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Irrigation requirements for alfalfa in the Nicola Valley Willcocks, Timothy John 1970

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IRRIGATION REQUIREMENTS FOR ALFALFA IN THE NICOLA VALLEY by TIMOTHY JOHN WILLCOCKS B.A., B.A.I., T r i n i t y C o l l e g e , Dublin,'1964 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of C i v i l Engineering We accept t h i s t h e s i s as conforming to the re q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1970 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced d e g r e e a t t h e 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 a g r e e 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 a g r e e t h a 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 p u r p o s e s may be g r a n t e d by t h e Head o f my Depar tment o r by h i s 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 no 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 . ( T . J . W i l l c o c k s ) Depar tment o f C i v i l E n g i n e e r i n g 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 V a n c o u v e r 8 , Canada Date 1 s t A p r i l 1970 ABSTRACT The N i c o l a V a l l e y , i n the dry i n t e r i o r of B r i t i s h Columbia, i s an important c a t t l e ranching area. A l f a l f a and grass hay are grown to provide winter feed f o r the c a t t l e , but due to the low annual p r e c i p i t a t i o n (9.5 i n s . at M e r r i t t ) and high r a t e of e v a p o t r a n s p i r a t i o n , i r r i g a t i o n i s necessary. Of the l i c e n c e d water supply, 95 percent i s l i c e n s e d to a g r i c u l t u r a l use. In t h i s study, which i s of the reconnaissance type, current i r r i g a t i o n p r a c t i c e s w i t h i n the area are d e s c r i b e d , and on the b a s i s of a v a i l a b l e data and some f i e l d measurements, a method i s developed from which i r r i g a t i o n and drainage requirements are determined f o r s e v e r a l t y p i c a l l o c a t i o n s . Seasonal e v a p o t r a n s p i r a t i o n was estimated from readings obtained from an Ogopogo carborundum block evaporimeter, and f o r M e r r i t t , Douglas Lake, and Quilchena, seasonal requirements were found to be 26, 19, and 24 acre i n s . / a c r e r e s p e c t i v e l y . The leaching or drainage requirement was found to be low i n the N i c o l a V a l l e y . A l o c a l maximum value of 8.3 percent was found, but drainage water not exceeding one percent of consumptive use was estimated f o r an average season. I t was considered advisable to add gypsum to i r r i g a t i o n waters i n c e r t a i n cases to prevent sodium a l k a l i s o i l s from developing; the more usual t e s t s i n d i c a t i n g sodium hazard gave u n s a t i s f a c t o r y r e s u l t s . The concept of e f f i c i e n c y of water use r e q u i r e s some c a r e f u l d e f i n i t i o n : i t i s pointed out that present d e f i n i t i o n s of water e f f i c i e n c y can be misleading. Conveyance e f f i c i e n c i e s were found to be h i g h l y v a r i a b l e w i t h seepage values of 8 percent to 96 percent per m i l e ; e f f i c i e n c y of d i s t r i b u t i o n of i r r i g a t i o n water w i t h i n a f i e l d was taken from comparative data. TABLE OF CONTENTS CHAPTER PAGE LIST OF TABLES i i i LIST OF FIGURES i v ACKNOWLEDGEMENTS v I. INTRODUCTION 1 I I . IRRIGATION: DEVELOPMENT AND PRACTICES 5 H i s t o r i c a l Development 5 I r r i g a t i o n Techniques 6 Crop Use of Water 9 The N i c o l a V a l l e y 10 D i s c u s s i o n 14 Summary 16 I I I . THE VARIABLES DETERMINING IRRIGATION REQUIREMENTS 17 Consumptive Use .. 17 Water i n the S o i l 17 Water Transpired and Evaporated 19 Scheduling 20 Methods of Estimating E v a p o t r a n s p i r a t i o n 21 Drainage Requirement 30 General 30 Theory of I r r i g a t i o n Drainage 31 Ions i n . I r r i g a t i o n Water 32 Drainage Requirement by Chemical A n a l y s i s 33 Drainage Requirement by T o t a l S a l i n i t y 35 Notes on Methods Outlined 36 i i CHAPTER PAGE E f f i c i e n c y 40 Conveyance E f f i c i e n c y 40 F i e l d Water A p p l i c a t i o n E f f i c i e n c y 40 Water D i s t r i b u t i o n E f f i c i e n c y 40 IV. IRRIGATION IN THE NICOLA VALLEY 43 Consumptive Use 43 M e r r i t t 43 Douglas Lake 46 Quilchena 47 Summary 49 Drainage Requirement 52 General S o i l Drainage 52 The Groundwater Flow P a t t e r n 52 V a r i a t i o n of S a l t Content 53 Q u a l i t y of Water f o r I r r i g a t i o n 54 Gypsum and Drainage Requirements 54 Summary 58 E f f i c i e n c y 69 Conveyance E f f i c i e n c y 69 Water Use, F i e l d Water A p p l i c a t i o n , and Water D i s t r i b u t i o n E f f i c i e n c i e s 70 P o s s i b l e Developments 71 Summary 73 V. RESULTS AND CONCLUSIONS 75 BIBLIOGRAPHY 81 APPENDIX 86 i i i LIST OF TABLES TABLE PAGE I. E v a p o t r a n s p i r a t i o n Equations . .. 27 I I . Seasonal E-T of A l f a l f a at M e r r i t t , B.C. and at Davis, C a l i f o r n i a , as Estimated by D i f f e r e n t Methods 28 I I I . E v a p o t r a n s p i r a t i o n Recorded at M e r r i t t and Douglas Lake, 1967 51 IV. Quilchena Creek. Measurements of p'H and E l e c t r i c a l C o n d u c t i v i t y 60 V. P o t e n t i a l I r r i g a t i o n Waters. Data on Chemical A n a l y s i s and E l e c t r i c a l C o n d u c t i v i t y 61 VI. Tests I n d i c a t i n g Q u a l i t y of I r r i g a t i o n Water 62 V I I . P o t e n t i a l I r r i g a t i o n Waters. Drainage Percentages and Gypsum Requirements 63 V I I I . N i c o l a V a l l e y . E l e c t r i c a l C o n d u c t i v i t y Measurements "and Drainage^Percentages 64 IX." Drainage Percentage and Gypsum Requirements Specimen C a l c u l a t i o n s 65 X. Water Conveyance and I r r i g a t i o n E f f i c i e n c y 74 XI. I r r i g a t i o n Requirements at M e r r i t t , Douglas Lake, and Quilchena . 80 i v LIST OF FIGURES FIGURE PAGE 1. Comparison of the E v a p o t r a n s p i r a t i o n of A l f a l f a at Davis, C a l i f o r n i a , 1955, and at M e r r i t t , B.C. 1967 ... 29 2. M e r r i t t . Average D a i l y Temperature, A p r i l and October. Average Monthly P r e c i p i t a t i o n 50 3. T h e o r e t i c a l Flow Patterns and Boundaries between D i f f e r e n t Flow Systems 66 4. O u t l i n e Plan of the Quilchena V a l l e y 67 5. Temporal and S p a t i a l V a r i a t i o n of C o n d u c t i v i t y along Quilchena Creek 68 ACKNOWLEDGEMENTS I have rece i v e d advice from many people i n the course of t h i s study, and have made use of data from numerous research and f i e l d workers. I should l i k e to thank a l l those who have helped me, d i r e c t l y or i n d i r e c t l y , i n p a r t i c u l a r the f o l l o w i n g : U. Berglund, G. Guichon, D. Huber, G. Rose, N. R u s s e l l , G. Turnbow, and N. W i l l i a m s , ranchers i n the N i c o l a V a l l e y , f o r t h e i r time spent i n d i s c u s s i n g v a r i ous aspects of i r r i g a t i o n i n the area, and f o r a l l o w i n g me to run c e r t a i n f i e l d t e s t s . A. L. van Ryswyck, Canada Department of A g r i c u l t u r e , and other s t a f f at the Experimental Farm at Kamloops. Prof. T. L. Coulthard, U n i v e r s i t y of B r i t i s h Columbia Department of A g r i c u l t t i r a l Engineering, p a r t i c u l a r l y f o r a n a l y s i s of water samples. Dr. L. Farstad and A. Bedwany, S o i l Survey, Dept. of A g r i c u l t u r e , f o r demonstrating s o i l s t r u c t u r e and chemistry both i n the o f f i c e and i n the f i e l d . J . D. Smuin, B.C. Dept. of Lands, F o r e s t s , and Water Resources, f o r a l l o w i n g me access to f i l e s on water l i c e n c e s . Dr. J . C. W i l c o x , A.R.D.A., Summerland Research S t a t i o n , f o r a l l o w i n g me to use unpublished data and f o r a s s i s t a n c e i n the e s t i m a t i o n of e v a p o t r a n s p i r a t i o n . P r o f . S. 0. R u s s e l l , U.B.C. Dept. of C i v i l Engineering, f o r ably s u p e r v i s i n g the development o f t h i s t h e s i s . Department of Lands, F o r e s t s , and Water Resources, Government of B r i t i s h Columbia, f o r enabling t h i s study to be undertaken. CHAPTER I INTRODUCTION At the request of the P r o v i n c i a l Government, the Water Resources group within the Department of C i v i l Engineering at the University of B r i t i s h Columbia i s making a study of the water resources of the Nicola-(9) Kamloops area. This area is t y p i c a l of several r e l a t i v e l y underdeveloped dry areas of B r i t i s h Columbia. In common with these i t is lacking both a comprehensive preliminary survey of i t s water resources and also ongoing research i n s p e c i f i c f i e l d s . In most desert regions of the world, water is a c r i t i c a l l y scarce commodity, and as such i t s use is normally governed by a s t r i c t set of p r i o r i t i e s . In c e r t a i n other regions the e f f e c t i v e p r e c i p i t a t i o n is s u f f i c i e n t to ensure that, with some conservation measures, an adequate supply can be guaranteed for a multitude of uses. The Nicola Valley area l i e s between these two extremes. At present, with a limited but v i t a l amount of conservation, there i s enough water for e x i s t i n g needs, but i n the future t h i s p i c t ure could become s i g n i f i c a n t l y a l t e r e d as a r e s u l t of increased demand, and the a v a i l a b l e water could become i n s u f f i c i e n t . The lowlands of the Nicola Valley generally receive less than 10 inches of p r e c i p i t a t i o n annually, and the area can be classed as semi-desert; the winters are moderately cold, and the summers hot and dry, with - 2 -maximum and minimum monthly temperatures of 64°F and 20°F. . No comprehensive study has ever been made of the p a t t e r n of water d i s t r i b u t i o n w i t h i n t h i s r e g i o n , w i t h regard to the qua n t i t y a v a i l a b l e w i t h i n the b a s i n , the qua n t i t y a c t u a l l y used, or to i t s q u a l i t y . The a v a i l a b i l i t y of water i n r e l a t i o n to the demand could be a l i m i t i n g f a c t o r on major developments, and should t h e r e f o r e be c a r e f u l l y considered i n any long range planning. The m i n e r a l , lumber, and range resources of the area govern such p o t e n t i a l developments, and w h i l e these are not pr e s e n t l y j u s t i f i e d may become so i n the near f u t u r e . Of the l i c e n s e d use of water w i t h i n the area the l a r g e s t consumer i s i r r i g a t i o n w i t h about 95 percent of the l i c e n s e d supply, w h i l e other uses are domestic w i t h 4 percent and i n d u s t r i a l w i t h 1 percent. In an assess-ment of the p a t t e r n of water d i s t r i b u t i o n , i r r i g a t i o n should t h e r e f o r e be given a high p r i o r i t y . This study i s concerned w i t h e s t i m a t i n g the water requirements of crops t a k i n g i n t o account the p r i n c i p a l f a c t o r s a f f e c t i n g i r r i g a t i o n usage; the f i n d i n g s should be a p p l i c a b l e , not only to the N i c o l a V a l l e y , but to other areas of B r i t i s h Columbia, bearing i n mind the f a c t that c l i m a t i c data i s g e n e r a l l y sparse. Estimates have been made f o r a season of high water demand so that even i n a s e r i e s of dry summers the estimated requirement should be adequate f o r crop growth. In order to compute the t o t a l seasonal i r r i g a t i o n needs of the N i c o l a V a l l e y i t i s necessary to determine the crop requirement at each - 3 -(9) e l e v a t i o n , and to combine t h i s w i t h an a r e a - e l e v a t i o n curve f o r the area. Crops consume water i n p r o p o r t i o n to t h e i r l e a f surface area, and thus a healthy stand of a l f a l f a under good i r r i g a t i o n management w i l l r e q u i r e more water than a poor stand, which i n turn w i l l r e q u i r e more water than grass. Both a l f a l f a and grass are grown i n the N i c o l a V a l l e y , but i n t h i s study a l f a l f a alone i s considered, since i t i s the greater water user. The s o i l s ' of the N i c o l a V a l l e y are considered to range from medium to marginal f o r a g r i c u l t u r a l purposes, but a f u l l s o i l survey i s at present under way, which w i l l give more s p e c i f i c i n f o r m a t i o n about the extent of i r r i g a b l e acreage. Factors a f f e c t i n g crop consumption of water are the physiographic p r o p e r t i e s of the r e g i o n such as e l e v a t i o n , r a d i a n t energy r e c e i v e d , e t c . , and l o c a l f a c t o r s such as s o i l and crop type, and stage of crop growth. Although the r a t e of water usage of a crop v a r i e s w i t h i t s stage of growth, f o r t h i s study an average value i s assumed to apply throughout the season. The qu a n t i t y of water a p p l i e d , i n a d d i t i o n to p r o v i d i n g f o r crop consumption, should a l l o w f o r drainage or l e a c h i n g , t h i s being dependent on the s a l i n i t y of the s o i l and of the i r r i g a t i o n water used. Since the appear-ance of surface s a l t s i s of frequent occurrence i n the N i c o l a V a l l e y , and si n c e study of the s a l i n i t y of i r r i g a t i o n water has p r e v i o u s l y been done only i n l i m i t e d areas of B r i t i s h Columbia, t h i s aspect was f u l l y considered. F i n a l l y , the u l t i m a t e i r r i g a t i o n requirement of a r e g i o n i s also dependent on the e f f i c i e n c y of water use which v a r i e s w i t h the method of - 4 -i r r i g a t i o n used. The m a j o r i t y of i r r i g a t i o n i n the area i s c a r r i e d out by surface methods, which have rece i v e d l i t t l e a t t e n t i o n i n the province; however, surface i r r i g a t i o n accounts f o r nearly 90 percent of the t o t a l i n the P a c i f i c North West, and comparisons are drawn i n t h i s study between methods used i n B r i t i s h Columbia and i n other parts of North America, p a r t i c u l a r l y w i t h respect to e f f i c i e n c y . This study e n t a i l e d s e v e r a l weeks of f i e l d work, during which time an e v a l u a t i o n * o f d i f f e r e n t techniques was made, c e r t a i n f i e l d t e s t s were run, and the author was able to f a m i l i a r i z e h i m s e l f w i t h the i r r i g a t i o n methods i n use i n the N i c o l a V a l l e y . As a r e s u l t , the study i s not j u s t an attempt to estimate crop water requirements for long range planning. A method f o r such e s t i m a t i o n i s g iven, and ap p l i e d to c e r t a i n l o c a l i t i e s w i t h i n the area to o b t a i n q u a n t i t a t i v e r e s u l t s . In a d d i t i o n , the study describes and compares the techniques p r e s e n t l y i n use. I t i s hoped that the f i n d i n g s w i l l provide information of immediate use to ranchers and to designers of i r r i g a t i o n systems. Because the study i s comparatively wide ranging i n nature, and sin c e some aspects have p r e v i o u s l y been s c a r c e l y covered i n B r i t i s h Columbia, the m a j o r i t y of the terms used i n i r r i g a t i o n and i n water and s o i l chemistry are defined or described f o r the sake of c l a r i t y . CHAPTER I I IRRIGATION--DEVELOPMENT AND PRACTICES i ) H i s t o r i c a l Development I r r i g a t i o n i s the c o n t r o l l e d a p p l i c a t i o n of water to a g r i c u l t u r a l land to supply crop requirements not s a t i s f i e d by r a i n f a l l . In a r i d and semi-arid lands crop growth may be e n t i r e l y dependent on the supply of outside water; a depth of up to 48 i n s . or more-per"season may be r e q u i r e d , depending on the growing c o n d i t i o n s . The f i r s t i r r i g a t i o n systems were developed i n the Middle East soon a f t e r the e a r l i e s t settlements came i n t o being, founded by N e o l i t h i c man as he turned from a nomadic herding existence to a s e t t l e d a g r i c u l t u r a l economy; such communities were probably located iri~'the 12"-20" r a i n b e l t . Flood p l a i n a g r i c u l t u r e was p r a c t i c e d by s e v e r a l e a r l y c i v i l i z a t i o n s , and the r i v e r N i l e has been used f o r f l o o d p l a i n and extended f l o o d p l a i n i r r i g a t i o n since 5,000 B.C. However, despite i t s long h i s t o r y , there have been numerous f a i l u r e s of i r r i g a t i o n systems, some of which are b e l i e v e d to have led to the d e c l i n e of e n t i r e c i v i l i z a t i o n s . For example, due p r i m a r i l y to a lack of under-standing of the s a l i n i t y problems inherent i n the a p p l i c a t i o n of r i v e r water there are now thousands of acres of unusable land i n the South West of the United S t a t e s , and i t appears that e a r l y c i v i l i z a t i o n s along the - 6 -Euphrates system decayed f o r the same reason. Modern i r r i g a t i o n i n America began when the Mormons s e t t l e d i n Utah i n 1847, and i t followed i n the wake of the C a l i f o r n i a n gold rush of 1849 to other parts of the West. Prospectors then spread northwards, and e s p e c i a l l y around 1870 there was a considerable i n f l u x i n t o B r i t i s h Colum-b i a . Many of these soon changed to c a t t l e ranching f o r a l i v e l i h o o d , and thus c a t t l e ranching became an important development i n the province. An immediate consequence of t h i s development was the p r o v i s i o n of winter feed, which i n t u r n r e q u i r e d i r r i g a t e d meadows, and e a r l y water l i c e n c e s f o r i r r i g a t i o n i n B r i t i s h Columbia were given out a hundred years ago. Winter f o o d s t u f f i s necessary i n a l l years, but very hard winters such as those of 1897 and 1969 have put the growth of forage crops at a premium. As the value of beef and a l s o land pressure increase i t becomes necessary to increase the o v e r a l l e f f i c i e n c y and scope of i r r i g a t i o n methods. This has meant extension of i r r i g a t e d acreages and i n t e n s i f i c a t i o n - - t h e growing of higher y i e l d i n g forage crops i n some areas, use of f e r t i l i z e r s , and improved i r r i g a t i o n p r a c t i c e s . i i ) I r r i g a t i o n Techniques E a r l y i r r i g a t i o n techniques have always employed s u r f a c e , or f l o o d i n g , methods of a p p l i c a t i o n of water to the land. In essence t h i s r e q u i r e s that the water be d i v e r t e d or pumped from i t s source i n t o a channel, whence i t i s conveyed to the f i e l d of a p p l i c a t i o n . By means of some form of o u t l e t - 7 -from the channel i t i s then allowed to flow under g r a v i t y across the f i e l d , e i t h e r i n s p e c i a l l y made furrows or c o r r u g a t i o n s , or as a sheet of water. When water has been f l o w i n g f o r s u f f i c i e n t time to allow the necessary i n f i l t r a t i o n i n t o the s o i l , the channel o u t l e t s are sealed o f f . With the a v a i l a b i l i t y of l i g h t w e i g h t aluminium p i p i n g , i n c r e a s i n g use has been made i n Canada since 1945 of overhead, or s p r i n k l e r , methods. Water i s sprayed out i n the form of ' r a i n ' drops from r o t a t i n g s p r i n k l e r heads which are connected by f i e l d l a t e r a l s and a main l i n e to the source of supply. This may be a stream or r e s e r v o i r g i v i n g a g r a v i t y d i s t r i b u t i o n , or an equivalent pumping set-up, e i t h e r permanently or temporarily mounted. The water pressure at the s p r i n k l e r head i s u s u a l l y of the order of 50 p . s . i . Since each s p r i n k l e r head covers a l i m i t e d range, the 'set' of p i p i n g and heads must u s u a l l y be moved about a f i e l d at r e g u l a r i n t e r v a l s . Hand sets are those r e q u i r i n g to be moved e n t i r e l y by hand, w h i l e automation i s seen i n wheelmoves, where a l i n e of s p r i n k l e r s i s moved across the£grouiid on large wheels, i n ' s o l i d s e t s ' where p i p i n g and heads are permanently i n s t a l l e d , and i n the ' r a i n gun 1 which e s s e n t i a l l y c o n s i s t s of a large high pressure nozzle w i t h a considerable range. B e t t e r c o n t r o l of the water used i s u s u a l l y achieved w i t h a s p r i n k l e r system, s i n c e i t i s r e l a t i v e l y easy to apply a s p e c i f i e d q u a n t i t y to a crop. By the same token a f l o o d system g e n e r a l l y gives a more uneven d i s t r i b u t i o n of water, and i n order to be sure of applying a c e r t a i n quantity to a l l parts of a f i e l d , o v e r - a p p l i c a t i o n i s necessary; consequently water tends to be 'wasted', and c e r t a i n plant n u t r i e n t s are washed out of the s o i l . - 8 -On the other hand the economics of f l o o d systems i n c e r t a i n areas can be more favourable. The i n i t i a l cost of i n s t a l l i n g such a system i n r e l a t i v e l y l e v e l land can be l e s s , and i t s t o t a l annual cost to the farmer i n c l u d i n g d e p r e c i a t i o n can be much lower than a s p r i n k l e r system. The annual cost of water i s i n some cases a d e c i d i n g f a c t o r ; i n areas of high cost water the economics of us i n g good c o n t r o l may d i c t a t e a s p r i n k l e r system, w h i l e the low p r i c e of water i n B r i t i s h Columbia due to i t s r e l a -t i v e abundance i n c e r t a i n parts of the province gives l i t t l e i n c e n t i v e to change from f l o o d systems. In a r e g i o n such as B r i t i s h Columbia where labour Itends .to'be (4) scarce and expensive, the trend i s towards increased automation. S p r i n k l e r systems are b e t t e r adapted to t h i s advance, although investment costs r i s e s t e e p l y . L i t t l e attempt has been made at improved design or automation of f l o o d i r r i g a t i o n systems i n the province although there i s scope f o r t h i s ; i n most cases i t i s simply assumed that f l o o d i r r i g a t i o n i s o l d fashioned and i n e f f i c i e n t . A f u r t h e r f a c t o r a f f e c t i n g t h i s trend i s the disappearance of the experienced f l o o d i r r i g a t o r , without whose ' a r t ' even a semi-automated system could run i n t o severe t r o u b l e . I t would appear that i n c e r t a i n areas there i s l i t t l e advantage to be gained by changing from a f l o o d system, w h i l e i n others s p r i n k l e r s are almost a n e c e s s i t y . However, the two methods are r e a l l y complementary to each other, and i n s p i t e of the present trend toward s p r i n k l e r s , f l o o d i r r i g a t i o n w i l l have a s i g n i f i c a n t r o l e to play f o r many years, p a r t i c u l a r l y f o r r e l a t i v e l y low value produce such as the forage crops grown i n the N i c o l a area. - 9 -i i i ) Crop Use o f Water I r r i g a t i o n w a t e r i s u t i l i z e d i n s e v e r a l d i f f e r e n t ways. The amount r e q u i r e d f o r p l a n t growth i s dependent upon c l i m a t i c c o n d i t i o n s such as r a d i a t i o n r e c e i v e d , a i r and s o i l t e m p e r a t u r e , and w i n d v e l o c i t y , and i s r e f e r r e d t o as Consumptive Use; i n t h i s s t u d y t h i s term i s used i n t e r -c h a n g e a b l y w i t h E v a p o t r a n s p i r a t i o n . I r r i g a t i o n w a t e r s a l l c o n t a i n a b a s i c q u a n t i t y o f d i s s o l v e d s a l t s , b u t a c r o p uses o n l y a v e r y s m a l l amount o f t h e s e . To p r e v e n t a r e s i d u a l b u i l d - u p o f s a l t s i n t h e s o i l an a d d i t i o n a l amount o f i r r i g a t i o n w a t e r known as t h e D r a i n a g e Requirement o r L e a c h i n g Requirement,''' must be added f o r the p u r p o s e o f f l u s h i n g out such u n d e s i r a b l e d e p o s i t s . For such f l u s h i n g o f s a l t s t o be e f f e c t i v e i t i s n e c e s s a r y t h a t t h e s u b s u r f a c e d r a i n a g e be adequate t o d r a i n away the a d d i t i o n a l w a t e r ; where t h i s d r a i n a g e i s not s u f f i c i e n t , and t i l e d r a i n s a r e n o t u s e d , s a l i n e o r a l k a l i n e d e p o s i t s may i n c r e a s e t o the p o i n t where t h e l a n d can be no l o n g e r used f o r g r o w i n g c r o p s . I n s u f f i c i e n t d r a i n a g e can a l s o cause w a t e r l o g g i n g w h i c h may k i l l some c r o p s such as a l f a l f a . These two r e q u i r e m e n t s , f o r E v a p o t r a n s p i r a t i o n and f o r D r a i n a g e , g o v e r n t h e amount o f w a t e r r e q u i r e d by a c r o p . However, i n o r d e r t o compute the o v e r a l l volume o f w a t e r t o be d i v e r t e d t o a f a r m , two o t h e r f a c t o r s must E i t h e r L e a c h i n g , . o r D r a i n a g e Requirement can be used i n t h i s c o n t e x t , b u t i n t h i s s t u d y l e a c h i n g i s g e n e r a l l y t a k e n to r e f e r t o t h e w a s h i n g from th e s o i l o f an a c c u m u l a t i o n o f s a l t s , w h i c h have a l r e a d y r e n d e r e d t h e ground more u n s u i t a b l e f o r c u l t i v a t i o n , w h i l e d r a i n a g e i s t a k e n t o r e f e r t o e x c e s s i r r i g a t i o n w a t e r passed t h r o u g h t h e s o i l t o p r e v e n t any such a c c u m u l a t i o n o f r e s i d u a l s a l t s . When t h i s q u a n t i t y i s e x p r e s s e d ~ a s ~ a p e r c e n t a g e o f the c o n s u m p t i v e use i t i s denoted the L e a c h i n g , o r D r a i n a g e P e r c e n t a g e . - 1 0 -be considered. The f i r s t i s the F i e l d A p p l i c a t i o n E f f i c i e n c y , which takes i n t o account the u n i f o r m i t y of d i s t r i b u t i o n and other ' w i t h i n - f i e l d ' l o s s e s , and the second i s the Conveyance E f f i c i e n c y which allows for water losses between the point of d i v e r s i o n and the f i e l d . I t may be noted that the sum of the Consumptive Use and Drainage requirements i s independent o f , while both the F i e l d A p p l i c a t i o n E f f i c i e n c y and the Conveyance E f f i c i e n c y are h i g h l y dependent on, the method of' i r r i g a t i o n used. (9) i v ) The N i c o l a V a l l e y  Topography R i s i n g at an e l e v a t i o n of about 5000 f e e t , the N i c o l a River traverses a r e g i o n composed l a r g e l y of the open grassland and sagebrush v e g e t a t i o n c h a r a c t e r i s t i c of the 'dry b e l t ' of B r i t i s h Columbia, before i t s confluence w i t h the Thompson River at Spences Bridge. This land ranges i n e l e v a t i o n from 1000'to 6000', c o n s i s t i n g mainly of plateau areas i n t e r s e c t e d by small a l l u v i a l v a l l e y s ; most of the a g r i c u l t u r e i s c a r r i e d on below 2500'. P r e c i p i t a t i o n The p r e c i p i t a t i o n of t h i s r e g i o n , depending l a r g e l y on e l e v a t i o n , ranges from 9" to 18" annually w i t h the r e s u l t that f o r e s t cover i s con s i d e r a b l y t h i c k e r at the higher l e v e l s where e v a p o t r a n s p i r a t i o n i s lower. Summer r a i n f a l l i s r a r e l y s u f f i c i e n t to support even dry land farming, and hence i r r i g a t i o n i s widespread; i t i s estimated that from one h a l f to two t h i r d s of the i r r i g a b l e land i s already under c u l t i v a t i o n . - 11 -Geology and S o i l s A survey of the s u r f i c i a l geology of the area i s at present the (2) most d e t a i l e d d e s c r i p t i o n a v a i l a b l e . The rock u n d e r l y i n g the land sur-face of the N i c o l a V a l l e y v a r i e s widely i n type, from limestone d e r i v i n g from sedimentary and l a c u s t r i n e d e p o s i t s , to igneous i n t r u s i o n s of g r a n i t e and b a s a l t which outcrop i n many pl a c e s . These changes are r e f l e c t e d i n s i m i l a r v a r i a t i o n s i n s o i l type and surface water q u a l i t y w i t h i n the area. The s o i l s are g e n e r a l l y poorly developed due to the low p r e c i p i -t a t i o n , and are v a r i a b l e i n depth; they are estimated to f a l l i n t o the categories of 'medium' to 'marginal'^ i n s o f a r as t h e i r value to a g r i c u l t u r e i s concerned. Generally they are calcareous by nature, w i t h l o c a l i s e d areas of high sodium content; f o r a g r i c u l t u r a l purposes they are d e f i c i e n t i n Nitrogen and Phosphorus . A g r i c u l t u r e The major a g r i c u l t u r a l e n t e r p r i s e i s c a t t l e ranching, which i n turn r e q u i r e s the p r o v i s i o n of winter feed; t h i s i s grown as i r r i g a t e d a l f a l f a or grass hay during the summer. At present the l i m i t i n g f a c t o r i n the development of c a t t l e ranching i s g e n e r a l l y the a v a i l a b i l i t y of summer rangeland, but as the ind u s t r y becomes more i n t e n s i f i e d , i t w i l l be neces-sary f o r i r r i g a t i o n to develop at a comparable r a t e . The present average y i e l d of hay i s about 3 tons/acre, but i n c e r t a i n areas w i t h the use of f e r t i l i z e r s and good i r r i g a t i o n p r a c t i c e s , t h i s can be increased to 6-8 tons/acre. At present, f e r t i l i z e r s are not used u n i v e r s a l l y , but only on the b e t t e r s o i l s where a l f a l f a i s grown. - 12 -On the more poorly drained s o i l s of the v a l l e y bottoms a mixture of grass arid a l f a l f a i s found; however the present trend i s toward the growing of good crops of a l f a l f a on the more permeable s o i l s of the lower benchlands. I r r i g a t i o n a) Surface About 80 percent of a l l i r r i g a t i o n i n the N i c o l a V a l l e y i s c a r r i e d out by t r a d i t i o n a l surface methods, w h i l e the comparative f i g u r e fo r the western states of North America i s rat h e r h i g h e r . A crop i s watered at the beginning and end of the growing season, s h o r t l y a f t e r cuts have been taken, and o c c a s i o n a l l y at other times during the season. I r r i g a t i o n i s e f f e c t e d by o b s t r u c t i n g the flow at c o n t r o l s t r u c t u r e s i n the main convenance d i t c h which causes the water l e v e l to r i s e i n the channel upstream, to the point where i t flows through small box o u t l e t s i n t o a f i e l d . The a v a i l a b l e water may be i n s u f f i c i e n t f o r more than four o u t l e t s (at perhaps 30 yard i n t e r v a l s ) to be used at the same time; thus the i r r i g a t i o n of a f i e l d may be e f f e c t e d i n s e v e r a l stages over some length of time. A f t e r r e l e a s e from the d i t c h the water i s allowed to run f r e e l y over the surface of the f i e l d . To o b t a i n even d i s t r i b u t i o n the i r r i g a t o r cuts small channels on s i t e i n order to spread the water most e f f e c t i v e l y . The q u a n t i t y of water required to cover the whole f i e l d depends on the f i e l d s lope, i t s h y d r a u l i c roughness, the s o i l p e r m e a b i l i t y , and the ra t e of i n f l o w . I t i s o f t e n d i f f i c u l t to provide s u f f i c i e n t water to reach the bottom of a f i e l d of h i g h l y permeable benchland s o i l w h i l e avoiding - 13 -the hazard of surface e r o s i o n near the top of the f i e l d , and a l s o , i n the v a l l e y bottoms where drainage i s l i k e l y to be poor, to prevent waterlogged c o n d i t i o n s d i s a s t r o u s to a l f a l f a . Flood i r r i g a t i o n methods are dependent on the considerable judgment and s k i l l of the experienced operator, as e x e m p l i f i e d by one i r r i g a t o r ' s comment: " I know the smell of my ground when i t ' s wet." There are numerous v a r i a t i o n s on the method o u t l i n e d above, a promising one being the use of f l e x i b l e gated p i p i n g which as yet has gained only very l i m i t e d acceptance. b) Overhead In the N i c o l a area, i r r i g a t i o n by s p r i n k l e r has been mostly used to supplement surface methods, but i t s use i s i n c r e a s i n g and i n a few places i t i s now predominating; hand s e t s , wheelmoves, and high pressure ' r a i n guns' are a l l found. B e t t e r c o n t r o l i s obtained w i t h s p r i n k l e r s , since the ground surface i s too uneven to allow e f f i c i e n t use of f l o o d i r r i g a t i o n . Generally the crop y i e l d i s s l i g h t l y g r e a t e r , the man hours required to operate a s p r i n k l e r (8) system (hand seO are almost the same, but the i n s t a l l a t i o n and o v e r a l l running costs are higher than f o r f l o o d i r r i g a t i o n . Water L i c e n c i n g P r a c t i c e Present water l i c e n c e s a l l o w a crop use i n the N i c o l a V a l l e y of from 21 acre i n s . / a c r e to 60 acre i n s . / a c r e , w i t h an average value of 24" f o r the higher e l e v a t i o n s and 30" f o r the lower. These f i g u r e s are based on e m p i r i c a l determinations of crop water needs, the e a r l i e r of which have - 14 -remained unchanged f o r a century; c e r t a i n allowances such as the unique case of 60" appear to have no f i r m b a s i s . Conveyance losses between the point of d i v e r s i o n and the f i e l d of use may not exceed 10 percent per m i l e , up to a maximum value of 25 percent. As shown i n Chapter IV.2. these allowed losses were exceeded i n nearly a l l cases, measured . Any losses a r i s i n g from the a p p l i c a t i o n of i r r i g a t i o n water are included by the Water Rights Branch i n the above allowances; the Branch recognizes no d i f f e r e n c e between the water requirements of surface and overhead methods. v) Discus s ion The p r i n c i p a l causes of water wastage i n i r r i g a t i o n p r o j e c t s are losses due to i n e f f i c i e n t conveyance, and the p r a c t i c e of applying to crops a considerably greater q u a n t i t y than i s re q u i r e d f o r growth. I t has been suggested that b e t t e r use could be made of water i n i r r i g a t i o n by determining more e x a c t l y the poi n t at which water needs to be ap p l i e d w i t h i n an i r r i g a t i o n c y c l e , a n d i t has als o been shown that a f t e r a c e r t a i n value i s reached, increased seasonal water a p p l i c a t i o n w i l l not always s i g n i f i c a n t l y increase crop product i o n . Such observations are v a l u a b l e , but i t would be unwise to neglect the o v e r a l l water requirements which should include a c e r t a i n q u a n t i t y of drainage water needed to leach r e s i d u a l s a l t s from the system. This drainage water may be a p p l i e d as an a d d i t i o n to consumptive use requirements at each i r r i g a t i o n , or i t may be added at l e s s frequent i n t e r v a l s . Which-ever i s the case, s u f f i c i e n t should be added to ensure e f f e c t i v e leaching of any s a l t accumulation, bearing i n mind that the consumptive use r e q u i r e -ment may not be i n any way reduced, f o r t h i s may cause 'mining' of the drainage water to support f u r t h e r crop e v a p o t r a n s p i r a t i o n . The long term neglect of the above f a c t o r s i s witnessed i n many thousands of barren acres of the United S t a t e s . To determine seasonal water requirements t h i s study should i d e a l l y consider i r r i g a t i o n requirements based on the r i s k of occurrence of a cumulative seasonal e v a p o t r a n s p i r a t i o n of a p a r t i c u l a r magnitude, w i t h p r e c i p i t a t i o n s i m i l a r l y i n c l u d e d . The water l i c e n s e d f o r use would then be based on a s p e c i f i c r i s k f a c t o r . The c o l l e c t i o n of the necessary data i n B r i t i s h Columbia i s g e n e r a l l y of too short record to make any r i s k a n a l y s i s , and acc o r d i n g l y c e r t a i n assumptions are made i n t h i s study, which i n areas of a more s o p h i s t i c a t e d technology would be regarded as somewhat (3) a r b i t r a r y . Due to t h i s lack of s o p h i s t i c a t i o n , techniques f o r determining accurate scheduling of i r r i g a t i o n s are l i m i t e d i n p r a c t i c e , the lack of equipment and manpower circumscribes a rancher's a b i l i t y to i r r i g a t e except w i t h i n a c e r t a i n c y c l e , and the areas of e f f e c t i v e a p p l i c a t i o n of such techniques are r e s t r i c t e d . In the N i c o l a V a l l e y these techniques may only cause an adjustment of computed water requirements of the order of inches, w h i l e present management p r a c t i c e s may u n w i t t i n g l y give a departure of the order of f e e t . - 16 -The question of preventing water wastage i n th i s area is as much one of enlightened p r a c t i c a l a p p l i c a t i o n , as one of theory, as expressed by a Greek i r r i g a t i o n i s t : " W h a t ' s the use of knowing exactly the true needs of plants for water when we apply to the lands wastefully and harm-f u l l y much more." This study is an attempt to gain a better understanding of the problem involved, with regard to both the p r a c t i c a l and t h e o r e t i c a l aspects. v i ) Summary I r r i g a t i o n has been practiced in B r i t i s h Columbia for over one hundred years, since the development of ranching in the Nicola area, and winter feed for c a t t l e i s grown with the aid of i r r i g a t i o n i n the hot, dry summers. The predominant crop is a l f a l f a with a r e l a t i v e l y low market value, which requires water c o n s t i t u t i n g 95 percent of the licensed supply i n the area. The amount of water used by a crop i s independent of the method of water a p p l i c a t i o n used, but the amount of water applied i s highly dependent on the delivery system. Considered i n this paper are both the t h e o r e t i c a l water requirements of a crop, and also c e r t a i n p r a c t i c a l considerations concerning the f i e l d a p p l i c a t i o n of water. CHAPTER I I I THE VARIABLES DETERMINING IRRIGATION REQUIREMENTS i 1. CONSUMPTIVE USE i ) Water i n the S o i l Above the water t a b l e , s o i l moisture i s h e l d i n suspension by hygroscopic a t t r a c t i o n to the s o i l p a r t i c l e s , by surface t e n s i o n between grains w i t h i n the small pores, and by the osmotic e f f e c t s of r e s i d u a l s a l t s ; the amount of t h i s C a p i l l a r y Moisture i s determined p r i m a r i l y by the g r a i n s i z e of the s o i l . A s o i l , which a f t e r s a t u r a t i o n i s allowed to become drained by g r a v i t a t i o n a l f o r c e s - - g e n e r a l l y taken as three days i n the f i e l d - - i s s a i d to be at F i e l d Capacity ( F . C ) , t h i s v a l u e , which depends on the type and depth of the s o i l , being measured i n inches of water w i t h i n the root zone. Movement of water from the s o i l i n to the c e l l s of plant roots i s governed by the p o t e n t i a l energy gradient between the s o i l water and the s o l u t i o n w i t h i n the c e l l s ; the gradient i t s e l f i s determined mainly by the osmotic s u c t i o n exerted by the c e l l s and by the surface t e n s i o n force due to s o i l g r a i n s . As the water supply diminishes due to p l a n t use, i n c r e a s i n g s u c t i o n i s required to e x t r a c t i t , u n t i l at some stage the energy gradient becomes i n s u f f i c i e n t to maintain the minimum flow of water required to keep the p l a n t a l i v e . This s t a t e , which develops at a t e n s i o n of about 15 atmos-pheres and at which crops d i e i s denoted the Permanent W i l t i n g Point (P.W.P.). - 18 -the value again measured i n inches of water, v a r y i n g w i t h the type of p l a n t . Between the F i e l d Capacity and the W i l t i n g Point l i e s a range of moisture contents at which plants can ab s t r a c t moisture from the s o i l , and t h i s i s r e f e r r e d to as the A v a i l a b l e Water Storage Capacity (A.W.S.C.) or Water Holding Capacity (W.H.C.) of the s o i l , governed by the r o o t i n g depth and type of s o i l : t h i s can vary from 3 percent by volume i n sand to 65 percent i n peat, but i n i r r i g a t e d s o i l s the usual value i s about 5-20 percent. The A v a i l a b l e Water Storage Capacity includes only that water which i s w i t h i n reach of the root zone, and i s there f o r e of p r a c t i c a l use. The root zorie - ' iof grass hay l i e s w i t h i n the top 12"-18" of the s o i l , but a legume such as a l f a l f a , w h i l e having i t s main roots w i t h i n the top 18" a l s o has deeper tap r o o t s . These give an o v e r a l l r o o t i n g depth of 3'-4', thus considerably i n c r e a s i n g the A.W.S.C. of the s o i l . A f u r t h e r c o n s t r a i n t i s supplied by the s o i l p r o f i l e i t s e l f , s ince i t i s not p o s s i b l e to compute the o v e r a l l A.W.S.C. by an a r i t h m e t i c summation of each l a y e r . A base m a t e r i a l of sandy g r a v e l o v e r l a i n by a loam s o i l four f e e t t h i c k may make f o r good i r r i g a t i o n but i f a shallow c l a y hardpan l a y e r i s found at a depth of two f e e t , not only i s the A.W.S.C. reduced by 50 percent but also drainage and s a l i n i t y problems are l i k e l y to r e s u l t . The s o i l p r o f i l e as a whole must be taken i n t o account when est i m a t i n g the • A.W.S.C., and estimates are best made by those experienced i n i r r i g a t i o n a g r i c u l t u r e . ' - 19 -i i ) Water Transpired and Evaporated During the bu i l d i n g of t i s s u e , a plant extracts water from the ground which i t then transpires to the atmosphere by way of i t s leaves; also, a small amount of evaporation of free water takes place d i r e c t l y from the ground surface i n the immediate proximity of the plant, and from the plant surface. These two means of water consumption are together referred to a Evapotranspiration (E-T) . The main atmospheric factors a f f e c t i n g evapotranspiration are Radiant Energy, Wind V e l o c i t y , Humidity, and Atmospheric Pressure, while the s i g n i f i c a n t s o i l factors are S o i l Temperature, and S o i l Moisture when thi s decreases below a c e r t a i n l e v e l . Measurements of temperature ( i . e . the degree-day approach) are often used to give an estimate of the integrated e f f e c t s of these v a r i a b l e s , and i t has also been found that temperature can be correlated with radiant (34) energy, the most important of these. A d d i t i o n a l features are provided by the plant i t s e l f . Pores on both sides of a leaf surface, referred to as stomata, vary both i n number and in c h a r a c t e r i s t i c for a l l types of crop, and t r a n s p i r a t i o n therefore depends also on the crop under consideration, being governed by stomatal response. Potential Evapotranspiration i s the maximum vapour f l u x from a sur-face which can occur under given c l i m a t i c conditions. The term p o t e n t i a l evapotranspiration (P.E.T.) includes the combined e f f e c t of plant trans-p i r a t i o n and surface evaporation; i t can only occur when water i s r e a d i l y a v a i l a b l e to plant roots, when the whole surface tends toward a 'wet - 20 -s u r f a c e . ' At any stage of growth t h e r e a f t e r , when s o i l moisture has neces-s a r i l y been decreased by t r a n s p i r a t i o n , f u r t h e r water i s e x t r a c t e d l e s s r e a d i l y by the r o o t s , and the a c t u a l e v a p o t r a n s p i r a t i o n f a l l s i n some degree below the p o t e n t i a l r a t e . The decrease i n s o i l moisture, i n t e g r a t e d throughout the root zone, i s r e f e r r e d to as the S o i l Moisture D e f i c i t . To what extent the r a t e of e v a p o t r a n s p i r a t i o n i s dependent on the • i • , , f. , , , . , f (20, 26, 29, 30, 32) s o i l moisture d e f i c i t has been a subject of controversy: experiments have shown that between f i e l d c a p a c i t y and permanent w i l t i n g p oint these two are l i n e a r l y r e l a t e d ; s i m i l a r l y , i t has been shown that e v a p o t r a n s p i r a t i o n remains r e l a t i v e l y constant u n t i l c l o s e to the permanent w i l t i n g p o i n t , when i t f a l l s away sh a r p l y . The type of s o i l a f f e c t s t h i s r e l a t i o n s h i p , and i t i s now g e n e r a l l y considered t h a t , above a c e r t a i n s o i l moisture content, p o t e n t i a l e v a p o t r a n s p i r a t i o n i s the l i m i t i n g f a c t o r , w h i l e below t h i s point the a v a i l a b i l i t y of water to the plant becomes l i m i t i n g . In p r a c t i c e i n Canada, a l i n e a r r e l a t i o n s h i p i s used under the A g r i c u l t u r a l R e h a b i l i t a t i o n and Development Act (A.R.D.A.) f o r the scheduling of i r r i g a t i o n s . i i i ) Scheduling The e x e r c i s e of determining how o f t e n i r r i g a t i o n water should be a p p l i e d , and the amount of water required at each a p p l i c a t i o n i s r e f e r r e d to as Scheduling. A crop i s best i r r i g a t e d when the d e f i c i t of the A.W.S.C. becomes 40 percent; the amount of water a p p l i e d should be enough to b r i n g t h i s - 21 -up to F i e l d Capacity. Since the f l u c t u a t i o n of a v a i l a b l e water i s u s u a l l y w i t h i n t h i s 40 percent, s o i l s are designated f o r i r r i g a t i o n purposes on t h i s b a s i s by A.R.D.A. Thus a '1" s o i l ' i s one r e q u i r i n g an a p p l i c a t i o n of 1" of water at each i r r i g a t i o n - - t h a t i s , having an A.W.S.C. of 2%". Methods of schedu-(21) l i n g are f u l l y o u t l i n e d i n the B.C. I r r i g a t i o n Guide, and f u r t h e r comments would be out of place here. i v ) Methods of Es t i m a t i n g E v a p o t r a n s p i r a t i o n ( r e f e r r e d to as E-T) In order to determine seasonal crop water needs, a means of measuring or e s t i m a t i n g seasonal e v a p o t r a n s p i r a t i o n i s necessary. The most d i r e c t method of measurement i s by l y s i m e t e r , but i t i s a slow and labo r i o u s process. A l y s i m e t e r i s a c y l i n d r i c a l can, two or more fe e t i n diameter and perhaps two feet deep, i n which p l a n t s are grown under simulated n a t u r a l c o n d i t i o n s . The can and contents are weighed at (33) r e g u l a r i n t e r v a l s to determine water loss by e v a p o t r a n s p i r a t i o n . This means of measuring the cumulative seasonal water d e f i c i t (or r e q u i r e -ment) can be the most accurate, but such data are not g e n e r a l l y a v a i l a b l e i n B r i t i s h Columbia. However, lys i m e t e r data have been used as a basis by the s e v e r a l i n v e s t i g a t o r s i n various parts of the world who have (25) derived formulae f o r e s t i m a t i n g E-T from c l i m a t o l o g i c a l data. Solar r a d i a t i o n i s the main source of energy f o r pl a n t growth, and t h i s i s taken i n t o account by most formulae i n the form of temperature, e i t h e r as a simple degree-day approach, or as a means to e s t a b l i s h a heat - 22 -index f o r a given s t a t i o n . Other m o d i f i c a t i o n s i n c l u d e c o r r e c t i o n f a c t o r s f o r the monthly percentage of daytime hours, f o r humidity, and f o r crop c o e f f i c i e n t s . (29) Since crop growth can be measured i n terms of e v a p o t r a n s p i r a t i o n , and since there appears to be no general agreement on the best method f o r es t i m a t i n g e v a p o t r a n s p i r a t i o n during a season, seven d i f f e r e n t methods of e s t i m a t i o n were ap p l i e d to the cumulative E-T at M e r r i t t , f o r the p a r t i c u -l a r l y hot summer of 1967, i n a l l cases t a k i n g the growing season as A p r i l 15th - September 30th (Table I I ) . The choice of these comparative methods (22) was governed by the a v a i l a b i l i t y of the data necessary f o r each. Each method of e s t i m a t i o n has been derived under c e r t a i n c l i m a t i c c o n d i t i o n s and i s based on an e m p i r i c a l r e l a t i o n s h i p which makes use of s p e c i f i c data. The formula used by each i s set out i n Table I ; d e t a i l s and governing c o n d i t i o n s are given more f u l l y inC; . The m a j o r i t y have been developed i n the a r i d South West of the United S t a t e s , which was considered to have not g r e a t l y d i f f e r e n t c l i m a t i c c o n d i t i o n s to those of the I n t e r i o r of B r i t i s h Columbia. Depending on the emphasis placed on the c r i t i c a l c l i m a t i c v a r i a b l e s by each formula, and on the r e l i a b i l i t y of t r a n s p o s i t i o n of crop c o e f f i c i e n t s from one region to another, each method w i l l have more or l e s s v a l i d i t y i f transposed from the United States to B r i t i s h Columbia. The crop c o e f f i c i e n t s i n most formulae have been derived from c o r r e l a t i o n w i t h crop behaviour under a c t u a l i r r i g a t i o n p r a c t i c e , and th e r e f o r e the formulae g e n e r a l l y p e r t a i n to a c t u a l E-T i n the f i e l d . - 23 -The c o e f f i c i e n t s themselves, depending on the type of crop grown and i t s (27) stage of maturity vary considerably throughout the season, but an average value i s considered adequate f o r the computation of seasonal water needs. The estimates were made f o r a l f a l f a , i n a l l cases s t a k i n g o ( 23) a minimum growing temperature of 42 F; i n the case of the Hedke method an a d d i t i o n a l estimate was made usin g a temperature of 32°F. Comparative estimates of seasonal E-T have a l s o been made f o r Davis i n ' C a l i f o r n i a i n 1955; i n t h i s case four out of the.seven e m p i r i c a l methods ' (31 28) used at M e r r i t t i n 1967 were al s o used at Davis. ' Ogopogo carborum-(35) dum block evaporimeters were used at M e r r i t t and a p a i r of black and (28) white atmometers at Davis, the r e s u l t s given by each of which may be t e n t a t i v e l y compared, s i n c e they operate on s i m i l a r p r i n c i p l e s : i n addi-t i o n , records were kept at Davis of the cumulative s o i l moisture d e f i c i t . Assuming the c l i m a t i c c o n d i t i o n s at each place to be r e l a t i v e l y s i m i l a r , the r e s p e c t i v e estimates of E-T at Davis and M e r r i t t were p l o t t e d against each other to o b t a i n any marked discrepancy ( F i g . 1). Aside from Munson's method, which was developed f o r the M i s s o u r i River Basin and western Iowa, the r e s u l t s show the atmometers/evaporimeter to give the highest estimate i n each case, followed again i n each case by the Blaney-C r i d d l e method (Table I I , and F i g . 1). The t o t a l s o i l moisture d e f i c i t at Davis amounted to 34.4", w i t h the atmometers r e c o r d i n g 34.7" of E-T. This c l o s e agreement was als o shown i n the other crops, i n d i c a t i n g that i n general the atmometer at Davis gave s a t i s f a c t o r y r e s u l t s . I t i s i n f e r r e d that the Ogopogo evapori-meter at M e r r i t t gave s i m i l a r l y s a t i s f a c t o r y r e s u l t s . - 24 -The Ogopogo evaporimeter, developed i n 1964 by Dr. J . C. Wilcox, i s constructed as f o l l o w s : a c y l i n d r i c a l carborundum block of about 2" diameter i s i n s e r t e d i n t o a polythene sleeve which i s connected by tubing to a r e s e r v o i r c o n t a i n i n g water and methanol; t h i s ensures a continuous supply of l i q u i d to the exposed end face of the b l o c k , thus a l l o w i n g evaporation to occur, which i s measured from the corresponding f a l l of the water l e v e l i n the r e s e r v o i r . The exposed face i s d i r e c t e d upward, and i s protected from r a i n by a glass s h i e l d placed 3" above i t . The a c t u a l e v a p o t r a n s p i r a t i o n from crops i n the f i e l d i s l i n e a r l y r e l a t e d to evaporation, as measured by t h i s evaporimeter, by an e m p i r i c a l f a c t o r which has been derived from f i e l d experience i n the Okanagan. Wit h i n an i r r i g a t e d area surrounded by dry land p r a c t i c e s appreciable d i f f e r e n c e s i n readings are caused by v a r i a t i o n s i n advected energy; to o b t a i n r e l i a b l e readings the s i t i n g of the instrument must ther e f o r e be standardised w i t h i n each r e g i o n of use. There i s no published c o r r e l a t i o n of Ogopogo w i t h l y s i m e t e r data. However, very high c o r r e l a t i o n s have been found by Wilcox i n the Okanagan between black b e l l a n i p l a t e evaporimeters and ly s i m e t e r data and s i m i l a r l y between black b e l l a n i p l a t e s and Ogopogo evaporimeters, thus suggesting a correspondingly high c o r r e l a t i o n between a c t u a l e v a p o t r a n s p i r a t i o n and (36) evaporimeter data. In 1967, f i v e d i f f e r e n t B e l l a n i type atmometers were f i e l d t ested (24) i n p a i r s . Each design s a t i s f i e d the ten b a s i c requirements f o r a p r a c t i c a l atmometer, but f a i l e d to s a t i s f y a l l of ten secondary r e q u i s i t e s of a t e c h n i c a l nature; however, the Ogopogo evaporimeter met a l l except - 25 -one, that being the n e c e s s i t y f o r the use of a c o r r e c t i o n f a c t o r f o r methanol mix. I t has been shown by comparison w i t h Bowen Ra t i o Techniques that t h i s evaporimeter overestimates e v a p o t r a n s p i r a t i o n on c e r t a i n days, and ( c,\ underestimates on o t h e r s . However, i t has been used s a t i s f a c t o r i l y at many s i t e s i n B r i t i s h Columbia since 1965, e s p e c i a l l y over a time period of a week or longer, and f u r t h e r estimates i n t h i s study make use of t h i s method to determine seasonal water requirements. v) Summary The water a v a i l a b l e i n the s o i l f o r p l a n t use i s c a l l e d the A v a i l a b l e Water Storage Capacity, the upper and lower l i m i t s of t h i s being set by the F i e l d Capacity and the Permanent W i l t i n g Point r e s p e c t i v e l y . E v a p o t r a n s p i r a t i o n i s governed by c l i m a t i c f a c t o r s , and by the p h y s i c a l p r o p e r t i e s of the p l a n t s and s o i l . Apart from d i r e c t measurements of e v a p o t r a n s p i r a t i o n by means of l y s i m e t e r s , a time consuming process, there are s e v e r a l e s t i m a t i n g methods a v a i l a b l e . Seven of these methods were a p p l i e d to M e r r i t t f o r the hot, dry summer of 1967, and i t was found that the highest estimate was given by Ogopogo carborundum block evaporimeter. A s i m i l a r comparison between methods was made at Davis, C a l i f o r n i a , i n 1955, where the highest estimates were found to be given by atmometers. In that experiment cumulative s o i l moisture d e f i c i t was a l s o recorded as - 26 -an independent check, and t h i s indicated the atmometer estimate to be accurate within 1 percent. By inference, the Ogopogo evaporimeter, a type of atmometer developed for use in the I n t e r i o r of B r i t i s h Columbia, i s also taken as giving a s a t i s f a c t o r y record of evapotranspiration. Data from t h i s i n s t r u -ment were used for a l l subsequent estimates of evapotranspiration made in thi s study. - 27 -TABLE I EVAPOTRANSPIRATION EQUATIONS NAME DATE ' PERIOD FOR U UNIT FOR T EQUATION ( i ) Hedke 1930 Annual Feet U= kH ( i i ) Lowry-Johnson 1942 Annual Feet U = 0.000156H + 0.8 ( i i i ) Thornthwaite 1944 Monthly Cm. U = 1.6 '10t, a TE ' where a = 0.000000675 (TE)3„ - 0.0000771 (TE) + 0.01792 TE + 0.4924 ( i v ) B l aney-Criddle 1950 m months Inches m U = k £ p t = kF I m where F = ^ ~ pt i (v) Hargreaves 1956 m months Inches U = kd(0.38 - 0.0038 h) x (t-32) ( v i ) ( 3 1> Munson 1962 m months Inches Use of mean temp, P.E. index, and t a b l e s . NOTATION monthly daytime c o e f f i c i e n t dependent upon l a t i t u d e , mean monthly r e l a t i v e humidity at noon. accumulated degree-days above minimum growing temperature f o r growing season, i n ( i ) ; or accumulated degree-days of maximum d a i l y temperature above 32°F f o r growing season, i n ( i i ) . annual, seasonal, or monthly consumptive-use c o e f f i c i e n t . percent of daytime hours of the year, o c c u r r i n g during the p e r i o d , d i v i d e d by 100. Thornthwaite's t e m p e r a t u r e - e f f i c i e n c y index, being equal to the sum of 12 monthly values of the heat index i = ( t / 5 ) ^ * ^ , where t i s mean monthly temp, i n °C. mean monthly temperature i n °F, i n ( i v ) , ( v ) ; or i n °C i n ( i i i ) . • e v a p o t r a n s p i r a t i o n of consumptive use f o r given p e r i o d . - 28 -TABLE I I SEASONAL E-T OF ALFALFA AT MERRITT, B.C., AND AT DAVIS, CALIFORNIA, AS ESTIMATED BY DIFFERENT METHODS AUTHOR DATE OF DERIVATION E-T IN INCHES AT MERRITT, B.C. 1967 15th Apr.-30th Sept. E-T IN INCHES AT DAVIS, CAL. 1955 Hedke (42°F.rain) 1924 Munson 1962 Hargreaves 1956 Lowry-Johnson 1942 Hedke (32°F.min) 1924 Thornthwaite 1944 Blan e y - C r i d d l e 1950 Atometers Ogopogo Evaporimeter S o i l Moisture 15.1 19 .7 22.6 23.2 23.7 25.1 28.3 30.5 36.5 24.0 23.4 31.0 34.7 34.4 - 29 -C O M P A R I S O N OF T H E E V A P O T R A N S P I R A T I O N OF A L F A L F A  AT D A V I S C A L I F O R N I A 1 9 5 5 , AND AT  M E R R I T T , B . C . 1 9 6 7 . 40 30 O ro LU co I f 20 in a. < 10 10 20 E - T AT M E R R I T T , B . C . 1967 - ins. (APRIL 15th - SEPT .30th) o 5. / /* / / / / / / / / / / / / / / / / / / / / 1. EVAPORIMETER 2. BLANEY - CRI C 3. THORNTHWAIT 4. L0 WRY - JOHNS 5. MUNSON -ATMOMETERS IDLE E >0N 30 34 F I G U R E I . - 30 -2. DRAINAGE REQUIREMENT i ) General To maintain good crop y i e l d s under i r r i g a t i o n i t i s e s s e n t i a l that excess water and s a l t s e n t e r i n g the s o i l be allowed to d r a i n to a depth below the root zone. Good drainage must be ensured so that crops do not become waterlogged or s a l t s accumulate w i t h i n the root zone. There are few, i f any, i r r i g a t e d areas of the world where i n s u f f i c i e n t drainage has not led to s a l i n i t y problems i n some degree; e a r l y c i v i l i z a t i o n s along the Euphrates r i v e r are b e l i e v e d to have c o l l a p s e d from t h i s reason, and thousands of acres i n the south-western United States have been rendered unusable by inadequate management. Where n a t u r a l drainage i s i n s u f f i c i e n t to remove excess water, t i l e d rains should be i n s t a l l e d . A l l waters whether derived from w e l l s , springs or streams, carry d i s s o l v e d s a l t s i n s o l u t i o n . The amount and type of these s a l t s vary g r e a t l y from place to p l a c e , source to source, and a l s o from time to time. Measurements taken i n the i n t e r i o r of B.C. show that concentrations of (46) t o t a l s a l t s i n d i f f e r e n t i r r i g a t i o n waters can vary by a f a c t o r of ten. However, the problem of converting such measurements in t o u s e f u l i n f o r m a t i o n i n terms of crop y i e l d s and most e f f e c t i v e water use does not appear to. have been adequately covered i n B r i t i s h Columbia, and c e r t a i n l y not i n the N i c o l a area. - 31 -Since i t was apparent that the presence of excess s a l t s i n the form of both 'white a l k a l a ' and 'black a l k a l i ' was not at a l l uncommon i n c e r t a i n parts of the N i c o l a V a l l e y , i t was considered that i n a study concerned w i t h o v e r a l l i r r i g a t i o n requirements t h i s aspect should be f u l l y i n v e s t i -gated . i i ) Theory of I r r i g a t i o n Drainage A f t e r the a p p l i c a t i o n of an i r r i g a t i o n , the water percolates through the s o i l and i s u t i l i z e d 'en r o u t e 1 by the crops, together w i t h a small percentage of i t s c o n s t i t u e n t s a l t s ; the greater the depth of p e r c o l a t i o n , the more concentrated becomes t h i s s a l t s o l u t i o n . As i t s s o l u b i l i t y product i s reached, each s a l t p r e c i p i t a t e s out of s o l u t i o n . Thus a c c r e t i o n s are formed i n the s o i l , o f t e n w i t h Calcium Carbonate found higher than any other s a l t , followed by Calcium Sulphate, w h i l e the more s o l u b l e ions, Sodium and C h l o r i d e , are washed to greater depth, perhaps below the root zone. As t h i s s a l t s o l u t i o n increases i n concentration w i t h depth, so the osmotic tension r i s e s and the W i l t i n g Point i s more q u i c k l y reached. To prevent t h i s o c c u r r i n g , excess water over and above the Consumptive Use requirement must be provided to act as drainage beyond the root zone. This Leaching, or Drainage Requirement depends on the q u a l i t y of the i r r i g a t i o n water used and on the maximum s a l i n i t y value allowed i n the s o i l . - 32 -i i i ) Ions i n I r r i g a t i o n Water Of the ions found i n i r r i g a t i o n waters, very small amounts of C h l o r i d e and Sulphate are required f o r plant growth; above t h i s l e v e l they have t o x i c e f f e c t s . Also required are greater amounts of Potassium, Calcium, Magnesium and N i t r a t e ; however the a c t u a l q u a n t i t y of these ions o c c u r r i n g n a t u r a l l y i n water i s always i n excess of requirements. Sodium, Carbonate, and Bicarbonate ions appear to have no d i r e c t b e n e f i t to growth; sodium ions i n p a r t i c u l a r c o n s t i t u t e a s p e c i a l hazard since they can b r i n g about the d e s t r u c t i o n of p a r t i c l e aggregates and form a c o l l o i d a l suspension with c l a y , thus g r e a t l y reducing the s o i l permeability and minimizing the e f f e c t s of any drainage. Notably, i f the s o i l water contains carbonate and bicarbonate i n excess of the calcium and magnesium present, sodium carbonate may be formed which d i s s o l v e s organic matter, thus blackening the soil--hence the term 'black a l k a l i 1 . The p o t e n t i a l (42) danger from sodium carbonate i s measured as Residual Carbonate, and such s o i l s are known as A l k a l i n e , or S o d i u m - a l k a l i s o i l s . Calcium does not have a d e l e t e r i o u s e f f e c t unless i n excess p r o p o r t i o n . I t i s the replacement of t h i s ion i n the s o i l s o l u t i o n by sodium that brings about the above changes i n s o i l p r o p e r t i e s . 'White a l k a l i ' i s the term d e s c r i b i n g surface s a l t d e p o s i t s ; these are o f t e n c a l -careous i n nature, and may be removed by adequate l e a c h i n g . S o i l s a f f e c t e d by such deposits are r e f e r r e d to as S a l i n e . Magnesium i s g e n e r a l l y regarded as a c t i n g i n the same manner as calcium; although i t i s reported that i n places i t s a c t i o n on the s o i l i s s i m i l a r to that of sodium. - 33 -The r a t i o of sodium present can be measured as Exchangeable Sodium  Percentage (E .S .P . ) , Sodium Adsorption Ration (S.A.R.), or Sodium Percen-tage (Na.%). Of the other t o x i c i o n s , Chlorides appear to be about twice as t o x i c (41) as Sulphates, and s o i l s a l i n i t y i s measured by Eaton i n terms of these two. (43) i v ) Drainage Requirement by Chemical A n a l y s i s Assuming that the land under c o n s i d e r a t i o n does not have an excess of any s p e c i f i c i o n , then the drainage requirement can be derived from an a n a l y s i s of the i r r i g a t i o n water, which should include the presence of Sodium, Calcium, Magnesium, C h l o r i d e , Sulphate and Bicarbonate i o n s , g e n e r a l l y expressed as m i l l i e q u i v a l e n t s per l i t r e (meq/1). Since the concentration of sodium and bicarbonate r e l a t i v e to calcium and magnesium i n i r r i g a t i o n waters i s e s p e c i a l l y s i g n i f i c a n t w i t h respect to s o i l p e r m e a b i l i t y and a l k a l i n i t y , any e s t i m a t i o n of the drainage r e q u i r e -ments should include an allowance based on the a d d i t i o n a l calcium required both to o f f s e t the d e l e t e r i o u s e f f e c t of the above io n s , and a l s o to make up the d e f i c i e n c y of calcium due to plant uptake. In a d d i t i o n to an e s t i m a t i o n of drainage percentage, the formulae below were designed to: a) Adjust the Sodium Percentage of the water to 70 percent. (60 - 70 percent i s g e n e r a l l y regarded as being the s a f e t y l e v e l ) b) Offset Bicarbonate p r e c i p i t a t i o n c) Supply the calcium needs of p l a n t s . - 34 -i v ) 1. Required Drainage ( t e n t a t i v e ) 100S d% = w 80-S w where S = s a l i n i t y of i r r i g a t i o n water expressed as C l + %S0. (meq/1) w 4 ( i . e . the summation of the c h l o r i d e and h a l f the sulphate present.) d% = t e n t a t i v e percentage of i r r i g a t i o n water e n t e r i n g the s o i l and passing through the root zone. i v ) 2. Calcium Requirement a) To adjust water to 70 percent sodium: Ca(a) = Na x 0.429 - (Ca + Mg) (meq/1) The plus or minus s i g n to be r e t a i n e d . b) To o f f s e t HCO^ p r e c i p i t a t i o n : Ca(b) = HC0 o x (100 - d%) , ... 3 (meq/1) 100 c) To supply calcium and magnesium taken by plants i n excess of sodium: Ca(c) = 0.30 x (100 - d%) , . Too ( m e q / 1 ) T o t a l calcium r e q u i r e d : Ca = Ca(a) + Ca(b) + Ca(c) (meq/1) This t o t a l m u l t i p l i e d by 234, gives the amount of gypsum (calcium sulphate, Ca SO^^H^O) which should be added i n pounds per acre-foot of i r r i g a t i o n water, i v ) 3. Required D r a i n a g e - - f i n a l With the a d d i t i o n of gypsum as given, the amount of added sulphate i s the same as calcium; t h i s amount must be added i n the drainage equation to o b t a i n the t o t a l sulphate. (S + % t o t a l Ca) x 100 • D/o = w  80 - (S + h t o t a l Ca) w where D7o i s the f i n a l percentage of the i r r i g a t i o n water e n t e r i n g the s o i l and passing through the root zone, and S and Ca are expressed as meq/1. - 35 -(5)1) v) Drainage Requirement by T o t a l S a l i n i t y The method of e s t i m a t i o n o u t l i n e d above makes f u l l allowance f o r any sodium hazard, and shows when i t i s necessary to add gypsum i n order to counteract t h i s hazard. However the values obtained from i t f o r drainage percentages are g e n e r a l l y low since the method does not account f o r the e f f e c t on crop growth of the t o t a l s a l t content of the i r r i g a t i o n water. A l s o , the method i s l a b o r i o u s , i n respect of the chemical analyses r e q u i r e d . I t i s g e n e r a l l y s u f f i c i e n t to base r e s u l t s on the o v e r a l l s a l i n i t y -(.in meq/1) of the s o i l water i n the root zone, regardless of the types of s a l t i n v o l v e d . Since the s a l i n i t y shows a p o s i t i v e l i n e a r increase w i t h the E l e c t r i c a l C o n d u c t i v i t y (E.C.) of any water, t h i s l a t t e r parameter i s a widely used measurement of s a l t determination. Measurement of the e l e c -t r i c a l c o n d u c t i v i t y of an i r r i g a t i o n water (E.C.^) i s r a p i d l y and con-v e n i e n t l y c a r r i e d out ' i n s i t u ' . I f a s o i l i s i r r i g a t e d w i t h water using a constant drainage percen-tage, an e q u i l i b r i u m i s u l t i m a t e l y set up between the incoming and the outgoing s a l t s to and from the system, the c o n c e n t r a t i o n of s a l t s i n the drainage water being dependent upon the percentage used. Conversely, i f the s a l i n i t y l e v e l i n the root zone i s not to exceed a s p e c i f i e d maximum va l u e , then assuming the presence of such a s a l t balance, the required J . , . . (52, 54) drainage percentage can be determined. Assuming the f o l l o w i n g c o n d i t i o n s apply: uniform a p p l i c a t i o n of i r r i g a t i o n water, no r a i n f a l l , no removal of s a l t i n the harvested crop, and - 36 -no p r e c i p i t a t i o n of s o l u b l e s a l t s i n the s o i l , then V. x C. = V, x C, 1 1 d d where V. = volume of i r r i g a t i o n water used, expressed as depth. V, = volume of drainage water used, d C, = allowable s a l i n i t y of drainage water, d and since Drainage Requirement (D.R.) i s defined as v7 1 then D.R. = C. l C d Using E.C. as a measure of s a l i n i t y D.R. = E.C.. where E.C.. i s the c o n d u c t i v i t y of the i r r i g a t i o n water i n millimhos per centimetre (mmhos/cm), taken as a mean value over the i r r i g a t i o n p e r i o d . E.C., i s the maximum s a l i n i t y allowed i n the root zone, taken i n t h i s study as 5 mmhos/cm ( i . e . C o n d u c t i v i t y of s a t u r a t i o n e x t r a c t ) . Then f i n a l l y , the Drainage Requirement f o r a l f a l f a i s given by: E - C - i n 7 E.C. — , or D/o = l b 0.05 v i ) Notes on Methods Outlined The second of the two methods o u t l i n e d f o r the determination of the drainage requirement-was given by the U.S. S a l i n i t y Laboratory S t a f f i n Handbook 6 0 , a n d i s used i n most s a l i n i t y work; the f i r s t method was (43) published s h o r t l y afterwards by F.J M. Eaton, an experienced worker i n t h i s f i e l d . - 37 -Eaton assumes a p a r t i c u l a r l e v e l of crop y i e l d i n the formulae given, but also suggests c e r t a i n adjustments to be made i f a d i f f e r e n t l e v e l i s d e s i r e d . The method of determination by t o t a l s a l i n i t y a n t i c i p a t e s a s p e c i f i c l e v e l of crop y i e l d at each value given by the c o n d u c t i v i t y of the satura-t i o n e x t r a c t of the s o i l . R e l a t i v e y i e l d i s determined by c u t t i n g , and weighing dry, the crop grown, .and by expressing t h i s as a percentage of the value obtained when the s a t u r a t i o n e x t r a c t i s of zero c o n d u c t i v i t y . Except f o r the very t o l e r a n t crops, most plants show progressive d e c l i n e i n growth and y i e l d w i t h i n c r e a s i n g s a l i n i t y . a) Choice of 5 mmhos/cm f o r E.C., a A l f a l f a , a moderately s a l t t o l e r a n t crop, has been found to y i e l d at 80 percent f o r an E.C.^ of 4 mmhos/cm and 60 percent for 6.mmhos/cm, under optimum conditions of seed v a r i e t y , i n s e c t , disease, and weed c o n t r o l , and (45) soil,;and water management. However, very l i t t l e r e l i a b l e i nformation i s a v a i l a b l e on the r e l a t i o n s h i p between pla n t growth and s a l i n i t y l e v e l s where other f a c t o r s , such as f e r t i l i t y , may be l i m i t i n g . At a l e v e l of 8 mmhos/cm, a l f a l f a germinates at a r a t e of about 50 (51) percent, which i s increased to 70 percent at 6 mmhos/cm. However, i t may be noted that the c o n d u c t i v i t y of water d r a i n i n g from the s o i l p r o f i l e i s l i k e l y to be higher than that at the surface where germination occurs, s i n c e s a l t s from the i r r i g a t i o n water g e n e r a l l y remain i n s o l u t i o n near the surface and there f o r e penetrate to greater depth. Since t h i s study i s concerned w i t h drainage water r a t h e r than surface water, the c r i t e r i o n f o r - 38 -germination would appear to be of doub t f u l importance. In c o n s i d e r a t i o n of the above f a c t o r s , an upper l i m i t of 6 mmhos/cm would appear to be the maximum l e v e l a l l o w a b l e . In t h i s study a value of 5 mmhos/cm i s taken, s i n c e y i e l d s are thereby increased w h i l e the low i n i t i a l values of the s a l i n i t y of the i r r i g a t i o n waters used i n the N i c o l a V a l l e y r e q u i r e r e l a t i v e l y l i t t l e drainage water. b) I n c l u s i o n of Annual P r e c i p i t a t i o n The drainage percentages above are c a l c u l a t e d as percentages of the " i r r i g a t i o n waters a p p l i e d o n l y , and are i n no way a f f e c t e d by r a i n f a l l . In order to al l o w f o r the e f f e c t of ions found i n rainwater, a weighted average of s p e c i f i c ions f o r the i r r i g a t i o n water and the rainwater should be taken. However, the i o n i c c o n s t i t u e n t s of rainwater i n B r i t i s h Columbia (44) are of n e g l i g i b l e q u a n t i t y compared to those of surface waters. c) Choice of Methods of Computation of Drainage Percentage I t i s recommended that the drainage percentage be determined from the second method o u t l i n e d . The f i r s t method need only be ap p l i e d i n areas where a sodium hazard i s a n t i c i p a t e d , i n order to decide i f a d d i t i o n of gypsum i s necessary. A p p l i c a t i o n of t h i s method to c e r t a i n waters of the N i c o l a V a l l e y , p a r t i c u -l a r l y Quilchena Creek, show that due to the presence of r e s i d u a l carbonate, l i m i t e d a d d i t i o n of gypsum may be required to prevent a l k a l i n e s o i l s from developing. The sodium hazard present does not appear to be of great s i g -n i f i c a n c e , but f u r t h e r analyses made w i t h i n the area could determine t h i s . - 39 -v i i ) Summary Poor drainage c o n d i t i o n s , and an accumulation of s a l t s i n the s o i l , although derived from separate causes, g e n e r a l l y occur i n r e l a t e d circum-stances, and are inherent i n an i r r i g a t i o n system. Drainage water i s required to leach r e s i d u a l s a l t s from the s o i l . Of these, sodium carbonate i s regarded as being the most u n d e s i r a b l e , w h i l e c h l o r i d e s and sulphates are al s o damaging; the :s6dium hazard can be measured as Exchangeable Sodium Percentage, Sodium Adsorption R a t i o , or Sodium Percentage, and the carbonates and bicarbonates as Resi d u a l Carbonate. An accumulation of calcium s a l t s can be removed from the s o i l by adequate l e a c h i n g , but sodium s a l t s r e q u i r e f u r t h e r treatment and can be extremely p e r s i s t e n t . The drainage requirement may be determined from chemical a n a l y s i s , whence any gypsum required to o f f s e t carbonate p r e c i p i t a t i o n i s al s o c a l -c u l a t e d , or from measurements of E l e c t r i c a l C o n d u c t i v i t y . The l a t t e r method i s recommended f o r general use. - 40 -3. EFFICIENCY As a r e s u l t of s o i l seepage, leaky p i p i n g , uneven water d i s t r i b u t i o n i n a f i e l d , and s o i l s of v a r i a b l e water h o l d i n g c a p a c i t y , the amount of water a c t u a l l y a v a i l a b l e f o r crop use i s always l e s s than that which has been d i v e r t e d to an i r r i g a t i o n system. The term used to cover a l l these losses i s ''Water Use E f f i c i e n c y ' or 'Farm E f f i c i e n c y . ' This can be f u r t h e r subdivided as f o l l o w s , the terminology used depending to some degree on whether surface or overhead systems are con-s idered: i ) Conveyance E f f i c i e n c y (100 - Percent Water Loss) denotes the e f f i c i e n c y of the system i n d e l i v e r i n g the water from i t s point of d i v e r s i o n to the area of i r r i g a t i o n . I t i s estimated from the percentage water loss over a c e r t a i n d i s t a n c e , and f o r case of comparison the distance quoted i n t h i s study i s one m i l e . i i ) F i e l d Water A p p l i c a t i o n E f f i c i e n c y i s given by the r a t i o of water added to the root zone during an i r r i g a t i o n a p p l i c a t i o n to the water d e l i v e r e d to the f i e l d . I t i s a measure of the e f f e c t i v e use of the water e n t e r i n g the f i e l d from a conveyance channel, and includes both the e f f i c i e n c y of water d i s t r i b u t i o n and v a r i a t i o n s i n depth of the s o i l p r o f i l e . i i i ) Water D i s t r i b u t i o n E f f i c i e n c y i n surface i r r i g a t i o n ! i s analogous to C o e f f i c i e n t of U n i f o r m i t y i n overhead i r r i g a t i o n , and i n d i c a t e s the u n i -f o r m i t y w i t h which water i s d e l i v e r e d to the surface of a f i e l d . I t i s defined as: (1-Average d e v i a t i o n from the average water absorbed) x 100 Average water absorbed - 41 -Whereas the C o e f f i c i e n t of U n i f o r m i t y can be computed e i t h e r from t h e o r e t i c a l c o n s i d e r a t i o n s , or from r e l a t i v e l y simple f i e l d t e s t s , Water D i s t r i b u t i o n E f f i c i e n c y cannot be so, and i s r a r e l y used. Both these terms are included i n F i e l d Water A p p l i c a t i o n E f f i c i e n c y , which gives a more comprehensive estimate of water wastage. i v ) In surface i r r i g a t i o n p r a c t i c e i t i s more usu a l to estimate e f f i c i e n c y as the r a t i o of the water requirement determined by a standard method to the water d e l i v e r e d to a f i e l d and spread r e l a t i v e l y evenly, w h i l e maintaining good y i e l d s . Where the amount of water a p p l i e d to a f i e l d i s decreased even to the point of reducing crop y i e l d , a high e f f i c i e n c y w i l l thus be i n d i c a t e d , although not i n f a c t j u s t i f i e d i n the l i g h t of reduced y i e l d s . I t would appear then that there i s not r e l i a b l e , yet r e l a t i v e l y simple method of e s t i m a t i n g water a p p l i c a t i o n e f f i c i e n c y i n surface i r r i g a t i o n prac-t i c e . In a d d i t i o n to the foregoing c r i t e r i a governing e f f i c i e n c y , i t should be recognised that other f a c t o r s are in v o l v e d . Excess water r e q u i r e d to leach r e s i d u a l s a l t s a l s o leaches plant n u t r i e n t s from the s o i l ; s i m i l a r l y , water l o s t from conveyance channels may not i t s e l f be a water l o s s from the r e g i o n a l h y d r o l o g i c system, but may cause f u r t h e r l e a c h i n g , and waterlogged c o n d i t i o n s . Such leaching i s l i k e l y to increase e u t r o p h i c a t i o n of adjacent l a k e s , e s p e c i a l l y i n areas where n i t r a t e and phosphate f e r t i l i s e r s are used, such as the N i c o l a V a l l e y . I t would appear that no e v a l u a t i o n has been made of i r r i g a t i o n water usage i n terms of the above f a c t o r s , and that i r r i g a t i o n p r a c t i c e s and t h e i r - 42 -e f f e c t s upon water bodies are g e n e r a l l y considered i n i s o l a t i o n to each other . CHAPTER IV IRRIGATION IN THE NICOLA VALLEY 1. CONSUMPTIVE USE The method used f o r es t i m a t i n g i r r i g a t i o n water requirements ( f o r Consumptive Use) i s o u t l i n e d i n some d e t a i l f o r the M e r r i t t area. Based on t h i s estimate, determinations were made f o r Douglas Lake and Quilchena; the means of t r a n s p o s i t i o n of data from M e r r i t t are a l s o described. A... MERRITT I) E v a p o t r a n s p i r a t i o n (35) Since the Ogopogo evaporimeter has only been i n use since 1965, i t i s not f e a s i b l e to p l o t the seasonal e v a p o t r a n s p i r a t i o n against chance of occurrence, nor i s i t p o s s i b l e to determine a maximum value f o r i t . However, the summer of 1967 was hot and dry and considered to represent a l e v e l of e v a p o t r a n s p i r a t i o n not g r e a t l y below the maximum that can be expected, although f o r i n d i v i d u a l short periods the 1967 values have si n c e been exceeded. The cumulative e v a p o t r a n s p i r a t i o n recorded at M e r r i t t from 4th A p r i l to 30th October 1967 was 32.0" (Table I I I ) P 6 ) - 44 -i i ) Growing Season The length of the growing season f o r a l f a l f a was taken as the time during which the mean d a i l y temperature exceeded 42°F.^~^ By f i t t i n g a normal curve to the mean monthly temperatures throughout the year, and ta k i n g only values above 42°F. the growing season i s deter-mined by Wilcox as A p r i l 10th to October 26th f o r M e r r i t t , a length of 201 days . In t h i s study, without the p r i o r assumption that a normal curve f i t t e d the seasonal temperature d i s t r i b u t i o n , the average d a i l y temperatures over a seven year period were p l o t t e d f o r A p r i l and October to o b t a i n 'average' l i n e s which were found to i n t e r s e c t the 42° base "temperature at A p r i l 3rd and October 27th ( F i g . 2 ) . This gave a mean length of growing season of 209 days, only one day of which, at the beginning of the season, was not covered by evaporimeter records. Since t o t a l s were recorded only once a week, t r a n s p i r a t i o n on t h i s day was taken tp be one seventh of that during the adjacent week of rec o r d . The cumulative e v a p o t r a n s p i r a t i o n at M e r r i t t adjusted f o r the length of the growing season was thus taken as 31.9". i i i ) Summer R a i n f a l l C o n t r i b u t i o n During the growing season the average t o t a l p r e c i p i t a t i o n from A p r i l (22) to October i n c l u s i v e , i s 4.7". _. 4 5 -This decreases the i r r i g a t i o n requirement f o r e v a p o t r a n s p i r a t i o n to 27.2". i v ) Winter S o i l Moisture C o n t r i b u t i o n The average p r e c i p i t a t i o n from November to March i s 4.7" ( F i g . 2). During t h i s period t r a n s p i r a t i o n i s almost zero, and the water l o s s i s composed of evaporation and sublimation from snow; no c o r r e l a t i o n of t h i s l o s s w i t h evaporimeter records i s a v a i l a b l e . However, making a 'safe' estimate f o r water, losses of 2-3" during the w i n t e r , then 2" of p r e c i p i t a t i o n i s stored i n the s o i l by the end of the w i n t e r , assuming that the A.W.S.C. of the s o i l i s great enough to hold i t . In good i r r i g a t i o n p r a c t i c e , the s o i l moisture d e f i c i t i s u s u a l l y not allowed to become greater than 40 percent i n which case 0.8" of water i s a v a i l a b l e f o r plant use i n the s p r i n g . S i m i l a r l y i t i s assumed by Wilcox that at the end of the season pl a n t s may e x t r a c t water from the s o i l u n t i l a d e f i c i t of approximately 60 percent i s reached, on the understanding that winter p r e c i p i t a t i o n w i l l r e p l e n i s h t h i s d e f i c i t . However, as shown above, the w i n t e r surplus at M e r r i t t i s about 2", of which 0.8" i s used i n the Spring. The increase of t h i s d e f i c i t from 40 percent to 60 percent gives only a f u r t h e r 0.4" of a v a i l a b l e water i n the f a l l . Thus the t o t a l s o i l - w a t e r c o n t r i b u t i o n i s 1.2", decreasing the seasonal i r r i g a t i o n requirement f o r e v a p o t r a n s p i r a t i o n to a value of 26". - 46 -B. DOUGLAS LAKE i ) Growing Season The e l e v a t i o n of Douglas Lake i s about 3000' compared w i t h 2000' at M e r r i t t , and f o l l o w i n g Wilcox's estimate based on e f f e c t s of d i f f e r e n c e s i n e l e v a t i o n encountered elsewhere, the growing season was taken as being three days shorter at each end . i i ) E v a p o t r a n s p i r a t i o n From A p r i l 4th to October 30th, 1967, the cumulative evapotranspira-t i o n at Douglas Lake was recorded as being 25.3". However, during the growing season as estimated, the cumulative value was 24.8". i i i ) R a i n f a l l and S o i l Moisture C o n t r i b u t i o n Due to lack of data, the average annual p r e c i p i t a t i o n at Douglas Lake was assumed to be the same as f o r M e r r i t t . This c o n t r i b u t i o n i s the r e f o r e 5.9" i n a l l , decreasing the evapo-t r a n s p i r a t i o n i r r i g a t i o n requirement to a value of 18.9", or 19" i n round numbers. - 47 -C. QUILCHENA i ) Growing Season The mean weekly temperature was found from l i n e a r r e g r e s s i o n to be 0.91 times that recorded at M e r r i t t ( C o e f f t . of c o r r e l a t i o n r = 0.95). The only records a v a i l a b l e f o r such c o r r e l a t i o n have been kept at Quilchena since 27th May 1969; due both to the shortness of the records and to the d i f f e r e n t s i t i n g of the instruments i n each p l a c e , any adjustment to the length of the growing season must of n e c e s s i t y be somewhat a r b i t r a r y . In view of t h i s f a c t and a l s o that any adjustment would be only marginal, the growing season taken f o r M e r r i t t was adopted u n a l t e r e d . i i ) Evapo trans p i r at ion No records of e v a p o t r a n s p i r a t i o n are kept at Quilchena. However, i t was considered that w i t h i n a short distance the r e l a t i o n of e v a p o t r a n s p i r a t i o n to temperature should h o l d r e l a t i v e l y constant between adjacent d i s t r i c t s f o r a time period of a week or longer. Radiant energy i s one of the v a r i a b l e s a f f e c t i n g e v a p o t r a n s p i r a t i o n but i t i s the most important one, and, as i l l u s t r a t e d i n Chapter I I I . l . has formed the p r i n -c i p a l input data to the estimates made by a l l i n v e s t i g a t o r s , who have taken temperature to be a.measure of t h i s energy. The r e l a t i o n between the seasonal t o t a l s of e v a p o t r a n s p i r a t i o n and temperature at M e r r i t t i n 1967 was,determined, and i t was f u r t h e r assumed that the r e l a t i o n s h i p could be d i r e c t l y transposed to Quilchena without - 48 -f u r t h e r adjustment Assuming then that: E v a p o t r a n s p i r a t i o n ( M e r r i t t 1967) Temperature ( M e r r i t t 1967) Ev a p o t r a n s p i r a t i o n (Quilchena 1967) Temperature (Quilchena 1967) and Temperature (Quilchena 1967) Temperature ( M e r r i t t 1967) Temperature (Quilchena 1969) Temperature ( M e r r i t t 1969) Then Temperature (Quilchena 1967) = t>2 x Temperature ( M e r r i t t 1967) and E v a p o t r a n s p i r a t i o n (Quilchena 1967) = x x Temperature ( M e r r i t t 1967) But, b1 = 3\f5l = 0.0183, and b 2 0.910 Hence E v a p o t r a n s p i r a t i o n (Quilchena 1967) = 0.0167 x Temperature ( M e r r i t t 1967) During the growing season taken, Sum of weekly mean temperatures = 1750°F Then sum of e v a p o t r a n s p i r a t i o n = 0.0167 x 1750 = 29.1 i i i ) R a i n f a l l and S o i l Moisture C o n t r i b u t i o n This was taken to be the same as f o r M e r r i t t , thus reducing evapo-t r a n s p i r a t i o n i r r i g a t i o n requirement to a value of 23.3", or 24" i n round numbers. - 49 -D. SUMMARY The mean growing season f o r M e r r i t t , based on seven years of temperature r e c o r d , was taken as 209 days. E v a p o t r a n s p i r a t i o n f o r t h i s period was taken from Ogopogo evapori-meter records made i n 1967, and adjusted f o r r a i n f a l l and s o i l moisture c o n t r i b u t i o n s . Thus the 'corrected' e v a p o t r a n s p i r a t i o n ( i . e . e v a p o t r a n s p i r a t i o n l e s s p r e c i p i t a t i o n c o n t r i b u t i o n , or consumptive use requirement f o r i r r i g a t i o n ) at M e r r i t t was found to be 26". S i m i l a r estimates were made, p a r t l y on the b a s i s of t r a n s p o s i t i o n of data from M e r r i t t , f o r Douglas Lake and Quilchena, and f o r these the consumptive use requirement was found to be 19" and 24" r e s p e c t i v e l y . - 50 -5 0 i ui rr z> < CC OJ a 2 45 42 40 35 1 1 1 • • 1 1 1 1 1 1_ MIT OF SE • GROW ASON l\ NG M E R R I T T A V E R A G E DAILY T E M P E R A T U R E ( 1 9 6 2 - 1 9 6 8 ) A P R I L 22 26 30 2 M A R C H 10 14 18 22 A P R I L 50 u. o I UJ <r => v-< or ui a s ui t-4 5 4 2 4 0 35 • • # 1 LIMIT OF GR S E A ! OWING SON i M E R R I T T • A V E R A G E D A I L Y T E M P E R A T U R E I 1 9 6 2 - 1 9 6 8 ) O C T O B E R 12 16 20 O C T O B E R 24 28 l 5 N O V E M B E R • 1-5 tn z i " ° < 10-5 o ui 5! o M E R R I T T A V E R A G E MONTHLY m o» oo (M in in oo •n m (M N in cn >n IO P R E C I P I T A T I O N 6 6 6 6 6 6 6 6 6 6 6 — M M F I G U R E 2 . - 51 -TABLE I I I EVAPOTRANSPIRATION RECORDED AT MERRITT AND DOUGLAS LAKE 1967 Week ending E-T i n inches M e r r i t t Douglas Lake Apr. May June J u l y Aug Sept Oct 10 .64 .62 17 .71 .64 24 .70 .58 1 .69 .57 8 1.05 .96 15 .86 .66 22 1.28 1.04 29 1.03 .73 5 1.19 1.09 12 1.03 .89 19 1.54 1.42 26 1.18 1.04 3 1.68 1.49 10 1.35 1.19 17 1.66 1.54 24 1.32 1.05 31 1.53 1.25 7 1.20 .92 14 1.51 1.27 21 1.86 1.00 28 1.40 1.01 4 1.41 .74 11 .91 .44 18 .94 .45 25 .98 .45 2 .74 .68 9 .51 .46 16 .50 .41 23 .25 .34 30 .38 .38 T o t a l 32.02 25.31 - 52 -2. DRAINAGE REQUIREMENT i ) General S o i l Drainage The s o i l s of the N i c o l a V a l l e y vary considerably both i n type and i n depth. Those of the a l l u v i a l fans have b e t t e r drainage p r o p e r t i e s than those of the v a l l e y s , mainly as a r e s u l t of t h e i r increased h y d r a u l i c g r a d i e n t . i i ) The Groundwater Flow P a t t e r n A mathematical model of ground water flow has been proposed by J . (49 50) T6th ' which, f o r a symmetrical b a s i n , envisages areas of upward and downward flow a l t e r n a t i n g across a v a l l e y r e g i o n , as shown i n F i g . 3. The longer the flow path of the water, the higher the co n c e n t r a t i o n of d i s s o l v e d s a l t s , so that s a l i n e waters w i l l be most l i k e l y found as springs i n v a l l e y bottoms. T6th's l o c a l system of ground water flow i s g e n e r a l l y accepted, and thus i t may be expected that w i t h i n an i r r i g a t e d v v a l l e y , under normal con-d i t i o n s , ground water flow w i l l c o n t r i b u t e to a stream along i t s e n t i r e l e n g t h , thereby continuously i n c r e a s i n g i t s c o n d u c t i v i t y . This was found to occur along Quilchena Creek, i n d i c a t i n g that ground water movement i s towards the creek. ( F i g . 5). - 53 -i i i ) V a r i a t i o n of S a l t Content I t has been found that f o r any one stream the s a l t content of the . . J • (47, 53) water increases w i t h decreasing e l e v a t i o n . Several f a c t o r s a f f e c t the s a l t content, i n c l u d i n g the p r o p o r t i o n of surface to seepage flow, the degree of adjacent s o i l l e a c h i n g , the under-l y i n g rock, and the distance downstream. Measurements were made using E l e c t r i c a l C o n d u c t i v i t y j a s an i n d i c a t o r , of the s a l i n i t y of some i r r i g a t i o n and other waters of the N i c o l a V a l l e y ; these are shown i n Table V I I I , together w i t h some comparative readings taken i n 1958. Quilchena Creek, w i t h an o v e r a l l length of some f i f t y m i l e s , and f a l l i n g from about 3500 feet to 2045 f e e t , shows the highest s a l t content. Readings taken over the s i x miles upstream of N i c o l a Lake (Table IV; F i g . 4) show a s i g n i f i c a n t trend of increase w i t h d i s t a n c e , and pH readings taken i n June 1969 over 36 miles of i t s length also show an o v e r a l l i n c r e a s e . These values have been p l o t t e d to a l i n e a r s c a l e against the distance downstream on Quilchena Creek from the Hamilton Common Indian Reserve as f a r as the road bridge on Highway 5; the distances have been reduced to s t r a i g h t l i n e distances between points ( F i g . 5 ) . . The f i r s t major d i v e r s i o n of water from Quilchena Creek to i r r i g a t i o n i s at S i t e No. 17, n e a r l y four miles upstream of N i c o l a Lake; below t h i s i t w i l l be seen that 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 i n the creek increases at a more r a p i d r a t e . This i n d i c a t e s the i n f l u e n c e of r e t u r n flow from i r r i g a t i o n , where the excess water a p p l i e d e i t h e r flows i n t o the creek from the land s u r f a c e , or as sub-surface drainage water. - 54 -i v ) Q u a l i t y of Water f o r I r r i g a t i o n As shown i n F i g . 4, i r r i g a t i o n water i s d i v e r t e d from Quilchena Creek at Sample S i t e s No. 17, 12, and 1. I n d i c a t i v e t e s t s of the water q u a l i t y (see Table VI) at these sources and o t h e r s , were made at d i f f e r e n t times of the season by determination of: E l e c t r i c a l C o n d u c t i v i t y Sodium Percentage Sodium Adsorption Ratio Residual Carbonate Also included above were two w e l l waters, and two points of ground-water seepage. As shown i n Table VII a l l values of these t e s t s except those of Residual Carbonate were w e l l w i t h i n the s p e c i f i e d s a f e t y l e v e l s . I n i t i a l data f o r these t e s t s are given In Table V. / / O \ v) Gypsum and Drainage Requirements from chemical a n a l y s i s , and from e l e c t r i c a l conductivity,(51) a) Derived from chemical a n a l y s i s , and f o r each case using readings f o r the date on which the Sodium Percentage was at i t s maximum recorded, the Drainage Requirement was found i n a l l cases except one to be l e s s than one percent of the Consumptive Use (Table V I I ) . To prevent sodium a l k a l i s o i l s from developing, i t was found that gypsum should probably be added to some of the i r r i g a t i o n waters. The - 55 -calculated quantities shown i n Table VII vary considerably, and this r e f l e c t s f l uctuations i n the chemical constituents of the water; because of these seasonal f l u c t u a t i o n s , any computed figures cannot be expected to remain constant. A maximum safety l e v e l of about 60-70 percent is given as a c r i t e r i o n for Sodium Percentage. Of the examples taken i n which addition of gypsum was found to be necessary to o f f s e t the sodium hazard, the maximum Sodium Percentage was found to be only 19 percent, and also the Sodium Adsorption Ratio was found i n each case to be less than one percent of the recommended safety value; from t h i s i t would appear that the recommended safety l e v e l s are not necess a r i l y r e l i a b l e . If there i s any 'residual carbonate' in.the water af t e r allowance for reaction with calcium and magnesium, i t i s possible that sodium carbonate may be formed; without reference to the quantity of sodium present, the danger of this occurrence i s indicated i n the Residual Carbonate test as a po s i t i v e value. Of seven of the cases for which a d d i t i o n a l gypsum was estimated to be necessary, this test gave p o s i t i v e values i n three cases. For the reason postulated i n the Appendix (2.5) the cation-anion balance i s uneven i n most samples; t h i s may indicate low estimates of re s i d u a l carbonate, and of drainage and gypsum requirements. From these l i m i t e d r e s u l t s i t would appear that Residual Carbonate i s a more r e l i a b l e i n d i c a t o r than either Sodium Percentage of Sodium Adsorption Ratio, of the sodium hazard present, and also, by inference, than other tests r e l y i n g only on anion evaluations (eg. Exchangeable Sodium 56 -Percentage). This i s i n general agreement w i t h Eaton's observations i n Egypt concerning the use of N i l e water f o r i r r i g a t i o n . The more.accurate an i n d i c a t i v e t e s t i s to be, the greater the amount of data needed f o r i t , and i n many cases a f u l l a n a l y s i s i s not j u s t i f i e d , nor do resources a l l o w f o r i t . The p r i n c i p a l anions and a l s o carbonates are required f o r the t e s t s o u t l i n e d , but there i s no i n d i c a t i v e t e s t a l l o w i n g f o r the d e l e t e r i o u s e f f e c t s of c h l o r i d e and sulphate. b) The Drainage Percentage was c a l c u l a t e d from E l e c t r i c a l C o n d u c t i v i t y f o r the same sources and f o r others i n the N i c o l a V a l l e y . The f i n d i n g s confirmed that only a small excess over and above the consumptive use requirements would be necessary f o r drainage, a maximum value of 8.3 percent being determined f o r the usu a l sources of i r r i g a t i o n water, and the mean value of t h i s p a r t i c u l a r source at Quilchena being 8 percent. Comparative r e s u l t s are shown i n Table V I I I , and some specimen c a l -c u l a t i o n s are given i n Table IX. c) Since the s o i l s of the N i c o l a V a l l e y are predominantly calcareous by nature, the i r r i g a t i o n water, being g e n e r a l l y low i n t o t a l s a l t content, may i t s e l f have a r e l a t i v e l y small e f f e c t on s o i l s a l i n i t y i n i r r i g a t e d areas. However, i t i s also probable that the water causes the e x i s t i n g s o l u b l e s a l t s i n the s o i l to move toward areas of poor surface drainage, (49, 50) ' thus causing f u r t h e r problems of s a l t accumulation. d) As shown i n Table V I I I the maximum value of drainage percentage found from f i e l d t e s t i n g i n the N i c o l a V a l l e y was 8 percent; a d d i t i o n of t h i s water should ensure that no s o i l d e t e r i o r a t i o n by s a l i n i t y w i l l occur: Such s o i l - 57 -d e t e r i o r a t i o n w i l l only occur i n the long term, and drainage water should t h e r e f o r e be computed as a percentage of the mean seasonal evapotranspira-t i o n . I t may be added at each i r r i g a t i o n or at longer i n t e r v a l s , and so may be cut f o r one or two seasons of high demand, provided that any d e f i c i t i s l a t e r made good. Since values of mean seasonal e v a p o t r a n s p i r a t i o n are not'..generally a v a i l a b l e f o r the I n t e r i o r of B r i t i s h Columbia, t h i s has been estimated by assuming the r a t i o of i t to the e v a p o t r a n s p i r a t i o n recorded i n 1967 to be the same as the r a t i o of the average of the mean monthly temperatures ( A p r i l 1st - October 31 s t ) over the 37-year period 1928-1965 to the average of the mean monthly temperatures ( A p r i l - October) i n 1967. This assumption f o l l o w s from Chapter I I I . l . where the Blaney-Criddle method, the evapotrans-p i r a t i o n estimates of which are shown to be r e l a t i v e l y s a t i s f a c t o r y , takes monthly e v a p o t r a n s p i r a t i o n to be d i r e c t l y p r o p o r t i o n a l to the mean monthly temperature.. This method represents an approximation, but sin c e the drainage percentage under c o n s i d e r a t i o n i s of r e l a t i v e l y small order, then the u l t i m a t e e r r o r due to such approximation i s considered to be very s m a l l . At M e r r i t t , the long term (37 years) and the 1967 average monthly temperatures ( A p r i l - October) were found to be 54.7°F and 58.5°F respec-t i v e l y , the 1967 value thus being 7 percent greater than the average. The d e v i a t i o n of the 1967 seasonal temperature from the mean was assumed to be the same f o r Douglas Lake and Quilchena as f o r M e r r i t t . Taking the f i n a l drainage water requirement to be added i n the long - 58 -term as the d i f f e r e n c e between the drainage percentage determined from spot t e s t s i n the f i e l d , and the d e v i a t i o n of the 1967 seasonal temperature from the average, a l s o expressed as a percentage, t h i s requirement at M e r r i t t was found to be (5-7 per c e n t ) , at Douglas Lake to be (3-7 p e r c e n t ) , and at Quilchena to be (8-7 percent) . Thus at Quilchena alone i s the a d d i t i o n of drainage deemed to be necessary, to a value of one percent o n l y . v i ) Summary F i e l d t e s t s i n d i c a t e d that groundwater i n the v i c i n i t y of Quilchena Creek flows towards the Creek; thus drainage water and any other r e t u r n flow from i r r i g a t i o n a l s o flow back i n t o the creek. - For d i f f e r e n t sources of water, determinations were made of E l e c -t r i c a l C o n d u c t i v i t y , Sodium Percentage, Sodium Adsorption R a t i o , and Residua l Carbonate; a l l v a l u e s , except a few f o r Residual Carbonate, f e l l w e l l w i t h i n the s p e c i f i e d s a f e t y l e v e l s . By f i e l d t e s t s of the p r i n c i p a l sources of i r r i g a t i o n water, making use of e l e c t r i c a l c o n d u c t i v i t y , the maximum value of the Drainage Percentage was found to be 8 percent. However, since t h i s drainage water should be added as a modified q u a n t i t y to the mean seasonal e v a p o t r a n s p i r a t i o n , and sinc e the 1967 seasonal value of e v a p o t r a n s p i r a t i o n was 7 percent greater than the mean, then a maximum value of l e s s than one percent need f i n a l l y be added to the 1967 values of consumptive use requirements. In some cases i t was found that gypsum should be added to i r r i g a t i o n waters to prevent sodium s o i l s from developing. Some of these cases are - 59 -indicated by p o s i t i v e values for Residual Carbonate. It i s suggested that to evaluate any sodium hazard, the Residual Carbonate test should be used as an i n d i c a t o r . TABLE IV QUILCHENA CREEK MEASUREMENTS OF pH AND ELECTRICAL CONDUCTIVITY SAMPLE DISTANCE pH E .C. (mmhos/cm) SITE ABOVE-BRIDGE NO. (miles) . -3,-4.6.69 23-24.6.69 20.7.69 31. 1 3.69 stream A 36 - length 7.45 25 5.75-direct 7.45 0.285 0.312 0. .349' 24 5.4 0.299 0 .348 23 4.85 0.305 22a 4.75 0.334 0 .358 22 4.65 0.304 0 .352 21 4.15 19 3.50 0.311 17 3.20 7.9 0.317 0.346 0 .355 16 2.70~ 0.317 15 2.05 0.320 0 .357 12 1.60 7 .75 0.332 0 .384 0 .386 9 1.20 0.333 0.398 0 .403 8 1.00" 0.341 5 0.80 0.343 4 0.65 7.6 0.353 0.405 0 .408 3 0.50 0.355 0.407 0 .407 2 0.10 0.368 0 .418 1 0 0.358 0.425 0 .417 20 Small groundwater flow 1.005 1.204 0 .888 27 Well at Quilchena 0.553 0.529 0 .542 A l l above values of e l e c t r i c a l conductivity are given for 25 C (77 F) TABLE V POTENTIAL IRRIGATION WATERS DATA ON CHEMICAL ANALYSIS AND ELECTRICAL CONDUCTIVITY DATE Na Ca Mg C l SO, CO. HCO, E.C. SAMPLE SITE NO. meq/1 meq/1 meq/1 meq/1 meq/1 meq/1 meq/1 mmhos/cm 4 . 6 . 6 9 1 7 0 . . 3 5 1 . 1 0 0 , . 7 7 0 . 0 4 2 0 . 3 0 - 1 . . 5 0 * 0 . 2 3 3 1 . 8 . 6 9 1 7 0 . 4 1 2 . 0 5 0 . . 7 0 0 . 1 0 4 0 . 2 4 - 2 . 9 2 0 . 3 5 5 4 . 6 . 6 9 1 1 0 . 2 3 1 . 4 4 0 . . 5 9 0 . 0 4 8 0 . 3 0 1 . 7 0 0 . 2 3 * 2 4 . 6 . 6 9 1 2 0 . 2 3 1 . 0 0 1 . . 4 6 0 . 0 5 1 0 . 4 0 0 . 3 2 1 . . 8 8 0 . 3 3 6 3 1 . 8 . 6 9 1 2 0 . 5 5 1 . 6 8 1 . 3 0 0 . 0 9 7 0 . 3 4 - 2 . 7 7 0 . 3 8 6 2 4 . 6 . 6 9 1 0 . 2 2 0 . 7 0 0 . 9 5 0 . 0 3 7 0 . 6 1 0 . 4 4 0 . 8 9 0 . 3 7 7 2 6 . 6 . 6 9 1 0 . 3 1 0 . 6 0 : I . 6 6 0 . 0 7 6 0 . 5 7 0 . 1 6 2 . 1 4 0 . 3 6 4 3 1 . 8 . 6 9 1 0 . 4 3 1 . 5 0 0 . 8 8 0 . 1 1 3 0 . 4 3 - 3 . 0 0 0 . 4 1 7 4 . 6 . 6 9 2 0 4 . 4 0 2 . 9 8 3 1 . 4 5 0 . 1 4 6 0 . 8 0 0 . 3 6 3 . 1 4 4 . 1 * 2 4 . 6 . 6 9 2 0 0 . 9 0 2 . 6 0 4 . 8 0 0 . 0 7 9 0 . 6 7 0 . 3 2 2 . 3 0 1 . 0 0 6 . 3 1 . 8 . 6 9 2 0 1 . 7 2 2 . 8 5 0 . 7 8 0 . 1 2 0 0 . 6 6 - 2 . 5 2 0 . 9 3 0 4 . 6 . 6 9 2 9 1 1 . 5 0 0 . 5 9 2 8 . 8 2 0 . 1 0 2 - 3 . 4 5 4 . 2 * 2 5 . 6 . 6 9 2 7 0 . 4 8 0 . 8 0 1 . 2 8 0 . 0 6 8 i 0 . 7 2 0 . 1 6 1 . 7 3 0 . 5 5 3 2 9 . 7 . 6 9 2 8 0 . 2 8 1 . 6 0 2 . 0 8 0 . 0 5 1 0 . 5 5 0 . 2 0 2 . 7 6 0 . 4 0 * 4 . 6 . 6 9 3 0 0 . 3 5 1 . 4 9 0 . 8 8 0 . 0 5 1 0 . 6 0 0 . 2 6 1 . 4 4 0 . 2 3 4 * Sample S i t e Locations (See a l s o F i g . 6 ) 1 7 , 1 2 , 2 0 2 9 2 7 2 8 3 0 Diversions to I r r i g a t i o n 'ij (Quilchena Creek) Small flow from groundwater (Quilchena Ranch) Small seepage from groundwater (Quil^chena Ranch) Well at Quilchena Hotel Well at 'Reaver Ranch N i c o l a R. at outflow from N i c o l a L. *E..C. Values taken from c o r r e l a t i o n w i t h c o n c e n t r a t i o n , as expressed by summa-t i o n of cations i n m e q / 1 . ( 5 1 ) **E.C. Reading taken on 2 4 . 7 . 6 9 - 62 -TABLE VI TESTS INDICATING QUALITY OF IRRIGATION WATER TEST FORMULA SAFETY LEVEL E l e c t r i c a l C o n d u c t i v i t y E.C. ! D i r e c t Measurement Levels given m;i max. approx. 0.4 mmhos/cm. Sodium Percentage Na7o Na Na + Ca + Mg 60 - 70% Sodium Adsorption R a t i o S.AR. Na / C a + Mg V 2 Max. 80, depending on E.C. Residual Carbonate (C0 3 + HC0 3)-(Ca + Mg) Waters of le s s than 1.25 meq/1 g e n e r a l l y safe f o r i r r i g a t i o n . - 63 -TABLE VII POTENTIAL IRRIGATION WATERS DRAINAGE PERCENTAGES AND GYPSUM REQUIREMENTS SAMPLE SITE RESIDUAL DRAINAGE % GYPSUM DRAINAGE % NO. DATE Na% S.A.R. 'CARBONATE BY EATON REQUIRED BY E.C. (meq/1) ( l b / a c r e : f j a _ 17 4, .6, .69 19 0 .36 •0.7 150 4.6 17 31. .8, .69 13 0 .35 0, .17 0.7 150 7.1 11 4, .6 .69 10 0 .23 01731 14 4.6 12 24. .6 .69 9 0 .21 ' 0.3 . None 6.7 12 31. .8, .69 16 ' • 0 .30 0\5> 75 7.7 1 24, .6. .69 12 0 .41 0.4 . None 7.5 1 26 .6. .69 12 0 .29 0. .04 0.8 68 7.3 1 31. .8 .69 15 0 .39 0. .62 1.1 255 8.3 20 4, .6 .69 11 1 .06 0.7 None :82 20 24 .6 .69 11 0 .47 0.5 None 20.1 20 .31. .8 .69 32 1 .27 0.6 , None 18.6 29 4 .6 .69 28 3 .00 0.6 \ None 84 27 25 .6 .69 19 0 .47 0 .7. 59 11.1 28 29 .7 .69 7 0 .21 0.4 None 8.0 30 4 .6 .69 13 0 .32 0.4 None 4.7 Sample S i t e Numbers: Locations are given i n Table V. - 64 -TABLE V I I I NICOLA VALLEY ELECTRICAL CONDUCTIVITY MEASUREMENTS AND DRAINAGE PERCENTAGES FROM READINGS MADE IN 1958 and 1969 SOURCE SAMPLING SITE E.C. 1958 E.C. , 1969 DRAINAGE (mmhos/cm) (mmh IOS /cm) REQUIREMENTS % N i c o l a R. In flow to Douglas L. - 0. 169 3.4 N i c o l a R. Outflow from Douglas L. - 0. ,145 2.9 Spahomin C. Douglas Lake I.R. - . 0. 132 2.6 Moore C. Beaver Ranch - 0. 286 5.7 Quilchena C. Inflow to N i c o l a L. - 0. 424 8.5 N i c o l a R. Outflow from N i c o l a L. - 0 . 240 4.8 N i c o l a R. M e r r i t t - 0. 236* 4.7 Coldwater R. M e r r i t t 0.130 0. 131* 2.6 Mamit.L. - 0. 008* 0.2 Guichon C. Near Mouth 0.312 - 6.2 N i c o l a R. Near Mouth 0.230 0. 170* 3.4-4.6 1958 Readings: Taken from " S u i t a b i l i t y f o r I r r i g a t i o n of Water from Lakes and Streams(40) Almost a l l made i n J u l y . Due to the summer being very dry, the average s a l t content of a l l samples was higher than u s u a l . 1969 Readings: Made from 24th - 26th J u l y *May not be f u l l y r e l i a b l e A l l Readings: Corrected f o r temperature to 25°C (77°F) - 65 -TABLE I X DRAINAGE" PERCENTAGE AND GYPSUM REQUIREMENT SPECIMEN CALCULATIONS Sample S i t e No. 17 Date: 31.8.69 i ) D r a i n a g e P e r c e n t a g e . a n d Gypsum Requirement by E a t o n m . ' n • A ( C l + h S 0 4 ) 100 (.104 + .120) 100 n 9 H T e n t a t i v e D r a i n a g e d = -_• 1 z = 1 =0.28 80 - ( c l + \ S 0 4 ) 80 - .22 C a l c i u m R e q u i r e d : a) Na x .429 - (Ca + Mg) = .41 x .429 - (2.05 + 0.70) = -2.57 meq/1 HC0 3 x (100 - d%) 2.92 x 99.7 . . . ioo = — 1 0 0 = 2 ' 9 1 m e q / 1 c) 0.30 x ^ l O O - d%) = 0 . 3 0 ^ 9 9 . 7 = 0 . 3 0 m e q / 1 T o t a l Ca r e q u i r e d = 3.21 - 2.57 = 0.64 meq/1 T h i s i s 0.64 x 234 = 150 l b o f gypsum per a c r e / f t . o f w a t e r F i n a l d r a i n a g e D = (0.224 ± 0.32) 100 = „ 7 7 80 - .54 i i ) D r a i n a g e P e r c e n t a g e by E l e c t r i c a l C o n d u c t i v i t y D r a i n a g e D = E.C.£ 27 0.05 0.05 = 5.4% 66 -£1° < ^ ct u- < e> o Q o Q 2 CL < t < O ^ H H X </> T H E O R E T I C A L F L O W P A T T E R N S A N D  B O U N D A R I E S B E T W E E N D I F F E R E N T  F L O W S Y S T E M S ( AFTER J . TOTH , 1963 ) . ACTUAL GROUND SLOPE-(ASSUMED SINUSOIDAL) MEAN SLOPE OF GROUND STANDARD DATUM Region of local system of groundwater flow. Region of intermediate system of groundwater flow. Region of regional system of groundwater flow Line of water movement. F I G U R E 3. - 68 -T E M P O R A L AND S P A T I A L VARIATION OF CONDUCTIVITY ALONG QUILCHENA C R E E K ( SEE A L S O T A B L E ) S A M P L E SITE No. 2 5 2 4 2 3 2 2 2 1 1 9 1 8 1 7 1 6 1 5 1 4 1 3 1 2 1 0 9 4 3 2 1 0 I 2 3 4 5 6 Dl S T A N C E , M E A S U R E D D O W N S T R E A M TOWARDS HIGHWAY BRIDGE ( S I T E I, AT MILE 5 - 8 7 ) - M I L E S F I G U R E 5 . - 69 -3. EFFICIENCY i ) Conveyance E f f i c i e n c y As d e s c r i b e d i n the p r e c e d i n g s e c t i o n , t h e E l e c t r i c a l C o n d u c t i v i t y o the w a t e r i n Q u i l c h e n a Creek i n c r e a s e s downstream, i n d i c a t i n g t h a t t h e c r e e k i s c o n t i n u o u s l y augmented by groundwater seepage. I n t u r n t h i s i n d i c a t e s a groundwater t a b l e w h i c h s t a n d s a t a l e v e l a t no p o i n t l ower t h a n the l e v e l o f the c r e e k a d j a c e n t , and whose mean d i r e c t i o n o f f l o w i s towards t h e c r e e k . The topography b e i n g r e l a t i v e l y homogeneous, i t i s p r o b a b l e t h a t t h i s i s a l s o the s i t u a t i o n i n o t h e r v a l l e y s i n t h e N i c o l a a r e a . Hence i t would appear t h a t e x c e s s i r r i g a t i o n w a t e r a p p l i e d , w h i c h i s g e n e r a l l y r e g a r d e d as b e i n g l o s t t o t h e s y s t e m , and t h e r e f o r e 'wasted', i n f a c t p e r c o l a t e s t o the w a t e r t a b l e , whence i t i s r e t u r n e d t o the c r e e k by a l o n g e r f l o w p a t h . Where t h e w a t e r t a b l e i s not deep, o v e r - i r r i g a t i o n may a f f e c t the time d i s t r i b u t i o n o f t h e r u n o f f p a t t e r n , but does not m a t e r i a l l y a f f e c t t h e o v e r a l l usage. I f the w a t e r i s o b t a i n e d from deep w e l l s , h o w e v e r , seepage w a t e r i s u n l i k e l y t o r e t u r n t o the same a q u i f e r and may become u n a v a i l a b l e f o r r e - u s e . Conveyance e f f i c i e n c i e s were measured ' i n s i t u ' a t s e v e r a l s i t e s t o o b t a i n a g u i d e t o such w a t e r l o s s e s i n t h e N i c o l a V a l l e y ( T a b l e X ) . For t h e sake o f ready c o m p a r i s o n t h e s e a r e a l s o g i v e n as p e r c e n t a g e l o s s e s p e r m i l e , u s i n g a l i n e a r c o n v e r s i o n ; such a c o n v e r s i o n i s n o t s t r i c t l y a c c u r a t e and has been i n c l u d e d o n l y f o r purposes o f i l l u s t r a t i o n . I t - 70 -w i l l be n o t e d t h a t t he l o s s e s , w h i c h range from 8 p e r c e n t t o 96 p e r c e n t per m i l e , a r e p a r t l y dependent on the n a t u r e o f t h e bed; m a t e r i a l . i i ) Water Use E f f i c i e n c y , F i e l d Water A p p l i c a t i o n E f f i c i e n c y , Water D i s t r i b u t i o n E f f i c i e n c y Measurements o f t h e s e e f f i c i e n c i e s have n o t been made i n the N i c o l a V a l l e y . I n p r a c t i c e a nomograph d e v e l o p e d by F r o s t , g i v i n g s p r i n k l e r l o s s e s i n a i r , has been adapted f o r use i n B r i t i s h C o l u m b i a f o r s p r i n k l e r i r r i -g a t i o n s y s t e m s , g i v i n g a range o f f i e l d a p p l i c a t i o n e f f i c i e n c i e s between 60 p e r c e n t and 99 p e r c e n t , d e p e n d i n g on c l i m a t i c c o n d i t i o n s . ^ 2 ' ' " ' A method by W i l c o x g i v e s v a l u e s o f 67 p e r c e n t t o 99 p e r c e n t ; t h i s assumes (36) t h e w i n d v e l o c i t y t o be below 5 m.p.h. an a s s u m p t i o n j u s t i f i e d i n the Okanagan, where the method was d e v e l o p e d , b u t p r o b a b l y not i n the N i c o l a V a l l e y . Some c o m p a r a t i v e v a l u e s o f f l o o d i r r i g a t i o n e f f i c i e n c i e s a r e g i v e n i n T a b l e X, w i t h examples t a k e n from Utah and Idaho, where t h e v a l l e y l a n d s l e n d t h e m s e l v e s t o more e a s i l y managed f l o o d i r r i g a t i o n p r a c t i c e s t h a n t h e s l o p i n g b e n c h l a n d s o f t h e I n t e r i o r o f B r i t i s h C o l u m b i a f ^ ' ^ ' E f f i c i e n c i e s have been d e t e r m i n e d f o r t h e s e cases as d e s c r i b e d i n C h a p t e r I I I . 3 ( i v ) . T a k i n g average f i g u r e s , s p r i n k l e r s a r e g i v e n as b e i n g 60-99 p e r c e n t e f f i c i e n t w h i l e the c o r r e s p o n d i n g f i g u r e s f o r a f l o o d s y s t e m would be 45-70 p e r c e n t . D i v e r s i o n o f w a t e r by p i p i n g causes v i r t u a l l y no l o s s , w h i l e open d i t c h e s show an average l o s s o f 33 p e r c e n t p er m i l e i n the N i c o l a - 7 1 -V a l l e y i i i ) P o s s i b l e Developments The a p p a r e n t w a t e r l o s s e s from s u r f a c e systems would seem to be about f i f t y p e r c e n t g r e a t e r t h a n from overhead s y s t e m s , but i t has been shown t h a t i n an a r e a such as t h e N i c o l a V a l l e y o v e r - i r r i g a t i o n i s u n l i k e l y t o m a t e r i a l l y a f f e c t t h e o v e r a l l w a t e r u s a g e , s i n c e the e x c e s s w a t e r s u p p l y r e t u r n s t o the c r e e k and can be r e - u s e d . In a r e a s where w a t e r i s o b t a i n e d from deep w e l l s , c a u s i n g p o t e n t i a l l y l a r g e seepage l o s s e s , such as A l b e r t a , U t a h , and C a l i f o r n i a , s e v e r a l d i t c h l i n i n g m a t e r i a l s have been d e v e l o p e d i n o r d e r t o o b v i a t e such seepage. These range from r e i n f o r c e d o r a s p h a l t i c c o n c r e t e , t o e a r t h l i n i n g s - - w i t h o r w i t h o u t b e n t o n i t e o r a g r a v e l c o v e r i n g l a y e r , b u r i e d a s p h a l t , v i n y l , i i i . . i . . . . c , , ( 3 , 6 1 , 6 2 , 6 3 , 6 4 , p o l y e t h y l e n e , and b u t y l - - e i t h e r r e i n f o r c e d o r as a s h e e t . 6 8 ) Where the c o s t o f w a t e r i s h i g h and i r r i g a t i o n development schemes ar e l a r g e , t h e n h i g h c o s t methods a r e j u s t i f i e d . T h i s i s not t r u e i n the N i c o l a V a l l e y , and d i t c h l i n i n g f o r f l o o d i r r i g a t i o n i s b e l i e v e d t o be g e n e r a l l y u n w a r r a n t e d ; i f t h e r e i s e x c e s s i v e seepage, however, s o i l n u t r i e n t s w i l l be l e a c h e d away, and i n cases the w a t e r t a b l e may r i s e so ( 7 2 ) as t o impede d r a i n a g e and cause w a t e r l o g g i n g . Some l i n i n g o f f i e l d l a t e r a l d i t c h e s w i t h b e n t o n i t e has been done s u c c e s s f u l l y a t Q u i l c h e n a ; i t has been shown by l a b o r a t o r y t e s t i n g t h a t a 5 p e r c e n t mix o f b e n t o n i t e can r e d u c e t h e s o i l p e r m e a b i l i t y by a f a c t o r o f 1 5 , and 1 0 p e r c e n t by 1 0 0 0 . F o r main conveyance c h a n n e l s , b e n t o n i t e would l i k e l y be washed o u t , - 72 -e s p e c i a l l y i n the c o a r s e r and g r a v e l s o i l s , b u t i t would appear t h a t a p r o m i s i n g l i n e r h e r e would be b u t y l s h e e t . T h i s need not be b u r i e d , can be ,;laid) e a s i l y i n a d i t c h , i s c o m p l e t e l y impermeable, and has a r e l a t i v e l y (63) low c o s t . I n c o n s i d e r a t i o n o f t h e s e v e r a l f a c t o r s i n v o l v e d , i t would appear t h a t i n s t e a d o f a r i g i d d e s i g n o f one t y p e o f system o n l y , i t i s p r e f e r a b l e t o d e s i g n an i r r i g a t i o n l a y o u t t o s u i t t he l a n d under c o n s i d e r a t i o n . T h i s d e s i g n may i n c l u d e : e i t h e r s p r i n k l e r o f s u r f a c e methods on r e l a t i v e l y f l a t l a n d , d epending on a v a i l a b i l i t y o f w a t e r , s u r f a c e p e r m e a b i l i t y , and d r a i n a g e . s p r i n k l e r s e t s on uneven gr o u n d . f l o o d i n g by g a t e d f l e x i b l e t u b i n g on some b e n c h l a n d s above conveyance c h a n n e l s . s p r i n k l e r s e t s on h i g h l y permeable g r o u n d . d i t c h l i n i n g s i n c e r t a i n i n s t a n c e s , e.g. c h a n n e l s on g r a v e l s u b s o i l , permeable f i e l d l a t e r a l s , e t c . A t p r e s e n t g a t e d f l e x i b l e t u b i n g i s s c a r c e l y u s e d , but has g r e a t advantage on some b e n c h l a n d s t o w h i c h w a t e r must be pumped; t h e a l t e r n a t i v e i s s p r i n k l e r s , w h i c h a r e l e s s easy t o h a n d l e and t r a n s p o r t , and a l s o c o s t more. S i m i l a r l y , f o r non-permanent p i p e l i n e l a y - f l a t t u b i n g i s more p o r t a b l e t h a n p i p e s , and i s more e a s i l y s t o r e d and h a n d l e d . S i z e s range from 4" t o 16" i n d i a m e t e r , w i t h a maximum p r e s s u r e f o r a 6" tube o f 70 p . s . i . - 73 -i v ) Summary I t appears t h a t where s u r f a c e w a t e r s a r e used f o r i r r i g a t i o n , w a t e r l o s s e s i n conveyance and a p p l i c a t i o n causes the w a t e r t o be r e t u r n e d t o the s y s t e m by means o f a l o n g e r f l o w p a t h , b u t n o t l o s t f rom i t . As o u t l i n e d i n C h a p t e r I I I . 3 , e f f i c i e n c y may be e s t i m a t e d i n s e v e r a l d i f f e r e n t manners. Water l o s s e s c a n , d e t e r m i n e changes i n t h e s u r f a c e and ground w a t e r h y d r o l o g y , and a l s o t h e r a t e o f l e a c h i n g o f p l a n t n u t r i e n t s f rom t h e s o i l , l e a d i n g t o a c c e l e r a t e d e u t r o p h i c a t i o n o f a d j a c e n t w a t e r b o d i e s . No a n a l y s i s o f t h e e f f e c t s o f such l e a c h i n g was made i n t h i s s t u d y , b ut i t would'appear d e s i r a b l e f o r t h e s e e f f e c t s t o be i n c l u d e d i n the c o n s i d e r a t i o n o f e f f i c i e n c y c r i t e r i a . C a n a l and d i t c h l i n i n g s can be e f f e c t e d by a v a r i e t y o f methods, but c o s t l y methods a r e d i f f i c u l t t o j u s t i f y i n t h e N i c o l a V a l l e y . Comparisons o f t h e e f f i c i e n c i e s o f w a t e r conveyance and o f i r r i g a t i o n a p p l i c a t i o n , between B r i t i s h C o l u m b i a and o t h e r a r e a s , show t h a t t a k i n g a verage f i g u r e s , s p r i n k l e r s a r e 60-99 p e r c e n t e f f i c i e n t w h i l e f l o o d i n g i s 45-70 p e r c e n t . L o s s e s i n w a t e r conveyance by p i p i n g a r e n e g l i g i b l e , w h i l e open d i t c h e s i n t h e N i c o l a V a l l e y show a l o s s o f 33 p e r c e n t per m i l e . I r r i g a t i o n systems d e s i g n s h o u l d be f l e x i b l e ; o v e rhead and s u r f a c e methods, and t h e i r m o d i f i c a t i o n s and d e v e l o p m e n t s , s h o u l d be c o n s i d e r e d on t h e i r own m e r i t s i n a g i v e n s i t u a t i o n . TABLE X WATER CONVEYANCE AND IRRIGATION EFFICIENCY SOIL TYPE PERCENTAGE WATER LOSS WATER USE FIELD WATER REFERENCE (100-CONVEYANCE EFFICIENCY) EFFICIENCY APPLICATION EFFICIENCY % per y a r d s % per m i l e Overhead S u r f a c e 1 % Overhead S u r f a c e % % 15 Q u i l c h e n a No. 1 g d i t c h . 3/6 & 23/7/69 ~V~29 Q u i l c h e n a No. 2 24 d i t c h . 23/6/69 & 23/7/69 G r a v e l l y t i l l . 29 24 / / 583 1804 96 23 B e r g l u n d No. 1 27/7/69 B e r g l u n d No. 2 27/7/69 Loam t o c l a y loam 44 11 / / 597 843 83 23 55 55* 73. F i n e sandy loam, v a r i a b l e 67 56 84 72* 65. 71. M a i n l y v e r y f i n e sandy loam 64 50 61 47* 67. S i l t loam and s i l t y c l a y . 61 60-99 67-99 43* 66. 21,60 36 48 / 5520 S i l t loam t o t i l l , 14 / 3080 v a r i a b l e 5 3 f 3 2 Q 2 60 / 4360 '- I n d i c a t e s b o r d e r o r downslope i r r i g a t i o n . CHAPTER V RESULTS AND CONCLUSIONS T h i s s t u d y o f i r r i g a t i o n i n the N i c o l a V a l l e y y i e l d e d g e n e r a l d a t a c o n c e r n i n g the use o f p r e s e n t methods, and s p e c i f i c d a t a c o n c e r n i n g t h e s e a s o n a l w a t e r r e q u i r e m e n t s o f c r o p s a t t h r e e s i t e s . Of t h e i r r i g a t i o n systems i n u s e , s u r f a c e a p p l i c a t i o n i s p r e d o m i n a n t ; t h i s t r a d i t i o n a l method i s w e l l adapted t o t e r r a i n where s u r f a c e w a t e r s can be g e a d i l y u s e d , and i n s p i t e o f t h e i n c r e a s i n g demand f o r s p r i n k l e r s , i s l i k e l y t o r e t a i n c o n s i d e r a b l e i m p o r t a n c e i n t h e f u t u r e . An i r r i g a t i o n s y stem i n t h i s a r e a i s a key f a c t o r i n a m a r g i n a l economy, and b o t h t h e d e s i g n and p l a n n i n g o f such an i r r i g a t i o n s y s t e m s h o u l d be s u f f i c i e n t l y f l e x i b l e t o i n c o r p o r a t e e i t h e r s u r f a c e o r overhead methods as a r e b e s t s u i t e d t o the t e r r a i n c o n c e r n e d . Fo r the measurement o f e v a p o t r a n s p i r a t i o n , the Ogopogo carborundum b l o c k e v a p o r i m e t e r was found t o be s a t i s f a c t o r y by c o m p a r i s o n w i t h o t h e r methods o f measurement and e s t i m a t i n g . Due t o l a c k o f d a t a , i t was not p o s s i b l e t o compute r e c o r d s o f c u m u l a t i v e s e a s o n a l e v a p o t r a n s p i r a t i o n w i t h t h e i r r i s k o f o c c u r r e n c e ; i n s t e a d t h e summer r e c o r d s f o r 1967 were assumed t o g i v e a n e a r maximum e s t i m a t e . A f t e r a d j u s t m e n t f o r r a i n f a l l and s o i l m o i s t u r e c o n t r i b u t i o n , t h e i r r i g a t i o n w a t e r r e q u i r e m e n t s o f e v a p o t r a n s p i r a t i o n a t t h r e e s i t e s were found t o be: 26" a t M e r r i t t , 19" a t Douglas Lake, and 24" a t Q u i l c h e n a . - 76 -The e s t i m a t e s f o r M e r r i t t and Douglas Lake were based on d i r e c t measurement, w h i l e t h a t f o r Q u i l c h e n a was based on d a t a t r a n s p o s e d from M e r r i t t by means o f c o r r e l a t i o n between t e m p e r a t u r e and e v a p o t r a n s p i r a t i o n . F o r the d e t e r m i n a t i o n o f d r a i n a g e o r l e a c h i n g r e q u i r e m e n t s , measure-ments o f e l e c t r i c a l c o n d u c t i v i t y o f i r r i g a t i o n w a t e r were found t o g i v e s a t i s f a c t o r y r e s u l t s ; however, c h e m i c a l a n a l y s e s a r e n e c e s s a r y t o o b t a i n a r e a l i s t i c e s t i m a t e o f any sodium h a z a r d p r e s e n t , and f o r t h e d e t e r m i n a -t i o n o f amounts o f gypsum t o be added t o i r r i g a t i o n w a t e r s . S i n c e t e s t s f o r t he d e t e r m i n a t i o n o f sodium h a z a r d , based on a n i o n e v a l u a t i o n s ( e g . Sodium A d s o r p t i o n R a t i o , and Sodium P e r c e n t a g e ) , do not appear t o be s a t i s f a c t o r y , c h e m i c a l a n a l y s e s a r e r e q u i r e d f o r i o n i c e v a l u a t i o n s o f Sodium, C a l c i u m , Magnesium, C a r b o n a t e , and B i c a r b o n a t e f o r t e s t s i n d i c a t i n g the q u a l i t y o f i r r i g a t i o n w a t e r s , and a l s o o f C h l o r i d e and S u l p h a t e f o r the d e t e r m i n a t i o n o f gypsum r e q u i r e m e n t s . I n c e r t a i n a r e a s , t h e s o i l i t s e l f may c o n t a i n s u f f i c i e n t s a l t s t o cause s a l i n e o r a l k a l i n e c o n d i t i o n s , and i n c o m p a r i s o n the i r r i g a t i o n w a t e r may be o f low, o r n e g l i g i b l e , t o t a l s a l i n i t y . F o r the same t h r e e s i t e s t he d r a i n a g e r e q u i r e m e n t s , d e t e r m i n e d from maximum v a l u e s o f s p o t measurements t a k e n " i n s i t u , " were found t o be 5 p e r c e n t a t M e r r i t t , 3 p e r c e n t a t Douglas L a k e , and 8 p e r c e n t a t Q u i l c h e n a . Samples were t a k e n o n l y a t Q u i l c h e n a , and c h e m i c a l a n a l y s i s o f t h e s e showed t h a t a d d i t i o n o f gypsum t o the i r r i g a t i o n w a t e r s would appear t o be n e c e s s a r y i n c e r t a i n c a s e s t o p r e v e n t s o d i u m - a l k a l i c o n d i t i o n s . The e f f i c i e n c y o f i r r i g a t i o n systems was c o n s i d e r e d i n r e l a t i o n t o - 77 -d a t a from o t h e r a r e a s . T a k i n g average f i g u r e s , s p r i n k l e r s have a d i s -t r i b u t i o n e f f i c i e n c y o f 60-99 p e r c e n t , compared w i t h f l o o d i n g a t 45-70 p e r c e n t . Water l o s s e s from open conveyance d i t c h e s i n the N i c o l a V a l l e y r u n a t an average o f 33 p e r c e n t p er m i l e , b u t range from 8 p e r c e n t t o 96 p e r c e n t , w h i l e l o s s e s from p i p e s a r e n e g l i g i b l e . Such e s t i m a t e s a r e based on t h e n o r m a l l y a c c e p t e d c o n c e p t o f i r r i g a -t i o n e f f i c i e n c y . However, i n an a r e a w i t h a s h a l l o w w a t e r t a b l e , w a t e r l o s t t h r o u g h seepage and poor d i s t r i b u t i o n i s i n f a c t r e t u r n e d to the f l o w s ystem, thus i n d i c a t i n g t h a t v a l u e s o f e f f i c i e n c y , a t l e a s t t o t h e w a t e r l i c e n s i n g a u t h o r i t y , a r e not as low as the f i g u r e s would s u g g e s t . D e s p i t e t h i s c o n s i d e r a t i o n , i t s h o u l d be remembered t h a t the e x c e s s w a t e r used i n i r r i g a t i o n may cause l e a c h i n g o f p l a n t n u t r i e n t s , w h i c h c o u l d a c c e l e r a t e e u t r o p h i c a t i o n o f a d j a c e n t w a t e r b o d i e s . S e a s o n a l w a t e r r e q u i r e m e n t s have been e s t i m a t e d by c o n s i d e r i n g t h e d r a i n a g e r e q u i r e m e n t t o g e t h e r w i t h a near-maximum s e a s o n a l v a l u e o f e v a p o t r a n s p i r a t i o n , t a k i n g as the example a c r o p o f a l f a l f a g i v i n g good y i e l d s , and assuming t h a t no s o i l d e t e r i o r a t i o n by s a l i n i t y w ould o c c u r . T h i s s o i l d e t e r i o r a t i o n can o n l y o c c u r I n t h e l o n g te r m , and t h e d r a i n a g e w a t e r has t h e r e f o r e been computed as a p e r c e n t a g e o f t h e mean s e a s o n a l e v a p o t r a n s p i r a t i o n . I t may be added a t each i r r i g a t i o n , o r a t l o n g e r i n t e r v a l s , and so may be c u t f o r one o r two seasons o f h i g h e v a p o t r a n s -p i r a t i o n , p r o v i d e d t h a t any d e f i c i t i s l a t e r made good.. The c r o p w a t e r s u p p l y must t h e r e f o r e be adequate t o meet the l a r g e r o f : - 78 -i ) The consumptive use r e q u i r e m e n t based on a y e a r o f h i g h demand, or i i ) The consumptive use r e q u i r e m e n t based on a y e a r o f h i g h demand, p l u s a m o d i f i e d d r a i n a g e r e q u i r e m e n t based on a l o n g term a v e r a g e ( L . T . A . ) . I n 1967 cons u m p t i v e use was found t o be 7 p e r c e n t g r e a t e r than i n t h e average s e a s o n , w h i l e p e r c e n t a g e f i g u r e s f o r t h e d r a i n a g e r e q u i r e m e n t i n the N i c o l a V a l l e y show a maximum v a l u e o f 8 p e r c e n t . Where t h e d r a i n a g e r e q u i r e m e n t i s l e s s t h a n , o r e q u a l t o 7 p e r c e n t , c o n d i t i o n i ) above w i l l a p p l y , w h i l e a t t h e h i g h e r f i g u r e o f 8 p e r c e n t c o n d i t i o n i i ) w i l l g o v e r n , and t h e n e c e s s a r y s u p p l y be g i v e n by: 1967 e v a p o t r a n s p i r a t i o n ( h i g h demand v a l u e ) , p l u s 8 p e r c e n t o f th e L.T.A. e v a p o t r a n s p i r a t i o n ( t o p r o v i d e d r a i n a g e w a t e r ) , l e s s 7 p e r c e n t o f t h e L.T.A. e v a p o t r a n s p i r a t i o n ( t o c a r r y o v e r some d r a i n a g e w a t e r t o n e x t s e a s o n ) . T h i s s i m p l i f i e s t o : 1967 e v a p o t r a n s p i r a t i o n p l u s one p e r c e n t o f t h e L.T.A. e v a p o t r a n s -p i r a t i o n . . Thus i n t h i s case a l o n e the t o t a l w a t e r needs a r e l e s s t h a n one p e r c e n t above the 1967 l e v e l o f e v a p o t r a n s p i r a t i o n . V a l u e s o f i r r i g a t i o n r e q u i r e m e n t s e s t i m a t e d f o r t h e N i c o l a V a l l e y a r e g i v e n i n T a b l e X I . In t he same manner as t h e s e a s o n a l w a t e r r e q u i r e m e n t s f o r i r r i g a t i o n have been d e t e r m i n e d f o r t h e above s i t e s , s i m i l a r e s t i m a t e s c o u l d be made d i r e c t l y o r t r a n s p o s e d f o r o t h e r p a r t s o f t h e v a l l e y . - 79 -T h i s s t u d y i s a p r e l i m i n a r y a t t e m p t t o d e f i n e c e r t a i n o f t h e w a t e r needs o f a r e g i o n . Much f u r t h e r work needs to be done, b o t h w i t h r e g a r d to w a t e r d i s t r i b u t i o n i n t h e N i c o l a V a l l e y and methods and t e c h n i q u e s o f i r r i g a t i o n a d a p t a b l e t o B r i t i s h C o l u m b i a . Some a s p e c t s o f the p r o b l e m w h i c h a r e amenable t o f u r t h e r s t u d y a r e s u g g e s t e d below. a) C r i t e r i a f o r t h e c h o i c e between, and d e s i g n o f , f l o o d and s p r i n k l e r i r r i g a t i o n systems i n any a r e a , c o n s i d e r i n g t e r r a i n , s o i l t y p e , a v a i l a b i l i t y o f w a t e r , and c o s t s o f i n s t a l l a t i o n and m a i n t e n a n c e . b) D e v e l o p i n g the concept o f r i s k a n a l y s i s , and d e f i n i n g the r i s k s a s s o c i a t e d w i t h v a r i o u s l e v e l s o f s e a s o n a l e v a p o t r a n s p i r a t i o n and r a i n f a l l . c ) The a d v i s a b i l i t y o f a d d i n g gypsum to i r r i g a t i o n w a t e r s , and the r e l a t i v e e f f e c t s o f w a t e r and s o i l q u a l i t y i n c a u s i n g a l k a l i n e ( 'black a l k a l i ' ) c o n d i t i o n s . Improved methods f o r t h e i n h i b i t i o n o f s a l i n e and a l k a l i n e c o n d i t i o n s . d) The s i g n i f i c a n c e o f c a n a l seepage l o s s e s and i n e f f i c i e n c y o f d i s t r i -b u t i o n o f i r r i g a t i o n w a t e r , b o t h from the v i e w p o i n t o f t h e ranche'rs whose w a t e r i s b e i n g 'wasted,' and a l s o the p o s s i b l e e f f e c t s on l o c a l w a t e r b o d i e s . - 80 -TABLE X I IRRIGATION REQUIREMENTS AT MERRITT, DOUGLAS LAKE, AND QUILCHENA MERRITT DOUGLAS LAKE QUILCHENA CONSUMPTIVE USE ( a c r e i n s . p e r a c r e ) 26 19 24 DRAINAGE PERCENTAGE* - found i n f i e l d - 5% 3% DRAINAGE REQUIREMENT 1% CROP REQUIREMENT ( a c r e i n s . p e r a c r e ) 26 19 24 FIELD APPLICATION EFFICIENCY - overhead - 60-99% 60-99% 60-99% FIELD APPLICATION EFFICIENCY - s u r f a c e - 45-70% 45-70% 45-70% FIELD REQUIREMENT - overhead -( a c r e i n s . per a c r e ) 26-43 19-32 24-40 FIELD REQUIREMENT - s u r f a c e - 37-58 ( a c r e i n s . p e r a c r e ) 27-42 34-53 * D r a i n a g e P e r c e n t a g e i s computed f r o m t a k i n g average v a l u e s o f E l e c t r i c a l C o n d u c t i v i t y ( T a b l e s V I I and V I I I ) i f more t h a n one r e a d i n g i s a v a i l a b l e . BIBLIOGRAPHY The r e f e r e n c e s g i v e n w i t h i n t h e b i b l i o g r a p h y a r e denoted n u m e r i c a l l y i n the t e x t . They have been s p l i t i n t o f o u r major s e c t i o n s each o f w h i c h i s t a k e n i n a l p h a b e t i c a l o r d e r ; the s e c t i o n h e a d i n g s a r e as f o l l o w s : A. I r r i g a t i o n - G e n e r a l B. E v a p o t r a n s p i r a t i o n and Consumptive Use C. S a l i n i t y and D r a i n a g e D. E f f i c i e n c y and Conveyance. - 82 -A. I r r i g a t i o n - G e n e r a l 1. C h r i s t o p o u l o s , C. "Consumptive Use R e q u i r e m e n t s , " P r o c e e d i n g s o f A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s ( D i s c u s s i o n ) , December 1959. 2. G e o l o g i c a l S u rvey o f Canada. Geology and M i n e r a l D e p o s i t s o f N i c o l a Map-Area, B r i t i s h C o l u m b i a . (W. E. C o c k f i e l d ) . Dept. o f Mines and T e c h n i c a l S u r v e y s . Memoir 249. 3. Great B r i t a i n , M i n i s t r y o f A g r i c u l t u r e , F i s h e r i e s and Food. Water f o r I r r i g a t i o n . Her M a j e s t y ' s S t a t i o n e r y O f f i c e , B u l l e t i n No. 202, 1967, 4. J e n s e n , M.C. P r i v a t e C o r r e s p o n d e n c e . Dept. o f A g r i c . E n g i n e e r i n g , W a shington S t a t e U n i v e r s i t y , P u l l m a n , W a s h i n g t o n . 5. Krogman, K. K. and L u t w i c k , L. E. "Consumptive Use o f Water by Forage Crops i n t h e Upper Kootenay R i v e r V a l l e y , " Can. J o u r . S o i l S c i e n c e . V o l . 41, No. 1, F e b r u a r y 1961. 6. O ' R i o r d a n , J . " E f f i c i e n c y o f I r r i g a t i o n Water Use," Ph.D. T h e s i s , Dept. o f Geography, 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 , Vancouver, B.C., 1969. 7. R a i k e s , R. L. Water, Weather, and P r e h i s t o r y . John B a k e r , London, 1968. 8. Rose, J . G. " I r r i g a t i o n f o r Hay P r o d u c t i o n , " U n p u b l i s h e d B. Sc. T h e s i s , Dept. o f A g r i c . Mechs., 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 , Vancouver, B.C. 9. 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 . Water Re s o u r c e s o f t h e N i c o l a - K a m l o o p s A r e a . R e p o r t No. 1 - P r e l i m i n a r y A p p r a i s a l . Dept. o f C i v i l Eng., Water Resources S e r i e s No. 1, 1969. B. E v a p o t r a n s p i r a t i o n and Consumptive Use 20. B a h r a n i , B. and T a y l o r , S. A. " E v a p o t r a n s p i r a t i o n o f A l f a l f a , " A g r o n . J o u r . 53, 1961, pp. 233-236. 21. B r i t i s h C o l u m b i a , Department o f A g r i c u l t u r e . B r i t i s h C o l u m b i a I r r i g a t i o n G u i d e . V i c t o r i a , B r i t i s h C o l u m b i a . 22. B r i t i s h C o l u m b i a . C l i m a t e o f B r i t i s h C o l u m b i a . Dept. o f A g r i c u l t u r e , V i c t o r i a , B r i t i s h C o l u m b i a , A n n u a l R e p o r t . 23. Canada, M e t e o r o l o g i c a l B r a n c h . The D i s t r i b u t i o n o f Growing-Degree Days i n Canada. ( C C . B o u g h n e r ) . Dept. o f T r a n s p o r t , F e d e r a l G o vt., Ottawa. 24. C a r d e r A. C. "Comparison o f S e v e r a l Atmometers A s s e m b l i e s , " Can. J o u r . P l a n t S c i e n c e . V o l . 49, No. 5. p. 535, September 1969. - 83 -25. Chow, V. T. Handbook of Applied Hydrology. McGraw-Hill, New York. 26. Eagleman, II. R. and Decker, W. L. "Role of S o i l Moisture i n Evapo-t r a n s p i r a t i o n , " Agron. Jour. 57, pp. 626-629, 1965. 27. G r a s s i and Chambouleyron. V a r i a t i o n s of E v a p o t r a n s p i r a t i o n of Lucerne w i t h Growth, R e v i s t a Facultad de Ciencas A g r a r i a s , Universidad Nacional de Cuyo, 12, No. 1, pp. 15-23, 1965. 28. H a l k i a s , N. A., Veihmeyer, F. J., and Hendrickson, A. H. "Determining Water Needs f o r Crops from C l i m a t i c Data," H i l g a r d i a , V o l . 24, No. 9, December 1955. 29. Hanks, R. J . , Gardner, H. R., and F l o r i a n , R. L. "Plant Growth-E v a p o t r a n s p i r a t i o n R e l a t i o n s f o r Several Crops i n the C e n t r a l Great P l a i n s , " Agron. Jour., V o l . 61, No. 1, Jan-Feb. 1969. 30. Holmes, R. M. and Robertson, G. W. " E v a p o t r a n s p i r a t i o n Versus P o t e n t i a l E v a p o t r a n s p i r a t i o n i n Dry Land A g r i c u l t u r e , " Trans. Amer. Soc. of  A g r i c . Engineers?,,p,Vol. 6, pp. 65-67, 1963. 31. Munson, W. C. "Method f o r Estimating Consumptive Use of Water f o r A g r i c u l t u r e , " Trans. Amer. Soc. C i v i l Engineers, V o l . 127, part I I I , pp. 200-212, 1962. 32. P e r r i e r , E. R., M c K e l l , C. M., and Davidson, J . M. "Plant - s o i l - w a t e r R e l a t i o n s h i p s of Orchard Grass," S o i l Science, V o l . 92, pp. 413-420, 1961. 33. Rose, C. W. A g r i c u l t u r a l P h y s i c s . Pergamon Press, London, 1966. 34. Walter, A. "A R e l a t i o n Between Incoming Solar R a d i a t i o n and Degree-Hours of Temperature," A g r i c . Meteorology. V o l . 6, No. 6, November 1969. 35. Wilcox, J . C. "A Simple Evaporimeter f o r Use i n Cold Areas," Water Resources Research. V o l . 3, No. 2, 1967. 36. . P r i v a t e Correspondence. A g r i c . R e h a b i l i t a t i o n and Development Act , Summerland Research S t a t i o n , Summerland, B r i t i s h Columbia. C. S a l i n i t y and Drainage 40. Canada, Dept. of A g r i c u l t u r e . " S u i t a b i l i t y f o r I r r i g a t i o n of Water from Lakes and Streams i n the Southern I n t e r i o r of B.C.," P u b l i c a t i o n 1179, Dept. of A g r i c u l t u r e . 41. Eaton, F. M. " T o x i c i t y and Accumulation of C h l o r i d e and Sulphate S a l t s i n P l a n t s , " Jour. A g r i c . Research, V o l . 64, p. 357, Jan-June 1942. - 84 -42. E a t o n , F. M. " S i g n i f i c a n c e o f C a r b o n a t e s i n I r r i g a t i o n W a t e r s , " S o i l S c i e n c e , V o l . 69, Jan-June 1950. 43. _______ "Formulas f o r E s t i m a t i n g L e a c h i n g and Gypsum Requirements o f I r r i g a t i o n W a t e r s , " Texas A g r i c . E x p e r i m e n t a l S t a t i o n , M i s c . P u b l . I l l , 1954. 44. Gorham, E. " F a c t o r s I n f l u e n c i n g S u p p l y o f M a j o r Ions to I n l a n d W a t e r s , w i t h S p e c i a l R e f e r e n c e t o the Atmosphere," G e o l . Soc. Ann. B u l l . , V o l . 72, pp. 795-840, 1961. 45. Hagan, R., H a i s e , H., and E d m i n s t e r , T. ( e d i t o r s ) . ' I r r i g a t i o n o f A g r i c u l t u r a l Lands. No. 11 i n t h e s e r i e s , Agronomy. 1967. 46. K e l l e y , W. P., A l k a l i S o i l s : T h e i r F o r m a t i o n , P r o p e r t i e s , and Reclama-t i o n . R e i n h o l d P u b l i s h i n g C o r p o r a t i o n , 1951. 47. K o r v e n H. C. and W i l c o x , J . C. " E f f e c t o f F l o w V a r i a t i o n s on the S a l t C o n t e n t and R e a c t i o n o f a M o u n t a i n C r e e k , " Can. J o u r . S o i l S c i e n c e . V o l . 44, 1964. 48. Reeve, R. C. " R e l a t i o n o f S a l i n i t y t o I r r i g a t i o n and D r a i n a g e R e q u i r e -ments," I n t . Comm. on I r r . and D r a i n . T r a n s . , 3 r d C o n g r e s s , Q u e s t i o n 10, pp. 175-187, 1957. 49. T o t h , J . "Groundwater F l o w i n S m a l l D r a i n a g e B a s i n s , " Groundwater, 1963. 50. T o t h , J . "Groundwater R e s o u r c e s , Olds A r e a ; O c c u r r e n c e and N a t u r a l Movement o f Groundwater," Res. Counc. o f A l t a . , B u l l . 17. 51. U.S. S a l i n i t y L a b o r a t o r y S t a f f . -'Diagnosis and Improvement o f S a l i n e and A l k a l i S o i l s , : U . S . Dept. o f A g r i c . Handbook 60, 1954. 52. van der M o l e n , W., and Boumans, J . " D r a i n a g e Requirements o f I r r i g a t e d S o i l s i n R e l a t i o n t o S a l i n i t y , " 8 t h I n t . Congr. S o i l S c i e n c e . V o l . I I , pp. 847-854, 1964. 53. W i l c o x , J . C , H o l l a n d , W. D., and MacDougald, J . M. " R e l a t i o n o f E l e v a t i o n o f a M o u n t a i n Stream t o R e a c t i o n and S a l t C o n t e n t o f the Water and S o i l , " Can. J o u r . S o i l S c i e n c e , V o l . 37, pp. 11-20, F e b r u a r y 1957. 54. W i l c o x , L., and R e s c h , W. " S a l t B a l a n c e and L e a c h i n g R e q u i r e m e n t , " U.S. Dept. o f A g r i c . Tech. B u l l . 1290. - 85 -D. E f f i c i e n c y and Conveyance 60. F r o s t , K. R. " E f f i c i e n c y o f S p r i n k l i n g , " S p r i n k l e r I r r i g . A s s n . , Open Tech. Conf., 1964. 61. L a u r i t z e n , C. W. " D i f f e r e n t Types o f C a n a l L i n e r , " J o u r . o f A g r i c . E n g i n e e r i n g . V o l . 34, pp. 407-410, June 1953. 62. . " L i n i n g s f o r I r r i g a t i o n C a n a l s , " I r r i g . Eng. and M a i n t . V o l . 10, December 1959, and V o l . 12, Ja n u a r y 1960. 63. . " B u t y l f o r C o l l e c t i o n , Conveyance,. and S t o r a g e o f Water," U t a h A g r i c . E x p e r i m e n t a l S t a t i o n , B u l l . 465. 64. Lee, B. F. " B e n t o n i t e L i n i n g , " S o i l Cons., p. 260, June 1957. 65. M y e r s , L. E., and H a i s e , H. R. "Water A p p l i c a t i o n o f S u r f a c e and S p r i n k l e r Methods - E f f i c i e n c y , " I n t e r . Comm. on I r r i g . and  D r a i n . 4 t h C o n g r e s s , Q u e s t i o n 12, R l , 1964. 66. P a i r , C. H. " E f f e c t o f Methods, e t c . , on Water A p p l i c a t i o n E f f i c i e n c y , " I n t e r . Comm. I r r i g . and D r a i n . , 5 t h C o n g r e s s , R10, Q u e s t i o n 16. 67. . "A Comparison o f I r r i g a t i o n E f f i c i e n c i e s O b t a i n e d under V a r i o u s Methods o f A p p l i c a t i o n , " U.S. Dept. o f A g r i c . , A g r i c . R e s e a r c h S e r v . , S o i l and Water Cons. Res. D i v . , N. W. B r a n c h . 68. P o h j a k a s , K. r e " B l a c k P o l y t h e n e as C a n a l L i n e r . Can. A g r i c . Eng., Ja n u a r y 1967. 69. R o b i n s o n , A. R., and Rohwer, C. "Me a s u r i n g C a n a l Seepage," U.S. Dept. o f A g r i c , Techn. B u l l . 1203, 1959. 70. R u s s e l l , N. "The Use o f B e n t o n i t e as a C a n a l Lining,"'-''" U n p u b l i s h e d B.S.A. T h e s i s , Dept. o f A g r i c , 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 , Vancouver, B.C. 71. S o m e r h a l d e r , B. R. "Comparing E f f i c i e n c i e s i n I r r i g a t i o n Water A p p l i c a t i o n , " A g r i c . E n g i n e e r i n g , V o l . 39, No. 3, 156-159, 1958. 72. U p p a l and S e h g a l . r e : Non L i n i n g o f D i t c h e s L e a d i n g to W a t e r l o g g i n g and S a l i n i t y . I n t e r . Comm. on I r r i g . and D r a i n . , Ann. B u l l . , p. 29, 1961. 73. U t a h S t a t e U n i v e r s i t y . " I r r i g a t i o n E f f i c i e n c y i n th e E s c a l a n t e V a l l e y , U t a h , " Utah S t a t e U n i v e r s i t y , U t a h Res. S e r v . 3 7 , May 1967. A P P E N D I X - 86 -1. FIELD TESTING i ) F i e l d t r i p s were made to Q u i l c h e n a Ranch f o r t h e purposes o f a s s e s s i n g i r r i g a t i o n i n t h e N i c o l a V a l l e y , and making s p e c i f i c f i e l d t e s t s , a t t h e f o l l o w i n g t i m e s d u r i n g t h e summer o f 1969: June 1 s t - 4 t h June 22nd - J u l y 1 1 t h J u l y 1 9 t h - August 3 r d D u r i n g t h e s e t i m e s o t h e r p l a c e s were v i s i t e d , i n c l u d i n g Summerland e x p e r i m e n t a l f a r m i n t h e Okanagan, t h e E x p e r i m e n t a l Farm a t Kamloops, and R i v e r l a n d Farms L t d . a t L i l l o e t . i i ) The pH o f c e r t a i n w a t e r s , e s p e c i a l l y Q u i l c h e n a C r e e k , was t a k e n as a f i r s t g u i d e t o s a l t c o n t e n t , b u t such measurements were sup e r c e d e d and a l s o e xtended by measurements o f E l e c t r i c a l C o n d u c t i v i t y . S i m u l t a n e o u s l y , w a t e r samples f o r c h e m i c a l a n a l y s i s were t a k e n a t s o u r c e s o f p a r t i c u l a r i m p o r t a n c e t o i r r i g a t i o n . i i i ) Conveyance e f f i c i e n c y was d e t e r m i n e d by t h e i n f l o w - o u t f l o w method, from f o u r d i f f e r e n t c h a n n e l s on two r a n c h e s . P o s s i b l e methods a r e g i v e n by R o b i n s o n and Rohwer . i v ) I n o r d e r to measure the e f f i c i e n c y o f a p p l i c a t i o n , t e s t s were f i r s t r u n t o d e t e r m i n e r a t e s o f i n f i l t r a t i o n ; f i v e s e p a r a t e t e s t s gave c o n f l i c t i n g r e s u l t s and i n d i c a t e d a) l a c k o f s o i l homogeneity w i t h i n s m a l l a r e a s , and b) t h e t e s t i t s e l f t o be u n s a t i s f a c t o r y . Any f u r t h e r a t t e m p t t o measure a p p l i c a t i o n e f f i c i e n c y was abandoned. - 87 -2. CONDITIONS AND METHODS OF TESTING 2.1. Mean D a i l y Temperature i ) M e r r i t t 1962-68 Ranger S t a t i o n , M e r r i t t , 1963-67 M e r r i t t ( C r a i g m o n t ) 1962 and 1968, a d j u s t e d t o M e r r i t t by monthly f a c t o r s . i i ) Q u i l c h e n a 1969 Thermohydrograph o p e r a t e d ( 2 7 t h May 1969, onward) by K. H a l l , D e p a r t -ment o f A g r i c u l t u r e , 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 . 2.2. Water Temperature Measured ' i n s i t u ' u s i n g a cup t y p e thermometer. 2.3. E v a p o t r a n s p i r a t i o n i ) M e r r i t t Ogopogo e v a p o r i m e t e r a t Ranger S t a t i o n , i i ) Douglas Lake Ogopogo evapor i m e t e r under A.R.D..A. o p e r a t o r . 2.4. E l e c t r i c a l C o n d u c t i v i t y Measured ' i n s i t u ' u s i n g a B a r n s t e a d C o n d u c t i v i t y B r i d g e : Model PM-70CB, w i t h a c e l l c o n s t a n t o f 0.1. Readings were c o r r e c t e d f o r t e m p e r a t u r e a c c o r d i n g t o the U.S. S a l i n i t y L a b o r a t o r y . - 88 -2.5. C h e m i c a l A n a l y s i s Samples were t a k e n i n p o l y e t h y l e n e ( n a l g e n e ) b o t t l e s and f r o z e n w i t h i n t h r e e h o u r s . A f t e r t r a n s p o r t t o 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 t h e y were r e f r o z e n u n t i l a n a l y s e d ; t r a n s p o r t t i m e t o o k from s i x h o u r s , t o a maximum o f t h r e e days f o r t h e l a s t s e t o f samples. D u r i n g t h i s time some a n i o n s , e s p e c i a l l y c a r b o n a t e s , may have b r o k e n down; t h e c a t i o n - a n i o n b a l a n c e i s uneven i n most sam p l e s , and t h i s would r e s u l t i n low e s t i m a t e s o f r e s i d u a l c a r b o n a t e , and o f d r a i n a g e and gypsum r e q u i r e m e n t s . 2.6. pH Measured ' i n s i t u ' u s i n g an I o n a l y s e r ( O r i o n R e s e a r c h ) S p e c i f i c Ion M e t e r : Model 401. 2.7 . Seepage L o s s e s Flow measurements were made w i t h a p r o p e l l e r meter; A. O t t - S m a l l C u r r e n t Meter C l . 

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