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Hydrograph separation using natural isotope and conductance methods in the West Kootenay area of British… Marquis, John Paul 1985

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HYDROGRAPH SEPARATION USING NATURAL ISOTOPE AND CONDUCTANCE METHODS IN THE WEST KOOTENAY AREA OF BRITISH COLUMBIA by JOHN PAUL MARQUIS B . S c , The U n i v e r s i t y o f V i c t o r i a , 1978 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Resource Management 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 January 1985 © John Paul Marquis, 1985 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by t h e head o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Gft f t f luf iTE S T O D v E S The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 £ 7 fflMBS ABSTRACT The storm r u n o f f of small s p r i n g s and seeps i n the West Kootenays was s u b j e c t e d to hydrograph s e p a r a t i o n u s i n g oxygen-18 and conductance methodologies. The r e s u l t s showed t h a t the v a s t m a j o r i t y of storm d i s c h a r g e was groundwater. Under peak flow c o n d i t i o n s , the r a t i o of prestorm water to storm water was 0.93 f o r Morley S p r i n g , 0.88 f o r Anderson Creek, 0.87 f o r E l l i o t t Creek, 0.84 f o r Chou Creek and 0.85 f o r Tank Creek. F u r t h e r comparison between prestorm d i s c h a r g e and storm water i n d i c a t e d t h a t the groundwater probably o r i g i n a t e d as s p r i n g snow melt. These i m p l i c a t i o n s are d i s c u s s e d with regard t o the v a r i o u s l o g g i n g development plans c u r r e n t l y being proposed f o r the study s i t e s . i ACKNOWLEDGEMENTS I would l i k e to extend my a p p r e c i a t i o n to D.A.A. Toews and D. Gluns of the M i n i s t r y of F o r e s t s i n Nelson f o r t h e i r i n t e r e s t and support i n t h i s study. My thanks to P. Whaite of the Department of Geophysics of the U n i v e r s i t y of B r i t i s h Columbia whose t a l e n t s were r e s p o n s i b l e f o r the maintenance of the mass spectrometer. I a l s o extend my g r a t i t u d e to Dr.. D. L. Golding of the F a c u l t y of F o r e s t r y of the U n i v e r s i t y of B r i t i s h Columbia whose guidance was paramount i n the completion of t h i s t h e s i s . F i n a l l y , a s p e c i a l thanks to my wife Sandra f o r her pa t i e n c e and proof r e a d i n g . i i TABLE OF CONTENTS A b s t r a c t i Acknowledgements i i Table of Contents i i i L i s t of Tables v L i s t of F i g u r e s v i Chapter 1 - I n t r o d u c t i o n Problem 1 O b j e c t i v e s 2 Review 4 Chapter 2 - Methods 22 Chapter 3 - Mountain S t a t i o n Study Area Area D e s c r i p t i o n 26 Study S i t e s and Methods 30 R e s u l t s 31 D i s c u s s i o n of F i n d i n g s 39 Co n c l u s i o n s 43 Chapter 4 - North Shore Study Area Area D e s c r i p t i o n 45 Study S i t e and Methods 46 R e s u l t s 47 D i s c u s s i o n of F i n d i n g s 52 Co n c l u s i o n s 52 i . . Chapter 5 - Slocan V a l l e y Study Area Area D e s c r i p t i o n 54 Study S i t e s and Methods •••• 56 R e s u l t s 58 D i s c u s s i o n of F i n d i n g s 58 C o n c l u s i o n s 65 Chapter 6 - Study C o n c l u s i o n s 67 Appendix A (glossary) 71 References 73 i v LIST OF TABLES Table Page 1. Rainwater data f o r Mountain S t a t i o n study area 32 2. Data obtained f o r the Tank Creek sampling s i t e 33 3. Data obtained f o r the P o s t l e S p r i n g sampling s i t e 35 4. Data obtained f o r the Anderson Creek sampling s i t e .... 37 5. Rainwater data f o r North Shore study area 49 6. Data obtained f o r the Morley S p r i n g sampling s i t e 50 7. Rainwater data f o r Slocan V a l l e y study area 59 8. Data obtained f o r the Chou Creek sampling s i t e 60 9. Data obtained f o r the E l l i o t t Creek sampling s i t e 62 v LIST OF FIGURES F i g u r e s Page 1. Small s c a l e map of study areas 3 2. Geometric hydrograph s e p a r a t i o n 9 3. Barne's method of geometric hydrograph s e p a r a t i o n on l o g a r i t h m i c s c a l e 11 4. Barn's method of geometric hydrograph s e p a r a t i o n on l i n e a r s c a l e . 12 5. Hewlett's constant slope method of hydrograph s e p a r a t i o n 13 6. I s o t o p i c hydrograph s e p a r a t i o n .' 17 7. Topographical map showing the Mountain S t a t i o n and North Shore Study areas 27 8. Sketch Map of the Mountain S t a t i o n study area 28 9. Tank Creek hydrograph 34 10. P o s t l e S p r i n g hydrograph 36 11. Anderson Creek hydrograph 38 12. Sketch map of North Shore study area 48 13. Morley S p r i n g hydrograph 51 14. Top o g r a p h i c a l map showing the Slocan V a l l e y study area 55 15. Sketch map of the Slocan V a l l e y study area 57 16. Chou Creek hydrogrph 61 17. E l l i o t t Creek hydrograph 63 v i CHAPTER 1 - INTRODUCTION Problem Wi t h i n the Nelson F o r e s t Region there are numerous small s p r i n g s and streams t h a t are c u r r e n t l y being used as sources of both domestic and i r r i g a t i o n a l water. Although l i c e n c e d by the M i n i s t r y of Environment, Water Management Branch, these r i p a r i a n p r o p r i e t o r s have no l e g a l recourse should t h i s resource be d i s r u p t e d due to an o f f i c i a l l y s a nctioned, but p o o r l y planned development scheme. The mandate of the Water Management Branch i s simply to i n s u r e t h a t the s p r i n g s are not l i c e n c e d beyond t h e i r s u s t a i n a b l e y i e l d and to e s t a b l i s h a temporal p r i o r i t y f o r water use. I t i s d i f f i c u l t , however to determine the exact y i e l d of these l o c a l water resources as they are very s u s c e p t i b l e to changes i n the weather. The accuracy of p r e d i c t i n g a s u s t a i n a b l e y i e l d i s f u r t h e r complicated by the f a c t t h a t on any given day a l i c e n c e e i s not l i k e l y to use h i s e n t i r e e n t i t l e m e n t and t h e r e f o r e a c o n s i d e r a b l e s u r p l u s may be generated. The mandate of the M i n i s t r y of F o r e s t s , however, i n c l u d e s managing B r i t i s h Columbia's f o r e s t resources f o r the b e n e f i t of a l l p r o v i n c i a l r e s i d e n t s . An apparent c o n f l i c t of i n t e r e s t a r i s e s when l i c e n c e d r i p a r i a n s i n t e r p r e t a proposed l o g g i n g p l a n as a t h r e a t to t h e i r water supply. Residents o f t e n f e e l t h a t the f o r e s t resource i s being managed without due c o n s i d e r a t i o n of l o c a l concerns. Such problems have r e c e n t l y been brought to the f o r e i n p u b l i c meetings convened by the Nelson Region of the M i n i s t r y of F o r e s t s to d i s c u s s proposed developments i n the Slocan V a l l e y and 1 Kootenay Lake areas ( F i g . 1 ) . These areas c o n t a i n many small flow systems. The p h y s i c a l c h a r a c t e r i s t i c s of these systems are not e a s i l y i d e n t i f i e d and as such they may present a management problem f o r f u t u r e development. With the aim of o b t a i n i n g an amicable s o l u t i o n t o these problems, the r e g i o n a l headquarters of the M i n i s t r y of F o r e s t s , i n c o n j u n c t i o n with the concerned d i s t r i c t , have i n t e n s i f i e d t h e i r s t u d i e s of the p h y s i c a l parameters governing the areas i n q u e s t i o n . O b j e c t i v e s The aim of t h i s study was to determine the r e l a t i v e c o n t r i b u t i o n s of prestorm water and storm r u n o f f to t o t a l flow i n s e l e c t e d small s p r i n g s and creeks w i t h i n the Kootenays. This w i l l be accomplished u s i n g both the i s o t o p i c and conductance methods of hydrograph s e p a r a t i o n . The r e s u l t s of t h i s a n a l y s i s w i l l i n d i c a t e the r e l a t i v e c o n t r i b u t i o n s of ove r l a n d flow, i n t e r f l o w and groundwater to t o t a l storm r u n o f f . As a secondary o b j e c t i v e , the r e l a t i v e c o n t r i b u t i o n s of the components to t o t a l storm r u n o f f w i l l be combined with p r e v i o u s l y e s t a b l i s h e d knowledge i n the f i e l d of f o r e s t hydrology to o b t a i n i n s i g h t i n t o the f u n c t i o n i n g of the l o c a l s p r i n g s and creeks i n the Nelson Lake and Slocan V a l l e y areas. T h i s i n f o r m a t i o n w i l l be used to ev a l u a t e how f u t u r e development plans might a f f e c t the q u a l i t y and q u a n t i t y of the water r e s o u r c e . I f adverse impacts are a n t i c i p a t e d recommendations w i l l be made as to how the v a r i o u s development schemes c o u l d be implemented to minimize any d e l e t e r i o u s e f f e c t s . 2 I I 1 1 1 5 10 15 20 25 kilometers (h i g h l i g h t i n g delineates study areas) F i g . 1 West Kootenays 3 Review In a'ddition to the v a r i a b l e s of geology, topography and c l i m a t e , n a t u r a l v e g e t a t i v e cover has a l a r g e i n f l u e n c e on watershed hydrology. I t has been shown t h a t v e g e t a t i v e cover decreases r u n o f f through i n t e r c e p t i o n and subsequent e v a p o r a t i o n (Helvey 19 71). A f o r e s t canopy w i l l reduce the t h r o u g h f a l l of p r e c i p i t a t i o n and thereby l i m i t the amount of water i n f i l t r a t i n g the ground. The magnitude of t h i s e f f e c t depends upon the type and i n t e n s i t y of the p r e c i p i t a t i o n , as w e l l as v a r i a b l e s such as percent crown c l o s u r e , t r e e h e i g h t and t r e e s p e c i e s . V e g e t a t i v e cover a l s o decreases the amount of r u n o f f through t r a n s p i r a t i o n (Hewlett and Nutter 1969). T h i s e f f e c t i s g r e a t e s t d u r i n g the s p r i n g and summer when the m a j o r i t y of p l a n t growth occu r s . The a c t u a l amount of water t r a n s p i r e d w i l l depend upon the type of p l a n t ( i t s s u r f a c e area and r o o t i n g depth) and the a v a i l a b i l i t y of water (as r e f l e c t e d i n the c l i m a t e and the a b i l i t y of the s o i l to r e t a i n a v a i l a b l e m o i s t u r e ) . C r o f t (1948) found t h a t e v a p o t r a n s p i r a t i o n of r i p a r i a n v e g e t a t i o n can account f o r up to 33% of t o t a l flow d u r i n g the l a t e summer. The r o o t i n g system of p l a n t s i s a l s o r e s p o n s i b l e f o r m a i n t a i n i n g a high v o i d r a t i o w i t h i n the s o i l . The v o i d r a t i o , i n t u r n , i n c r e a s e s d e t e n t i o n storage thus d e c r e a s i n g peak flow, p r o l o n g i n g r u n o f f and m a i n t a i n i n g a high p e r c o l a t i o n r a t e . I f the v e g e t a t i o n i s removed the s o i l may become more compacted r e s u l t i n g i n an i n c r e a s e i n the r a t i o of o v e r l a n d flow to subsurface flow (Chamberlin 1972). R e t e n t i o n storage, on the other hand, i s p r i m a r i l y a f u n c t i o n of s o i l p a r t i c l e s i z e . V e g e t a t i v e cover can i n d i r e c t l y a f f e c t the amount o f moisture 4 h e l d by the s o i l through i n p u t s of decomposing l i t t e r . Although f o r e s t h a r v e s t i n g may cause a temporary r e d u c t i o n i n the o r g a n i c m a t e r i a l a v a i l a b l e to the s o i l i t i s u n l i k e l y to have a l a r g e e f f e c t upon the r e t e n t i o n storage as the time r e q u i r e d f o r r e g e n e r a t i o n of v e g e t a t i v e cover i s s h o r t i n comparison to s o i l g e n e s i s . A w e l l developed p l a n t canopy w i l l a l s o reduce ev a p o r a t i o n from the s o i l s u r f a c e by b l o c k i n g i n c i d e n t r a d i a t i o n . T h i s e f f e c t i s f u r t h e r enhanced by v e g e t a t i o n which lowers the vapour pressure g r a d i e n t by s h e l t e r i n g the moist s o i l from s u r f a c e winds. V e g e t a t i v e cover a l s o i n f l u e n c e s the q u a n t i t y and d i s t r i b u t i o n of a snow pack (Golding 1974) . In a dense f o r e s t the o v e r a l l snow pack w i l l be reduced due to i n t e r c e p t i o n . In a more open or patch cut f o r e s t the accumulation may be i n c r e a s e d due to the turbulence caused by the uneven canopy. With very l i t t l e v e g e t a t i v e cover, however, the snow pack may be reduced due to d r i f t and scour. When the d i f f e r e n t e f f e c t s of v e g e t a t i v e cover are t a l l i e d , i t seems q u i t e c l e a r t h a t the t o t a l d i s c h a r g e of a watershed w i l l not be reduced i f the f o r e s t cover i s removed, and i n f a c t , i n most cases i t w i l l i n c r e a s e (Anderson, Hoover and Reinhart 1976). Due to the many d i f f e r e n t f o r c e s exerted by v e g e t a t i v e cover over r u n o f f p a t t e r n s and c o n s i d e r i n g the d i f f i c u l t y of o b t a i n i n g p r e c i s e , r e l i a b l e data, pretreatment q u a n t i f i c a t i o n of t h i s statement i s d i f f i c u l t . These f a c t o r s a l s o make t h i s e m p i r i c a l r e l a t i o n s h i p s i t e - s p e c i f i c and t h e r e f o r e the i n f o r m a t i o n 5 concerning one watershed cannot be t r a n s f e r r e d to another area without a high p r o b a b i l i t y of e r r o r . In some i n s t a n c e s , however, the e f f e c t of v e g e t a t i v e cover on t o t a l y i e l d i s not as important as the time d i s t r i b u t i o n of r u n o f f . Some r e s e a r c h e r s have shown t h a t p l a n t cover can improve s o i l s t r u c t u r e and thereby i n c r e a s e i t s p e r c o l a t i o n r a t e and moisture storage c a p a c i t y . T h i s e f f e c t can i n t u r n lead to an i n c r e a s e i n groundwater flow as opposed to s u r f a c e r u n o f f (Bates 1934, Tennessee V a l l e y A u t h o r i t y 1955). The net r e s u l t of these e f f e c t s i s to more evenly d i s t r i b u t e r u n o f f throughout the year. These r e s u l t s , however, are o n l y l i k e l y to occur i n extreme cases such as the r e v e g e t a t i o n of abused farmland. S t u d i e s have a l s o shown t h a t removal of v e g e t a t i v e cover w i l l i n c r e a s e the t o t a l amount of water a v a i l a b l e f o r r u n o f f which, i n t u r n , w i l l i n c r e a s e flow d u r i n g the summer and f a l l p e r i o d s when the demand f o r water i s g r e a t e s t (Reinhart, Eschner, Trimble 1963). Rbthacher (1970) found t h a t f o r a watershed i n Oregon, 80% of a measured i n c r e a s e i n r u n o f f took p l a c e d u r i n g the winter months. The 20% of the i n c r e a s e d r u n o f f t h a t o c c u r r e d over the summer, however, represented a 150% i n c r e a s e i n the pretreatment low flow measurements, f o r every square k i l o m e t e r c l e a r c u t t h i s 6 r e p r e s e n t s an i n c r e a s e of 1.3 x 10 1 per day. Rothacher (1970) a t t r i b u t e s t h i s i n c r e a s e to reduced e v a p o t r a n s p i r a t i o n , which leads to a g r e a t e r amount of water being h e l d i n both r e t e n t i o n and d e t e n t i o n storage. There s t i l l seems to be c o n s i d e r a b l e c o n t r o v e r s y over the e f f e c t s of f o r e s t h a r v e s t i n g p r a c t i c e s on peak flows. Although Anderson and Hobba (1959) determined t h a t an observed i n c r e a s e i n 6 the s i z e of peak streamflow was a t t r i b u t a b l e to l o g g i n g p r a c t i c e s , H a r r i s (1977) f a i l e d to d e t e c t any s i g n i f i c a n t d i f f e r e n c e i n the s i z e of peak flow a f t e r c l e a r c u t t i n g a watershed i n western Oregon. S t u d i e s conducted by Cheng (1975) and d e V r i e s and Chow (1973) i n B r i t i s h Columbia found a decrease i n the s i z e of peak flows a f t e r c l e a r c u t t i n g as d i d Harr and McCorison (1979) i n Oregon. de V r i e s and Cheng a t t r i b u t e d t h i s r e d u c t i o n to the d i s r u p t i o n of the subsurface channel networks due to l o g g i n g . Other s t u d i e s (Harr, Harper, K r y g i e r , Hsieh 1975, Harr 1976) found an i n c r e a s e i n peak r u n o f f , but a t t r i b u t e d i t t o a high degree of s o i l d i s t u r b a n c e and not to the removal of v e g e t a t i v e cover. The f a c t t h a t f o r e s t s are a renewable resource means t h a t under normal l o g g i n g p r a c t i c e s the system w i l l tend to r e t u r n t o i t s n a t u r a l s t a t e once the treatment i s completed. Again, the exact r a t e of recovery w i l l depend upon many f a c t o r s , but n a t u r a l r e v e g e t a t i o n u s u a l l y reduces the i n i t i a l e f f e c t s on water y i e l d by about 50% a f t e r the f i r s t 10 years (Anderson, Hoover, R e i n h a r t 1976) . The hydrology of a watershed i s not onl y a f f e c t e d by i t s v e g e t a t i v e cover but a l s o by p r a c t i c e s a s s o c i a t e d with f o r e s t h a r v e s t i n g , such as road b u i l d i n g , s k i d d i n g and s l a s h burning (Harr, Harper, K r y g i e r , Hsieh 1975) . These p r a c t i c e s u s u a l l y have the e f f e c t of s o i l compaction and thereby reduce i n f i l t r a t i o n r a t e s and storage c a p a c i t i e s . Under extreme c o n d i t i o n s , such as on the s u r f a c e s of roads, compaction may r e s u l t i n the ge n e r a t i o n of s u r f a c e flow , which can lead t o 7 h i g h e r peak flows d u r i n g storm c o n d i t i o n s and lower flows under d r i e r c o n d i t i o n s . The magnitude of t h i s e f f e c t , however, i s l i k e l y to be small as the area d e d i c a t e d to road c o n s t r u c t i o n u s u a l l y r e p r e s e n t s o n l y a small p r o p o r t i o n of the t o t a l watershed. Zimmer (1981) found t h a t u n l e s s at l e a s t 12% of the watershed was covered by road c o n s t r u c t i o n there was no s i g n i f i c a n t change i n the magnitude of peak flows. The d i v e r s i o n of subsurface flow to s u r f a c e r u n o f f i s f u r t h e r i l l u s t r a t e d i n a study conducted by Megahan (1972) . He found t h a t the cut bank of a haul road i n t e r c e p t e d 28% of a l l subsurface flow with the r e s u l t of d e c r e a s i n g s o i l moisture i n down slope l o c a t i o n s . As p r e v i o u s l y noted, the change i n the hydrology of a watershed a f t e r f o r e s t h a r v e s t i n g may be p a r t i a l l y due to the change i n the r a t i o of d i r e c t r u n o f f to base flow. U n t i l the advent of s t a b l e i s o t o p e methodologies, the s e p a r a t i o n of a hydrograph i n t o i t s component p a r t s of s u r f a c e flow and i n t e r f l o w (storm r u n o f f ) and groundwater flow (prestorm r u n o f f ) was accomplished g e o m e t r i c a l l y (Wilson 1969). One of the most common methods of i s o l a t i n g base flow from the r e s t of the hydrograph i n v o l v e s e x t r a p o l a t i n g the prestorm r e c e s s i o n a l limb to a p o i n t under the peak of the storm hydrograph ( F i g . 2). From here the l i n e i s extended f o r a d i s t a n c e N on the r e c e s s i o n a l limb of the stream hydrograph a c c o r d i n g to the equation: 0.11 N=A (Eq.l) where N i s time i n days from the peak of the hydrograph and A i s the area of the drainage b a s i n i n square k i l o m e t e r s ( L i n s l e y , Kohler, Paulhus 1976) . Anything below t h i s l i n e i s l a b e l e d as 8 Time (days) F i g . 2 Geometric Hydrograph Separation base flow, while the p a r t of the hydrograph above the l i n e i s co n s i d e r e d to be d i r e c t r u n o f f . In the example c i t e d i n F i g . 2, 43% of the peak r u n o f f i s l a b e l e d as o r i g i n a t i n g as prestorm water. Another method of hydrograph s e p a r a t i o n o r i g i n a l l y d e vised by Barnes i n 1939 e n t a i l s p l o t t i n g the di s c h a r g e measurements on a l o g a r i t h m i c s c a l e and time on a l i n e a r s c a l e (Ward 1967). The base flow i s then determined by extending the r e c e s s i o n limb of the hydrograph backwards from i t s p o i n t of i n f l e c t i o n u n t i l i t i n t e r s e c t s a v e r t i c a l l i n e dropped from the p o i n t of maximum d i s c h a r g e . From here the l i n e i s then connected to the i n i t i a l i n f l e c t i o n p o i n t of the hydrograph. Using the same data as c i t e d i n F i g . 2 t h i s second method a l l o c a t e s approximately 52% of the peak r u n o f f to prestorm water ( F i g s . 3 & 4). Hewlett a l s o has an a r b i t r a r y method of i s o l a t i n g the .prestorm component of a hydrograph (Hewlett, Hibbard 1967). His constant slope method extends a tangent from the i n i t i a l i n f l e c t i o n p o i n t on the r i s i n g limb u n t i l i t i n t e r s e c t s the r e c e s s i o n limb. The slope of t h i s l i n e was s e t to 3.66 2 1/s/km /hr . The i l l u s t r a t i o n of t h i s method i n F i g . 5 i n d i c a t e s t h a t approximately 65% of peak flow o r i g i n a t e d as prestorm water. From the hydrographs d e p i c t i n g these methods i t i s ev i d e n t t h a t each a t t r i b u t e s a d i f f e r e n t v alue t o the base flow component. As such they do not r e f l e c t q u a n t i t a t i v e measurements and are onl y v a l i d when used i n a n a l y t i c a l comparisons (e.g., the c l a s s i f i c a t i o n of stream response t o p r e c i p i t a t i o n i n p u t s ) . The advent of q u a n t i t i v e methods of hydrograph s e p a r a t i o n began i n 1967 when LaSala obtained a c l o s e c o r r e l a t i o n between 10 1000 J 100 Flow ( l / s ) 10 -I peak r i s i n g limb >^  recession limb storm water* prestorm water hydrograph separation l i n e T 8 1 2 3 4 5 6 7 Time (days) Fig. 3 Barnes method of hydrograph separation on a logarithmic scale r o 700 600 500 400 Flow (l/s) 200 -I _00 peak rising limb / \ recession limb - hydrograph separation line J storm water \ \ \ \ \ v. \ prestorm water v ^ \ I , , 1 4 5 Time (days) Fig. 4 Barnes method of hydrograph separation converted to a linear scale Fig. 5 Hewlett's constant slope method of hydrograph separation the t o t a l d i s s o l v e d s o l i d (TDS) l o a d i n g of stream water samples and the stream's d i s c h a r g e . A few years l a t e r Pinder and Jones (1969) and Newbury, Cherry and Cox (1969) used the r e l a t i v e c o n c e n t r a t i o n s of v a r i o u s ions i n groundwater and stream d i s c h a r g e as a method of hydrograph s e p a r a t i o n . The study conducted by Pinder and Jones (1969) took plac e i n three watersheds i n Nova S c o t i a . Instead of measuring the r e l a t i v e abundance of TDS w i t h i n the water samples they separated groundwater flow from d i r e c t r u n o f f by measuring the r e l a t i v e c o n c e n t r a t i o n s of s p e c i f i c i o n s . When these values were averaged they found t h a t at peak d i s c h a r g e groundwater accounted f o r as much as 42% of t o t a l r u n o f f . During the study, however, Pinder and Jones found t h a t prestorm water taken from the head waters of a stream contained a p p r e c i a b l y fewer ions than water samples taken from the lower reaches of the same water course. They a t t r i b u t e d t h i s f i n d i n g t o the d i f f e r e n c e i n the g e o l o g i c a l composition of the s u b s t r a t e and to the amount of time the water was r e s i d e n t i n the v a r i o u s s t r a t a p r i o r to d i s c h a r g e . The accuracy of t h i s method of hydrograph s e p a r a t i o n i s t h e r e f o r e i n f l u e n c e d by the chemical r e a c t i o n s t a k i n g p l a c e between r u n o f f and the s u b s t r a t e . In the study conducted by Newbury, Cherry and Cox (1969) s p e c i f i c ions were a l s o used as the b a s i s of hydrograph s e p a r a t i o n but they were a l s o a b l e to prove a c l o s e c o r r e l a t i o n between the average c o n c e n t r a t i o n of the sum of the ions and the e l e c t r i c a l c o n d u c t i v i t y of the water sample. In a d d i t i o n to d i f f e r e n t i a t i n g between prestorm water and storm water they were able to separate d i r e c t r u n o f f i n t o o v e r l a n d flow and i n t e r f l o w . By u s i n g a network of piezometers they were able to show t h a t the c o n c e n t r a t i o n of s u l f a t e ions i n i n t e r f l o w was n e g l i g i b l e . W i t h i n the study s i t e the time r e q u i r e d f o r r u n o f f to pickup t r a c e s of s u l f a t e was such t h a t o n l y groundwater d i s p l a y e d any a p p r e c i a b l e c o n c e n t r a t i o n of t h i s i o n . T h i s study showed the groundwater component of t o t a l r u n o f f to be as h i g h as 41%. From these s t u d i e s i t i s obvious t h a t the use of ions as a method of hydrograph s e p a r a t i o n can q u a n t i f y the amount of r u n o f f a t t r i b u t a b l e to groundwater. Although the i n h e r e n t i n a c c u r a c y of t h i s method may be c o n s i d e r a b l e , u n l i k e the g r a p h i c a l methods of hydrograph s e p a r a t i o n i t r e f l e c t s the t r u e dynamics of the r u n o f f system. In the mid 1970's Sk l a s h , Farvolden and F r i t z (1975) began u s i n g the r a t i o of oxygen-18 to oxygen-16 i n water as a means of hydrograph s e p a r a t i o n . T h e i r study was based oh the premise t h a t due to recharge and d i s p e r s i o n processes, groundwater a t t a i n s a uniform i s o t o p i c content t h a t r e f l e c t s the average of the annual p r e c i p i t a t i o n events. T h e r e f o r e the water d e p o s i t e d by a storm t h a t has a d i f f e r e n t r a t i o of oxygen-18 to oxygen-16 would produce a change i n the i s o t o p i c content of the prestorm water. Since oxygen-18 i s a s t a b l e i s o t o p e , i t s r e l a t i v e abundance can o n l y be changed through f r a c t i o n a t i o n or mixing. F r a c t i o n a t i o n i n water i s dependent upon d i f f e r i n g vapor p r e s s u r e s , and under the s a t u r a t e d c o n d i t i o n s of a p r e c i p i t a t i o n event i s u n l i k e l y to r e s u l t i n a p e r c e p t i b l e d i f f e r e n c e i n the i s o t o p i c r a t i o . As a r e s u l t , the i s o t o p i c content of prestorm water can only be a l t e r e d through mixing w i t h storm water. For 15 s h o r t d u r a t i o n p r e c i p i t a t i o n events the change i n the number of oxygen-18 atoms present i n t o t a l r u n o f f w i l l p r o v i d e a means by which prestorm water can be d i s t i n g u i s h e d from the water accumulated by the drainage b a s i n d u r i n g the storm. A more d e t a i l e d e x p l a n a t i o n of the use of n a t u r a l i s o t o p e s i n hydrology can be found i n F r i t z (1981) and Faure (1977). The study areas s e l e c t e d by Sklash, Farvolden and F r i t z (1975) were two l a r g e (700 sq. km) watersheds i n southern O n t a r i o . The s o i l s were p r i m a r i l y g l a c i a l sand and t i l l and were predominantly used as farm land. On 16 May 1974 a storm d e p o s i t e d approximately 2.5 cm of r a i n on the study areas and hydrographs and water samples were c o l l e c t e d . Sklash's i n t e r p r e t a t i o n of the r e s u l t s of i s o t o p i c a n a l y s i s showed t h a t at peak d i s c h a r g e s , up to 70% of the flow was groundwater. The p r o p o r t i o n of groundwater c o n t r i b u t i n g t o the storm d i s c h a r g e was found to be l a r g e r i n downstream areas than i n upstream areas. T h i s t r e n d was a t t r i b u t e d i n p a r t to more e f f i c i e n t groundwater drainage i n downstream areas. F i g . 6 i s an example of the data obtained at one of the sampling s i t e s . I t i s the same hydrograph as t h a t used i n the p r e v i o u s examples but i n t h i s i n s t a n c e the s e p a r a t i o n l i n e q u a n t i t a t i v e l y r e p r e s e n t s the amount of groundwater c o n t r i b u t i n g t o the storm r u n o f f . T h i s method of hydrograph s e p a r a t i o n r e v e a l s t h a t 66% of the peak, r u n o f f can be a t t r i b u t e d t o prestorm water. The prevalance of oxygen-18 i n any g i v e n sample i s always expressed as a r a t i o (r) of the abundance of the h e a v i e r oxygen atoms to those of oxygen-16. 18 16 r(sample)= 0/ 0 (Eq. 2) F i g . 6 Isotopic method of hydrograph separation By convention t h i s v alue i s compared to a standard r a t i o and the d i f f e r e n c e recorded as a d e l (d) value (Jacobs, R u s s e l l , Wilson 1974). 18 d 0 = [ r ( s a m p l e ) - r ( s t a n d a r d ) ] / r ( s t a n d a r d ) (Eq. 3) I f the sample has a higher r a t i o of oxygen-18 atoms than does the standard i t i s s a i d t o be e n r i c h e d and i s denoted by a 18 p o s i t i v e value (e.g., d O=+5.0). I f the r e v e r s e i s t r u e , the sample i s s a i d t o be d e p l e t e d and the numerical v a l u e i s preceded 18 by a n e g a t i v e s i g n (e.g., d O=-5.0). In most s t u d i e s t h i s v alue i s then m u l t i p l i e d by v1000 to g i v e a f i n a l d e t e r m i n a t i o n i n p a r t s per thousand (%«,) or g/1. When determining the oxygen-18 content of water the most wid e l y used r e f e r e n c e i s Standard Mean Ocean Water (SMOW), and by convention t h i s i s taken as having an i s o t o p i c content of par 18 ( i . e , d 0=0.0). Since both oxygen-18 and oxygen-16 are s t a b l e i s o t o p e s (not undergoing r a d i o a c t i v e decay) t h e i r r e l a t i v e abundance i s c o n t r o l l e d through f r a c t i o n a t i o n (c~) . dx/x °«- = (Eq. 4) dy/y Where <x i s the f r a c t i o n a t i o n f a c t o r , x i s the amount of oxygen-18 atoms i n a s p e c i f i c phase, (e.g., l i q u i d ) , and dx i s the amount of oxygen-18 atoms i n another phase, (e.g. gaseous). y i s the number of oxygen-16 atoms i n the f i r s t phase and dy i s the number of oxygen-16 atoms i n the second phase. The f r a c t i o n a t i o n f a c t o r o between l i q u i d water and water vapour i n e q u i l i b r i u m a t 25 C, equals 1.0092. In other words, l i q u i d water i s e n r i c h e d by 9.2 p a r t s per thousand of oxygen-18 molecules when compared to water 18 vapour. The f r a c t i o n a t i o n f a c t o r i s d i r e c t l y dependent upon the temperature. As temperature decreases the f r a c t i o n a t i o n f a c t o r i n c r e a s e s . For example, the f r a c t i o n a t i o n f a c t o r f o r water a t o 0 C 1.0111. Wi t h i n the ecosystem, t h i s r e l a t i o n s h i p i s e x h i b i t e d by d i f f e r e n t p h y s i c a l e f f e c t s . These e f f e c t s are summarized by S i e g e n t h a l e r (1979), where he r e c o g n i z e s three d i s t i n c t c a t e g o r i e s : 1. The temperature phenomenon, which i s i l l u s t r a t e d by a gradual decrease i n heavy i s o t o p e c o n c e n t r a t i o n when going from lower to higher l a t i t u d e s . For example the oxygen-18 content of p r e c i p i t a t i o n a t the p o l e s averages about -50% o. whereas at the equator t h i s v alue i s near 0%„. T h i s i s f u r t h e r demonstrated by the seasonal v a r i a t i o n i n i s o t o p i c content of p r e c i p i t a t i o n . P r e c i p i t a t i o n from winter storms i s l i k e l y t o be more d e p l e t e d i n oxygen-18 molecules then p r e c i p i t a t i o n r e s u l t i n g from a summer storm. 2. The c o n t i n e n t a l phenomenon, which manifests i t s e l f as a decrease i n the oxygen-18 content of p r e c i p i t a t i o n as one moves i n l a n d from the c o a s t of a c o n t i n e n t . As an a i r mass moves i n l a n d oxygen-18 molecules are p r e f e r e n t i a l l y removed d u r i n g the condensation p r o c e s s . 3. The a l t i t u d e phenomenon, which i s r e v e a l e d by the lowering of oxygen-18 content with an i n c r e a s e i n a l t i t u d e . Q u a n t i t a t i v e l y the average g r a d i e n t f o r oxygen-18 i s approximately 0.2%o per 100 m. In most cases, hydrograph s e p a r a t i o n as determined with 19 conductance data i s u n l i k e l y to be as accurate as the r e s u l t s o btained from i s o t o p i c measurements because the i o n i c composition of a s o l u t i o n i s not a c o n s e r v a t i v e p r o p e r t y . The magnitude of the d i s c r e p a n c y w i l l vary a c c o r d i n g to the parameters of i o n i c c o n c e n t r a t i o n of the s o l u t i o n and the s u b s t r a t e , the temperature, pH and the r e s i d e n t time of the s o l u t i o n i n the groundwater system. Since conductance measures on l y the abundance of i o n i c s p e c i e s , the t o t a l d i s s o l v e d s o l i d l o a d i n g of a sample i s determined u s i n g the f o l l o w i n g formula: TDS=AC N (Eq. 5) I f the conductance (C) i s measured i n microsiemens (uS) the t o t a l d i s s o l v e d s o l i d s (TDS) i s expressed i n mg/1. The constant (A) v a r i e s between 0.55 and 0.75 depending upon the i o n i c composition of the s o l u t i o n . To determine the exact value of t h i s c onstant the TDS l o a d i n g of a sample must be found u s i n g another method of a n a l y s i s . U s u a l l y t h i s a l t e r n a t e method i n v o l v e s the e v a p o r a t i o n of a given volume of water and the weighting of the s o l i d r e s i d u e s . To use the i s o t o p i c or conductance methods as t o o l s f o r hydrograph s e p a r a t i o n , a number of c o n d i t i o n s must be met. F i r s t l y , the prestorm water i n the stream and the storm p r e c i p i t a t i o n must be s i g n i f i c a n t l y d i f f e r e n t i n oxygen-18 content ( i e . the p r e c i p i t a t i o n must be e i t h e r e n r i c h e d or d e p l e t e d w i t h r e s p e c t to the prestorm r u n o f f ) . T h i s requirement i n s u r e s t h a t there w i l l be a change i n the oxygen-18 r a t i o of the storm r u n o f f due to mixing of prestorm water and p r e c i p i t a t i o n . In most cases the oxygen-18 content of the groundwater i s 20 homogeneous and r e f l e c t s the average value of preceding p r e c i p i t a t i o n events. The time base f o r c a l c u l a t i n g t h i s average w i l l depend upon the r a t e of turnover of groundwater w i t h i n the system. Secondly, the storm must be s u f f i c i e n t l y l a r g e to cover most of the watershed and produce enough p r e c i p i t a t i o n to i n f l u e n c e the hydrograph. These c o n d i t i o n s apply e q u a l l y to the conductance method of hydrograph s e p a r a t i o n . As i s o t o p e and conductance methods are only capable of s e p a r a t i n g d i s c h a r g e i n t o prestorm and storm water the f o l l o w i n g assumptions must be made i n order to f u r t h e r s u b d i v i d e r u n o f f i n t o i t s component p a r t s of groundwater flow, subsurface storm flow or i n t e r f l o w , o v e r l a n d flow and channel i n t e r c e p t i o n . Since o v e r l a n d flow and channel i n t e r c e p t i o n only occur d u r i n g p r e c i p i t a t i o n events they do not c o n t r i b u t e to prestorm r u n o f f . Furthermore, as Freeze (1974) p o i n t e d out, o n l y convex sl o p e s t h a t feed deeply i n c i s e d stream channels are l i k e l y t o generate i n t e r f l o w i n any a p p r e c i a b l e q u a n t i t i e s . As such c o n d i t i o n s are not found w i t h i n the examined study areas i t i s u n l i k e l y t h a t i n t e r f l o w i s a major c o n t r i b u t o r to storm r u n o f f . For the most p a r t then, a l l prestorm water can be c o n s i d e r e d as groundwater flow. 21 CHAPTER 2 - METHODS In each of the study areas a s p e c i f i c s i t e was s e l e c t e d where the stream d i s c h a r g e c o u l d be e a s i l y measured. The method of flow measurement v a r i e d to account f o r the d i f f e r e n c e s i n topography, a n t i c i p a t e d peak stage h e i g h t and p r e e x i s t i n g s t r u c t u r e s such as water supply i n t a k e s . Stream water samples were obtained and flow c o n d i t i o n s were monitored. The exact sampling scheme used i n each of the study s i t e s w i l l be d e t a i l e d l a t e r i n t h i s paper. A t r a n s e c t of r a i n gauges was e s t a b l i s h e d throughout each watershed to account f o r the p o s s i b i l i t y of d i f f e r e n t i a l f r a c t i o n a t i o n w i t h i n the r a i n f a l l (due to a l t i t u d e ) . The r a i n gauge network encompassed the f u l l range of e l e v a t i o n s w i t h i n each b a s i n . The study area of each b a s i n was then roughly sketched i n order to o b t a i n a more d e t a i l e d understanding of f a c t o r s such as v e g e t a t i v e cover, geology, s o i l s and topography. With the advent of a storm event the stream water sampling frequency was i n c r e a s e d . The a c t u a l i n t e r v a l between each s u c c e s s i v e measurement v a r i e d a c c o r d i n g to the time r e q u i r e d to complete one c i r c u i t of a l l the sampling s i t e s w i t h i n the study area. Once the storm had passed, r a i n water samples were c o l l e c t e d from the v a r i o u s r a i n gauges. The post-event sampling frequency and d u r a t i o n were governed by the r e c e s s i o n r a t e of the hydrograph, although each s i t e was monitored f o r a t l e a s t 24 h a f t e r the peak flow c o n d i t i o n was recorded. A l l samples were s t o r e d i n a i r - t i g h t p l a s t i c b o t t l e s u n t i l r e q u i r e d f o r a n a l y s i s . The samples were analyzed f o r oxygen-18 content u s i n g the mass spectrometer i n the Department of Geophysics of the U n i v e r s i t y of B r i t i s h Columbia (Ahern 1975). This instrument f i r s t e s t a b l i s h e s an e q u i l i b r i u m i n oxygen-18 atoms between the water sample and the c a r r i e r carbon d i o x i d e . The molecules of carbon d i o x i d e are then passed through a magnetic f i e l d which a c c e l e r a t e s them along a c u r v i l i n e a r path. The r e s u l t i s t h a t the molecules c o n t a i n i n g oxygen-18 atoms separate from those p o s s e s s i n g only oxygen-16 atoms due to the d i f f e r e n c e i n t h e i r molecular weights. The two r e s u l t i n g beams are then focused i n t o separate c o l l e c t i o n cups where they generate a c u r r e n t t h a t i s dependent upon t h e i r r e l a t i v e abundance. The p r o c e s s i n g of t h i s s i g n a l y i e l d s the r a t i o of oxygen-18 to oxygen-16 molecules i n the o r i g i n a l sample. This f a c i l i t y enables readings a c c u r a t e to 0.15% (one and a h a l f p a r t per ten thousand). C o n d u c t i v i t y measurements were made u s i n g a CDM 2e conductance meter which simply measures the flow of e l e c t r o n s through a 1 cm d i s t a n c e of s o l u t i o n . The accurate r e s o l u t i o n of the conductance meter i s 2.0 uS. The instrument was c a l i b r a t e d by immersing the d e t e c t o r head i n t o a 0.2 mole s o l u t i o n of p o t a s s i u n c h l o r i d e which was o s t a b i l i z e d a t 18 C. Under these c o n d i t i o n s the meter was a d j u s t e d to read a conductance of 11,160 uS ( A n a l y t i c a l Q u a l i t y C o n t r o l Laboratory, 1972). The samples were then f i l t e r e d to remove any suspended sediments or o r g a n i c m a t e r i a l s . A f t e r each r e a d i n g the d e t e c t o r head was r i n s e d i n d i s t i l l e d water to reduce the l i k e l i h o o d of inter-sample contamination. Each r e a d i n g was c o r r e c t e d f o r temperature so t h a t the f i n a l measurements r e f l e c t o the conductance of the sample a t 25 C. 23 Both i s o t o p i c and conductance analyses were done i n d u p l i c a t e and the mean values c a l c u l a t e d . From the flow measurement data, stream hydrographs were c o n s t r u c t e d . The instantaneous prestorm r u n o f f (Qs) was c a l c u l a t e d u s i n g the standard mixing equation ( F r i t z , Cherry, Weyer, Sklash, 1976): Ct - Ce Qs = Qt (Eq. 6) Cp - Ce Where Qt i s the volume of the instantaneous t o t a l r u n o f f , Ct i s the i s o t o p i c or conductance value of the t o t a l r u n o f f , Ce i s the i s o t o p i c or conductance value of the p r e c i p i t a t i o n and Cp i s the i s o t o p i c or conductance value of the prestorm r u n o f f . The subsurface component of the hydrograph was p l o t t e d u s i n g both types of a n a l y s i s . An example of t h i s c a l c u l a t i o n , u s i n g the data obtained from the Chou Creek s i t e y i e l d s the f o l l o w i n g f i g u r e s : Subsurface flow c a l c u l a t i o n s u s i n g data from Table 5 a t 1520 h r s . 9 September 1982. Using i s o t o p i c data: (17.15) - (13.53) Q S 0.55 Qs = 0.48 1/s (Eq. 7) (17.66) - (13.53) Using conductance data* (274) - (13) Q S = 0.55 Qs = 0.46 1/s (Eq. 8) (322) - (13) Equation 6 assumes t h a t the measured v a r i a b l e w i t h i n the prestorm water i s uniform and s t a b l e throughout the p e r i o d of measurement. As mentioned e a r l i e r , because of i t s c o n s e r v a t i v e p r o p e r t i e s , t h i s assumption i s probably s a f e as regards oxygen-1. 18. The i o n i c c o n c e n t r a t i o n of prestorm water, on the other hand, may be i n f l u e n c e d by chemical processes and t h e r e f o r e may c o n t r a d i c t t h i s assumption over a long p e r i o d of measurement. The equation f u r t h e r assumes t h a t the measured v a r i a b l e w i t h i n the p r e c i p i t a t i o n remains constant throughout the p e r i o d of measurement. Although a p a r t i c u l a r storm event may vary i n i t s i s o t o p i c or i o n i c content through time, the accuracy of t h i s assumption can be monitored through the a n a l y s i s of p r e c i p i t a t i o n samples. 25 CHAPTER 3 - MOUNTAIN STATION STUDY AREA Area D e s c r i p t i o n The f i r s t study area to be examined covered approximately 270 ha and l a y j u s t e a s t of Nelson c i t y l i m i t s ( F i g . 7). The slope o i s convex and has a mean i n c l i n a t i o n of 36 i n the lower r e g i o n s o and 12 near the top. Instead of a s i n g l e l a r g e water course, the area i s d r a i n e d by a number of small i n t e r m i t t e n t creeks ( F i g . 8 ) . The g e o l o g i c a l maps of t h i s r e g i o n i n d i c a t e t h a t the bedrock belongs to the Rossland V o l c a n i c group. The s o i l s w i t h i n the area are predominantly Calamity, Sombric Humo-Feric Podzols (Jungen 1980) . Calamity s o i l s are w e l l to r a p i d l y d r a i n e d but may be a s s o c i a t e d with minor i n c l u s i o n s of i m p e r f e c t l y d r a i n e d seepage areas. T h i s area belongs to the I n t e r i o r Cedar-Hemlock zone of e c o l o g i c a l c l a s s i f i c a t i o n (Watts 1983). The h i l l s i d e was logged approximately 70 years ago and i s now l a r g e l y covered with mature Douglas f i r and l a r c h , except f o r a c e n t r a l r e g i o n i n which a steep slope p r o v i d e s a poor c o l l u v i a l s o i l . In the c e n t r a l p a r t of the slope the v e g e t a t i o n i s more open and i s dominated by lodgepole p i n e . At the time of t h i s i n v e s t i g a t i o n there were a t o t a l of 34 water l i c e n c e s h e l d w i t h i n the study area, with a t o t a l demand of 3 470 m /day. One of the more h e a v i l y l i c e n c e d streams (64.6 3 m /day) and the one of primary importance i n t h i s study was Tank Creek. Tank Creek seems to o r i g i n a t e from a number of small seeps a t about the 900 m l e v e l . P o s t l e S p r i n g i s c h a r a c t e r i s t i c of such a seep and was a l s o s e l e c t e d as a monitoring s i t e i n t h i s study. 26 5 I 1 3 I 5 kilometers ( h i g h l i g h t i n g delineates study areas) i n s e r t depicts area of sketch map F i g . 7 Mountain Station and North Shore Study Areas 27 F i g . 8 M o u n t a i n S t a t i o n s t u d y a r e a 28 From the s u r f a c e g u l l y i n g , i t was e v i d e n t t h a t the length of the stream v a r i e d with seasonal r u n o f f p a t t e r n s . L o c a l r e s i d e n t s i n the Mountain S t a t i o n area confirmed t h i s o b s e r v a t i o n . They r e p o r t e d a decrease i n flow as the summer pro g r e s s e s . To date however, onl y minor water shortages have been experienced and these were d u r i n g q u i t e severe drought c o n d i t i o n s . The B r i t i s h Columbia F o r e s t S e r v i c e p r o p o s a l f o r the Mountain S t a t i o n r e g i o n c a l l s f o r f o r e s t h a r v e s t i n g i n the area of F i v e M i l e Creek. At present, the most l i k e l y route f o r a main haul road t r a n s e c t s the Mountain S t a t i o n study area a t approximately the 1100 m l e v e l . P h y s i c a l examination of the topography i n t h i s area r e v e a l s a r a t h e r abrupt change i n s o i l c o n d i t i o n s . Below the s i t e the s o i l i s r e l a t i v e l y deep and e x h i b i t s d i s t i n c t h o r i z o n s . Above the s i t e , however, the s o i l i s l e s s developed and shows sign s of c o l l u v i a l d e p o s i t s . There a l s o appears to be a change i n s o i l moisture c o n d i t i o n s as i n f e r r e d from a change i n b i o t a . The area below the proposed road i s covered by hemlock and Douglas f i r while the upper area c o n t a i n s an abundance of more x e r o p h y t i c s p e c i e s such as lodgepole p i n e . T h i s evidence, p l u s the f a c t t h a t there i s an abrupt i n c r e a s e i n the slope above t h i s p o i n t tends to support the hypothesis t h a t the proposed haul road i s s i t e d a t the top of a d i s c h a r g e area. L o c a l r e s i d e n t s i n the Mountain S t a t i o n area are concerned t h a t l o g g i n g development w i l l have a d e t r i m e n t a l e f f e c t upon t h e i r water supply. 29 Study S i t e s and Methods In a d d i t i o n to the monitoring p o i n t s on Tank Creek and P o s t l e S p r i n g ( F i g . 8), Anderson Creek was a l s o examined. The Inland Waters D i r e c t o r a t e of the Water Survey of Canada maintains a r e c o r d i n g stream gauge and weir j u s t above the C i t y of Nelson's r e s e r v o i r ( F i g . 7). The Anderson Creek watershed covers 907 ha The b a s i n areas of the other study s i t e s c o u l d not be a c c u r a t e l y determined due to fre q u e n t u n d u l a t i o n s i n the r e l i e f . Furthermore i t i s u n l i k e l y t h a t r e l i e f i s a good i n d i c a t i o n of b a s i n area when used on such a small s c a l e because the f r a c t u r e d nature of the parent m a t e r i a l and bedrock w i l l undoubtedly a l l o w water to t r a n s e c t these boundaries. The flow a t Tank Creek monitoring s i t e was measured by sandbagging a 30 cm wide weir i n t o the stream bank. Although no leaks were v i s i b l e , t here was probably c o n s i d e r a b l e seepage around the ends of the weir as the s o i l i n t h i s area appeared t o have a hig h p e r m e a b i l i t y . The water a t the P o s t l e S p r i n g monitoring p o i n t was c o l l e c t e d from a rock f a c e by an earthen berm and then d i r e c t e d through a p l a s t i c pipe i n t o a s e t t l i n g box. Flow measurements were then made u s i n g the bucket and stopwatch method. The a c t u a l sampling f r e q u e n c i e s f o r the s p e c i f i c study s i t e s w i t h i n the Mountain S t a t i o n study area are l i s t e d i n Tables 2, 3 and 4. Wi t h i n the Mountain S t a t i o n study area r a i n gauges were p l a c e d along the Tank Creek t r a n s e c t a t the 650, 900, 1125 and 1350 m e l e v a t i o n s ( F i g . 8, 1350 raingauge not showen). In a d d i t i o n , two r a i n gauges were p l a c e d i n the Anderson Creek watershed, one near the monitoring p o i n t at an e l e v a t i o n of 750 m 30 and the other approximately 500 m f u r t h e r upstream at an e l e v a t i o n of 900 m. R e s u l t s A storm meeting a l l the requirements f o r q u a n t i t a t i v e hydrograph s e p a r a t i o n , as d e t a i l e d i n the review s e c t i o n of t h i s paper, covered the study area a t approximately 0100 h on 11 August 1982. P r i o r to t h i s storm the s o i l i n the watersheds was c l o s e to s a t u r a t i o n as a number of small p r e c i p i t a t i o n events (< 2mm having no e f f e c t upon the stream hydrograph) had preceded the f r o n t a l system. The storm ended a t about 1100 h on the same day having reached a maximum i n t e n s i t y of 14 mm/h and p r e c i p i t a t i n g a t o t a l of 32 mm of r a i n . A n a l y s i s of the r a i n water samples produced the v a l u e s l i s t e d i n Table 1. Table 2 l i s t s the sampling frequency and flow measurement data f o r Tank Creek, and F i g . 9 d e p i c t s these data as a hydrograph. The stream i n c r e a s e d i t s flow 5.7 1/s from i t s prestorm d i s c h a r g e . The i s o t o p i c content of the storm r u n o f f a l s o i n c r e a s e d as the r a i n water c o n t a i n e d s u b s t a n t i a l l y more oxygen-18 than d i d the prestorm r u n o f f , as a consequence, the d e l value of the stream water i n c r e a s e d from -18.22%„ to a high of -17.21% 0. The 12 uS c o n d u c t i v i t y of the r a i n water o b v i o u s l y had a d i l u t i o n e f f e c t upon the stream water as i t caused the c o n d u c t i v i t y to drop from 206 uS to a low of 190 uS. The c o r r e l a t i o n between the i s o t o p i c and the conductance methods of hydrograph s e p a r a t i o n f o r Tank Creek r e s u l t e d i n a Pearson r value of -0.97. Furthermore a t w o - t a i l e d t - t e s t i n d i c a t e d t h a t t h i s c o r r e l a t i o n was s i g n i f i c a n t at the 0.001 l e v e l . 31 Table 1 The Res u l t s of the Analyses o f Rainwater Samples f o r the Mountain S t a t i o n Study S i t e TANK CREEK TRANSECT 18 ELEVATION DATE TIME RAIN CONDUCTANCE 0 (m) (mm) (uS) ( % • ) 650 11 Aug 0845 10 13 -12.72 1110 9 8 -12.80 1310 12 12 -12.66 900 11 Aug 0900 12 15 -12.58 1140 9 8 -12.59 1325 12 17 -13.03 1125 12 Aug 1225 31 14 -12.83 1350 12 Aug 1250 34 15 -12.72 ANDERSON i CREEK TRANSECT 18 ELEVATION DATE TIME RAIN CONDUCTANCE 0 (m) (mm) (uS) ( % o ) 750 11 Aug 0725 10 12 -12.48 1040 8 16 -12.68 1230 13 7 -12.91 900 12 Aug 1130 31 11 -12.62 32 Table 2 The R e s u l t s of the Analyses of Stream Flow Samples f o r the Tank Creek Study S i t e 18 TIME DATE FLOW CONDUCTIVITY 0 (1/s) (uS) 0930 9 Aug 7.3 204 -18.03 1600 10 Aug 4.2 206 -18.18 0230 11 Aug 3.0 206 -18.22 0845 11 Aug 4.4 197 -17.63 1110 11 Aug 8.7 190 -17.21 1310 11 Aug 7.3 197 -17.55 1515 11 Aug 6.5 199 -17.75 1720 11 Aug 6.1 201 -17.98 1920 11 Aug 5.7 203 -18.02 0945 12 Aug 4.6 202 -18.16 1830 12 Aug 4.4 205 -18.19 Rain water 12 -12.7: peak flow = 8.7 1/s prestorm water at peak flow as c a l c u l a t e d through i s o t o p i c a n a l y s i s = 7.0 1/s or 8 l % of t o t a l flow. prestorm water at peak flow as c a l c u l a t e d through a n a l y s i s of conductance = 7 . 8 1/s or go % of t o t a l flow. 3 3 2 5 _ 20 -Flow ( l / s ) " 15 10 _ 5 -2400 12CJ0 9 Aug 2400 T T conductance separation l i n e isotope separation l i n e 1260 10 Aug 24< ' 1200 11 Aug Time (days) Fig.9 Tank Creek Hydrograph 2400 1 1 r 1200 12 Aug - 5 h 10 15 U 20 R a i n f a l l (mm/hr) 2400 Table 3 The R e s u l t s of the Analyses of Stream Flow Samples f o r the P o s t l e Spring Study S i t e 18 TIME DATE FLOW CONDUCTIVITY 0 (1/s) (US) 0900 9 Aug 0.27 228 -18.15 1545 10 Aug 0.27 230 -18.22 0250 11 Aug 0.27 230 -18.24 0900 11 Aug 0.27 228 -17.95 1140 11 Aug 0.27 225 -17.93 1325 11 Aug 0.27 225 -17.97 1530 11 Aug 0.27 229 -18.14 1740 11 Aug 0.27 229 -18.15 0820 12 Aug 0.28 228 -18.17 1900 12 Aug 0.27 230 -18.19 Rain water 12 -12.7: peak flow = 0.27 1/s prestorm water at peak flow as c a l c u l a t e d through i s o t o p i c a n a l y s i s = 0.25 1/s or 92% of t o t a l flow. prestorm water at peak flow as c a l c u l a t e d through a n a l y s i s o f conductance = 0.26 1/s or 96% of t o t a l flow. 35 a. 10 Postle Spring Hydrograph Table 4 The R e s u l t s of the Analyses of Stream Flow Samples f o r the Anderson Creek Study S i t e 2 bas i n area = 9.07 km 18 TIME DATE FLOW CONDUCTIVITY 0 (1/s) (uS) (%. ) 0950 9 Aug 75 99 -17.80 1630 10 Aug 70 96 -17.82 0200 11 Aug 67 98 -17.83 0725 11 Aug 107 92 -17.72 1040 11 Aug 181 90 -17.39 1230 11 Aug 208 85 -17.40 1430 11 Aug 173 89 -17.49 1650 11 Aug 134 93 -17.58 1855 11 Aug 123 93 -17.63 0850 12 Aug 95 95 -17.68 1800 12 Aug 80 96 -17.76 Rain water 12 -12.72 peak flow = 211 1/s prestorm water at peak flow as c a l c u l a t e d through i s o t o p i c a n a l y s i s = 192 1/s or 91% of t o t a l flow. prestorm water at peak flow as c a l c u l a t e d through a n a l y s i s o f conductance = 179 1/s or 85% of t o t a l flow. 37 9 Aug 10 Aug 11 Aug 12 Aug Time (days) Fig. 11 Anderson Cerrk Hydrograph Table 3 and F i g . 10 d e p i c t s i m i l a r measurements f o r the P o s t l e S p r i n g monitoring s i t e although the magnitudes of the e f f e c t s are g r e a t l y decreased due to the small s i z e of the seep. The s t a t i s t i c a l a n a l y s i s f o r t h i s study s i t e r e s u l t e d i n a r value of -0.85 and the t value i n d i c a t e d t h a t t h i s was s i g n i f i c a n t at the 0.01 l e v e l . The data c o l l e c t e d at Anderson Creek monitoring s i t e are given i n Table 4 and F i g . 11. The c o r r e l a t i o n f o r t h i s study s i t e proved to be -0.83 and t h i s value was s i g n i f i c a n t to the 0.01 l e v e l . D i s c u s s i o n of F i n d i n g s The lack of response to the p r e c i p i t a t i o n as e x h i b i t e d by the flow data obtained f o r P o s t l e S p r i n g , i n d i c a t e s t h a t the di s c h a r g e from the s p r i n g was independent of the storm event, as the r e l i a b l e d e t e c t i o n l i m i t f o r t h i s method of flow measurement i s w e l l below 0.01 1/s. The oxygen-18 and conductance data however, r e v e a l a d e f i n i t e a b e r r a t i o n . The 0.31 %o change i n the i s o t o p e content of the s p r i n g water i s w e l l above the a n a l y t i c a l l i m i t a t i o n s of the mass spectrometer and t h e r e f o r e i n d i c a t e s the presence of a d i l u t i o n e f f e c t w i t h i n the system. A s i m i l a r c o n c l u s i o n can be drawn from the 5 uS drop i n the conductance v a l u e s . These data suggest t h a t the major f a c t o r c o n t r o l l i n g the flow r a t e i s the h y d r a u l i c c o n d u c t i v i t y of the porous medium as opposed to the h y d r a u l i c head. In t h i s p a r t i c u l a r i n s t a n c e i t seems t h a t the rock f r a c t u r e s c a r r y i n g the water t o the s u r f a c e were a l r e a d y a t c a p a c i t y p r i o r to the storm event, and t h e r e f o r e 39 the expected i n c r e a s e i n h y d r a u l i c head caused by the p r e c i p i t a t i o n had l i t t l e e f f e c t . N e v e r t h e l e s s the d e t e c t i o n of the d i l u t i o n e f f e c t i n d i c a t e s t h a t a t peak flow approximately 6% of the water e x p e l l e d from the s p r i n g o r i g i n a t e d from the storm. T h i s storm water probably o r i g i n a t e d as a combination of both channel i n t e r c e p t i o n and subsurface storm flow. I t s lack of impact upon t o t a l r u n o f f i s probably a r e f l e c t i o n of the e r r o r s i n v o l v e d i n flow measurement on such a small s c a l e . The data obtained f o r Tank Creek shows t h a t approximately 85% of the peak r u n o f f can be a t t r i b u t e d t o prestorm water. Since t h i s creek has i t s o r i g i n i n seeps s i m i l a r to P o s t l e Spring and s i n c e P o s t l e Spring had a prestorm component of 94%, i t i s l i k e l y t h a t the 9% i n c r e a s e i n s u r f a c e r u n o f f i s gained between the 900 m and the 650 m l e v e l s as t h i s i s the d i f f e r e n c e i n e l e v a t i o n between the P o s t l e S p r i n g and the Tank Creek monitoring p o i n t s . F i e l d examination of the slope suggests t h a t the lower r e g i o n s are most r e s p o n s i b l e f o r t h i s phenomenon. As the slope of the h i l l s i d e decreases, the s u r f a c e area d r a i n e d by Tank Creek i n c r e a s e s . The l a r g e r s i z e of the Anderson Creek watershed as compared to Tank Creek can e a s i l y be d i s c e r n e d from the data. The time t o peak f o r Tank Creek was approximately 8 h whereas Anderson Creek took 10.5 h to reach i t s maximum flow. Although these times to peak val u e s are not exact, due to the i n t e r m i t t e n t sampling schedule, the r e s o l u t i o n i s s u f f i c i e n t l y d e t a i l e d t o confirm t h i s t r e n d . When the oxygen-18 and conductance v a l u e s are averaged they show t h a t 88% of the peak flow can be a t t r i b u t e d to prestorm water. Because i n t e r f l o w i s an u n l i k e l y occurrence i n t h i s type 40 of t e r r a i n , as p r e v i o u s l y noted, and as no overland flow was observed throughout the storm i t would appear t h a t most of the 12% of the water t h a t o r i g i n a t e d from the storm entered the stream as groundwater flow. The minor c o n t r i b u t i o n of channel i n t e r c e p t i o n i s i n d i c a t e d by the r e c e s s i o n limbs of both types of a n a l y s i s . I f channel i n t e r c e p t i o n were a l a r g e f a c t o r i n storm r u n o f f one would expect to see a sharp r e d u c t i o n i n the c o n t r i b u t i o n of storm water a f t e r the p r e c i p i t a t i o n had stopped. The minor c o n t r i b u t i o n of channel i n t e r c e p t i o n i s f u r t h e r supported by the measurements of the s u r f a c e area of Anderson Creek. When t h i s v a l u e . i s expressed as a f u n c t i o n of the whole watershed area i t i s seen t h a t channel i n t e r c e p t i o n accounts f o r l e s s than 0.05% of the storm water r u n o f f . T h i s c a l c u l a t i o n i s only approximate, however, as the exact s u r f a c e area of Anderson Creek and i t s ephemeral c o n t r i b u t e r s i s d i f f i c u l t t o determine. Furthermore, the i n t e r c e p t i o n of some of the p r e c i p i t a t i o n by the canopy of the r i p a r i a n v e g e t a t i o n w i l l tend to f u r t h e r decrease the amount of r u n o f f a t t r i b u t a b l e to channel i n t e r c e p t i o n as c a l c u l a t e d by t h i s method. Since the area of the Anderson Creek drainage b a s i n i s known 2 to be 9.07 km and assuming t h a t the p r e c i p i t a t i o n r e l e a s e d by the storm over t h i s area was a uniform 32 mm, a number of rough c a l c u l a t i o n s can be made i n order to q u a n t i f y the storm r u n o f f . 8 From the data i t would appear t h a t approximately 2.9 x 10 1 of r a i n f e l l on the Anderson Creek watershed. Because of f a c t o r s such as canopy i n t e r c e p t i o n and subsequent e v a p o r a t i o n the net amount of storm water i n j e c t e d i n t o the drainage b a s i n i s 41 unknown. I f , however, through i n t e r p o l a t i o n , the t o t a l r u n o f f and mean s e p a r a t i o n limbs of the Anderson Creek hydrograph are extended to the p o i n t of convergence the t o t a l r u n o f f of the 7 storm hydrograph i s estimated as 1.55 x 10 1 (17.0mm), of t h i s 6 value o n l y 1.22 x 10 1 (1.3mm) can be a t t r i b u t e d t o storm water. Hewlett's hydrograph response f a c t o r i s a q u a n t i t a t i v e e x p r e s s i o n of the e f f i c i e n c y of a drainage b a s i n and i s d e f i n e d as the r a t i o of storm r u n o f f to p r e c i p i t a t i o n (Hewlett 1967). U s u a l l y t h i s c a l c u l a t i o n i s based on annual data and the value of d i r e c t r u n o f f i s determined u s i n g Hewlett's constant slope method of hydrograph s e p a r a t i o n . T h i s measurement has some va l u e when a p p l i e d to s p e c i f i c storm events. Using the data as determined i n the present study Anderson Creek has a response f a c t o r of 0.042. T h i s value i n d i c a t e s t h a t Anderson Creek has a very w e l l r e g u l a t e d response to p r e c i p i t a t i o n events. The hydrograph response f a c t o r f o r Anderson Creek as i n d i c a t e d by Hewlett's constant slope method of hydrograph s e p a r a t i o n i s q u i t e s i m i l a r i n t h a t i t renders a value of 0.057. The d i s c r e p a n c y between these two v a l u e s i s l i k e l y a t t r i b u t a b l e to the d i f f e r e n t v a l u e s obtained f o r d i r e c t r u n o f f as determined by the i s o t o p i c method of hydrograph s e p a r a t i o n and Hewlett's constant slope method. The rainwater samples from the d i f f e r e n t e l e v a t i o n s were found t o be remarkably s i m i l a r i n both oxygen-18 content and conductance. The absence of any a l t i t u d e e f f e c t i s probably a t t r i b u t a b l e to the f a c t t h a t the p r e v a i l i n g winds were from the south-west, which p l a c e s the study area i n a l o c a l i z e d r a i n shadow s i n c e the systems w i l l engage the other s i d e of the mountain f i r s t . As a r e s u l t , p r e c i p i t a t i o n o r i g i n a t e d from an even c l o u d base which had a uniform i s o t o p i c content. The v a s t d i f f e r e n c e between the d e l value of the r a i n water (-12.72%0) and the prestorm r u n o f f (-18.18%0) i s e x p l a i n e d by the seasonal f r a c t i o n a t i o n e f f e c t . The lower temperatures of w i n t e r w i l l reduce the oxygen-18 c o n c e n t r a t i o n of p r e c i p i t a t i o n d u r i n g these months. The water then i n f i l t r a t e s i n t o the groundwater system d u r i n g the s p r i n g melt. C o n t i n u a l sampling f o r oxygen-18 throughout the year may p r o v i d e i n s i g h t i n t o the s i z e and recharge r a t e of t h i s a q u i f e r . C o n c l u s i o n s The obvious c o n c l u s i o n i s t h a t d u r i n g the summer the m a j o r i t y of the r u n o f f i n the Mountain S t a t i o n drainage system o r i g i n a t e s as groundwater and t h a t the i n f r e q u e n t summer storms can p l a y only a minor r o l e i n groundwater recharge. By f a r the dominant f a c t o r i n the hydrology of t h i s area i s the recharge of the groundwater system by snow melt. Heatherington (1977) drew s i m i l a r c o n c l u s i o n s when he i n v e s t i g a t e d two small watersheds i n the Creston area of the East Kootenay. T h i s i s f u r t h e r supported by examination of the r u n o f f r e c o r d f o r Anderson Creek and the m e t e o r o l o g i c a l records f o r Nelson. The r e c o r d shows t h a t approximately 61% of annual r u n o f f occurs d u r i n g the peak snowmelt months of May and June whereas onl y 14% of annual p r e c i p i t a t i o n occurs d u r i n g the same time p e r i o d . The proposed road a t the south end of the study area may cause a minor i n c r e a s e i n the s p r i n g season r u n o f f as the r e s u l t of d i r e c t i n g upslope snow melt i n t o stream channels but with the c o r r e c t placement of c u l v e r t s t h i s i s u n l i k e l y to be a problem. Since i t appears t h a t the road i s to be l o c a t e d a t the top of the groundwater d i s c h a r g e area i t i s u n l i k e l y to cause a n o t i c e a b l e decrease i n the s u s t a i n e d y i e l d of the l o c a l c r e e k s . The proposed road i s a l s o s u f f i c i e n t l y upstream of any of the present water l i c e n c e s to p r e c l u d e a sedimentation problem. Although these f i n d i n g s are only based on a s i n g l e s e t of data i t seems u n l i k e l y t h a t the c o n s t r u c t i o n of the haul road i n i t s proposed l o c a t i o n w i l l have any s e r i o u s e f f e c t upon the q u a n t i t y or the q u a l i t y of the water w i t h i n the study area. 44 CHAPTER 4 - NORTH SHORE STUDY AREA Area D e s c r i p t i o n The North Shore study area i s on the south-east s i d e of Mount Nelson approximately 3 km o u t s i d e of the c i t y l i m i t s along highway 3A toward B a l f o u r ( F i g . 7). Morley S p r i n g , which was the s o l e m onitoring p o i n t i n t h i s study area, i s l o c a t e d near the bottom of an o l d rock s c r e e . The slope above the monitoring o p o i n t i s a f a i r l y uniform 38 and i s p a r t i a l l y covered with immature Douglas f i r and l a r c h . About 25% of the slope i s e i t h e r exposed bedrock or o l d s l i d e a reas. Although the h i l l s i d e was logged o f f approximately 50 years ago i t would appear t h a t most of the mass movement and shallow s o i l h o r i z o n s predated t h i s o p e r a t i o n . The geology of t h i s area i s q u i t e d i f f e r e n t from t h a t of the Mountain S t a t i o n study area as the bedrock belongs t o the Nelson G r a n i t e group. Examination of a number of p r o f i l e s i n d i c a t e d t h a t the s o i l i n t h i s area i s a Buhl Creek, L i t h i c Humo-feric Podzol (Jungen 1980). T h i s type of s o i l i s c l a s s i f i e d as being r a p i d l y d r a i n e d although there may be some s i t e s t h a t are i m p e r f e c t l y d r a i n e d due to long p e r i o d s of continuous seepage. The e c o l o g i c a l c l a s s i f i c a t i o n of t h i s area has i t belo n g i n g t o the I n t e r i o r Ceadr-Hemlock zone (Watts 1983). At present the water from Morley S p r i n g i s t o t a l l y d i v e r t e d i n t o a l a r g e h o l d i n g tank which i s l o c a t e d upslope of highway 3A. From there the water c r o s s e s the road and i s d i s t r i b u t e d t o 8 i n d i v i d u a l l i c e n c e h o l d e r s . The system i s l i c e n c e d f o r a t o t a l 3 3 of 31 m /day which i s 7 m /day more than c o u l d be s u p p l i e d by the prestorm flow on the day measured. In most circumstances t h i s 45 o v e r - l i c e n c i n g i s not a problem as not everyone uses t h e i r f u l l e n t i t l e m e n t every day and the l a r g e storage tank provides a means by which the s u r p l u s water can be h e l d f o r f u t u r e use. Under l a t e summer drought c o n d i t i o n s , however, the l i c e n c e e s are o f t e n f o r c e d t o adopt a r a t i o n i n g scheme. T h i s s c e n a r i o i s t y p i c a l of many areas along the north shore of Kootenay Arm. The r e g i o n i s a popular r e c r e a t i o n s i t e and i s expanding r a p i d l y . The a v a i l a b i l i t y of a p o t a b l e water supply i s one of the l i m i t i n g f a c t o r s i n r e c r e a t i o n a l and r e s i d e n t i a l development. At present there i s no c e n t r a l water works to s e r v i c e t h i s r e g i o n and r e s i d e n t s seem r e l u c t a n t to use lake water f o r domestic purposes. As a r e s u l t , a l l s p r i n g s and seeps i n t h i s area are h e a v i l y l i c e n c e d . The Water Management Branch has d i f f i c u l t y i n a s s e s s i n g the exact p o t e n t i a l of each of the s p r i n g s i n t h i s area, and d u r i n g dry s p e l l s the s e n i o r l i c e n c e h o l d e r s complain t h a t they are unable to o b t a i n t h e i r f u l l e n t i t l e m e n t . The oxygen i s o t o p e and conductance analyses may shed some l i g h t on the dynamics of the system and thereby permit more accurate l i c e n c i n g . Study S i t e and Methods The flow a t the Morley S p r i n g monitoring s i t e was measured u s i n g the bucket and stopwatch method. Since the e n t i r e flow was d i v e r t e d i n t o a p l a s t i c drainage pipe a t i t s o r i g i n t here was no need to b u i l d an a d d i t i o n a l s t r u c t u r e . Although a l l of the s u r f a c e flow was trapped there may have been some leakage through the stream bed. Leakage would a f f e c t the data i n an a b s o l u t e sense, but would make l i t t l e d i f f e r e n c e from a pragmatic 46 s t a n d p o i n t as t h i s water i s a l s o l o s t to p o t e n t i a l users of the re s o u r c e . Rain gauges were p l a c e d next to the flow monitoring p o i n t a t an e l e v a t i o n of 550 m and f u r t h e r up the slope a t the 1000 m l e v e l ( F i g . 12). R e s u l t s The same storm t h a t was recorded a t the Mountain S t a t i o n study area was monitored f o r the North Shore study area. Between the hours of 0100 and 1130 on 11 August 1982 the storm d e p o s i t e d an average of 31mm of r a i n (Table 5). In response to t h i s p r e c i p i t a t i o n , Morley S p r i n g i n c r e a s e d i t s flow from a pre-event low of 0.30 1/s. to a peak of 0.38 1/s. The conductance values a l s o changed from 141 to 129 uS and the oxygen-18 content i n c r e a s e d from -18.27 % Q to -17.83 %o . The inter-method c o r r e l a t i o n f o r t h i s study s i t e i s -0.88 and the t w o - t a i l e d t -value i n d i c a t e s a s i g n i f i c a n c e to g r e a t e r then the 0.001 l e v e l . T h i s data can be found i n Table 6 or g r a p h i c a l l y represented i n F i g . 13. In order to determine how a c c u r a t e l y the i s o t o p i c and conductance methods were d u p l i c a t e d , the data f o r each of the two runs were s u b j e c t e d to s t a t i s t i c a l a n a l y s i s . The s t a t i s t i c a l r e s u l t s f o r the conductance method i n d i c a t e d a p e r f e c t c o r r e l a t i o n ( ie r=1.0). Furthermore, a t w o - t a i l e d t - v a l u e of -20.06 with 123 degrees of freedom e f f e c t i v e l y e l i m i n a t e s the p r o b a b i l i t y of t h i s c o r r e l a t i o n o c c u r i n g by chance. The i n t r a -method c o r r e l a t i o n c o e f f i c i e n t f o r the i s o t o p i c data was s i m i l a r l y h i g h , y i e l d i n g a r v a l u e of 0.99. Again the t w o - t a i l e d 47 F i g . 12 North Shore study area 48 Table 5 The R e s u l t s of the Analyses o f Rainwater Samples f o r the North Shore Study Area MORLEY SPRING TRANSECT 18 ELEVATION DATE TIME RAIN CONDUCTANCE 0 (m) (mm) (uS) (%•) 5 5 0 i i AUG 0 8 3 0 7 8 - 1 2 . 7 1 1 0 5 0 7 1 1 - 1 2 . 7 5 1 2 5 0 1 5 1 4 - 1 2 . 8 1 1 0 0 0 1 2 Aug 1 0 3 5 3 4 1 6 - 1 2 . 6 3 4 9 Table 6 The R e s u l t s of the Analyses of the Stream Flow Samples f o r the Morley Spring Study S i t e 18 TIME DATE FLOW CONDUCTIVITY 0 (1/s) (uS) ( % o 1005 9 Aug 0.31 127 -17.90 1645 10 Aug 0.30 138 -18.18 0215 11 Aug 0.30 141 -18.27 0830 11 Aug 0.29 133 -18.02 1050 11 Aug 0.31 133 -17.78 1250 11 Aug 0.33 129 -17.83 1450 11 Aug 0.38 132 -17.96 1705 11 Aug 0.31 134 -18.07 1905 11 Aug 0.30 137 -18.19 1010 12 Aug 0.30 138 -18.25 1815 12 Aug 0.30 139 -18.28 Rain water 12 -12.7: peak flow = 0.38 1/s prestorm water at peak flow as c a l c u l a t e d through i s o t o p i c a n a l y s i s = 0.36 1/s or 95% of t o t a l flow. prestorm water at peak flow as determined through a n a l y s i s of conductance = 0.35 1/s or 91 % of t o t a l flow. 50 0.6 -0.5 o.u -\ji Flow (l/s) i -0.3 -0.2 -0.1 -5 10 - 15 20 Rainfall (mm/hr) 2400 Time (days) Fig. 13 Morley Spring Hydrograph t - v a l u e i n d i c a t e d t h a t the p r o b a b i l i t y of t h i s c o r r e l a t i o n o c c u r i n g randomly was zero. D i s c u s s i o n of F i n d i n g s The average of the two types of a n a l y s i s showed t h a t approximately 93% of the peak flow was due to prestorm water. I t i s i n t e r e s t i n g to note t h a t even a f t e r 31 mm of p r e c i p i t a t i o n the flow of Morley S p r i n g i n c r e a s e d o n l y 0.09 1/s. Although t h i s i n c r e a s e i s c o n s i d e r a b l y more than t h a t a t P o s t l e S p r i n g i t would seem to r e p r e s e n t a s i m i l a r system. Since there was no s i g n of any o v e r l a n d flow and because Morley S p r i n g o r i g i n a t e s from a rock f a c e , the 7% of r u n o f f t h a t i s a t t r i b u t a b l e to storm water must have entered the system as e i t h e r groundwater or i n t e r f l o w . C o n c l u s i o n s As i n the Mountain S t a t i o n study s i t e i t appears t h a t most of the storm r u n o f f i s a t t r i b u t a b l e to groundwater. In t h i s case there i s l i t t l e t h a t can be done to i n c r e a s e the r a t e of flow. Although there are c u r r e n t l y no f o r e s t h a r v e s t i n g p r o p o s a l s f o r the North Shore area, i t i s u n l i k e l y t h a t such o p e r a t i o n s would i n f l u e n c e the water q u a n t i t y through a l t e r i n g the e v a p o t r a n s p i r a t i o n r a t e s , as the water resource i s probably independent of water used l o c a l l y i n p l a n t t r a n s p i r a t i o n . Since i t i s l i k e l y t h a t a l a r g e p a r t of the r u n o f f from Morley S p r i n g i s the r e s u l t of snow melt, as i n d i c a t e d by the low value of oxygen-18 i n the prestorm water, the l a r g e s c a l e removal of the f o r e s t cover can be expected to r e s u l t i n an i n c r e a s e d r a t e of a b l a t i o n of the winter snow pack. T h i s i n c r e a s e d r a t e of m e l t i n g may i n t u r n reduce the amount of water a v a i l a b l e f o r r u n o f f d u r i n g the summer months. Furthermore i f the h i l l s i d e i s logged, c a u t i o n should be taken when road b u i l d i n g , s i n c e the sl o p e i s not s t a b l e and Morley S p r i n g l i e s a t the bottom of an o l d s c r e e . F u r t h e r s l i d e s may bury the resource and render i t unuseable. I t i s u n l i k e l y t h a t the small s p r i n g s and seeps of the North Shore area w i l l be ab l e t o meet the requirements of f u t u r e r e s i d e n t s . E x t e n s i v e development of t h i s area w i l l r e q u i r e the c o n s t r u c t i o n of a c e n t r a l i z e d r e s e r v o i r system or a change i n a t t i t u d e by l o c a l r e s i d e n t s concerning the use of lake water f o r domestic purposes. 53 CHAPTER 3 - SLOCAN VALLEY STUDY AREA Area D e s c r i p t i o n The area examined w i t h i n the Slocan V a l l e y i s near South Lemon Creek and encompasses approximately 285 ha ( F i g . 14). o Although the lower r e g i o n has an average slope of 20 the topography i s q u i t e u n d u l a t i n g with numerous s m a l l , almost f l a t a r eas. Most of these l e v e l s t r e t c h e s of ground have been c l e a r e d The slope i n the upper r e g i o n s , however, i s much more uniform and o has a mean i n c l i n a t i o n of 32 . The r e g i o n i s l a r g e l y covered with mature Douglas f i r and l a r c h . T h i s study area a l s o belongs to the I n t e r i o r Cedar-Hemlock zone of e c o l o g i c a l c l a s s i f a c t i o n (Watts 1983). The geology of the area i s s i m i l a r to t h a t of the North Shore study area, with bedrock c o n s i s t i n g of Nelson G r a n i t e . Approximately 70% of the s o i l w i t h i n the study area belongs t o the Slocan s e r i e s of Ortho Humo-feric Podzols w h i l e the remaining 30% belongs to the Buhl Creek s e r i e s (Jungen 1980). The Slocan s e r i e s i s a s s o c i a t e d with a moderately compact g l a c i a l t i l l p arent m a t e r i a l and, as such, i s w e l l d r a i n e d . There are c u r r e n t l y 11 water l i c e n c e s h e l d w i t h i n the study 3 area which r e p r e s e n t a t o t a l demand of 72 m /day. Of t h i s t o t a l , 3 a demand of 52 m /day i s p l a c e d on E l l i o t t Creek, which has i t s o r i g i n i n many small upslope t r i b u t a r i e s . E l l i o t t Creek goes permanently underground approximately 200 m s h o r t of the main highway. T h i s i s probably due to the coarse g r a v e l s which u n d e r l i e s o i l s w i t h i n the r i v e r v a l l e y . The high p e r m e a b i l i t y of the s u b s t r a t e permits r a p i d i n f i l t r a t i o n , and the stream water merely p e r c o l a t e s down to the water t a b l e and t r a v e l s to the k i l o m e t e r s ( h i g h l i g h t i n g d e l i n e a t e s study area) ( i n s e r t d e p i c t s a r e a o f s k e t c h map) F i g . 15 Slocan V a l l e y 55 Slocan R i v e r as groundwater. 3 The remaining 20 m /day of the t o t a l l i c e n c e demand i s assigned to Chou Creek. Chou Creek o r i g i n a t e s i n a 1 ha area of f l a t land which i s l o c a t e d a t the base of a steep slope ( F i g . 15). In t h i s area a number of small c o l l e c t i o n trenches have been dug by the l o c a l r e s i d e n t s to improve flow c o n d i t i o n s . The creek then flows on the s u r f a c e f o r approximately 300 m before going underground. The exact s u r f a c e length of Chou Creek i s l a r g e l y dependent upon the s o i l moisture c o n d i t i o n s , as d u r i n g storm events i t may be extended another 200 m downstream. The r e s i d e n t s of the area have experienced water r e s t r i c t i o n s d u r i n g low flow c o n d i t i o n s , and are concerned by one of the M i n i s t r y of F o r e s t s p r o p o s a l s i n the Slocan V a l l e y access p l a n which c a l l s f o r c o n s t r u c t i o n of a haul road j u s t above t h e i r water d i v e r s i o n p o i n t s . Although nothing has been f o r m a l i z e d , i t would appear t h a t t h i s p roposal i s the most v i a b l e o p t i o n from e n g i n e e r i n g and f i n a n c i a l s t a n d p o i n t s . T h e r e f o r e , t h i s study was conducted to g a i n a b e t t e r understanding of the hydrology of the area, with the hope t h a t t h i s i n f o r m a t i o n would f o r e s t a l l any d e l e t e r i o u s development. Study S i t e s and Methods E l l i o t t Creek i s c u r r e n t l y gauged by the Inland Waters D i r e c t o r a t e of the Water Survey of Canada. T h i s weir was a l s o s e l e c t e d as a monitoring s i t e i n the p r e s e n t study. Flow from Chou Creek was measured u s i n g the bucket and stopwatch method, and u t i l i z e d the e a r t h berm and p l a s t i c pipe of the uppermost d i v e r s i o n p o i n t . As p r e v i o u s l y mentioned, Chou Creek o r i g i n a t e s 56 F i g . 15 Slocan Valley study area 57 as an area source, and because of the lack of a d e f i n i t e stream channel the monitoring p o i n t was designed to measure t h a t p a r t of the t o t a l flow which c o u l d a c t u a l l y be d i v e r t e d f o r u s e f u l purposes. Rain gauges were p l a c e d a t the 600, 900 and 1200 m e l e v a t i o n s , the lower two of which are i n d i c a t e d on F i g . 15. R e s u l t s A f r o n t a l system passed over the study area a t 1000 h on 9 September 1982. P r e c i p i t a t i o n continued f a i r l y c o n t i n u o u s l y u n t i l 0600 h the f o l l o w i n g morning, d e p o s i t i n g an average of 25 mm of r a i n . The data produced by the a n a l y s i s of the rainwater samples i s l i s t e d i n Table 7. The antecedent s o i l moisture c o n d i t i o n s were near s a t u r a t i o n , as a p r e v i o u s weather system had dropped r a i n over the study area approximately 3 days e a r l i e r , and s i n c e t h a t time the temperature had remained c o o l and the sky o v e r c a s t . Table 8 l i s t s the data obtained f o r Chou Creek and F i g . 16 d e p i c t s t h i s i n f o r m a t i o n as a hydrograph. S i m i l a r data can be found f o r E l l i o t t Creek i n Table 9 and F i g . 17. The c o r r e l a t i o n c o e f f i c i e n t between the two types of a n a l y s i s was -0.69 f o r Chou Creek and -0.61 f o r E l l i o t t Creek and the corresponding t v a l u e s i n d i c a t e l e v e l s of s i g n i f i c a n c e of 0.10 and 0.05 r e s p e c t i v e l y . D i s c u s s i o n of F i n d i n g s The Chou Creek hydrograph shows t h a t approximately 84% of the t o t a l peak r u n o f f i s prestorm water. The E l l i o t t Creek hydrograph i s q u i t e s i m i l a r as i t shows 87% of the peak flow as prestorm water. U n f o r t u n a t e l y , due to the d i f f i c u l t y i n measuring the drainage area of Chou Creek these two watersheds can not be compared on a u n i t area b a s i s . The s i m i l a r i t y between 58 Table 7 The Res u l t s of the Analyses of Rainwater Samples f o r the Slocan V a l l e y Study S i t e ELLIOTT CREEK TRANSECT 18 ELEVATION DATE TIME RAIN CONDUCTANCE 0 (m) (mm) (uS) (%o ) 600 9 Sep 1200 2 16 -13.60 1530 6 11 -13.50 1900 5 9 -13.69 2130 3 16 -13.44 10 Sep 1230 8 14 -13.52 900 10 Sep 1320 24 20 -13.48 1200 10 Sep 1350 27 15 -13.19 59 Table 8 The R e s u l t s of the Analyses of Stream Flow Samples f o r the Chou Creek Study S i t e 18 TIME DATE FLOW CONDUCTIVITY 0 (1/s) ( U S ) (%c 0600 8 Sep 0.16 320 -17.63 1530 8 Sep 0.16 322 -17.66 1150 9 Sep 0.41 304 -17.44 1520 9 Sep 0.55 274 -17.15 1855 9 Sep 0.52 288 -17.31 2120 9 Sep 0.48 285 -17.27 0850 10 Sep 0.38 315 -17.42 1145 10 Sep 0.36 305 -17.08 2200 10 Sep 0.30 312 -17.19 0550 11 Sep 0.25 318 -17.34 Rain water 13 -13.53 peak flow =0.56 1/s prestorm water at peak flow as c a l c u l a t e d through i s o t o p i c a n a l y s i s = 0 .48 1/s or 86% of t o t a l flow. prestorm water at peak flow as c a l c u l a t e d through a n a l y s i s of conductance = 0.46 or 82% of t o t a l flow. 60 Rainfall (mm/hr) 8 Sep 9 Sep 10 Sep 11 Sep Time (days) Fig. 16 Chou Creek Hydrograph Table 9 The R e s u l t s of the Analyses of Stream Flow Samples f o r the E l l i o t t Creek Study S i t e 2 bas i n area = 2.4 km 18 TIME DATE FLOW CONDUCTIVITY 0 (1/s) (uS) (%• 0610 8 Sep 5 195 -18.55 1550 8 Sep 5 199 -18.57 1200 9 Sep 7 189 -18.40 1535 9 Sep 10 187 -18.31 1905 9 Sep 16 184 -18.26 2130 9 Sep 18 180 -18.02 0900 10 Sep 14 179 -17.86 1155 10 Sep 13 187 -17.85 2210 10 Sep 11 189 -17.90 0610 11 Sep 10 193 -17.96 Rain water 13 -13.53 peak flow = 18.5 1/s prestorm water at peak flow as c a l c u l a t e d through i s o t o p i c a n a l y s i s = 16.0 1/s or 86% of t o t a l flow. prestorm water at peak flow as c a l c u l a t e d through a n a l y s i s o f conductance = 16.5 1/s or 89% of t o t a l flow. 62 i2bo 1 1 Sep 2400 1 2 0 0 8 Sep 2400 1200 9 Sep 12bo 10 Sep 241 241 Time (days) Fig. 17 E l l i o t t Creek Hydrograph the two cr e e k s , however, i s f u r t h e r i l l u s t r a t e d i n the magnitude of the i n c r e a s e d flow. The peak d i s c h a r g e of Chou Creek was 3.5 times as high as the prestorm low, whereas the flow of E l l i o t t Creek i n c r e a s e d 3.8 times. The obvious d i f f e r e n c e between the hydrograph obtained f o r Chou Creek and t h a t recorded f o r E l l i o t t Creek i s the time t o peak f a c t o r . Chou Creek took only 3.5 h to reach i t s peak from the prestorm low whereas E l l i o t t Creek took 11 h Given t h a t the h y d r a u l i c c o n d u c t i v i t y and g r a d i e n t s are s i m i l a r i n both catchments t h i s anomaly o b v i o u s l y r e f l e c t s the d i f f e r e n t s i z e of the r e s p e c t i v e drainage areas. S i z e d i f f e r e n c e s are a l s o i l l u s t r a t e d i n the r e c e s s i o n limb of the Chou Creek hydrograph. The secondary peaks i n d i c a t e d by the conductance and i s o t o p e a n a l y s i s l i n e s were probably caused by a small shower a f t e r the passage of the main f r o n t a l system and do not show up i n the t o t a l r u n o f f hydrograph because of sampling e r r o r . Although s u b j e c t e d to the same shower these peaks are not d e t e c t a b l e on the r e c e s s i o n limb of the E l l i o t t Creek hydrograph. T h i s masking e f f e c t i s probably due to the de l a y i n c u r r e d by the l a r g e r creek as the r e s u l t of channel r o u t i n g . When the r a i n water samples were analyzed f o r t h e i r oxygen-18 content they were again found t o be almost i d e n t i c a l d e s p i t e t h e i r e l e v a t i o n a l d i f f e r e n c e s . I t i s i n t e r e s t i n g to note, however, t h a t the i s o t o p i c spread between the r a i n water and the prestorm groundwater i s l e s s than found i n the other two study areas. One c o n t r i b u t i n g f a c t o r t o t h i s t r e n d may be r e l a t e d t o the change i n the r a t i o of snow melt groundwater to summer r a i n storm groundwater. As the summer progresses the snow melt component of the groundwater decreases due to r u n o f f , w h i l e the r a i n component of the groundwater i s added to by storms. T h i s t r e n d may be f u r t h e r enhanced by the decrease i n the i s o t o p i c content of the r a i n water i t s e l f . As the warmer temperatures of summer abate, the f r a c t i o n a t i o n r a t i o w i l l change. Although t h i s t r e n d i s based on only two storms, i t would seem to support the theory t h a t the m a j o r i t y of groundwater i s snow melt. C o n c l u s i o n s I t i s obvious from the data c o l l e c t e d i n t h i s study area, t h a t again the l a r g e m a j o r i t y of storm d i s c h a r g e o r i g i n a t e s from groundwater. In the case of E l l i o t t Creek the proposed development should, i f anything, i n c r e a s e the stream flow due to a r e d u c t i o n i n e v a p o t r a n s p i r a t i o n . In the case of Chou Creek however, the e f f e c t of the proposed development i s not as c l e a r . The convoluted topography and type of s u r f i c i a l d e p o s i t s w i t h i n the study s i t e make exact d e l i n e a t i o n of the watershed d i f f i c u l t . I t i s u n l i k l y t h a t r e l i e f i s a good i n d i c a t o r of subsurface d i v i d e s . Given the s i z e of the study s i t e then, any attempt to estimate the area d r a i n e d by Chou Creek i s l i k e l y to be dominated by measurement e r r o r s . I t i s t h e r e f o r e i m p o s s i b l e to determine the percentage of the watershed t h a t would be d i s r u p t e d by road development. Although one would normally expect an i n c r e a s e i n snow pack accumulation as the r e s u l t of the p a r t i a l c l e a r i n g a s s o c i a t e d with road c o n s t r u c t i o n , the p r e c e d i n g f a c t p r e c l u d e s a c c u r a t e q u a n t i f i c a t i o n of t h i s e f f e c t . The c o n s t r u c t i o n of a haul road t h a t t r a n s e c t s the Chou Creek 65 area, however, may compact the s u r f i c i a l m a t e r i a l enough to s i g n i f i c a n t l y reduce i t s h y d r a u l i c c o n d u c t i v i t y . I f t h i s s u r f i c i a l m a t e r i a l i s compacted down to an impermeable l a y e r i t may cause the d i v e r s i o n of upslope r u n o f f out of the Chou Creek watershed. C u l v e r t i n g alone would be an i n e f f e c t i v e s o l u t i o n t o the problem as i t w i l l l i k e l y r e s u l t i n an i n c r e a s e d s u r f a c e r u n o f f r a t e and thereby reduce the c r i t i c a l low flow c o n d i t i o n s . A b e t t e r s o l u t i o n t o the problem i s to i n c r e a s e the d i s t a n c e between the proposed development and Chou Creek. I f the haul road were b u i l t f u r t h e r upslope of the Chou Creek" d i s c h a r g e area, and i f care was taken i n the placement of c u l v e r t s so as not to d i v e r t s u r f a c e water out of the drainage b a s i n , the proposed development i s u n l i k e l y to have any s i g n i f i c a n t e f f e c t upon the water q u a l i t y or q u a n t i t y of the s p r i n g . 66 CHAPTER 6 ~ STUDY CONCLUSIONS The f i n d i n g s of t h i s study i n d i c a t e t h a t the amount of r u n o f f a t t r i b u t e d to prestorm water can be determined u s i n g e i t h e r i s o t o p i c or conductance methods. I t would appear t h a t the use of these methodologies i n hydrograph s e p a r a t i o n produce v a l i d r e s u l t s r e g a r d l e s s of the s i z e of the watercourse, and t h a t the l i m i t i n g f a c t o r i n t h i s type of procedure i s the accuracy of flow measurement. Furthermore, t h i s study a l s o i n d i c a t e s t h a t groundwater i s the major r u n o f f component of storm hydrographs w i t h i n the area of the Kootenays s t u d i e d . T h i s f i n d i n g i s c o n s i s t e n t with the r e c e n t s t u d i e s of Martinec (1975), F r i t z , Cherry, Weyer, and Sklash (1976) and Sklash and Farvolden (1979), but i s i n c o n t r a d i c t i o n to the e a r l i e r s t u d i e s of Horton (1933) and Hewlett and H i b b e r t (1967) where the v a s t m a j o r i t y of storm r u n o f f was a t t r i b u t e d to storm water. The f a c t t h a t the m a j o r i t y of storm r u n o f f i s groundwater p r o v i d e s f u r t h e r i n s i g h t i n t o the conceptual models of storm flow g e n e r a t i o n . W ithin the study areas the o v e r l a n d flow model as o r i g i n a l l y proposed by Horton i n 1933 and l a t e r modified by. Beston i n 1964 can be e l i m i n a t e d as major c o n t r i b u t o r s t o storm r u n o f f as both of these t h e o r i e s imply t h a t storm water i s the major component of peak r u n o f f . The theory of subsurface storm flow or i n t e r f l o w , as developed by Hewlett and Nutter i n 1967 s t a t e s t h a t the major component of storm r u n o f f i s p r e c i p i t a t i o n which has i n f i l t r a t e d the upper s o i l h o r i z o n s and t r a v e l s to the stream l a t e r a l l y above the w a t e r t a b l e . The p r o d u c t i o n of t h i s t r a n s l a t o r y flow r e q u i r e s a heterogeneous s o i l which f a v o u r s h o r i z o n t a l as opposed to v e r t i c a l h y d r a u l i c c o n d u c t i v i t y . Although these c o n d i t i o n s are not r a r e w i t h i n the areas examined i n t h i s study, Hewlett and N u t t e r ' s model cannot account f o r the high percentage of r u n o f f a t t r i b u t a b l e to prestorm water. The r e s u l t s of the present study, however, are s i m i l a r to those of Sklash and Farvolden (1979) i n t h a t they both a t t r i b u t e a l a r g e percentage of storm r u n o f f to prestorm water. In t h e i r work Sklash and Farvolden t h e o r i z e d t h a t t h i s r u n o f f component may r e s u l t from the f o r m a t i o n of a groundwater r i d g e . They s p e c u l a t e t h a t such a r i d g e may form near the stream channel where the water t a b l e i s c l o s e to the s u r f a c e and the time r e q u i r e d f o r p e r c o l a t i o n to the water t a b l e i s minimal. Such a groundwater r i d g e w i l l r e s u l t i n an i n c r e a s e d h y d r a u l i c g r a d i e n t near the stream channel and thereby p r o v i d e an e x p l a n a t i o n f o r the r a p i d response of the stream to p r e c i p i t a t i o n . T h i s r u n o f f theory, however, was developed by modeling i s o t r o p i c homogeneous c o n d i t i o n s of h y d r a u l i c c o n d u c t i v i t y and t h e r e f o r e may not be an a c c u r a t e p r e d i c t o r of the processes i n v o l v e d i n the more v a r i e d environment found w i t h i n a n a t u r a l drainage b a s i n . In some cases, the r a p i d r u n o f f may be caused by the p e r c o l a t i o n of the w e t t i n g f r o n t . In,such a model a decrease i n the t h i c k n e s s of the c a p i l l a r y f r i n g e c o u l d be a t t r i b u t e d to i n c r e a s e d p r e s s u r e w i t h i n the s o i l ; t h i s , i n t u r n would i n c r e a s e the h y d r a u l i c g r a d i e n t of the water t a b l e , f r e e i n g more water to r u n o f f . To o b t a i n f u r t h e r i n f o r m a t i o n on these t h e o r i e s , the experimental design as used i n the present study would have to be augmented with a network of piezometers. 6 8 The f i n d i n g t h a t most of the storm-generated r u n o f f i n the present study area c o n s i s t s p r i m a r i l y of prestorm groundwater i s u s e f u l i n f o r m a t i o n to the f o r e s t h y d r o l o g i s t , as i t give s some i n d i c a t i o n of the s u s c e p t i b i l i t y of the watershed t o the d e l e t e r i o u s e f f e c t s of f o r e s t h a r v e s t i n g p r a c t i c e s . In circumstances such as the ones of t h i s study, the d i v e r s i o n of p r e c i p i t a t i o n from groundwater to s u r f a c e water flow (as may r e s u l t from road c o n s t r u c t i o n or s o i l compaction) i s u n l i k e l y t o have an a p p r e c i a b l e e f f e c t on the o v e r a l l hydrology of the watershed as any r e d u c t i o n i n the groundwater flow as a r e s u l t of these p r a c t i c e s w i l l r e p r e s e n t o n l y a small p a r t of the t o t a l groundwater component. Furthermore, when i n c o r p o r a t i n g the other e f f e c t s of f o r e s t h a r v e s t i n g , such as the r e d u c t i o n of canopy i n t e r c e p t i o n and t r a n s p i r a t i o n , any p o t e n t i a l r e d u c t i o n i n the groundwater component i s l i k e l y t o be t o t a l l y masked by an o v e r a l l i n c r e a s e of water a v a i l a b l e f o r r u n o f f . In r e v i e w i n g the r e s u l t s of inter-method s t a t i s t i c a l a n a l y s i s there seems to be a reasonable c o r r e l a t i o n f o r the Mountain S t a t i o n and North Shore study areas although the same can not be s a i d f o r the Slocan V a l l e y study s i t e s . As a l l u d e d t o e a r l i e r the poor c o r r e l a t i o n s found w i t h i n the Slocan V a l l e y study area may be a t t r i b u t e d to some type of chemical r e a c t i o n t h a t i s a f f e c t i n g the i o n i c composition of the r u n o f f . Although a adequate e x p l a n a t i o n f o r t h i s f i n d i n g can not be s u b s t a n t i a t e d on a s i n g l e s e t of data, t h i s anomaly would tend t o support the continued use of both methods of a n a l y s i s as independant checks. A c o n t i n u a t i o n of our s t u d i e s over a longer p e r i o d of time may p r o v i d e a d d i t i o n a l i n s i g h t i n t o the p h y s i c a l c h a r a c t e r i s t i c s 69 governing the flow system. For i n s t a n c e , the data f o r a l l three study s i t e s were obtained when the prestorm s o i l moisture c o n d i t i o n s were near s a t u r a t i o n . T h i s c o n d i t i o n can be e x p l a i n e d as a combination of both the c l o s e p r o x i m i t y of preceding storm events and the f a c t t h a t the study s i t e s r e p r e s e n t a l o c a l groundwater d i s c h a r g e a r e a . I t would be i n t e r e s t i n g t o repeat t h i s study under d i f f e r e n t s o i l moisture c o n d i t i o n s t o see what e f f e c t t h i s v a r i a b l e has on the flow system. A d d i t i o n a l i n f o r m a t i o n may a l s o be obtained by conducting a s i m i l a r experiment with longer d u r a t i o n and higher i n t e n s i t y storms. With a d d i t i o n a l data the h y d r a u l i c c o n d u c t i v i t i e s and d e t e n t i o n storage c a p a c i t i e s of the watershed c o u l d be c a l c u l a t e d . A f i n a l improvement may be to conduct experiments i n d i f f e r e n t seasons. As p r e v i o u s l y mentioned, i t would appear t h a t the m a j o r i t y of the groundwater flow had i t s o r i g i n s as snow melt. I f sampling were continued throughout the wint e r i t may be p o s s i b l e to determine the l o c a t i o n of the recharge area and the expanse of the a q u i f e r . 70 Appendix A GLOSSARY Channel i n t e r c e p t i o n - p r e c i p i t a t i o n f a l l i n g on the water co u r s e . Detention storage - pore water which i s s u s c e p t i b l e to the i n f l u e n c e s of g r a v i t y . D i r e c t r u n o f f - the sum of channel i n t e r c e p t i o n , o v e r l a n d flow and i n t e r f l o w . Discharge - the volume of water flowing from the watershed. F r a c t i o n a t i o n - changing the o r i g i n a l i s o t o p i c composition of a s o l u t i o n through the p r e f e r e n t i a l c o n c e n t r a t i o n o f l i g h t e r i s o t o p e s . Groundwater - water below the p h r e a t i c s u r f a c e . Groundwater flow - that p a r t of the t o t a l stream d i s c h a r g e that moves to the water course l a t e r a l l y below the water t a b l e as sa t u r a t e d flow. H y d r a u l i c c o n d u c t i v i t y - a parameter governing the flow o f a f l u i d through a porous medium that i s dependent upon both the p r o p e r t i e s of the medium and the f l u i d . H y d r a u l i c g r a d i e n t - the change i n the h y d r a u l i c head over a given d i s t a n c e . I n f i l t r a t i o n - the process by which water passes through the s o i l s u r f a c e . I n t e r f l o w - (subsurface storm flow) t h a t p a r t o f the t o t a l stream d i s c h a r g e that moves to the water course l a t e r a l l y through the upper s o i l h o r i z o n s as s a t u r a t e d or unsaturated flow. Mixing - changing the o r i g i n a l i s o t o p i c composition o f a s o l u t i o n by adding water of a d i f f e r e n t i s o t o p i c c o n t e n t . Overland flow - ( s u r f a c e flow) t h a t p a r t o f t o t a l stream d i s c h a r g e that moves to the water course l a t e r a l l y over the s o i l s u r f a c e without i n f i l t r a t i o n . P e r c o l a t i o n - the advance of water through the s o i l . Prestorm water - a l l the water present i n the watershed p r i o r to a p a r t i c u l a r p r e c i p i t a t i o n event. 71 Retention pores. storage water held by c a p i l l a r y f o r c e i n small Storm water - that p a r t of the t o t a l stream d i s c h a r g e that i s added to the watershed by a p a r t i c u l a r p r e c i p i t a t i o n event. Subsurface flow - flow through a porous media i n both the s a t u r a t e d and unsaturated s t a t e . Water t a b l e - the s u r f a c e at which f l u i d p r e ssure i s equal to atmospheric p r e s s u r e . 72 REFERENCES Ahern, T.K. (1975) An Oxygen-18/Oxygen-16 Study of Water Flow i n Natura l Snow. Masters T h e s i s , Department of Geophysics and Astronomy, U n i v e r s i t y of B r i t i s h Columbia. A n a l y t i c a l Q u a l i t y C o n t r o l L a b o r a t o r y . N a t i o n a l Environmental Center. 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