l d . 114 F i g u r e 31; A T O T v s s l o p e : ( Q ) IS00 A a -H EH \OOO O EH < 55 u EH s < O EH 5oO L E G E U O : i:3o 1:40 I'.SO A T O T 6 40 ^ l O i O m*" (r T o r ) ( 14 rO (it ^) (18 ' T O T 1* ' A t i : a o (1 .11O 1:40 (1.43°) C 5 o ( I . I S ' ) S L O P E (0) 2 The l i m i t i n g s o l u t i o n p a i r { ( A T 0 T , v) = (800 m , 0.38)). was 2 chosen by s e t t i n g the upper l i m i t A T 0 T at 800 m . Here, the r a d i u s o f the t o t a l catchment d e p r e s s i o n (ri>0T = 1 6 m ^ e x c e e ^ s one q u a r t e r the width o f the s p o r t s f i e l d (55 m). T h i s c o n s t r a i n t was based s o l e l y upon o b s e r v a t i o n s made o f the d e p r e s s i o n i n the f i e l d . For t h i s l i m i t i n g case the s u r f a c e 2 s l o p e o f 1:40 was used. I m p l i c i t l y , A T 0 T = 800 m corresponds w i t h the p a r t i t i o n i n g c o e f f i c i e n t (v = 0.38). In t u r n , v = 0.38 corresponds w i t h the upper bound i n f i l t r a t i o n r a t e ( q i r j = -7 -1 4.2x10 m.s ); see F i g u r e s 29 and 30. The key p h y s i c a l c o n s t r a i n t a f f e c t i n g i n f i l t r a t i o n i n the unponded p a r t o f the f i e l d , however, was the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the 's u r f a c e l a y e r ' ( K ^ ) . The 'su r f a c e l a y e r ' was p e r v i o u s and, t h e r e f o r e , must have a lower l i m i t ( K 1 U ) . Although i n d e t e r m i n a t e , g i v e n the data o b t a i n e d , the lower bound K i y f o r the unponded case was chosen a r b i t r a r i l y at m = l . O x l O - 8 m.s - 1. The pond water balance equation (Eq. 3.14) can a l s o be w r i t t e n f o r the case where ponded water e i t h e r l e a v e s s t o r a g e or remains c o n s t a n t . W r i t t e n i n terms o f volume r a t e s : AQ R/At + AQ Q/At <, AQ /At (3.38) Re p r e s e n t i n g volume i n p u t s i n t o the pond, the volume r a i n f a l l r a t e (AQ R/At) and the volume ov e r l a n d flow r a t e (AQ Q/At) are both d i r e c t l y dependent upon the r a i n f a l l r a t e ( q _ ) . The con s t a n t volume i n f i l t r a t i o n r a t e (AQ^/At) i s dependent upon the — 6 c o n s t a n t i n f i l t r a t i o n r a t e under the pond ( q l p = -1.7 xlO m . s - 1 ) . S i n c e the in p u t and i n f i l t r a t i o n r a t e s are independent 116 o f each o t h e r , the minimum r a i n f a l l r a t e s capable o f g e n e r a t i n g , f i r s t , o v e r l a n d flow and, second,, growth o f the pond are c a l c u l a b l e . The d i f f e r e n c e between the i n f i l t r a t i o n volume r a t e (AQj/At) and the sum o f the 'input' volume r a t e s (AQ Q/At + AQ_/At) t h a t exceeds (AQ T/At) accounts f o r the volume r a t e o f K X water going i n t o s t o r a g e . When (AQj/At) i s l e s s than (AQ Q/At + AQ_/At) the d i f f e r e n c e accounts f o r the r a t e of water l e a v i n g K s t o r a g e ; see F i g . 32. 2 In the unponded area, by s e t t i n g A T 0 T a t 800 m , w i t h a c o r r e s p o n d i n g p a r t i t i o n i n g c o e f f i c i e n t o f v = 0.38 and f l u x -7 -1 d e n s i t y q = 4.2x10 m.s , the minimum r a i n f a l l r a t e (q.,) r e q u i r e d f o r water t o accumulate as s t o r a g e i n the pond i s -7 -1 -1 5.3x10 m.s (- 1.9 mm.h ). From the 'Short D u r a t i o n R a i n f a l l , I n t e n s i t y , D u r a t i o n , Frequency Data' p r o v i d e d f o r North Vancouver, Lynn Creek, the r a i n f a l l r a t e (q^ = 1.9 mm.h-1) i s not e s p e c i a l l y h i g h . Thus, one would i n f e r t h a t ponding i s h i g h l y probable on the Lower Premier S p o r t s f i e l d g i v e n the f i e l d c o n d i t i o n s both noted and assumed i n the pond water balance model. K i r p i c h ' s e m p i r i c a l l y d e r i v e d formula (Eq. 3.39) was a l s o used t o check whether s u f f i c i e n t time was a v a i l a b l e f o r o v e r l a n d flow to reach the pond from the perimeter o f the t o t a l catchment area ( A T Q T ) ( K i r p i c h , 1940). The formula r e p r e s e n t s a simple t h e o r e t i c a l way to determine the 'time o f c o n c e n t r a t i o n (t ) 1 f o r r u n o f f t o flow some d i s t a n c e over a g i v e n s l o p e . K i r p i c h ' s formula: t c = 0.02 L 0 - 7 7 s - 0 ' 3 8 5 (3.39) g i v e n ; i ) t = time o f c o n c e n t r a t i o n (minutes). 117 F i g u r e 32; AO/At vs q R o o.S" / .O . . 5 2.© 2.5 mwvW. RAIMFAUU R A T E . 118 i i ) L = 11 m; l e n g t h o f s l o p e from the perimeter o f the catchment area, to the edge o f the pond at t 2 -i i i ) S = 1:40; s l o p e r a t i o . The 'time of c o n c e n t r a t i o n ' ( t = 31 s) was c a l c u l a t e d . T h i s x c ' r e l a t i v e l y s m a l l time i s r e f l e c t e d i n the instantaneous s t a r t t o pond r i s e ' C , as i n d i c a t e d on the A p r i l 14, Pond Depth Hydrograph. T h i s confirms t h a t time was not a c o n s t r a i n t f o r the f o r m a t i o n o f the pond. 3.7 The Determination o f the 'Surface Layer' S a t u r a t e d  H y d r a u l i c C o n d u c t i v i t y ( K ^ ) f o r the Unponded Case S i n c e was l e s s than q R the i n f i l t r a t i o n r a t e was ' p r o f i l e - c o n t r o l l e d ' ( H i l l e l , 1971). For the s p o r t s f i e l d case, the ' p r o f i l e ' c o n t r o l l e d i n f i l t r a t i o n r a t e was o n l y dependent upon the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the ' s u r f a c e l a y e r ' and the ' d r i v i n g f o r c e ' c a u s i n g water to flow through i t . S o l u t i o n s f o r v a r i o u s v a l u e s o f , t h e r e f o r e , must comply w i t h Darcy's Law (Eq. 2.1). Darcy's Law may a l s o be w r i t t e n i n the form o f Eq. 3.40. q i U = " K 1 U ( ^ T / A z ) (3.40) The h y d r a u l i c g r a d i e n t f o r downward, v e r t i c a l flow, f o r the unponded case i s : q i u - " K iu ( AV A z + 1 } (3.41) 119 Rearranged, K1U = " q l U / ( A ^ p / A z + 1 ) ; - 6 - 7 x l ° 7 ^ q i u < 0 ( 3 - 4 2 ) Assuming t h a t the 'surface l a y e r ' has a c o n s t a n t s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K ^ ) , and assuming steady s t a t e flow, a c o n s t a n t h y d r a u l i c p o t e n t i a l g r a d i e n t (A\|) /Az + 1) must e x i s t to d r i v e water through the l a y e r at a constant r a t e ( q l u ) . The ' d r i v i n g f o r c e ' i s thus o n l y dependent upon the t h i c k n e s s o f the ' s u r f a c e l a y e r ' (Az) and the drop i n p r e s s u r e p o t e n t i a l across i t (A\jjp/Az). For the c o n d i t i o n o f steady s t a t e , A\})p/Az i s c o n s t a n t . A c c o r d i n g t o Eq. 3.43: A\|)p/Az = (\|)p(J - \|>pl)/Az (3.43) In the a n a l y s i s i t i s assumed t h a t the sheet flow r u n o f f i s n e g l i g i b l y t h i n and the p r e s s u r e p o t e n t i a l a t the s u r f a c e remains co n s t a n t a t \|> Q = 0 m. Consequently, f o r a s a t u r a t e d ' s u r f a c e l a y e r ' o f known t h i c k n e s s (Az), the h y d r a u l i c g r a d i e n t a c r o s s the l a y e r depends e n t i r e l y upon the v a r i a b l e p r e s s u r e p o t e n t i a l (^ p l) a t i t s lower i n t e r f a c e . Although (^p^) i s unknown i t can be estimated. T h i s was done by ag a i n a p p l y i n g the p r e d i c t i v e model developed by Campbell (1974), and the a n a l y t i c a l methods d e s c r i b e d by Bybordi (1968) and C h i l d s (1969); see S e c t i o n 3.5. The upper bound i n f i l t r a t i o n r a t e (q -7 -1 = -4.2x10 m.s ), which was proposed i n S e c t i o n 3.6, was used as an upper bound f l u x d e n s i t y ( q 0 ) . The ' s u r f a c e l a y e r ' lower i n t e r f a c e p r e s s u r e p o t e n t i a l (^ p l = -0.60 m) was thus 120 c a l c u l a t e d . I t i s a f u n c t i o n o f the i n f i l t r a t i o n r a t e ( q i r j) and the h y d r o l o g i c c h a r a c t e r i s t i c s o f the s u b - l a y e r s o i l m a t e r i a l s . By a p p l y i n g Eq. 3.42, assuming a 'surface l a y e r ' t h i c k n e s s (Az = 0.015 m), the upper bound s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K 1 0 ) was c a l c u l a t e d : K 1U = -(-4.2x10 )/(0.60/0.015 + 1) (3.42a) = 1.0x10 - 8 m.s - l (3.42b) I t i s on l y c o i n c i d e n t a l t h a t t h i s computed upper bound K 1 L J a l s o equals the a r b i t r a r i l y chosen lower l i m i t K . 121 4. SUMMARY, CONCLUSIONS, AND MANAGEMENT RECOMMENDATIONS 4.1 Summary and Con c l u s i o n s Acknowledging t h a t the t h e s i s o b j e c t i v e s were management-related, the c o n c l u s i o n s p l a c e an emphasis on the importance o f c o r r e c t l y managing the p h y s i c a l c o n d i t i o n s o f a s p o r t s f i e l d s o i l . Prom the l i t e r a t u r e i t i s l e a r n e d t h a t c o n s i d e r a b l e a t t e n t i o n , from a v a r i e t y o f d i f f e r e n t sources, has been g i v e n t o s p o r t s f i e l d c o n s t r u c t i o n designs f o r wet c l i m a t i c c o n d i t i o n s . In p a r t i c u l a r , s o i l m a t e r i a l s and s o i l p r o f i l e l a y e r i n g have r e c e i v e d c o n s i d e r a b l e a t t e n t i o n . The emphasis has been p l a c e d on the use o f sands or sandy types o f s o i l , as w e l l as on t h e i r placement s p e c i f i c a t i o n s , and on the depth and s p a c i n g o f d r a i n s . The main c o n c l u s i o n from t h i s study, however, i s t h a t no matter how f a v o u r a b l e the i n i t i a l c o n d i t i o n s are, w i t h r e s p e c t t o s o i l m a t e r i a l s and t h e i r p r e p a r a t i o n , i f c e r t a i n s o i l or f i e l d a l t e r i n g processes are not managed c o r r e c t l y , s e r i o u s e f f e c t s are i n c u r r e d t o the l o n g term success o f the s p o r t s f i e l d . For the Lower Premier S p o r t s f i e l d , as the case i n p o i n t , these processes r e s u l t e d i n a reduced s u r f a c e i n f i l t r a b i l i t y t h a t caused s e r i o u s ponding problems. The proce s s e s o f p a r t i c u l a r concern, which gave r i s e t o the phenomenon o f ponding, were the form a t i o n o f a 'surface l a y e r ' o f low s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y and the development o f a s u r f a c e d e p r e s s i o n on the f i e l d . By q u a n t i f y i n g these concerns the f i e l d manager should be b e t t e r informed about the h y d r o l o g i c problems he i s co n f r o n t e d w i t h . The Lower Premier S p o r t s f i e l d i s b a s i c a l l y a s a n d f i e l d 122 amended i n p a r t w i t h sawdust. The h i g h s a t u r a t e d h y d r a u l i c c o n d u c t i v i t i e s (K ) o f the sands used, t h e i r placement s p e c i f i c a t i o n , and the drainage d e s i g n i n c o r p o r a t e d i n t o the c o n s t r u c t i o n o f the f i e l d a l l c o n t r i b u t e d to the f a v o u r a b l e i n i t i a l c o n d i t i o n s o f the f i e l d . Although the s p o r t s f i e l d f u n c t i o n e d s a t i s f a c t o r i l y d u r i n g i t s f i r s t few years i t e v e n t u a l l y developed the ponding problem, which had s e r i o u s a f f e c t s on the u t i l i t y and management o f the f i e l d . From a s o i l h y d r o l o g i c p o i n t o f view the ponding was seen as an i n f i l t r a t i o n problem. 'Ponding' occurs when the i n t e n s i t y o f i n c i d e n t r a i n f a l l on the s u r f a c e o f the s p o r t s f i e l d exceeds i t s ' i n f i l t r a b i l i t y ' . The c o n d i t i o n s c a u s i n g the s p o r t s f i e l d ponding a c t u a l l y presented an i n t e r e s t i n g s c e n a r i o f o r c l a s s i c a l ' R a i n f a l l I n f i l t r a t i o n ' theory (Rubin and S t e i n h a r d t , 1963). The theory s t a t e s c o n c l u s i v e l y t h a t water ponds, or runs o f f , under these c o n d i t i o n s . ( H i l l e l , 1971). The study presented here a p p l i e s the theory to the case o f ponding i n a r e l a t i v e l y w e l l - d e f i n e d catchment d e p r e s s i o n t h a t c o n c e n t r a t e s r u n o f f i n t o the pond. To analyze the extent o f the h y d r o l o g i c problems, the 'cone' dimensioned pond water balance model was developed and a p p l i e d . Pond r i s e and r e c e s s i o n measurements pro v i d e d the h y d r o g r a p h i c data f o r the model. These measurements i n the v e r t i c a l dimension gave a p r e c i s e e v a l u a t i o n o f how the pond grew and c o n t r a c t e d . I t s h o r i z o n t a l expansion, however, was confounded by the more or l e s s e l l i p t i c a l shape o f the pond and the d i f f i c u l t y o f d e l i n e a t i n g i t s perimeter. An i n v e r t e d r i g h t c o n i c a l geometry was assumed f o r the pond. The model showed t h a t the volume terms i n the pond water balance were s t r o n g l y 123 a f f e c t e d by the s u r f a c e s l o p e o f the f i e l d . By d e c r e a s i n g the s l o p e i n the model the volumes o f water i n c r e a s e d . The i m p l i c a t i o n s o f t h i s were d i r e c t l y r e l a t e d to the s e v e r i t y o f the d e p r e s s i o n on the f i e l d and the management p r a c t i c e s or c o n d i t i o n s t h a t allow t h i s t o happen. The f a c t t h a t the s p o r t s f i e l d was c o n s t r u c t e d on top o f c o n s o l i d a t i n g l a n d f i l l m a t e r i a l s undoubtedly c o n t r i b u t e d to the f o r m a t i o n o f the d e p r e s s i o n . However, i t would be presumptuous to conclude t h a t the ponding problem i s unique t o such s u b - s o i l c o n d i t i o n s . The c o n i c a l model approach pr o v i d e d a p a r t i c u l a r l y important i n s i g h t w i t h r e s p e c t to the ponding phenomenon. I t e s t a b l i s h e d t h a t the r a i n f a l l volume (Q_) t h a t was r e c e i v e d d i r e c t l y by the pond alone was i n s u f f i c i e n t t o account f o r i t s growth. The o n l y other p o s s i b l e source o f water was r u n o f f f l o w i n g i n t o the pond. Of p a r t i c u l a r i n t e r e s t , however, was the e x t e n t t o which ov e r l a n d flow c o n t r i b u t e d to the pond water balance. The r e s u l t s o f the model showed t h a t over the p e r i o d analysed n e a r l y f o u r times as much water was c o n t r i b u t e d through 3 o v e r l a n d flow (Q Q = 1.5 m ) as was r e c e i v e d d i r e c t l y from 3 r a i n f a l l (Q R = 0.4 m ). I t was e v i d e n t t h a t the p a r t i t i o n e d r a i n f a l l , c o n t r i b u t i n g t o overland flow, represented a s i g n i f i c a n t i n p u t i n t o the system. The s o i l p r o p e r t i e s and h y d r o l o g i c c h a r a c t e r i s t i c s o f the s o i l p r o f i l e u l t i m a t e l y determine the s u r f a c e i n f i l t r a b i l i t y o f the s p o r t s f i e l d . I f the r a i n f a l l r a t e (q^) exceeds the i n f i l t a b i l i t y o f the s u r f a c e i n a steady s t a t e system, the f l u x d e n s i t y o f water moving v e r t i c a l l y downwards through the s o i l i s governed by the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the s o i l and the h y d r a u l i c g r a d i e n t a c t i n g as a ' d r i v i n g f o r c e ' , a c c o r d i n g to 124 Darcy's Law. An important assumption made i n the t h e s i s , however, was t h a t steady s t a t e i n f i l t r a t i o n , r a t h e r than t r a n s i e n t flow c o n d i t i o n s , e x i s t e d . T h i s assumption was thought to be reasonable though r e c o g n i z i n g the constancy o f s l o p e o f the pond depth hydrographs. The assumption i s a l s o i n keeping with.the r a p i d i t y o f s o i l moisture and p r e s s u r e p o t e n t i a l r e d i s t r i b u t i o n g e n e r a l l y a s s o c i a t e d w i t h sands. From i n s p e c t i o n o f the s o i l p r o f i l e i t was e v i d e n t t h a t a d e f i n i t e ' s u r f a c e l a y e r ' had formed i n the upper p a r t o f the 'Top Layer'. I t was v i s i b l y darker and more compacted than the other l a y e r s i n the s o i l . From the a n a l y s i s i t was e s t a b l i s h e d t h a t the low i n f i l t r a b i l i t y was r e l a t e d t o a l a r g e drop i n the ' e f f e c t i v e ' s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K e f f ) f ° r the 'Top Layer'. T h i s reduced i n f i l t r a b i l i t y , moreover, was caused by the dominant h y d r a u l i c r e s i s t a n c e o f the 'surface l a y e r ' w i t h i n the 'Top Layer'. By e s t i m a t i n g the p r e s s u r e p o t e n t i a l s (^1^) at the ' s u r f a c e l a y e r ' i n t e r f a c e a low s a t u r a t e d h y d r a u l i c — 8 — 1 c o n d u c t i v i t y f o r the 'surface l a y e r ' ( K l p = 5.2x10 m.s ) was c a l c u l a t e d . The range o f s a t u r a t e d h y d r a u l i c c o n d u c t i v i t i e s t h a t was determined f o r the 'surface l a y e r ' under the pond (3.3x10 -1 -7 -1 m.s < K i p < 4.9x10 m.s ) was compared wi t h the v a l u e o b t a i n e d f o r the unponded case. The range o f K l p v a l u e s was — 8 — 1 h i g h e r than the estimated = 1.0x10 m.s . The e x p l a n a t i o n f o r t h i s d i s c r e p e n c y , g i v e n equal 'surface l a y e r ' t h i c k n e s s e s and reduced h y d r a u l i c g r a d i e n t s f o r the unponded case was r e l a t e d t o the t o r n and d i s r u p t e d s u r f a c e i n the area under the pond. T h i s d i s r u p t i o n was c h a r a c t e r i z e d by bare patches, deep r u t s and d e p r e s s i o n s . Such d i s r u p t i o n i s expected at c e n t r e -125 f i e l d because of the g r e a t e r p l a y i n t e n s i t y a t t h a t l o c a t i o n . Away from c e n t r e - f i e l d t h i s d i s r u p t i o n was not as p r e v a l e n t . The h i g h e r h y d r a u l i c c o n d u c t i v i t i e s ( K i p ) estimated f o r the 's u r f a c e l a y e r ' under the pond r e f l e c t e d t h i s d i s r u p t e d s u r f a c e . E f f e c t i v e l y the e n t i r e area under the pond was t r e a t e d as an i n f i l t r o m e t e r . K l p / t h e r e f o r e , was an ' e f f e c t i v e ' estimate, or average. I t does not re p r e s e n t the s o i l p r o p e r t y o f a uniform ' s u r f a c e l a y e r ' . The s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the a c t u a l ' s u r f a c e l a y e r ' s o i l , t h e r e f o r e , would l i k e l y be c l o s e r to the estimate g i v e n i n the unponded case. A summary o f the c o n c l u s i o n s d e r i v e d from the t h e s i s study are: i ) The ' f r e e ' water expressed on the Lower Premier S p o r t s f i e l d s u r f a c e was due t o ponding and not f l o o d i n g . i i ) Overland flow was a major c o n t r i b u t o r t o the ponding phenomenon. i i i ) The ov e r l a n d flow component (Q Q) was h i g h l y s e n s i t i v e to the s l o p e o f the p l a y i n g s u r f a c e . Using ste e p e r s l o p e s i n the model generated h i g h e r r a i n f a l l p a r t i t i o n i n g c o e f f i c i e n t v a l u e s ( v ) . i v ) Ponding and ove r l a n d flow would not occur without a s o i l l a y e r o f low s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y a c t i n g as a h y d r o l o g i c b a r r i e r t o the s u r f a c e i n f i l t r a b i l i t y o f the f i e l d . A 'surface l a y e r ' s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K 1) i n the order o f — 8 —1 10 m.s was c a l c u l a t e d . 126 4.2 Recommendations 4.2.1 Management recommendations The 'surface l a y e r ' , w i t h i t s low s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K ), reduced the i n f i l t r a b i l i t y o f the s p o r t s f i e l d below the i n f i l t r a t i o n requirement f o r the r a i n f a l l i n t e n s i t i e s r e c e i v e d . Given the s u r f a c e d e p r e s s i o n near c e n t r e - f i e l d , s u r f a c e r u n o f f c o n t r i b u t e d s i g n i f i c a n t l y t o the growth o f the pond. Two important management recommendations, t h e r e f o r e , are proposed t o improve the c o n d i t i o n o f the f i e l d . F i r s t , s u r f a c e d e p r e s s i o n s cannot be allowed t o develop. With a f l a t or s l i g h t l y crowned s u r f a c e , the ponding would not have o c c u r r e d . The i n i t i a l d e s i g n f o r the s p o r t s f i e l d , i n f a c t , s p e c i f i e d a f l a t p l a y i n g s u r f a c e , but m a i n t a i n i n g t h i s c o n d i t i o n demands c o n t i n u a l upkeep. The j u d i c i o u s a p p l i c a t i o n o f ' t o p d r e s s i n g 1 sand i s r e q u i r e d t o compensate f o r s e t t l i n g and s u b s o i l c o n s o l i d a t i o n . I t i s p a r t i c u l a r l y important t h a t the •t o p d r e s s i n g ' sand be the same as t h a t used i n the 'Toplayer' ( i e . the 'Fraser R i v e r ' sand). The second recommendation i s t h a t the 'surface l a y e r ' must not be allowed t o form. Even i f the pond would not occur without the s u r f a c e d e p r e s s i o n , the presence o f the s a t u r a t e d ' s u r f a c e l a y e r ' would l e a v e the p l a y i n g s u r f a c e weak and un p l a y a b l y soggy. I t s e l i m i n a t i o n would r e q u i r e s i m i l a r management p r a c t i c e s s i m i l a r t o those g i v e n t o t h a t c h c o n t r o l . These i n c l u d e : i ) 'hollow t i n e d c o r i n g ' t h a t p e n e t r a t e s through the 127 ' s u r f a c e l a y e r ' . Moreover, the removed cores should be c o l l e c t e d . i i ) the c o l l e c t i o n of ' c l i p p i n g s ' , i i i ) r a k i n g the 'thatch' t o remove d e t r i t a l o r g a n i c matter. i v ) e l i m i n a t i n g o r g a n i c amendments from the sand s p e c i f i c a t i o n s . The above steps are p r i m a r i l y taken to reduce the accumulation o f o r g a n i c matter at the f i e l d s u r f a c e . Presumably, the development o f the pore clogged ' s u r f a c e l a y e r ' r e p r e s e n t s an a c c e l e r a t i v e p r o c e s s , f o r as more d e t r i t a l o r g a n i c matter accumulates i n the l a y e r the more i t becomes a p r e f e r r e d r o o t i n g medium. The decomposed o r g a n i c matter has much high e r m oisture and n u t r i e n t r e t e n t i o n p r o p e r t i e s . With the a d d i t i o n a l r o o t i n g a c t i v i t y , sloughed r o o t and rhizome m a t e r i a l s add f u r t h e r t o the accumulation pr o c e s s . Simply s t a t e d the accumulation o f t h i s m a t e r i a l must be brought under c o n t r o l . An a d d i t i o n a l s t r a t e g y should be s e t i n p l a c e to reduce the p r o d u c t i o n o f p l a n t matter near the s u r f a c e . These i n c l u d e : v) the encouragement of deep r o o t i n g , which i s important f o r the a d d i t i o n a l shear s t r e n g t h i t g i v e s t o the s o i l and because i t r e p r e s e n t s p l a n t growth away from the s u r f a c e . Deep r o o t i n g i s p a r t l y f a c i l i t a t e d by m a i n t a i n i n g a deep water t a b l e . T h i s r e q u i r e s t h a t a p p r o p r i a t e drainage d e s i g n be employed. I t i s a l s o f a c i l i t a t e d by the deep placement of f e r t i l i z e r s . For sands g r a n u l a r and 'slow r e l e a s e ' forms are p r e f e r r e d t o l i m i t l e a c h i n g l o s s e s . S o l u b l e forms o f n i t r o g e n should be avoided. I n i t i a l l y , by i n c o r p o r a t i n g 128 n u t r i e n t f e r t i l i z e r s i n t o the sands d u r i n g t h e i r placement deep t u r f g r a s s r o o t i n g i s encouraged. L a t e r on methods must be used to e i t h e r i n j e c t the granules or implant them. P o s s i b l y t h i s might be done as p a r t o f the c o r i n g p r o c e s s , or w h i l e ' s p i k i n g ' or ' s l i c i n g ' the t u r f g r a s s . B r o a d c a s t i n g n i t r o g e n f e r t i l i z e r s should be abandoned, i f p o s s i b l e , simply because i t c o n c e n t r a t e s n u t r i e n t s at the s u r f a c e . Because o f t h e i r a c i d i f y i n g e f f e c t , broadcasted ammonium-based n i t r o g e n f e r t i l i z e r s would a l s o tend to r e t a r d the decomposition o f o r g a n i c matter i n the s o i l environment near the s u r f a c e , v i ) r e d u c i n g the amounts of n i t r o g e n f e r t i l i z e r s a p p l i e d . N i t r o g e n encourages l e a f y top growth and e x c e s s i v e amounts are commonly a p p l i e d t o ensure a l u s h green, c o n t i n u a l l y rejuvenated, sward on the f i e l d s u r f a c e . The d e s i r e d a e s t h e t i c b e n e f i t s from t h i s p r a c t i c e must be weighed a g a i n s t the c o s t s o f managing these a d d i t i o n a l top growth y i e l d s . T h i s i n c l u d e s the c o s t s a t t r i b u t a b l e t o the d i s e a s e and i n s e c t p e s t problems a s s o c i a t e d w i t h producing too s u c c u l e n t a top growth. Moreover, a d d i t i o n a l p h y s i c a l damage i s caused by wear on o v e r l y s u c c u l e n t p l a n t s . v i i ) s c h e d u l i n g the use o f the s p o r t s f i e l d t o minimize s e r i o u s d i s r u p t i o n o f i t s s u r f a c e . 4.2.2 Research recommendations The most s e r i o u s l i m i t a t i o n t o the study was the 129 v e r i f i c a t i o n o f the s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y (K.^) o f the ' s u r f a c e l a y e r ' . Assuming the model d u l y represented f i e l d — 8 — 1 c o n d i t i o n s , low K 1 v a l u e s i n the order o f 10 m.s had to e x i s t f o r ponding t o occur. Admittedly, these are low K values t o be expected from a sandy s o i l . Confidence i n the model would have been enhanced i f these values had been measured. Another concern was the assumption t h a t steady s t a t e flow c o n d i t i o n s e x i s t e d throughout the s o i l p r o f i l e . T h i s was p a r t i c u l a r l y important as i t was r e l a t e d t o the p r e s s u r e p o t e n t i a l p r o f i l e d i s t r i b u t i o n , and thus the u n s a t u r a t e d flow c o n d i t i o n s below the ' s u r f a c e l a y e r ' . For the sand/sawdust mixture a measured K(\))p) c h a r a c t e r i s t i c curve would have been most b e n e f i c i a l . Measurements o f p r e s s u r e p o t e n t i a l s a t d i f f e r e n t depths would a l s o have been r e a s s u r i n g . For f u r t h e r r e s e a r c h i t i s recommended t h a t g r e a t e r a t t e n t i o n be g i v e n to piezometry and tensiometry i n the f i e l d . The other area o f r e s e a r c h brought i n t o q u e s t i o n i s the p r o p e r t i e s and processes r e l a t e d t o the f o r m a t i o n o f the ' s u r f a c e l a y e r ' . The p r o p e r t i e s o f the decomposed o r g a n i c matter w i t h i n the l a y e r were on l y touched upon i n t h i s t h e s i s . The nature o f the pore c l o g g i n g m a t e r i a l and the process o f how i t c l o g s the pores o f the sand are u n c l e a r . Recommendations f o r f u r t h e r r e s e a r c h i n c l u d e d e t e r m i n i n g the decomposition r a t e s o f t h i s m a t e r i a l under s i m i l a r environmental c o n d i t i o n s . I t i s recommended t h a t s t u d i e s be c a r r i e d out to determine what c u l t u r a l p r a c t i c e s and methods might be a p p l i e d t o reduce the accumulation and p r o d u c t i o n o f o r g a n i c matter found i n the ' s u r f a c e l a y e r ' . 130 5. REFERENCES AND BIBLIOGRAPHY Adams, W.A. 1986. P r a c t i c a l aspects o f s p o r t s f i e l d drainage. S o i l Use and Management. 2(2):51-54. Adams, W.A., V . I . Stewart, and D.J. Thornton. 1971. The assessment o f sands f o r use i n s p o r t s f i e l d s . J o u r n a l o f  the Sports T u r f Research I n s t i t u t e . 47:77-85. ASTM Committee E-29. 1972. 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