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Regulation of water yield and quality in British Columbia through forest management Golding, Douglas Lawrence 1968

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REGULATION OF WATER YIELD AND QUALITY IN BRITISH COLUMBIA THROUGH FOREST MANAGEMENT DOUGLAS LAWRENCE GOLDING BcScsFo, University of New Brunswick, 1953 M.SoFo, Purdue University, I96I A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of FORESTRY We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA January, I968 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r equ i r emen t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r ag ree tha t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y pu rposes may be g r a n t e d by the 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 . It i s u n d e r s t o o d tha 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 not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department The U n i v e r s i t y o f B r i t i s h Co lumb i a Vancouve r 8, Canada i A B S T R A C T T h e e c o n o m y o f n o t o n l y B r i t i s h C o l u m b i a b u t , a c c o r d i n g t o r e c e n t w a t e r - d i v e r s i o n p r o p o s a l s , m u c h o f w e s t e r n N o r t h A m e r i c a i s d e p e n d e n t o n t h e w a t e r r e s o u r c e s o f B r i t i s h C o l u m b i a . B e c a u s e o f i t s i m p o r t a n c e , t h e w a t e r r e s o u r c e s o f t h e p r o v i n c e m u s t b e m a n a g e d p r o p e r l y , r e q u i r i n g i n -f o r m a t i o n o n t h e a m o u n t o f t h e r e s o u r c e , i t s s p a t i a l a n d t e m p o r a l d i s -t r i b u t i o n , a n d how t h e s e f a c t o r s m a y b e i n f l u e n c e d . R e s e a r c h h a s s h o w n t h a t f o r e s t m a n a g e m e n t i n f l u e n c e s t h e y i e l d , r e g i m e , a n d q u a l i t y o f w a t e r . A c o m p r e h e n s i v e r e v i e w o f s u c h r e s e a r c h w a s p r e s e n t e d a n d r e l a t e d t o w a t e r s h e d m a n a g e m e n t i n B r i t i s h C o l u m b i a . L e g i s l a t i o n , a d m i n i s t r a t i o n , a n d p r o b l e m s o f w a t e r m a n a g e m e n t w e r e d i s c u s s e d w i t h p a r t i c u l a r r e f e r e n c e t o f o r e s t m a n a g e m e n t . I t was r e c o m -m e n d e d t h a t B . C . F o r e s t S e r v i c e f i e l d s t a f f b e i n c r e a s e d a n d t h a t w a t e r -s h e d m a n a g e m e n t r e c e i v e g r e a t e r e m p h a s i s a t t h e F o r e s t S e r v i c e T r a i n i n g S c h o o l , I n s t i t u t e o f T e c h n o l o g y , a n d 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 . T h e d i v i s i o n o f j u r i s d i c t i o n b e t w e e n t h e f e d e r a l a n d p r o v i n c i a l g o v e r n -m e n t s w a s s u g g e s t e d a s t h e r e a s o n f o r t h e p a s s i v e r o l e o f t h e f e d e r a l g o v e r n m e n t i n w a t e r r e s o u r c e s . B e c a u s e C a n a d a 1 s p r e s e n t w a t e r a d m i n i s -t r a t i o n i s i n a d e q u a t e f o r t h e f u t u r e , t h e f e d e r a l g o v e r n m e n t s h o u l d a s s u m e r e s p o n s i b i l i t y f o r i n i t i a t i n g a c t i o n o n w a t e r - r e s o u r c e d e v e l o p m e n t , a n d t h e p r o v i n c e s s h o u l d b e w i l l i n g t o f o r e g o some d e g r e e o f p r o v i n c i a l r i g h t s i n t h e i n t e r e s t o f c o m p r e h e n s i v e m a n a g e m e n t o f t h e r e s o u r c e . T h e w a t e r r e s o u r c e s o f t h e p r o v i n c e w e r e e x a m i n e d a n d f o u r w a t e r -s h e d - m a n a g e m e n t r e g i o n s w e r e d e s i g n a t e d ( C o a s t a l , P e a c e R i v e r , I n t e r i o r , a n d C o l u m b i a M o u n t a i n s ) o n t h e b a s i s o f c l i m a t i c f a c t o r s , w a t e r n e e d s , i i and flood and erosion potential. Forest-management was related to the objectives of watershed management in each region. One objective of watershed management in the Interior Region is increasing water supplies. Tree Farm License No. 9» in the Okanagan Valley was used to demonstrate forest-management effects on water yield. Yield could be increased five per cent by substituting for the present forest management one based on financial rotations and consideration of water as an important secondary product. Statistical calibration of Windermere and Sinclair Greeks in the East Kootenays was presented, and the effect of logging on streamflow from Watching Greek near Kamloops was analysed graphically. Water balance and other studies were presented for Terrace Greek watershed on Tree Farm License Noo 9» Other watershed research in British Columbia was reviewed and research needs discussed. A comprehensive research program was recommended, to begin with intensely-instrumented research watersheds ih the Coastal and Interior Regions. A rational mathematical rainfall-interception model was developed using forest-stand variables, most of which can be measured on aerial photos, and data from interception studies carried out in British Columbia and the United States. i i i ACKNOWLEDGEMENTS The writer wishes to acknowledge the guidance of Dr. P. G. Haddock, Dr. J. H. G. Smith, and Prof. Wo W. Jeffrey during the course of this study, and to thank Prof. T. L. Coulthard, Prof. J. deVries, and Dr. B. G. Griffith for their assistance and review of the thesis. Acknowledgement is also made of assistance given by S. M. Simpson Limited, Kelowna, B.C<>; Mr. P. N. Sprout, Soil Survey Branch, B.C Depart-ment of Agriculture, Kelowna; and Mr. R« J» Talbot, District Engineer, Water Rights Branch, B.C. Water Resources Service, Kelowna, BoC The author is grateful for the use of files of the B.C. Water Resources Service and maps produced by the Department of Geography, University of British Columbia. financial support was provided by the National Research Council, VanDusen Graduate Fellowship in Forestry, and Faculty of Forestry Graduate Fellowship. iv T A B L E O F C O N T E N T S Page A B S T R A C T i ACKNOWLEDGEMENTS . . . . . . . o i i i T A B L E O F C O N T E N T S . O o . . o o o o 0 o » o o . . . o e o o o o . . . iv L I S T O F T A B L E S .xvii L I S T O F F I G U R E S . . xix L I S T O F MAPS • • • . • • . • • . . < » . o . . . . o . o o o e o . o o xxi C h a p t e r l o I N T R O D U C T I O N e . . . . e o o . . . . « . e « . . » o o » o o o « 1 I I . F O R E S T S AND T H E H T D R O L O G I C A L C Y C L E . k X • o « * « e o o « o e o o o o o o o o o 0 o « e * e o c « ^ A n n u a l R a i n f a l l k E f f e c t o f W i n d • 7 E v a p o r a t i o n o f F a l l i n g R a i n 9 I n t e r c e p t i o n o . . . . . . . . . . » • • • • • • • • • • 9 V a r i a t i o n b e t w e e n s p e c i e s 1^ V a r i a t i o n w i t h s e a s o n . . . . . . . . . . 16 V a r i a t i o n w i t h s t a n d d e n s i t y a n d a g e . . . . . . . . 1? SteillflOW O O O O O O O O . O O O . . . . o o o o o o 19 FOg d r i p 0 . . . . 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 . 21 W a t e r l o s s 23 V Chapter Page Evaporation from Foliage . . . . . . . . . . . . . . . . 24 Moisture Storage in Vegetation . „ 25 Condensation . . « . 25 2o Snow . . « o e « e o . . « o o . « . . . . » » . » . . » . 26 Interception . • • » « . « « o « . » » « o « . » . . . » 26 Accumulation . . . . . . . . . 29 In the open 30 In the forest • 31 Evaporation from Snow 33 Melting of Snow o . . o . . . . . . . . . . . . . . . . 37 3. Evapotranspiration . . . . . . . . . . . . 40 Methods of Measurement . . . . . . . . . . . . 40 Tent method 40 Quick-weighing method 41 Sap velocity method 42 Energy budget method . . . . . . . . . . . . . . . 43 Eddy fluctuation method . 44 Soil moisture budget 44 Potted plant method 46 Lysimeters . o o . o . o . o e o o e . . . . . . . . 46 Results of Investigations . . . . . . . . . . 48 4. Streamflow . . . . . . . . . . . . 52 Annual Discharge . . . . . 52 vi Chapter Page Flow Regime . . . » „ „ . . . . . . . . 57 Wagon Wheel Gap, Colorado • 57 San Gabriel River, California 57 Coweeta, North Carolina . . . . . . . . 57 Pine Tree Branch, Tennessee 58 H.J. Andrews Experimental Forest, Oregon 58 Fernow Experimental Forest, West Virginia 59 Fraser Experimental Forest, Colorado 59 Shackham Brook, Central New York 60 Snowmelt and Water Yield . . . 60 5. Erosion 62 Erosion Studies 64 Erosion Hazard Ratings . . . . . . . . . . . . 66 Erosion Control 71 6. Water Quality 74 Effect of Logging on Water Quality 77 Logging . . . . . 77 Stream channels 80 Roads 80 Fire 85 ?. Forests and Fish 8? Water Yield and Regime 88 Debris in Channels • • 90 C h a p t e r P a g e W a t e r T e m p e r a t u r e s 90 I I I . A D M I N I S T R A T I O N O F WATER RESOURCES 92 1. J u r i s d i c t i o n 92 B r i t i s h N o r t h A m e r i c a A c t 92 R e l e v a n t s e c t i o n o f t h e a c t . 92 I n t e r p r e t a t i o n . . . . . . 93 2. E v o l u t i o n o f W a t e r P o l i c y 93 C a n a d a 93 r E a r l y c o n f e r e n c e s 94 C o n s e r v a t i o n C o m m i s s i o n . . . . . . . . 94 R e c o n s t r u c t i o n C o n f e r e n c e 95 R e s o u r c e s f o r T o m o r r o w C o n f e r e n c e 96 C a n a d i a n C o u n c i l o f R e s o u r c e M i n i s t e r s 96 F e d e r a l - P r o v i n c i a l P r e m i e r s ' C o n f e r e n c e 97 B r i t i s h C o l u m b i a 98 G o l d F i e l d s A c t 98 W a t e r a c t s C, 99 W a t e r R e s o u r c e s S e r v i c e 99 3. A g e n c i e s A d m i n i s t e r i n g T h e W a t e r R e s o u r c e . . . . . . . . . 1 0 0 F e d e r a l A g e n c i e s 1 0 1 P r o v i n c i a l A g e n c i e s 103 F e d e r a l - P r o v i n c i a l a n d I n t e r n a t i o n a l A g e n c i e s . . . . . 1 0 4 O t h e r A g e n c i e s 1 0 6 4 . D i s c u s s i o n 107 Chapter Page Problems o o . . . o o o o » o . e » o BoNoA. Act o o o e . o o o o o o o o o o e • >o o o o o o o o o Provincial attitudes . o Federal attitudes . . . Administration « o . « c Data collection o o . . Recommendations '. . o o o • Federal level . 0 0 0 0 Provlnoial level , 0 0 0 Data collection . . . . IV. WATER RESOURCES OF BRITISH COLUMBIA l o Climatic Regions .• Precipitation » o . . . . o Amount o o o o o o o o o 0 0 0 0 0 0 0 0 o o o o o o o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 O O 0 0 0 0 o o 0 o. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o o o o o o o Seasonal distribution . . . 0 . 0 Extremes 0 0 0 0 0 0 0 0 0 . 0 0 0 0 Intensity 0 0 0 0 0 0 0 0 0 0 0 0 Relation to watershed management o Potential Evapotranspiratlon . 0 0 0 0 Actual Evapotranspiratlon 0 «. e 0 . o Moisture Deficit . . . . . . » . Runoff Regions 0 0 . 0 0 0 0 0 0 0 • O • 9 • o • 3© Water Needs « * ' « * o 9 « o « 0 © © O © • 9 © « Q * 0 © 0 © O 9 O » 0 • ix Chapter P a g Q 4. Watershed Management Regions 135 Coastal Region . . . . . . . . . . . . . . 135 Peace River Region . . . . . . . . . . . 135 Columbia Mountain Region 135 Interior Region . . . . . . . . . . 136 5. Water Diversion Schemes . . . . . . . . . . . . 136 NAWAPA 137 Location • • 138 Conception 139 Engineering 140 National water policy 141 Other Diversion Schemes 146 Kootenai River diversion . . . . . 146 Clearwater-Red Deer River diversion 147 The GRAND canal 1*8 V. FOREST MANAGEMENT AND THE WATER RESOURCE IN BRITISH COLUMBIA . 149 1. Watershed Management and Legislation 149 Establishing the Forest Service . . 149 Forest Reserves • 150 The Royal Commission of 1955-1956 <> 153 The Forest Act of British Columbia . 155 2. Erosion 158 Examples of Erosion .» 159 X Chapter Page Brodie Creek flood 159 Giveout Creek slide . . . 162 Unnamed Creek flood 164 River Bank Erosion 165 Salmon River - Falkland area 165 Shuswap River - Mabel Lake area 166 Elk River - Fernie area 166 Sedimentation I67 Large-Scale Earth Movement . . . . . . . I69 Hope-Princeton slide . . . . . I69 Ocean Falls snow slide 170 Granduc avalanche 170 Lillooet slide 170 Ramsay Arm slide 171 Indian Arm slide . . . . . . . . . 171 Revelstoke avalanche . . . . . . . . . . . . . . . . 172 Recognition of the Problem of Erosion 172 Administrative Measures . . . . . . . 174 Training of Forest Service personnel 174 Forest Service staffing 175 Protective clauses in timber-sale contracts . . . . 178 Enforcement of contract conditions . 179 Timber harvest subsidies 180 x i C h a p t e r P a 8 e L o g g i n g M e a s u r e s t o R e d u c e E r o s i o n 182 P l a n n i n g • 182 C u t t i n g m e t h o d . . . . . . 183 L o g g i n g m e t h o d 183 R o a d C o n s t r u c t i o n M e t h o d s t o R e d u c e E r o s i o n 189 R o a d l o c a t i o n a n d d e s i g n . . . . . . . . . . . . . . 189 R o a d c o n s t r u c t i o n • 191 D r a i n a g e 193 S t r e a m c h a n n e l s . . . . . . . . . . 195 R o a d a n d D r a i n a g e M a i n t e n a n c e , 196 R o a d m a i n t e n a n c e . . . . . . . . , 196 P o s t - l o g g i n g e r o s i o n - c o n t r o l m e a s u r e s . . . . . . . 197 S l a s h B u r n i n g « 198 E r o s i o n H a z a r d R a t i n g 202 3. Q u a n t i t y a n d T i m i n g o f R u n o f f 204 I n c r e a s e i n T o t a l W a t e r Y i e l d 205 U n m a n a g e d f o r e s t . . . . . . . . . . . • 207 P r e s e n t f o r e s t m a n a g e m e n t . . . . . . . 215 F o r e s t m a n a g e m e n t a n d w a t e r p r o d u c t i o n . . . . . . . 216 F o r e s t m a n a g e m e n t p r i m a r i l y f o r w a t e r 218 C o n t r o l o f p h r e a t o p h y t e s 219 T i m i n g o f W a t e r Y i e l d s . . . . . . . . . . . • 221 T i m i n g o f w a t e r d e m a n d . . . . . . . . . . . . . . . 221 x i i Chapter Page Timing of water yield 222 Snowpack management 225 Transpiration reduction 228 Shuswap Diversion to the Okanagan 229 Flooding 231 4. Fisheries 237 Aerial Spraying of Forests • 238 Pesticides 238 Silvicides 241 Discussion .' 241 Logging Operations 242 Log Driving 246 VI. THE MODEL APPROACH TO FOREST HYDROLOGY 250 1. Introduction . . . . . . . . . . 250 2. Models For Watershed Management • 251 Review of Watershed Models 253 A Rational Interception Model . . . . . 254 Objective 254 Beginning assumptions 255 Constructing the model 256 Adjusting for beginning assumptions 260 3. Further Research Needs 265 x i i i Chapter Page VIIo WATERSHED STUDIES IN BRITISH COLUMBIA . . . . . . . . . . . . . 26? l o Research Watersheds o o o o o o . o . o o o o o o o o o o o 26? Objectives of Research Watersheds . o o o o o o o o o . 268 Representative Watersheds . o o . o o o o . 000000 269 Experimental Watersheds . . . . . . . . n o o . . . . . 270 Homogeneity . 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 271 Vegetation o o . o o o o o o o o o o o o o o o . o o 27^ Geology . o . o . o o o o o o o o o o o o o . o o o 275 Soil . o o o . o o o o o . o o o o o o o o o o o o . 275 Topography 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 276 Drainage o o o o o o o o o o o o o o o o o o o o o . 7^7 Meteorology 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 277 Power o o o o o o o o o o o . o o o o o o o o o o o 277 Experimental watershed selection . . . o o o o o . o 278 2. Okanagan Valley - Terrace and Esperon Creeks . . o . . . . 280 ObjeCtiVeS O O O O O O O O O O O O O . O O O O . O O O . 280 Description of the Region . 0 0 0 . 0 0 0 0 0 0 0 . 0 0 282 L0cat3.cn 0 0 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 282 Physiography 0 0 0 . 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 0 286 Climate o . o o o o o o o o o o o o o o o . o o o . 287 Study Area o o o o . o o . o o o o o o o o o o o . o o . 289 Location o o o . o o o o o o . o o o o o o o o . o . 289 Geology and soils . 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 289 Chapter Forest t j r p e o o o o o o o o o o o o o o o o o o o o o o 293 The Stlldy 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 294 Instrumentation 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 294 Water balance 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 295 Are a-elevation relationship 0 0 0 0 0 0 0 0 0 0 0 0 0 0 J06 Stage-discharge curves 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 311 Hydro graphs o o o o o o o o o o o o o o o o o o o o o o 3H Mass curves of runoff 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 314 Throughfall in a forest opening 0 0 0 0 0 0 0 0 0 0 0 0 316 Meteorological data 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 316 East Kootenays - Windermere and Sinclair Creeks o o o o o o o 318 Objectives o o o o o o o o o o o o o o o o o o o o o o o o 3**-8 Description of the Region 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 319 l i O C a t l O n o o o o o o o o o o o o o o o o o o o o o o o 319 Physiography 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 319 Climate o o o o o o o o o o o o o o o o o o o o o o o o 3^2 The Study Area o o o o o o o o o o o o o o o o o o o o o o 323 Location o o o o o o o o o o o o o o o o o o o o o o o 323 Geology o o o o o o o o o o o o o o o o o o o o o o o o 325 Forest type o o o o o o o o o o o o o o o o o o o o o o 325 Calibrating the Watershed 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 327 Kamloops Area - Watching Creek 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 334 Objectives o o o o o o o o o o o o o o o o o o o o o o o o 334 Chapter '  Page Description of the Region O o o o » o o o o o o o o o o 33^ LrOC&tXOn o o o o o o o o o a o o o o o o o o o o o 33^ * Physiography O O O O Q O O » O O O O O Q . » » O O O 335 Gllfliat6 o o o o o o o o o o o o o o o o o o o o o o 33^  The S tudy Are a o o o o o o o o o o o o o o o o o o o o 33^ LOCatiOn O O O O O O O O O O O O O O O O O O O O O 33^ SoiJLs o o o o o o o o o o o o o o o o o o o o o o o 337 Forest type o o o o o o o o o o o o o o o o o o o o 337 The Stlidy o o o o o o o o o o o o o o o o o o o o o o o 33^ 5« Hydrologic Studies on the University of British Columbia Research Forest o o o o o o » o » » o o o o » < > o o o o o t > 345 6» Other Watershed Studies in British Columbia ° « » <. o « » <> 347 Trapping Creek Representative Basin » » » » » . <. » o . 347 Serpentine and Nicomekl Representative Basins . <> o •> <> 348 Okanagan Study Basin = Carrs Landing 8 < . o 0 . o » . < . 348 Mass Balance of Woolsey, Placeg and Sentinel Glaciers . 349 Watershed Management Theses, University of British Columbia e o o o o o s o o o o o o o o o a o o o o o o 349 Vancouver and Victoria Municipal Watersheds o o < , < . < , <. 350 7o Watershed Research Needs in British Columbia „ » <> » o o » 352 xvi C h a p t e r P a g e V I I I . SUMMARY AND C O N C L U S I O N S • 357 B I B L I O G R A P H Y 362 A P P E N D I X I. M E T E O R O L O G I C A L O B S E R V A T I O N S ON TERRACE-ESPEBOH CHEEK WATERSHED 396 A P P E N D I X I I . C A L I B R A T I O N O F WINDERMERE C R E E K W I T H S I N C L A I R CREEK . . . 4 0 4 x v i i L I S T OF T A B L E S T a b l e P a g e 1. Snow a c c u m u l a t i o n u n d e r d i f f e r e n t c o v e r c o n d i t i o n s i n c e n t r a l New Y o r k ( F r o m E s c h n e r a n d S a t t e r l u n d 1963.) . . 33 2. R a t i o o f c l a s s a r e a t o a r e a o f B r i t i s h C o l u m b i a a n d c l a s s p r e c i p i t a t i o n t o t o t a l p r e c i p i t a t i o n b y m e a n a n n u a l p r e c i p i -t a t i o n c l a s s e s . 119 3. S p r i n g - s u m m e r p r e c i p i t a t i o n i n i n c h e s a n d a s a p e r c e n t a g e o f a n n u a l p r e c i p i t a t i o n , a n d 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 B r i t i s h C o l u m b i a 121 4. I r r i g a t e d a n d p o t e n t i a l l y i r r i g a b l e l a n d i n B r i t i s h C o l u m b i a , a n d w a t e r r e q u i r e m e n t s ( f r o m B . C . N a t . R e s . C o n f . 1964, T a b l e s 3 a n d 4) 133 5. A r e a b y a g e c l a s s o f f o r e s t c o v e r t y p e s o n T r e e F a r m L i c e n c e N o . 9 ( f r o m S . M . S i m p s o n L t d . 1962) 207 6. E s t i m a t e d w a t e r y i e l d i n c r e a s e f r o m l o g g i n g T . F . L . N o . 9» b y c o v e r t y p e 214 7. C l i m a t e a n d w a t e r y i e l d i n t h e O k a n a g a n , B . C . , a n d a t t h e F r a s e r E x p e r i m e n t a l F o r e s t , C o l o r a d o 224 8. M o n t h l y , a n n u a l m e a n , a n d e x t r e m e t e m p e r a t u r e s i n ° F . ( S o u r c e : B . C . D e p t . o f A g r i c . 1963) 290 9. F r o s t o c c u r r e n c e i n t h e O k a n a g a n V a l l e y ( S o u r c e : S . M . S i m p s o n L t d . 1962) 291 10. M o n t h l y a n d a n n u a l p r e c i p i t a t i o n i n i n c h e s ( S o u r c e : B . C . D e p t . A g r i c . I963) . 291 11. C o m p u t e d ( b y t h e T h o r n t h w a i t e m e t h o d ) a n d o b s e r v e d r u n o f f . . 297 12. A r e a - e l e v a t i o n r e l a t i o n s - ,p!speron C r e e k w a t e r s h e d 309 13. A r e a - e l e v a t i o n r e l a t i o n s - T e r r a c e C r e e k w a t e r s h e d 309 14. D i s c h a r g e f r o m S i n c l a i r a n d W i n d e r m e r e C r e e k s , I96I-I965 . . . 329 x v i i i Table Page 15. Rainfall and mean temperatures for Pass Lake and Kamloops for May-September averaged for the years V)6Z to 1965 337 Al. Dally precipitation at Meteorological Stations Nos. 1, 2, and 3 on the Terrace-Esperon Creek Watershed for the period June 23 - September 30, 1966 (Source: recording tipping-bucket rain gauge c h a r t s ) . . • 396 A2. Weekly precipitation for Meteorological Stations Nos. 1, 2, 35 for the open site; and for different distances from the bole of a tree in the forest site, for the period June 17-0ctober 13» I966, on the Terrace-Esperon Creek watershed . . . . . . . . . 399 A3. Snow survey measurements for Okanagan Valley snow courses for 1966 and averaged for the length of record 400 A4. Evaporation from Ogopogo evaporimeters from June 10 to October 28, I966, at Meteorological Station No. 1, Terrace-Esperon Creek watershed 401 A5. Evaporation from Ogopogo evaporimeters from June 10 to October 28, I966, at Meteorological Station No. 2, Terrace-Esperon Creek watershed , 402 A6. Evaporation from Ogopogo evaporimeters from June 10 to October 28, 1966, at Meteorological Station No. 3» Terrace-Esperon Creek watershed . . . . . . . 403 A?. Sum of squares and products for annual discharge in area-inches from Windermere Creek (Y) and Sinclair Creek (X), I96I-I965 . . 404 A8. Partial analysis of covariance for period of calibration of Windermere Creek (Y) with Sinclair Creek (X) . . . . . . . . . 405 A9. Monthly water balance calculated by Thornthwaite's method using climatic data for McCulloch, &C. (elevation /,,100 f t . ) , and observed runoff from Terrace Creek for the water year October 1965 - September 1966 406 L I S T O F F I G U R E S F i g u r e P a g e 1. H y d r o g r a p h s f o r M i s s i o n , T e r r a c e a n d E s p e r o n C r e e k s a n d p r e -c i p i t a t i o n f o r M c C u l l o c h , B o C , M a y - A u g u s t , I965 302 2. H y d r o g r a p h f o r T e r r a c e C r e e k , O c t o b e r 1, 1 9 6 5-September 30, 1966 303 3. H y d r o g r a p h f o r E s p e r o n C r e e k , O c t o b e r 1, 1 9 6 5-September 30, 4. H y d r o g r a p h o f L a m b l y C r e e k a b o v e S t e v e n s d i v e r s i o n f o r w a t e r y e a r s 1924, 1925 a n d 1927 305 5. H y d r o g r a p h s o f m e a n m o n t h l y d i s c h a r g e M a r c h - S e p t e m b e r f o r M i s s i o n a n d W h i t e m a n C r e e k s . o o o . s o o o . o . o e . o . . 30? 6. M a r c h o f m e a n m o n t h l y p r e c i p i t a t i o n , a c t u a l , a n d p o t e n t i a l e v a p o t r a n s p i r a t l o n a t M c C u l l o c h , B r i t i s h C o l u m b i a , b a s e d o n T h o m t h w a i t e ' s e q u a t i o n s 308 7. A r e a - e l e v a t i o n c u r v e s f o r E s p e r o n a n d T e r r a c e C r e e k w a t e r s h e d s . 310 80 S t a g e - d i s c h a r g e c u r v e f o r E s p e r o n C r e e k , 1965» f o r u s e w i t h s t a f f - g a u g e m e a s u r e m e n t s o f s t a g e . . . . . . . . . . . . . . . 312 9. S t a g e - d i s c h a r g e c u r v e f o r T e r r a c e C r e e k , 1965* f o r u s e w i t h s t a f f - g a u g e m e a s u r e m e n t s o f s t a g e . . . . . . . . . 313 10. M a s s c u r v e o f r u n o f f f o r T e r r a c e - E s p e r o n C r e e k s , J u n e - A u g u s t , 1965 . 315 11. T h r o u g h f a l l i n a n o p e n i n g i n a n E n g e l m a n n s p r u e e - s u b a l p i n e f i r s t a n d a t d i f f e r e n t d i s t a n c e s f r o m t h e b o l e o f a n E n g e l m a n n s p r u c e , 1 8 i n . d b h , 90 f t . i n h e i g h t , a n d 25 f t . c r o w n w i d t h . . 317 12. A r e a - e l e v a t i o n c u r v e s f o r W i n d e r m e r e a n d S i n c l a i r C r e e k w a t e r -Sh@dS o o o o o o o « o o o o o o o o o o o o e o o « e o o o o 3*"^  13o R e g r e s s i o n o f y i e l d f r o m W i n d e r m e r e C r e e k w a t e r s h e d o n y i e l d f r o m S i n c l a i r C r e e k w a t e r s h e d . . . . . . . . . . . . . . . . . 331 XX Figure Page 14. Accumulated June-August runoff from Watching Creek for periods I95O-I953 and 1962-1965 . . . . . . . . . . . . . . . . . . . . . 340 15. Mass curve of runoff from Watching Creek over precipitation at Kamloops, 1950-1953 and I962-I965 . 341 16. Maximum and minimum June flows from Watching Creek, 195°-1953 and I962-I965, with means for each period . 3^ 3 17. Mean and minimum June-August flows from Watching Creek, 1950-1953 and I962-I965, with means for each period . . 3**4 xxi LIST OF MAPS Map Page 1. Mean annual precipitation in British Columbia « . . . 118 2. Mean annual potential evapotranspiration after Thornthwaite . . . 125 3. Mean annual moisture deficit after Thornthwaite . . . . . . . . . 12? 4. British Columbia's major river basins . . . . . . . . . 128 5. Mean annual actual evapotranspiration after Thornthwaite . . . . 130 6. Terrace-Esperon Creek watershed 292 1 CHAPTER I. INTRODUCTION The report of the f i r s t Royal Commission on the forest resources of British Columbia stated that the future of the province depended on water, and recognized the relationship between water yields and forested mountain slopes (Fulton et a lo 1910)a Recent statements by proponents of water-diversion schemes imply that the economy of not only British Columbia but much of Canada and the United States depends on water from this provinces Because of its importance, the water resources of British Columbia must be managed properly, and to properly manage the resource there must be information available as to the amount of the resource, i t s distribution in space and times and how these factors may be influencedo The influence of the forest on such factors of the hydrologic cycle as precipitation and runoff has long been debated9 but only in the past 25 years has much research been carried outc Research has shown that forest management has considerable effect on the yields regimej and qual-ity of water0 This research is reviewed in this thesis and related to watershed management in the various regions of British Columbiac As a resource9 water is peculiar in that i t flows across political boundaries9 and the use to which i t is put in one area affects its useful-ness in other areas» The British North America act of I867 set forth the division of governmental powers between the Dominion and provincial governmentso Some of the problems of water management in Canada stem from this divisiorio The legislative responsibility of managing the water resource, its implications, and the evolution of water policy in Canada 2 a n d B r i t i s h C o l u m b i a a r e d i s c u s s e d h e r e i n . B r i t i s h C o l u m b i a ' s w a t e r r e a c h e s t h e p r o v i n c e a s p r e c i p i t a t i o n a n d a s i n f l o w f r o m o t h e r r e g i o n s 0 F ew o f t h e r i v e r s h a v e t h e i r s o u r c e o u t s i d e B r i t i s h C o l u m b i a , t h e C o l u m b i a , r i s i n g i n t h e U n i t e d S t a t e s , b e i n g t h e o n l y i m p o r t a n t r i v e r i n t h i s c a t e g o r y . I n p u t s i n t h e f o r m o f p r e c i p i t a t i o n a r e c o m p a r e d w i t h t h e w a t e r o u t p u t s o f e v a p o r a t i o n , t r a n s p i r a t i o n , a n d r u n o f f , t o o b t a i n some u n d e r s t a n d i n g o f t h e s p a t i a l a n d t e m p o r a l d i s t r i b u t i o n o f t h e w a t e r r e s o u r c e i n B r i t i s h C p l u m b i a . W a t e r d i v e r s i o n s h a v e b e e n s u g g e s t e d t h a t w o u l d t r a n s f e r w a t e r f r o m B r i t i s h C o l u m b i a t o a s f a r away a s M e x i c o . A w i d e l y - h e l d v i e w i s t h a t a n a b u n d a n t w a t e r s u p p l y i s v e r y i m p o r t a n t i n a t t r a c t i n g i n d u s t r y t o t h i s p r o v i n c e , s o t h a t w a t e r t r a n s f e r h a s s e r i o u s i m p l i c a t i o n s w i t h r e g a r d t o d e v e l o p m e n t o f t h e p r o v i n c e ' s i n d u s t r i a l s e c t o r . Some o f t h e m o r e w i d e l y -p u b l i c i z e d d i v e r s i o n s c h e m e s a r e e x a m i n e d w i t h r e g a r d t o t h e i r e c o n o m i c i m p l i c a t i o n s a s w e l l a s i n r e l a t i o n t o t h e e v o l u t i o n o f w a t e r p o l i c y i n C a n a d a . U n t i l 1965» l i t t l e w a t e r s h e d r e s e a r c h h a d b e e n c o n d u c t e d i n B r i t i s h C o l u m b i a . I n t h a t y e a r t h e I n t e r n a t i o n a l H y d r o l o g i c D e c a d e was i n s t i t u t e d , p r o v i d i n g i m p e t u s f o r i n c r e a s e d s t u d y o f w a t e r r e s o u r c e s . . I n B r i t i s h C o l u m b i a , m a n y i n v e s t i g a t i o n s w e r e b e g u n b y f e d e r a l a n d p r o v i n c i a l a g e n c i e s a n d 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 . T h e s e a r e d i s c u s s e d i n t h i s t h e s i s w i t h p a r t i c u l a r a t t e n t i o n t o a r e s e a r c h w a t e r s h e d e s t a b l i s h e d b y t h e F a c u l t y o f F o r e s t r y , 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 o d e t e r m i n e t h e e f f e c t s o f i n t e n s i v e f o r e s t m a n a g e m e n t o n w a t e r y i e l d a n d t i m i n g i n t h e O k a n a g a n V a l l e y . 3 Watershed research, especially in the United States, has provided much information on the influence of forest management on water but its transposition to other regions, e.g., British Columbia, is not always valid because of variation in climate, vegetation, and soils. Research must be expanded in British Columbia to provide information on the relation of forest management to water in the different regions of this province. Needs and type of research that may best satisfy these needs are discussed hereino While there is a lack of knowledge of the influence of forest manage-ment on water in British Columbia, use should be made of knox-dedge that has been gained elsewhere that is applicable to this province. An example of this use is the section in this thesis on erosion control during logging and road building. Mathematical models are becoming more widely used in forestry to pre-dict the effect of management practices. A case can be made for the use of such models., developed with existing knowledge, to predict the effect of forest management on water y i e l d o The models can be refined as more know-ledge becomes ayailablec, An example of this is the rainfall interception model, given in this thesis, that has been developed by the author using interception data mainly from the western United Stateso ij. CHAPTER II o FORESTS AND THE HYDROLOGICAL CYCLE To set the stage for discussion of the relation of forest man-agement in British Columbia to the resource9 water9 i t is necessary to consider the influence of the forest on the individual components of the hydrological eycle 0 The hydrologic cycle denotes the movement of waters either as liquid or vapour, from the atmosphere to the earth and back; to the atmosphere, this cycle repeating continually.. This chapter^ in reviewing the literature pertaining to the influence of the forest on the hydrologic cycle 8 indicates those fac-tors of the forest which do have an influences, the degree of this influ-ence8 and the scope of the research that has been carried out in this fieldo Some of the investigations reported here are not necessarily directly applicable to British Columbia in that the species and other eonditionsc, such as climates are different from those met in this province, Howevar9 some knowledge of these investigations is nes-essary to appreciate the forests" influence on the water resource^ to isolate water problems in British Columbiag, and to consider ways of alleviating those problems in which the forest plays a parte l o RAIN Annual Rainfall The component of the hydrologic cycle that is most obviously the immediate source of water for use at or near the surface of the earth is precipitation.. The effect of forest on precipitation has been debated 5 for many years by observers who cited various kinds of evidence to sup-port their views» Such views ranged from belief in a decrease in the sum total of precipitation falling on the globe as forest areas have been denuded.,, to the opposite belief (Belgrand 1854f cited by Marsh 1965)" Between the extremesa views were held such as were expressed by Marsh (1965s V 158)5 "We may well admit that i t (forest removal) has lessened the quantity jof precipitation] which annually falls within particular limits," The poet Frederick Paludan-Muller (I896, p0 11022),, in writing? Afric's barren sands Where nought can grows because i t raineth notj And where no rain can f a l l to bless the land ? Because nought grows there0 expressed the view held by Clave (1862)s Blanqui (1843)» Coultas (1860)9 Herschel (1875)8 Pavari (1962),, and Zon ( 1 9 2 ? ) 9 (GLaves Coultas^ Blanqui cited by Marsh 1 9 6 5 ) 0 A similar view is that a wet region fur-nishes abundant evaporatien for the production of more rain (Humphreys 193? cited by Penman 1 9 6 3 ) 0 McKay (I965) stated that showers often follow rainy days because of the evaporation from the wet terrain 9 yet he did n©t hold the views expressed by Humphreys. Warren (19^5)s using data on precipitation near the Sal ton Sea in California before and after the forming of the lake 9 concluded that the body of water (440 square miles in area) had not affected precipi-tation.. Bernard8 s (19^ -5) data on precipitation and evaporation in the Belgian Congo indicated no forest influence on the amount of precipita-tion.. Penman (I963) agreed with Bernard's conclusion8 though not with 6 his method of arriving at i t . Molchanov (i960) also argued against the view that the presence of forests increases precipitation. The evidence which apparently supports the theory of the forest increasing precipitation is largely circumstantials according to Penman (1963)9 who based his opinion on meteorological considerations only.. He stated that the addition of moisture to the atmosphere, by evapor~ ation or transpirations, is not a necessary or sufficient condition for an increase in precipitation near the surface from which the moisture has come* Recently, however, i t has been suggested that sublimated tree terpenes may act as condensation nuclei for water vapour in the atmosphere.. Hickman (1966) wondered about the possible effect of this on precipitation a The view was also held that the forest influenced not only the amount of precipitation.but other aspects of the weather as wello Caimi (I857) attributed the increased frequency of hail storms on the fertile plains of Lombardy to the cutting of forests in the Alps and Appennlneso Young (i860) reported that after the forests between the Riviera and Montferrat had been cut, greater destruction was wrought by hail in the region of northwestern Italy.. Marsh (I965) wrote that the forest affected local climate, espe-cially temperatureo His evidence was the greater depth of frost in soils in the open. Some writers held that the cutting of forests had altered the mean atmospheric temperature of large parts of the globe0 Webster (1843) wrote that the weather in the United States was more inconstant after the cutting of large tracts of woodland and that the warm weather 7 o f a u t u m n e x t e n d e d f u r t h e r i n t o w i n t e r a n d c o l d w e a t h e r f u r t h e r i n t o s u m m e r . A b j o r n s e n (1855) r e p o r t e d t h e l a t e n e s s o f s p r i n g i n m a n y d i s -t r i c t s o f S w e d e n a f t e r t h e f o r e s t s h a d b e e n c l e a r e d o f f . E f f e c t o f W i n d B e f o r e d i s c u s s i n g t h e i n f l u e n c e o f t h e f o r e s t o n i n t e r c e p t i o n , t h r o u g h f a l l , a n d e v a p o r a t i o n , i t s e f f e c t o n w i n d s h o u l d b e c o n s i d e r e d . . M u c h o f t h e i n f l u e n c e o f t h e f o r e s t o n t h e s e v a r i a b l e s i s d u e t o i t s e f f e c t o n w i n d . E x t r e m e v i e w s h a v e b e e n h e l d b y s o m e , f o r e x a m p l e , D u s s a r d ( 1 8 4 2 ) who b l a m e d t h e d e s t r u c t i o n o f t h e f o r e s t s o f t h e C e v e n n e s i n s o u t h - c e n t r a l F r a n c e f o r t h e m i s t r a l « o r n o r t h w e s t w i n d , w h o s e c h i l l i n g b l a s t s i n s p r i n g a r e o f t e n f a t a l t o t e n d e r v e g e t a t i o n a l o n g t h e M e d i t e r r a n e a n c o a s t . H o w e v e r , t h i s s e c t i o n w i l l d e a l w i t h e v i d e n c e t h a t i s l e s s c i r c u r n s t a n t i a l o A s w i n d m o v e s a c r o s s a s u r f a c e , f r i c t i o n a l r e s i s t a n c e i s e x e r t e d b y t h e s u r f a c e , d e c r e a s i n g t h e w i n d s p e e d p r o p o r t i o n a l t o t h e r o u g h n e s s o f t h e s u r f a c e . T h e w i n d v e l o c i t y i n t h e f o r e s t i s u s u a l l y o n l y 2 0 t o 4 0 p e r c e n t o f t h a t i n t h e o p e n ( K i t t r e d g e 1948). T h e w i n d v e l o c i t y i n t h e f o r e s t g r a d u a l l y i n c r e a s e s a b o v e t h e h e i g h t o f t h e t r e e s , t h e h e i g h t a t w h i c h t h e o p e n v e l o c i t y i s a t t a i n e d i n c r e a s i n g w i t h w i n d s p e e d o K i t t r e d g e , u s i n g d a t a f r o m t h e S h a s t a E x p e r i m e n t a l F o r e s t , s h o w e d t h a t w i n d s p e e d i s r e d u c e d f o r 15 f e e t a b o v e t h e f o r e s t c a n o p y f o r a w i n d s p e e d i n t h e o p e n o f 5 m . p . h . , a n d f o r 70 f e e t a b o v e w h e n w i n d s p e e d i n t h e o p e n i s 15 m . p . h . 8 M o l o h a n o v (I960) d e s c r i b e d a n i n v e s t i g a t i o n i n t o t h e e f f e c t o f t h e f o r e s t o n w i n d s p e e d i n a d j a c e n t o p e n i n g s o f d i f f e r e n t w i d t h s . O n l y i n o p e n i n g s e x c e e d i n g 2,200 f e e t i n w i d t h d i d t h e w i n d r e a c h 100 p e r c e n t o f t h a t i n o p e n c o n d i t i o n s . V a r i a t i o n s i n w i n d s p e e d a b o v e , a c r o s s , a n d a d j a o e n t t o a f o r e s t e d a r e a , a l o n g w i t h t h e c h a n g i n g v e r t i c a l a n d h o r i z o n t a l w i n d c o m p o n e n t s c a u s e v a r i a t i o n s i n p r e c i p i t a t i o n a t p r o x i m a t e p o i n t s . S u c h w i n d v a r i a -t i o n s a l s o a f f e c t i n t e r c e p t i o n a n d e v a p o r a t i o n a n d , t h e r e f o r e , t h e a m o u n t o f p r e c i p i t a t i o n r e a c h i n g a n y p o i n t . B u r g e r (1951)» s u m m a r i z i n g 20 y e a r s o f S w i s s o b s e r v a t i o n , r e p o r t e d t h a t i n l a r g e f o r e s t c l e a r i n g s t h e p r e c i p i -t a t i o n c a t c h may b e m o r e t h a n i n n e a r b y o p e n c o u n t r y . G e i g e r (1965) t o o k m e a s u r e m e n t s o f p r e c i p i t a t i o n i n s e v e n c l e a r i n g s o f d i f f e r e n t s i z e i n a m i x e d s t a n d o f 80-foot p i n e ( P i n u s s p . ) a n d b e e c h ( F a g u s s p . ) . H e r e p o r t e d t h a t f o u r m o n t h s o f s u m m e r r e c o r d s s h o w e d t h a t l e a s t r a i n (8? p e r c e n t o f t h a t i n t h e o p e n ) ; f e l l i n t h e s m a l l e s t c l e a r i n g s (39 f e e t i n d i a m e t e r ) b e c a u s e o f i n t e r c e p t i o n b y t r e e c r o w n s ; i n c l e a r i n g s o f 1.47H ( w h e r e H i s t r e e h e i g h t ) r a i n f a l l was f i v e p e r c e n t g r e a t e r t h a n i n t h e o p e n ; i n c l e a r i n g s o f 3»36H r a i n f a l l was two p e r c e n t g r e a t e r t h a n i n t h e o p e n . G e i g e r a t t r i b u t e d t h i s t o t h e c a l m e r a i r , b u t t h e d o w n w a r d c o m p o n -e n t o f t h e w i n d a s i t p a s s e d i n t o t h e o p e n i n g may b e p a r t o f t h e r e a s o n . H u r s h (1948) r e p o r t e d a two p e r c e n t g r e a t e r p r e c i p i t a t i o n i n a c l e a r i n g o f 3H t h a n i n t h e o p e n . 9 Evaporation of Falling Rain Pavari ( 19°2) reported that air temperatures above a pine forest in Italy were constantly cooler (up to 4°G.) than in the open, up to 1,600 feet, and cooler in the morning up to 3>300 feet. If this condi-tion exists during storms, precipitation may be greater on forest areas due to reduced evaporation of the falling rain in the cooler air. If rainfall is greater over a forest i t has not been proven to the satis-faction of a l l observers, as indicated in the section on precipitation. The problems involved in measuring evaporation over forest and non-forest are obvious, and the absence of data on this phenomenon indicates its difficulty of measurement or the view that the differences are insignifi-cant. Interception Rain that has been caught and temporarily held by vegetation: a^.) returns to the atmosphere by evaporation from the foliage, termed interception loss; (b) is absorbed by the foliage; (c) drips off the foliage to the ground, termed throughfall; and (d) runs down branches and reaches the ground via the stem, termed stemflow. In many investigations of the hydrologic role of the forest, inter-ception of precipitation has been calculated by the formula.: 1 = Po - Pc where I = interception Po = precipitation in the open Pc = precipitation under the canopy This assumes that Po is equal to the catch that would be received above the canopy. Some investigations cast doubt on this. An Australian report (Anon. 19^9) indicated that the average annual rainfall measured above 10 the canopy was only 77 per cent of that measured nearby in the openD Law (1958) recorded a 13 per cent lower average rainfall catch with tree-top gauges than in the open at ground level. Presumably this difference is due to turbulence created by the tree tops. Within a stand there are wide variations in the amount of precipi-tation intercepted by the canopyo Interception by single trees is usually greatest near the bole, decreasing with distance from the bole. In gaps between the trees i t varies with the size of the gap. In large gaps interception may be negative, i.e., the precipitation reaching the ground may be greater than in open areas (Burger 1951» Geiger 19&5, Hursh 1948). In a mature stand of Jeffrey pine (Pinus jeffreyi Grev. and Balf.) in southern California, the percentage interception varied from 100 per cent of total precipitation at the base of a tree to 81 per cent under the edge of the crown for rains of 0.01 inches; from 94 per cent to 48 per cent for rains of 0.06 to 0.10 inches; from 74 per cent to 5 per cent for rains of 0.11 to 0.30 inches; and from 53 per cent to 4 per cent for rains of 0.31 to 1.00 inches (Kittredge 1948). In a dense stand of 40-year old white and red pine (Pinus strobus L. and Pinus resinosa Ait.) in Ontario for the period May to October, interception was 57 per cent at one foot from the bole, 27 per cent under average crowns, and 16 per cent in small openings (Beall 1934). Neiderhof and Wilm (1943) incorporated the distance from any point in an opening to the edge of the nearest crown in mature lodgepole pine (Pinus contorta Dougl.) in the equation: 11 I = 0.234P - 0.102r + 0.423 where I = interception in inches P = precipitation in inches r = distance from any point in an opening to the edge of the nearest crown, in feet. A numerical example of the above equation will illustrate its use. When seasonal rainfall, P, is six inches, interception, I, is zero where the distance from the point in the opening to the edge of the crown, r, is 18 feet. When r is zero, i„e., at the edge of the crown, I is 1»82 inches, or 30 per cent of the seasonal rainfall of six inches. The obvious method of determining average interception, and the standard method in use today, is to average a number of rain gauge catches under the canopy. However, the wide range of interception often requires a large number of gauges to arrive at a reliable average, even for a limited area.0 Recognizing this, Kittredge (1948) suggested an alternate method. The method he proposed i s to gauge interception at different positions with respect to boles, crowns, and openings, and weight these figures by the proportion of the total area occupied by the different parts of the crown and the openings,, A sampling scheme using aerial photos might be used to determine the area weighting factors = If adjustment were deemed necessary for speed and direction of wind i t could be accomplished by recording interception at the predetermined positions during storms having winds of various speeds and directions. However?, by recording interception for a given period, varying wind speeds and directions would probably be sampled in proportion to their average occur-rence and give a value sufficiently precise 0 12 H o r t o n (1919) d e r i v e d e q u a t i o n s t o e s t i m a t e t h e t o t a l i n t e r c e p t i o n b y i n d i v i d u a l t r e e s a n d s t a n d s . F o r a n i n d i v i d u a l t r e e s X S *f* K £ T o o o o o o o o o o o o o o o o o o e o e o o ( l ) i n i n c h e s o n t h e ' p r o j e c t e d a r e a o f t h e c r o w n w h e r e I = t o t a l i n t e r c e p t i o n S = d e p t h o f i n t e r c e p t e d s t o r a g e J K = r a t i o o f e v a p o r a t i n g l e a f s u r f a c e t o t h e p r o j e c t e d a r e a o f t h e c r o w n E = e v a p o r a t i o n r a t e i n i n c h e s p e r h o u r T = d u r a t i o n o f s t o r m i n h o u r s . o r , e x p r e s s e d a s a p e r c e n t , J# - 100 fS f KET~| ........... . . . ..... (2) L i T J w h e r e i = i n t e n s i t y o f r a i n i n i n c h e s p e r h o u r . F r o m e q u a t i o n (2) i t i s s e e n t h a t p e r c e n t i n t e r c e p t i o n d e c r e a s e s a s r a i n f a l l i n t e n s i t y a n d d u r a t i o n i n c r e a s e . F o r s t a n d s s e q u a t i o n (1) b e c o m e s . I = s + P K E T I PS w h e r e P s = i n c h e s o f p r e c i p i t a t i o n o v e r t h e w a t e r s h e d d i v i d e d b y t h e n u m b e r o f s h o w e r s f o r t h e m o n t h s w h e n t h e t r e e s w e r e i n l e a f . F o r a n y g i v e n s t a n d t h e i n t e r c e p t i o n s t o r a g e , S , a n d t h e p r o p o r t i o n o f t h e p r e c i p i t a t i o n i n a n y s h o w e r e v a p o r a t e d b e f o r e i t r e a c h e s t h e g r o u n d s KET« may b e c o n s i d e r e d c o n s t a n t . W i t h o u t c o r r e c t i o n f o r s t e m f l o w t h e P s r e l a t i o n i s a l i n e a r f u n c t i o n o f t h e p r e c i p i t a t i o n p e r s h o w e r . H o r t o n f o u n d t h a t S v a r i e d f r o m 0 .01 t o 0 . 0 5 a n d K E T f r o m 0 .01 t o 0 .23 f o r a P s v a r i e t y o f s t a n d s a n d s p e c i e s . 13 For two stands of ponderosa pine (Pinus ponderosa Laws0) in Colorado, Johnson's (1942) data gave I = 0.04+ 0 o 0 6 P s and I = 0.02+ O.llPs Rowe (1941) reported a linear trend for the winter months for the partly evergreen brush type of Ceanothus. oak (Quercus sp.) and buckeye (Aesoulus sp.), at North Fork, California. I = 0.02 +0.23PS Neiderhof and Wilm (1943), working in lodgepole pine in Colorado found evidence that interception decreases with decreasing stand density and volume. Kittredge (1948) graphed the data of Horton (1919) and Mitchell (1930) for elm (Ulmus sp.), basswood (Tilia sp.), maple (Acer sp.), oak, pine, hemlock (Tsuga sp.), beech, ash (Fraxinus sp.), and jackpine (Pinus banksiana Lamb.). Without correction for stemflow, interception ranged from 40 to 100 per cent of precipitation in showers of less than 0.1 inch and 10 to 40 per cent in showers of less than 0.4 inchesp with intermediate values for the intervening range. ELdmann (1959) presented data obtained over a period of five years on 26 European beech (Fagus sylvatica Ehrh.) and 30 Norway spruce (Picea  excelsa Link.) stands in the Sauerland Mountains of West Germany. Ages ranged from 20 to 140 years with about one-half of each group in the 60 to 100 year range. Interception per cent decreased as rainfall increased. For rainfall less than 1 mm. (0.04 in.) spruce intercepted 82 per cent, 14 b e e c h 72 p e r c e n t ; f o r r a i n f a l l g r e a t e r t h a n 20 mm. (0o80 i n * ) s p r u c e i n t e r c e p t e d 24 p e r c e n t a n d b e e c h 18 p e r c e n t . I t w a s r e p o r t e d ( A n o n 1949) t h a t i n M o n t e r e y p i n e ( P i n u s r a d i a t a D . D o n . ) o v e r 40 p e r c e n t o f l i g h t r a i n was i n t e r c e p t e d b u t o n l y 10 p e r c e n t o r l e s s o f h e a v y r a i n . T a n o k a (195*0 r e p o r t e d s i m i l a r v a l u e s f o r l i g h t a n d h e a v y r a i n o n s e e d l i n g t r e e s i n J a p a n ( c i t e d b y P e n m a n 1963)<> H i r a t a (1929) g a v e d a t a c o v e r i n g a m u c h g r e a t e r r a i n f a l l r a n g e i n s t a n d s o f 35-y©ar o l d s u g L ( C r y p t o m e r i a j a p o n i e a ) . h e i g h t 62 f e e t , a t M e g u r o , T o k y o . I n t e r c e p t i o n r a n g e d f r o m 63 p e r c e n t f o r r a i n s o f l e s s t h a n 3 mm. ( 0.12 i n . ) t o 5 p e r c e n t f o r r a i n s o f 132.8 mm. (5«228 i n . ) . V a r i a t i o n b e t w e e n s p e c i e s . K i t t r e d g e (1948, p . 109) w r o t e : T h e d i f f e r e n c e i n i n t e r c e p t i o n b e t w e e n s t a n d s o f d i f f e r e n t s p e c i e s a n d o f d i f f e r e n t s t a g e s i n n a t u r a l s u c c e s s i o n w o u l d b e e x p e c t e d t o i n c r e a s e a s a p a r t i c u l a r s p e c i e s o r t y p e r e p r e s e n t e d a m o r e a d v a n c e d s t a g e i n t h e s u c c e s s i o n . T o i n d i c a t e t h e s u o c e s s i o n a l t r e n d , K i t t r e d g e u s e d d a t a f o r s e a s o n a l i n t e r c e p t i o n f r o m d i f f e r e n t l o c a l i t i e s a n d p i e c e d t h e m t o g e t h e r t o a r r i v e a t t h e s e r i e s : j a c k p i n e i n W i s c o n s i n , a n i n t o l e r a n t p i o n e e r s p e c i e s - i n t e r c e p t i o n o f 21 p e r c e n t ( M i t c h e l l 1930); w h i t e a n d r e d p i n e i n O n t a r i o - 37 p e r c e n t ( B e a l l 1934); m a p l e - b e e c h c l i m a x i n New Y o r k - 43 p e r c e n t ; t o l e r a n t c l i m a x h e m l o c k i n C o n n e c t i c u t - t h e max imum i n t e r c e p t i o n o f 48 p e r c e n t ( M o o r e 1910). P e r e i r a (1952) h a d s i x y e a r s o f d a t a f o r i n t e r c e p t i o n b y c y p r e s s a n d b a m b o o p l a n t a t i o n s a t 8,700 f e e t i n t h e A b e r d a r e M o u n t a i n s o f E a s t A f r i c a , a n d c o m p a r e d h i s r e s u l t s w i t h t h o s e f o r h a r d w o o d s ( o a k , h i c k o r y 15 ( C a r y a s p . ) a n d p o p l a r ( P o p u l u s s p . ) ) i n N o r t h C a r o l i n a . I n t e r c e p t i o n p e r c e n t r a n g e d f r o m c y p r e s s ( C u p r e s s u s s p . ) , 55? b a m b o o , 5^ 5 N o r t h C a r o l i n a h a r d w o o d s , 58. f o r r a i n f a l l s o f 0.25 t o 2.5 mm. (0.0098 t o O.O98 i n . ) , t o 13, 11, a n d 8 f o r t h e t h r e e s p e c i e s r e s p e c t i v e l y f o r r a i n f a l l s o f g r e a t e r t h a n 44 mm. (1.7 i n . ) . T h e m e a n v a l u e s w e r e 26, 20, a n d 23 mm. (1.0, 0.79, a n d 0.9 i n . ) r e s p e c t i v e l y . L u c h s h e v (1940) g a v e s e a s o n a l m e a n v a l u e s o f i n t e r c e p t i o n p e r c e n t a s : s p r u c e , 28 - 37; p i n e , 28; a n d o a k , 15 - 22. S t a l h f e l t (1944) g a v e a v a l u e f o r i n t e r c e p t i o n b y s p r u c e i n S w e d e n o f 50 p e r c e n t ( a n d f o r t h e m o s s a n d l i t t e r o n t h e g r o u n d , 9-18 p e r c e n t ) . B u r g e r ' s (1951) m e a s u r e m e n t s o n s p r u c e i n S w i t z e r l a n d s h o w e d 47 p e r c e n t i n t e r c e p t i o n . V a u g h a n a n d W i e k e (1947) s t a t e d t h a t t w o - t h i r d s o f t h e r a i n f a l l i n g o n t h e c a n o p y i n t h e u p l a n d c l i m a x f o r e s t o f M a u r i t i u s r e a c h e d t h e f o r e s t f l o o r . A u s t r a l i a n e x p e r i e n c e w i t h M o n t e r e y p i n e a n d e u c a l y p t u s s h o w e d m e a n i n t e r c e p t i o n o f 29 a n d 4 p e r c e n t r e s p e c t i v e l y ( M i l l e t t 1944)0 H e l v e y a n d P a t r i c (I965) r e v i e w e d p u b l i s h e d a n d u n p u b l i s h e d i n t e r -c e p t i o n s t u d i e s c a r r i e d o u t i n h a r d w o o d s t a n d s o f e a s t e r n U n i t e d S t a t e s . T h e y f o u n d v e r y c l o s e a g r e e m e n t a m o n g i n d i v i d u a l s t u d i e s o f m a t u r e , , m i x e d h a r d w o o d s , a n d t h e y c o n s t r u c t e d e q u a t i o n s t o p r e d i c t t h r o u g h f a l l a n d s t e m f l o w f r o m t h e d a t a o f t h e s e s t u d i e s . T h e a u t h o r s s p e c u l a t e d t h a t s i m i l a r u n i f y i n g p a t t e r n s m i g h t b e n o t e d f r o m o t h e r r e g i o n a l s u m m a r i e s , , S t u d i e s i n A l a s k a i n m a t u r e c o n i f e r o u s s t a n d s i n d i c a t e d t h a t t h r o u g h f a l l d i f f e r e d l i t t l e f r o m t h a t r e p o r t e d i n o t h e r m a t u r e r a i n f o r e s t s o f w e s t e r n N o r t h A m e r i c a ( P a t r i c I966). T h e a u t h o r s u g g e s t e d t h a t i f t h e t a b u l a t i o n o f t h o s e s t u d i e s t h a t h a v e b e e n c a r r i e d o u t i n 16 s i m i l a r f o r e s t t y p e s a r e r e g a r d e d a s r a n d o m s a m p l e s f r o m a s i n g l e f o r e s t p o p u l a t i o n , a d d i t i o n a l t h r o u g h f a l l m e a s u r e m e n t s a r e n o t n e e d e d . I n P a t r i c ' s (1966) s t u d y , t h r o u g h f a l l was 72.5 p e r c e n t o f t h e 40.8 i n . o f r a i n f a l l t h a t f e l l f r o m J u l y 13 t o D e c e m b e r 23 , I965. T h r o u g h f a l l w a s n e g l i g i b l e d u r i n g s t o r m s o f 0.05 i n . o r l e s s , a n d v a r i a -t i o n s i n b a s a l a r e a p e r a c r e h a d n o c o n s i s t e n t e f f e c t o n t h r o u g h f a l l . V a r i a t i o n w i t h s e a s o n . I n v e s t i g a t i o n s c a r r i e d o u t d u r i n g d i f f e r e n t s e a s o n s o f t h e y e a r i n d i c a t e t h a t t i m e o f y e a r a l s o i n f l u e n c e s i n t e r -c e p t i o n . E i d m a n n (1959) r e p o r t e d t h a t t h e p e r c e n t i n t e r c e p t i o n was g r e a t e r i n t h e M a y - O c t o b e r p e r i o d t h a n i n t h e N o v e m b e r - A p r i l p e r i o d f o r b o t h s p r u c e a n d b e e c h , t h e p e r c e n t a g e s b e i n g 31 a n d 20 f o r s p r u c e , a n d 11 a n d 4 f o r b e e c h . I n R u s s i a , L u c h s h e v a n d P e t r o v s k i (1939) r e p o r t e d t h a t f o r s p r u c e t h e m a x i m u m i n t e r c e p t i o n o f summer r a i n f a l l was 5 Dim. (0.2 i n . ) a n d 3 mm. (0.1 i n . ) f o r a u t u m n r a i n s . L e y t o n a n d C a r l i s l e (1959)» f r o m t h e i r m e a s u r e m e n t s f o r L a w s o n c y p r e s s ( C h a m a e c y p a r i s l a w s o n i a n a ( A . M u r r 0 ) P a r i . ) , r e p o r t e d a d e c r e a s i n g i n t e r c e p t i o n f r o m t h e p e a k i n J u l y - A u g u s t o f 17-18 p e r c e n t t o 3 p e r c e n t i n N o v e m b e r . I n a s u g a r m a p l e ( A c e r s a c c h a r u m M a r s h . ) - h e m l o c k ( T s u g a c a n a d e n s i s ( L . ) C a r r . ) f o r e s t i n n o r t h e r n W i s c o n s i n , M i t c h e l l (1930) r e c o r d e d i n t e r -c e p t i o n o f 24.6 p e r c e n t d u r i n g t h e s p r i n g w h e n t r e e s w e r e i n l e a f a n d 15.8 p e r c e n t a f t e r t h e l e a v e s f e l l i n t h e f a l l . O l d m i x e d h a r d w o o d i n w e s t e r n N o r t h C a r o l i n a i n t e r c e p t e d 17 p e r c e n t o f t h e p r e c i p i t a t i o n i n s u m m e r a n d 6.6 p e r c e n t i n w i n t e r ( K i t t r e d g e 1948). O l d s h o r t l e a f p i n e ( P i n u s e c h i n a t a M i l l . ) i n t h e same l o c a l i t y h a d i n t e r c e p t i o n o f 15.7 p e r c e n t d u r i n g w i n t e r m o n t h s a n d 16.1 d u r i n g s u m m e r . 17 For most evergreen species a. large proportion of the annual leaf f a l l i s concentrated in the autumn and the new foliage develops in the spring. There is less foliage in winter, the difference being reflected in interception. Another reason for the decreased interception loss of conifers in winter might be that because of lower air temperature and higher humidity less water is evaporated. Interception loss, which by definition (p. 9) is precipitation that has been intercepted by and evap-orated from foliage, is therefore less and throughfall greater. An example of this was given by Pearson (1913) for ponderosa pine at 7,250 feet elevation in Arizona. Interception was 40 per cent, a higher value than would be expected from this species in that region where i t grows in open stands and has foliage of low density. In other inves-tigations the interception was, for mature stands of ponderosa pine in Idaho, 22 per cent and 2? per cent (Connaughton 1935)» and for young stands in Colorado, 18 per cent (Johnson 1942). The reason suggested by Kittredge (1948) for the surprisingly high figure of 40 per cent is the high "evaporative power" of that region. Variation with stand density and, age. Delfs et al. (1958) com-pared interception and stem-flow in pure spruce stands of different ages in the Oberharz Mountains during 1952-1955* Measurements were made on "normal" crown cover, those on the plantation being shortly after crown closure. The results showed that interception is greatest in sawtimber, averaging 36 per cent, followed by poles, 28 per cent, saplings, 21 per cent, and in the. young plantation, 0.6 per cent. 18 I n M a i n e , i n t e r c e p t i o n u n d e r s p r u c e a n d b a l s a m f i r ( A b i e s  b a l s a m e a ( L . ) M i l l . ) was 37 p e r c e n t , w h e r e a s s t a n d s c o n t a i n i n g a c o m -p o n e n t o f l i g h t - f o l i a g e d w h i t e b i r c h ( B e t u l a p a p y r i f e r a M a r s h . ) w i t h t h e s p r u c e a n d f i r h a d a v a l u e o f 26 p e r c e n t ( K i t t r e d g e 1948). A m a t u r e s t a n d o f D o u g l a s f i r ( P s e u d o t s u g a m e n z i e s i i ( M i r b . ) F r a n c o ) i n W a s h i n g t o n , w i t h a c r o w n d e n s i t y o f 65 p e r c e n t , i n t e r c e p t e d 34 p e r c e n t o f t h e r a i n -f a l l , w h i l e a 2 5 - y e a r o l d s t a n d w i t h d e n s e c a n o p y i n t e r c e p t e d 43 p e r c e n t ( S i m s o n 1 9 3 1 ) . K i t t r e d g e (19^) a l s o r e p o r t e d t h a t t h e i n t e r c e p t i o n p e r c e n t d e c r e a s e s a s i n d i c e s o f d e n s i t y , s u c h a s n u m b e r o f t r e e s a n d b a s a l a r e a p e r a c r e , d e c r e a s e . V a r i a t i o n s w i t h t h e a g e o f t h e s t a n d may b e i l l u s t r a t e d b y t h e f o l l o w i n g f i g u r e s f o r b e e c h i n S w i t z e r l a n d ( Z o n 1 9 2 7 ) : A g e i n y e a r s — — 20 50 60 90 M e a n a n n u a l i n t e r c e p -t i o n i n p e r c e n t 2 27 23 27 T h e m a x i m u m i n t e r c e p t i o n p e r c e n t o c c u r r e d a t 50 y e a r s w h i c h was t h e a g e a t w h i c h c u r r e n t a n n u a l i n c r e m e n t c u l m i n a t e d . K i t t r e d g e (1948) s u g g e s t e d t h a t a l t h o u g h t h e t r e n d s o f i n t e r c e p t i o n a n d i n c r e m e n t d o n o t e x a c t l y c o r r e s p o n d , i n t e r c e p t i o n i n w e l l - s t o c k e d s t a n d s i s s i m i l a r t o t h e c u r v e o f c u r r e n t g r o w t h w h i c h i n t u r n i s a f u n c t i o n o f t h e a m o u n t o f f o l i a g e . I n t e r c e p t i o n r e l a t i v e t o p r e c i p i t a t i o n a n d c r o w n d e n s i t y w a s s t u d i e d i n t h e U t a h j u n i p e r ( J u n i p e r u s o s t e o s p e r m a ( T o r r . ) L i t t l e ) a n d a l l i g a t o r j u n i p e r ( J . d e p p e a n a S t e u d . ) t y p e s o n t h e B e a v e r C r e e k w a t e r -s h e d i n A r i z o n a ( S k a u 1964). I n t e r c e p t i o n was c a l c u l a t e d b y d e d u c t i n g s t e m f l o w a n d t h r o u g h f a l l f r o m g r o s s p r e c i p i t a t i o n , a n d c a n o p y d e n s i t y was d e t e r m i n e d b y t h e u s e o f t h e c a n o p y c a m e r a . S t e m f l o w , w h i c h was 19 only one to two per cent of total precipitations began after the compara-tively large value of 0,20 to 0,30 in<> of precipitation had falleno Throughfall was predicted with reasonable accuracy for either species by the equation I s 0,044 + 0,865 (gross precipitation in inches) ~ 0,216 (canopy density index as a decimal fraction of 1 ,000), Stemflow, Stemflow has been found to increase with the amount of precipitation per shower and, for some species and stands at least, the relation i s linear (Kittredge 1948), Stemflow begins only after a certain amount of rain has fallen, the amount differing for different species, Stemflow may start at an amount of rain as low as 0,01 in, for smooth^barked trees 9 or as high as 0,7 in, for rough-barked trees (Kittredge 1948), Wilm and Niederhof (1941) computed regression equa-tions for three species at 9 9 500 f t , elevation in Colorado, For lodge-pole pine, Sfv a 3583Pr - 1090 For alpine f i r (Abies lasioearpa (Hook,) Nutt,)s Sfv = l603Pr - 387 For Engelmann spruce (Pioea engelmannii Parry)9 Sfv = 1053Pr - 301 where Sfv = stemflow in cubic inches Pr = precipitation per shower in inches In this investigation i t was found that stemflow started only after 0,3 in, of rain had fallen. In a 25-year old plantation of Canary pine (Pinus canarienses C, Smith) at Berkeley, California, the equation for the stand was Sfd = 0„03Pr - 0.02 where Sfd = inches depth on the area of the projected crown For individual trees in this stand the Y intercept varied from -0.002 to -0.036, and the regression coefficient from 0.005 to 0.11. No relation was found for this variation but a relation was shown with the excess or deficit of height relative to that of surrounding trees. The relatively-t a l l and relatively short trees showed high stemflow, 2.5 to 9 per cent of precipitation compared to one per cent for those of average heighto A nearly linear relation between annual volume of stemflow and basal area of individual trees was found by Wicht (1941) for gray poplar (Populus x canescens (Ait.) Sm.) in South Africa. The author reported that the ratio of stemflow from sample trees to stemflow from a l l trees on an acre equalled the ratio of basal area of the sample tree to total basal area on the acre. Hoppe's (I896) data also indicated that for European beech the volume of stemflow increased linearly with the stem basal areas and crown areas of the trees (reported by Kittredge 1948). On the other hand, the stemflow as a per cent of precipitation decreased with increasing crown area, from 19 per cent at less than 108 sq. f t . of crown area to 15°5 per cent at 150 sq. f t . Twenty-five year old shortleaf pine stands in North Carolina yielded one to five per cent of precipitation as stemflow (Munns and Sims 193&; cited by Kittredge 1948). Mature lodgepole pine in Colorado yielded less than 0.1 per cent of precipitation as stemflow. A 32-year old stand 21 of lodgepole pine yielded 1.5 per cent of the total seasonal precipita-tion whereas a nearby aspen (Populus sp.) stand of the same age yielded only l o l per cent (Dunford and Neiderhof 1944), This low stemflow value for the smooth-barked aspen i s contrary to the evidence of high values for smooth-barked trees. An 86-year old beech stand in Austria had stemflow starting at 0.1 in. of rain, reaching 21 per cent of precipitation in rains greater than one inch. The average for rains of a l l intensities was 15.4 per cent for beech, 203 per cent for spruce, and 0.7 per cent for the rough-barked pineQ In rains greater than 0.6 in. per cent stemflow exceeded per cent interception for the beech (Hoppe I896; reported by Kittredge 1948)o Hamilton and Howe (1949) reported that trees with smooth, upright stems carried 25 per cent of the rainfall to the ground, whereas trees with spreading branches and rough bark carried only about seven per cent. Kittredge (1948) presented a graph of amount of stemflow over rainfall by species. In order of increasing stemflow they are: shag-bark hickory (Carya ovata (Mill,) K, Koch), oak, hemlock, basswood, pine, elm;) ash, maple, and beech. Fog drip. Fog drip can occur where fog impinges on vertical sur-faces and drips from the foliage. The effect i s limited to where fog is prevalent and is usually an edge effect only, not reaching far into a forest. Data for the Taurus Mountains in Turkey indicated that in a very foggy month the "rain" at the edge of a forest may be three times as 22 great as that in the open, and over a period of four years i t was one and one-half times as great (Linke 1921, reported by Penman 1963)0 At Kisantu in the Belgian Congo, fog drip acoounted for 12 per cent of the annual rainfall of 63 in. (Aubreville 1949). Isaac (1946) reported that on a ridge in Oregon, two miles from the ocean, the rainfall under the trees was one and one-quarter times as great as in the open. The amount of fog water caught by a stand of Taiwan spruce (Picea glehnii sensu Matsum. and Hay.) in Japan was six to ten times the amount deposited on the ground in the open (Hori 1953)° Kashiyaraa (1956) showed the effect of a model shelter belt of conifers 6.5 f t . high and 43 f t . wide, on the coast of Japan. Intercepted fog reaching the ground under the trees was about 0.04 in./nr. on the windward fringe, or about 100 times the rate in the flat, treeless grassland. The extremes that have been recorded are from one of the best-known examples, Table Mountain, S. Africa. Monthly values ranged from 21? mm„ (8.54 in.) to 398 mm. (15.67 in.) (Nagel 1956). Oberlander (1956) measured fog drip during a period of 40 summer days without rain in the San Francisco peninsula, California. Under a 20-ft. tanoak (Lithocarpus densiflorus (Hook, and Am.) Rehd.), 59 in. of fog drip were recorded, more than the total rainy-season rainfall in the surrounding area. In contrast, Kittredge (195*0 reported that fog drip rarely reached 0.01 in./day at Berkeley;, California. Grunow (1955) reported that in Austrian spruce forests interception can be compensated for by fog drip. Hirata (1929) (cited by Kittredge 1948), in Japan, indicated that for the months of April and July, 1922, 23 there were apparently positive contributions by fog drip, i 0 e 0 , total rain recorded under the canopy, taking into consideration the loss due to interception, was greater than i n the open. Rubner (1932), (reported by Kittredge 1948), studying spruce forests i n Germany, came to the conclusion that fog drip was proportional to the ratio of vertical crown area to horizontal crown area» Fog drip under ceanothus (Geanothus leucodermis Greene) increased as the height of the shrub increased (Kittredge 1948 )„ Water loss* I t has been generally accepted that precipitation interception by foliage causes a loss of water from the site* However, the results of recent studies seem to indicate that there i s l i t t l e , i f any, net loss of water from the site because of a compensating reduction i n transpiration caused by the evaporation of the intercepted moisture,, Burgy and Pomeroy (1958) reported that i n a study using grasses and sunflower plants i n nutrient solutions i n a greenhouse, transpiration was less from wet leaves than from dry leaves* McMillan and Burgy (19°0) carried out a similar study with grasses i n lysimeters i n which s o i l moisture was maintained by irr i g a t i o n between f i e l d capacity and 50 per cent of f i e l d capacity* Results were similar to those reported by Burgy and Pomeroy (1958)o Goodell (1963) discussed the results of the studies noted above and made several points concerning the apparent compensation for interception by reduced transpiration* He questioned the magnitude of the compensa-tion i n view of (1) the fact that plants regulate transpiration when water av a i l a b i l i t y i s limited, (2) the probability that more energy i s 24 available for evapotranspiration from wet leaves due to heating of the water film by radiation from the leaf. On dry leaves this escapes into the air, and (3) in cold winter climates, soil moisture availability more than energy may limit transpiration. Interception may then increase the amount of water evaporated by increasing the amount of water to which the excess energy ca.n be applied. In summary, interception varies from a very small percentage of rainfall for heavy rains to 100 per cent for very light rains. Interception increases with increasing stand volume and density, and varies with species, age, and season. Stemflow begins after a certain amount of rain has fallen (as low as 0.01 in. for smooth-barked trees and as high as 0,7 in. for rough-barked trees), increases as rainfall intensity and amount in-crease, and ranges from zero to 25 per cent of rainfall. Fog drip as high as 45 in./month has been recorded and in localized areas may contribute as much water as does rainfall. Evaporation from Foliage Most of the water intercepted by foliage, other than stemflow, is evaporated. "Most" is used because of evidence of direct intake of water by aerial plant tissue. Fine seedlings whose tops were kept in a moisture-saturated atmosphere with roots sealed in empty flasks, transferred water from the atmosphere to the flask through the roots (Stone et al. 1956). Moisture movement was attributed to the vapor-pressure gradient between the saturated atmosphere and the air in the flasks. Slatyer (1956) also demonstrated this phenomenon. The importance of this in the hydrologic cycle is not known, but such atmospheric and soil conditions would not be expected to occur often in most climates. 25 Moisture Storage in Vegetation Satterlund (1959) indicated that the change in moisture content of the vegetation itself can be an appreciable factor in the water balance of a watershed. By calculating the possible changes in moisture content of different species throughout the season he concluded that a rough, and probably conservative, estimate of possible vegetation storage ranged from 0 , 0 5 in» for an 80-year old beech stand on a poor site (1 ,030 cubic feet/ acre) to 0 o 8 l i n 0 for a Douglas f i r stand, age 1 0 0 , on a good site (19,820 cubic feet/acre). Condensation Whether condensation of water vapor from the atmosphere, i,e,, dewa i s a significant part of the moisture reaching the ground is doubt-ful. According to Zon (192?) dew and frost in northern latitudes amount to only 0 , 4 to 0 , 8 in, annually. In meadows in England one inch of dew annually has been reported (Kittredge 1948), Harrold and DreibelMs (1945) reported that monthly averages for the years 1943 and 1944 ranged from 0,12 in, in July to 0 . 8 5 in, i n January in lysimeter studies at Coshocton, Ohio, However, i t was later found that the lysimeter weight changes were affected by grease seals on the lysimeters. The authors stated (Harrold and Dreibelbis 1962) that the previously published values of dew are much too large. At the Femow Experimental Forest in West Virginia, 0,259 in, of dew was recorded during the period May - November, 1962, The July -September amount was only 1 , 2 per cent of the 10 ,76 in, of precipitation 26 that occurred during that period (Hornbeck 1964)<> Lloyd ( I 9 6 I ) reported that total dew recorded in northern Idaho for the July - September, 1958» period was Go39 in<> s or 13 per cent of the 2 0 96 in 0 of rainfall during that time0 The values given in the previous paragraph are for dewfall in the open« Lloyd ( I 9 6 I ) found no dewfall under a closed forest canopy but heavy dew on top of a closed canopy of aldero Geiger (1965) stated that dew falling in the open was greater than in the forest^ the dew being deposited on the upper crown surface in the forests It appears9 then5. that the amount of dew, whether on the crown in the forest^ or on the ground in the cpen§, is usually a small percentage of the precipitationo That which is deposited on crowns is lost to evaporations, but transpira= tion losses are probably reduced because of thiso Probably soil moisture loss by evaporation is reduced also by evaporation of dew on the groundo Therefore i t appears that the influence of the forest on this variable in the hydrologie cycle is slighto 2o SNOW Interception There is wider variation in snowfall measurement than in rainfall measurement because of the greater affect of wind on the falling snowo Snow interception has usually been estimated by subtracting gauge or snow course measurements taken beneath the canopy from similar measure-ments taken In forest openings0 However$> the sum of intercepted snow and accumulation under the canopy does not necessarily equal snow accumulation 27 in the open. In storms of low wind speed and wet snow, the annual catch at crown level i s about the same as the catch in small openings (Rowe and Hendrix 1951)9 D u t the relation i s not known for single stormss especially when snow is dry and wind speed is high. Another factor clouding the issue of comparisons of snowfall in forest and in openings is the effect of wind turbulence on the accumulation in the openo The accumulation in the open i s used as the base but is itself affected by turbulence, which in turn is influenced by such factors as size and orientation of opening, and height and roughness of tree crowns. The effect of roughness of the upper surface of the forest canopy on falling snow has received very l i t t l e study as well. Komarov (1963, cited by Miller 1964, p. 2) stated that deposition of snow "depends on the difference between at least the cube of the i n i t i a l and final velocities" of the wind, so that a small decrease in wind speed results in a large deposition of snow. Where the roughness of the forest canopy is increased9 e.go, where there is a forest opening, greater deposition of snow would be expected. Another aspect of the problem is the definition of interception as applied to snow. - In a preceding section, interception loss was de-fined as that moisture which is caught by the foliage and evaporated. Snow that has been intercepted by tree crowns may remain there for a considerable time (Lull and Rushmore I96I). A thaw or high winds may cause the snow to be deposited on the groundo Therefore, the moisture loss involved is not equal to the i n i t i a l interception, but only to the amount of sublimation and evaporation that has occurred while the snow 28 was lodged in the crowns0 In the studies reported belows interception is snow intercepted by crowns and interception loss means only that part evaporatedo Penman (1963) quoted a study by Rutkovski and Kuznetsoya. (1940) indicating that maximum snow wa.s held under mature broad-leaved stands9 young stands holding about the same as in the open, and conifers usually lesso Interception of snow at an elevation of 4,500 f t 0 in southern Idaho amounted to 30 per cent of the total f a l l in an old stand of ponderosa pine with a partial understory (Connaughton 1935)° In a sim= il a r stand without the understory the value was 25 per cent, and in an open stand of ponderosa pine and lodgepole pine, 20 to 30 fto high9 only five per cento Interception loss from a. dense pine stand at the Central Sierra Snow Laboratory in April, 1958, was eight per cent of the precipitation (West and Knoerr 1958)<= Interception during snow storms in an 80-year old ponderosa pine stand at Bass Lake, California^ was 10 per cent of precipitation (Rowe and Hendrix 1951)° Kittredge (1953) reported sim-i l a r data for other forest types0 Interception losses during .an average-size storm of two inches were 11 per cent for mature ponderosa pinea 15 per cent for mixed conifers, and 16 per cent for dense stands of mature red or white f i r (Abies concolor (Gordo and Glendo) Lindlo and A 0  magnifies. Ao Murr0)o The effect of forest cutting on interception losses is about proportional to the amount of the cuto Kittredge (1953) reported for a selectively-cut forest, a 50 Pe** cent decrease In interception for a 50 P©r cent removal of the tree canopy0 29 Miller (1964), in analysing data published by Kittredge in 1953» concluded that selective logging influences interception less by changing crown cover than by removing dominant trees that project above the canopy, and perhaps by making forest edges more porous. Both conditions act directly upon snow which, because of the wind, has a large horizontal component to i t s f a l l . Goodell (1959) reported that a dense coniferous forest in Colorado can, by interception of snow and direct evaporation, allow a loss of up to 30 P©r cent of annual snowfall. Reductions in loss due to logging were estimated by Anderson and GLeason (1959) for a winter in which pre-cipitation was 38 to 41 in.; 3-4 in. for a strip-cut area, 2.3 in. for a block-cut area, and 106 in. for a selection-cut area. As an indication of the weight of snow which may accumulate on foliage the results of Seppanen's (1959) investigations are given. In pine stands of medium density at nine snow stations in Finland the 2 snow lodging on branches averaged 2,600 kg./lOCm. of ground area, or 104 tons/acre, on January 16, 1959« The range was from 1,400 to 4,500 2 kg./100m. (56 to 179 tons/acre). Accumulation The effect of wind on the catch of rain was discussed in a pre-vious section. The effect of wind on snow accumulation is much greater because of the greater buoyancy of snow flakes compared to rain dropSc The effect i s more obvious also because the snow does not generate runoff immediately, and the precipitation of many storms often accumulates before 30 melting and running o f f o The following literature survey indicates the forest management practices which may affect snow accumulation, and the size of the in-fluence. In the open. In the lee of a shelterbelt in South Dakota at the end of February 100 in, of snow accumulated, whereas to windward, and beyond the influence of the belt to leeward, the depth of snow was less than 20 in. Maximum drifts were at 3H (H is the height of the tree or stand) and the effect was noticeable as much as 8H to leeward (Stoeckeler and Dortignac 1941)» Ffolliot et a l o (19^5)» working in the Coconino National Forest, Arizona, measured the water equivalent of snow on the day following each storm0 The study areas a l l had north-east aspect with slope less than 10 per cent, and the wind direction during the study was south-west. Snow accumulation in inches of water equivalent was a maximum at IH, while the snow-melt rate was least at the edge of the opening, increasing to approximately 1§H where i t levelled off. Martinelli (19&5) investigated the depths of snow accumulated behind slat-and-wire fences in alpine areas of central Colorado. The results are pertinent in that they show the effect on snow deposition of air flow barriers and the extent of the effect. In the investigation, snow fences of 1.2 and 2,4 m. (3°9 and 7.9 ft.) were used to determine i f such barriers would produce snow fields that would persist until late summer. The research showed. (1) a positive effect on snow accumulation 31 usually extended 8H to 12H beyond the fences, occasionally extending to 20H on level terrain, (2) in steeper areas, especially where wind flowed downslope before striking the fences, this distance decreased to 6H to 8H, (3) the values for level terrain f a l l close to the 10H to 25H reported by Schneider (1959)» (4) the more frequent values of 8H to 10H also agree with that found using the equation attributed to German workers by Pugh (1950, cited by Martinelli 1965), L = 36 + 5H K where L = length of drift in feet H = height of fence in feet K = proportionality factor of 0o9 for the type of fence, (5) the maximum depth of snow was at 3H to 5H» (6) maximum depth of snow varied from 0„5H to 0„6H at one catchment, to 102H to 1«5H at another0 In the forest. Hoover and Shaw (1962), at the Fraser Experimental Forest, Colorado, determined that a forest opening is most effective as a snow trap i f i t is at least 2H wide, and that openings should not be greater than 10H wide. Many studies show that snow accumulation i s maximum in openings of approximately IH in width and the opening should be in the form of a cut strip of that width (Church 1912, Kittredge 19539 Anderson 195°* and Anderson, Rice and West 1958)° Anderson and Gleason (1959) gave a graph of snow accumulation in forest openings which showed that snow depth leeward of the opening was less than to windward, indicating that snow was "stolen" from the leeward forest, i«e., total accumulation in the open was made at the expense of 3 2 a c c u m u l a t i o n i n t h e f o r e s t « H o w e v e r , i n s u c h d r i f t s t h e s n o w p a c k p e r -s i s t s l o n g e r , p r o l o n g i n g r u n o f f 0 I n m a t u r e 7 0-foot l o d g e p o l e p i n e n e a r F r a s e r , C o l o r a d o , W i l m a n d C o l l e t (1940) f o u n d t h a t f r o m u n d e r t h e c r o w n s o u t i n t o t h e o p e n i n g s b e t w e e n t h e t r e e s t h e w a t e r e q u i v a l e n t o f t h e s n o w i n c r e a s e d l i n e a r l y a t t h e r a t e o f o n e i n c h i n 15 f t . T h e r e l a t i o n was m a i n t a i n e d f r o m a d i s t a n c e o f JO f t . b e n e a t h t o JO f t . b e y o n d t h e e d g e s o f t h e c r o w n s i n t o t h e o p e n i n g s . A s t u d y o f t h e e f f e c t o f c r o w n c o v e r o f p o n d e r o s a p i n e o n s n o w a c c u m u l a t i o n n e a r F l a g s t a f f , A r i z o n a , s h o w e d ; i n a n o p e n i n g i n t h e f o r e s t a c c u m u l a t i o n w a s I5.6 p e r c e n t g r e a t e r t h a n i n a n e x t e n s i v e o p e n i n g ; u n d e r l i t t l e c o v e r a c c u m u l a t i o n was 7°4 p e r c e n t g r e a t e r ; u n d e r p a r t i a l c o v e r , 5°8 p e r c e n t l e s s ; a n d u n d e r c o m p l e t e c o v e r 32.5 p e r c e n t l e s s ( J a e n i c k e a n d F o e r s t e r 1915)<> M a n y s t u d i e s o f t h e r e l a t i o n o f c r o w n c o v e r t o s n o w a c c u m u l a t i o n f a i l t o d e s c r i b e a d e q u a t e l y t h e f o r e s t d e n s i t i e s , b u t u s e s u c h t e r m s a s " l i t t l e " , " p a r t i a l " , a n d " f u l l " . I n a s t u d y b y E s c h n e r a n d S a t t e r l u n d (I963) d e n s i t y w a s d e s c r i b e d q u a n t i t a t i v e l y a n d i s t h e r e f o r e m o r e m e a n -i n g f u l o T a b l e 1 i s a c o m b i n a t i o n o f t w o t a b l e s f r o m t h e i r r e p o r t . D e p t h o f s n o w a n d w a t e r e q u i v a l e n t w e r e m e a s u r e d w e e k l y f r o m N o v e m b e r , 1 9 6 1 , t o A p r i l , 1962o C o l u m n 4 i s t h e max imum w a t e r e q u i v a l e n t r e c o r d e d o n t h e s i t e d u r i n g t h e p e r i o d , a n d c o l u m n 5 i s t h e sum o f t h e p o s i t i v e i n -c r e m e n t s b e t w e e n s a m p l i n g d a t e s . 33 T a b l e 1. Snow a c c u m u l a t i o n u n d e r d i f f e r e n t c o v e r c o n d i t i o n s i n c e n t r a l New Y o r k ( F r o m A s c h n e r a n d S a t t e r l u n d 1963.) C o v e r B a s a l a r e a p e r a c r e s q . f t . W i n t e r c r o w n d e n s i t y p e r c e n t M a x . a c c u m u l a -t i o n o n g r o u n d i n c h e s w a t e r e q u i v a -l e n t T o t a l a c c u m u -l a t i o n N o v . 30-A p r . 27 i n c h e s w a t e r e a u i v a l e n t O p e n land.e«o 0 0 2.25 6.07 B r u s h y h a r d w o o d s . . 31 2.8 5.15 9.23 N o r t h e r n h a r d w o o d s . . 133 7.6 4.90 7 .28 T h i n n e d r e d p i n e . . . 109 85 4.90 6.44 D e n s e r e d p i n e . . , 196 93 4.05 5.33 T h i n n e d N o r -way s p r u c e . 163 94 3.05 5d3 D e n s e N o r -way s p r u c e . 139 96 3.25 4.80 D i l s a n d A r e n d (1956) i n v e s t i g a t e d t h e a c c u m u l a t i o n o f s n o w u n d e r r e d p i n e o f d i f f e r e n t s t a n d d e n s i t i e s i n M i c h i g a n . T h e a c c u m u l a t e d d e p t h o f s n o w d e c r e a s e d a s t h e b a s a l a r e a o f t h e s t a n d i n c r e a s e d ( f r o m 1 8 i n . i n t h e o p e n 9 t o 12 i n . i n a s t a n d o f 8 0 s q . f t . / a c r e , t o 9 i n . i n a s t a n d o f 190 s q . f t . / a c r e ) . T h e s n o w i n t e r c e p t e d b y t r e e c r o w n s was r e p o r t e d a s l o s t b y e v a p o r a t i o n a n d s u b l i m a t i o n . E v a p o r a t i o n f r o m Snow B e c a u s e t h e s n o w p a c k p e r s i s t s f o r some t i m e b e f o r e m e l t i n g i s c o m p l e t e , t h e a m o u n t o f m o i s t u r e l o s t f r o m t h e p a c k b y e v a p o r a t i o n h a s 34 been the subject of numerous invest!gations0 One method of estimating such loss is by periodic weighing of glass jars containing snow= A study at 7 » 0 0 0 f t o elevation in Utah using glass jars showed a mean evaporation rate of 0 0 0 1 7 in„/day for November 7 to May 4 0 During the snow season ( 1 8 0 days) the total evaporation was three inches, or 14 per cent of snowfalio Evaporation increased at an accelerated rate with increasing air temperature (Baker 1 9 1 ? ) = Croft ( 1 9 4 4 ) reported mean evap-oration of Q o 0 4 ino/day for May at 8 5 ,700 f t 0 elevation in the same areao On May 8 S evaporation from snow cores in pans was 0 o 0 5 i n 0 where exposed to wind and 0 C 0 2 In, where there was no wind movement,, The effect of solar radiation was small as shown by the difference in evaporation between sun and shade of only 0 o 0 0 2 i n 0 Church ( 1 9 3 4 ) reported the following November - March evaporation for a study conducted with pans of snow at tree-crown level at Lake Tahoe, Nevada: open meadow9 8 0 5 in= of water equivalent; semi-open pine forest 9 4 8 8 i n e ; f i r stand9 2 „ 4 i n 0 In inches/day the respective amounts were 0 c 0 5 ? 9 0o0329 and 0 o 0 l 6 o Houk (19ZL9 cited by Kittredge 1 9 4 8 ) determined the rate of evaporation from snow from December9 1 9 1 ? 9 to Februarys 1 9 1 8 , in 0hio9 to be C-O023 in 0/day 0 Measurements of evaporation were made for several years under a range of conditions from open meadow to dense forest.on the Stanislaus National Forest in Galiforniao Median evaporation for a l l stations and 35 years was 0o007 iru/24 hours0 For 1936 the median was 0o013 and in 1938, -0,002 in,/24 hours (the negative value indicating that condensation ex-ceeded evaporation). For individual forest types the medians ranged from a maximum of 0,12 in,/day under a mature, open stand of ponderosa pine, to -0,002 in,/day in. dense stands of white f i r , red f i r , and ponderosa pine. Records taken morning and evening at a limited number of stations showed that evaporation exceeded condensation in 83 per cent of the day periods, and condensation exceeded evaporation in 72 per cent of night periods (Kittredge 1948). Apparently evaporation from snow on Pacific slopes of the western mountains is much less than that in the interior, the difference presumably being associated with more humid winds from, the Pacific Ocean, In large, exposed openings in California, evaporation minus con-densation totaled 2,1 in, during the winter of 1957-19585 in small forest openings gains by condensation essentially balanced losses; and under forest canopies a net gain of 2.3 in. was measured. Only during a dry spell in late February to April, 1958, did significant evaporation from snow surfaces occur (Anderson 1958). Similar results were obtained at the Central Sierra Snow Laboratory. February to June loss in a small forest opening was 0,8 in. while under the canopy the loss was 0,3 in, (Anderson 1958), Hutchison (I966) compared evaporation from snow and soil surfaces in the central Rocky Mountains, Colorado, during the spring of 1961, Measurements were made in forest openings at 9,000 feet elevation using 36 evaporation pans set in the soil or snow. Evaporation losses from wet soil surfaces were much greater than from adjacent melting snow surfaces, aver-aging 0 O1705 in. for soil and O0O36I in, for snow, from April 21 to May 9° This may be 33.plained by increased atmospheric vapour pressure during spring due to increases in ares, of exposed wet soil and available energy. Vapour pressure gradients between both surfaces and the air will then decrease but the gradient between soil and air will decrease least because the soil temperature can rise under a given level of energy input and the vapour pressure of the soil water will rise correspondingly. The vapour pressure of the melting snow surface i s fixed at a value correrponding to 32°F. Bergen and Swanson (1964) studied evaporation from snow at 9*000 f t . elevation in Colorado using the energy budget method. Measurements were made of snow temperature and density j, soil heat flux, incident radiation and the difference between this flux and reflected or emitted radiation from the snows wind speed8 shear, and air temperatures at intervals above the surface^, and air humidity. Daytime evaporation losses ranged from 0.02 to 0.0? i n c and averaged Qo04 in. for the five measurements made from February 13 to March 23* Nighttime condensation ranged from 0,00059 to 0.012 in. =, averaging 0.0076 in„ for four measurements. At the Central Sierra Snow Laboratory evapora,tion was greater in the open than in the forest during the day, and less in the open than in the forest at night (West 1959)° 37 I n s u m m a r y , t h e e v a p o r a t i o n r a t e r a n g e s f r o m a h i g h o f s l i g h t l y o v e r 0.1 i n . / d a y t o a l o w o f -0.002 i n . / d a y , t h e m o s t common r a t e r e -p o r t e d b e i n g a p p r o x i m a t e l y 0.02. T h e r a t e i s h i g h e r i n t h e o p e n t h a n i n t h e f o r e s t , d e c r e a s i n g w i t h i n c r e a s i n g d e n s i t y t o t h e p o i n t w h e r e c o n d e n s a -t i o n e x c e e d s e v a p o r a t i o n . M e l t i n g o f S n o w T h e i n f l u e n c e o f t h e f o r e s t o n s n o w m e l t d e p e n d s o n i t s i n f l u e n c e o n t h o s e s o u r c e s o f e n e r g y i n v o l v e d i n s n o w m e l t i n g . T h o s e s o u r c e s a r e s o l a r ( s h o r t w a v e ) r a d i a t i o n , t e r r e s t r i a l ( l o n g w a v e ) r a d i a t i o n , c o n -v e c t i o n h e a t t r a n s f e r f r o m t h e a i r , l a t e n t h e a t o f v a p o r i z a t i o n b y c o n -d e n s a t i o n f r o m t h e a i r , c o n d u c t i o n o f h e a t f r o m t h e g r o u n d , a n d t h e h e a t c o n t e n t o f r a i n . E q u a t i o n s h a v e b e e n c o n s t r u c t e d t o p r e d i c t m e l t u s i n g d a t a o n t h e s o u r c e s o f e n e r g y i n v o l v e d ( R a n t z 1964). A H t h e h y d r o m e t e o r o l o g i c a l d a t a a r e s e l d o m a v a i l a b l e , h o w e v e r , a n d a p p r o x i m a t i o n s b a s e d o n e m p i r i c a l e v i d e n c e a r e n e c e s s a r y . R e c o r d e d m e l t r a t e s u n d e r v a r i o u s c o n d i t i o n s a r e t h e r e f o r e o f v a l u e i n e s t i m a t i n g a p p r o x i m a t e r a t e s f o r o t h e r a r e a s . I n U t a h f o r t h e p e r i o d A p r i l 22 - M a y 9 t h e a v e r a g e m e l t r a t e p e r d e g r e e - d a y was 0.054 i n . w a t e r e q u i v a l e n t ( C l y d e 1931? c i t e d b y K i t t r e d g e 1948). A d e g r e e - d a y i s a d e p a r t u r e o f o n e d e g r e e p e r d a y i n t h e d a i l y m e a n t e m p e r a t u r e f r o m a n a d o p t e d r e f e r e n c e t e m p e r a t u r e , i n t h i s c a s e f r o m 32 ° F . H o r t o n (1915) r e p o r t e d 0.05 i n . w a t e r e q u i v a l e n t / d e g r e e - d a y a s t h e m e l t r a t e i n t h e s u n i n New Y o r k s t a t e . 38 E x a m p l e s o f t h e e f f e c t o f f o r e s t c o v e r o n s n o w m e l t i n t h r e e a r e a s o f t h e C a s c a d e R a n g e i n W a s h i n g t o n w e r e p r o v i d e d b y G r i f f e n (1918) f o r D o u g l a s f i r , m o u n t a i n h e m l o c k ( T s u g a m e r t e n s i a n a (Bongo) Carre), a n d l o d g e p o l e p i n e . M e a s u r e m e n t s t a k e n a f t e r t h e s n o w h a d j u s t d i s a p p e a r e d i n t h e o p e n s h o w a g r e a t e r d e p t h o f s n o w w i t h g r e a t e r c r o w n d e n s i t y , a s w e l l a s a l o n g e r - l a s t i n g m e l t p e r i o d s H a r t (1963), w o r k i n g i n New H a m p s h i r e , r e p o r t e d m e l t r a t e s i n i n c h e s w a t e r e q u i v a l e n t p e r d e g r e e - d a y f o r t h e p e r i o d M a r c h 29 - A p r i l 12 a s f o l l o w s . 0.16 — o p e n f i e l d 0.10 — h a r d w o o d s t a n d o f c r o w n c l o s u r e 2 4 p e r c e n t , b a s a l a r e a 87 s q . f t . / a c r e 0.05 — w h i t e p i n e s t a n d o f c r o w n c l o s u r e 90 p e r c e n t , b a s a l a r e a 199 s q . f t . / a c r e 0 . 0 4 — r e d p i n e s t a n d o f c r o w n c l o s u r e 83 p e r c e n t , b a s a l a r e a 229 s q . f t . / a c r e . L u l l a n d R u s h m o r e (1961) r e p o r t e d m e l t r a t e s o f 0.06 i n . w a t e r e q u i v a l e n t / d e g r e e - d a y f o r h a r d w o o d s a n d 0 o 0 3 f o r s p r u c e - f i r i n t h e A d i r o n d a c k s . S o z y k i n (1959) r e p o r t e d o n o b s e r v a t i o n s made a t t h e M o s k v a - V o l g a w a t e r s h e d , n o r t h - w e s t o f M o s c o w . A c c u m u l a t i o n a v e r a g e d 15 mm. (0.59 i n . ) l e s s i n f o r e s t t h a n i n o p e n a n d t h e m e l t s e a s o n l a s t e d e i g h t d a y s l o n g e r w i t h t h e r a t e a v e r a g i n g 16.7 m m . / d a y (0.66 i n . / d a y ) i n t h e f o r e s t a n d 32.6 m m . / d a y (1.28 i n . / d a y ) i n t h e o p e n . A n d e r s o n (1963) r e p o r t e d t h a t m a x i m u m s h a d e r e s u l t s i n l e a s t m e l t b u t 85 p e r o e n t s h a d e i s n e a r l y a s e f f e c t i v e . T r e e s t o t h e s o u t h o f t h e s n o w p a c k h a v e a m a r k e d i n f l u e n c e o n m e l t b u t t r e e s t o t h e n o r t h a r e o n l y 39 12 p e r c e n t a s e f f e c t i v e l n p r e v e n t i n g m e l t . T r e e s t o t h e n o r t h d o i n t e r c e p t s k y r a d i a t i o n a n d p r o t e c t s n o w b e c a u s e o f t h i s , b u t t h e y a l s o a b s o r b d i r e c t s o l a r r a d i a t i o n a n d r a d i a t e l o n g - w a v e r a d i a t i o n , some o f w h i c h r e a c h e s t h e s n o w p a c k . F o r e s t s r e d u c e t h e a m o u n t o f l o n g - w a v e r a d i a t i o n f r o m c l o u d s a n d a t m o s p h e r e t h a t r e a c h e s t h e s n o w p a c k a t n i g h t , h o w e v e r . T h e t r a p p i n g o f c o l d a i r a t t h e d o w n - h i l l m a r g i n o f f o r e s t o p e n i n g s may b e a n i m p o r t a n t m e c h a n i s m i n d e l a y i n g w i n t e r s n o w m e l t . T h e d o w n - h i l l s i d e s o f s u c h o p e n i n g s a l w a y s c o n t a i n m o r e s n o w t h a n t h e u p h i l l s i d e s ( A n d e r s o n , R i c e , a n d W e s t 1958)• T h e l o n g e r t h e s n o w p a c k p e r s i s t s t h e g r e a t e r i s t h e l i k e l i h o o d o f r a p i d m e l t r a t e , a n d c o n s e q u e n t r a p i d r u n o f f , a s t h e t r a n s i t i o n f r o m c o l d w i n t e r p r o c e e d s i n t o t h e w a r m e r c o n d i t i o n s o f s p r i n g ; g r e a t e r t o o i s t h e l i k e l i h o o d o f h e a v y r a i n f a l l s w e l l i n g r u n o f f f r o m t h e r i p e s n o w p a c k . T h e t i m i n g o f h i g h t e m p e r a t u r e o r h e a v y r a i n m a y c h a n g e t h e f o r e s t ' s i n f l u e n c e f r o m f a v o r a b l e t o u n f a v o r a b l e . When t h e c r i t i c a l wa rm p e r i o d c o m e s e a r l y w i t h l a r g e s n o w p a c k a c c u m u l a t i o n s i n b o t h f i e l d a n d f o r e s t , f o r e s t s p r o b -a b l y c o n t r i b u t e l e s s r u n o f f a n d s l o w e r r u n o f f t h a n o p e n a r e a s ; w h e n w a r m w e a t h e r c o m e s l a t e , w i t h a n a p p r e c i a b l e s n o w p a c k o n l y i n f o r e s t s , t h e r e v e r s e i s l i k e l y t o b e t r u e . C o n s e q u e n t l y , a m i x o f f o r e s t a n d o p e n may b e t h e b e s t l a n d u s e p a t t e r n t o a m e l i o r a t e h i g h r u n o f f c o n d i t i o n s . I n s u m m a r y , s n o w - m e l t r a t e s v a r y b e t w e e n 0.04 i n . w a t e r e q u i -v a l e n t / d e g r e e - d a y i n d e n s e p i n e s t a n d s t o 0.16 i n . i n t h e o p e n , w i t h v a l u e s a s h i g h a s 1.28 i n . / d a y b e i n g r e c o r d e d . 40 3. EVAPOTRANSPIRATION Many studies have been made to determine the amount of water evapotranspired by different crops. Investigations of water use by forests have been carried out, using various methods, for the past 50 years, but due to the limitations of experimental techniques, results do not show a high degree of agreement. Ideally, data would be available on transpiration in inches of water for each species, age, and size-class, but the problem is very difficult for anything larger than a seedling (Kittredge 1962), Methods of Measurement Swans on and Lee (1966) discussed three techniques for estimating evapotranspiratlon: (1) measuring the rate of vapor production of a plant enclosed in a plastic greenhouse, (2) weighing excised portions of plants to determine the rate of water loss, and (3) measurement of sap velocity by detecting the movement of heat, dye, or radioactive tracers. Tent method. In the plastic greenhouse, or tent, method, a pump is used to inflate the tent which encloses the plant. The difference in moisture content of outgoing air and ingoing air, combined with the rate of air exchange, gives a measure of the water loss from within the en-closure. Because the water loss includes not only transpiration from the sample plant but also evapotranspiratlon from the soil surface and low-growing shrubs, the same parameters are measured for a tent without an enclosed plant. This value is deducted from the fi r s t measurement to 41 o b t a i n a n e s t i m a t e o f t r a n s p i r a t i o n f r o m t h e s a m p l e t r e e . H o w e v e r , t h e v a l u e o b t a i n e d b y t h i s m e t h o d i s n o t l i k e l y t o b e t h e s ame f o r a n a t u r a l l y - e x p o s e d p l a n t b e c a u s e o f t h e e f f e c t o f t h e t e n t o n t h e e n v i r o n m e n t w i t h i n i t . T h e g r e a t e s t e f f e c t i s r e s t r i c t e d a i r m o v e m e n t i n t h e t e n t c a u s i n g a i r t e m p e r a t u r e s t o r i s e b y 10 t o 15 d e g r e e s w h e n c o m b i n e d w i t h t h e r a d i a n t e n e r g y t r a p p e d b y t h e p l a s t i c t e n t . T h e p l a s t i c , b e i n g m o r e t r a n s p a r e n t t o s h o r t - w a v e r a d i a t i o n t h a n t o l o n g -w a v e r a d i a t i o n , a d m i t s t h e s h o r t - w a v e r a d i a t i o n f r o m t h e s u n o r s k y b u t t r a p s m u c h o f t h e h e a t r a d i a t i o n f r o m t h e g r o u n d a n d p l a n t f o l i a g e w i t h -i n t h e t e n t . A v a r i a t i o n o f t h i s m e t h o d r e q u i r e s t h e g r o u n d a n d a l l v e g e t a t i o n w i t h i n t h e t e n t , e x c e p t t h e t e s t p l a n t , t o b e c o v e r e d , s o t h a t t h e o n l y e v a p o t r a n s p i r a t i o n i s b y t h e t e s t p l a n t ( U . S . D e p t . A g r . 1937)« T h e t e n t m e t h o d m a y b e m o r e u s e f u l i n m e a s u r i n g t h e r e l a t i v e r a t e s o f w a t e r l o s s b y d i f f e r e n t p l a n t s o n a d j a c e n t p l o t s . E v e n h e r e , h o w e v e r , a n a s s u m p t i o n m u s t b e m a d e , i . e . , a l t h o u g h t h e p l a n t s d i f f e r i n f o r m a n d p h y s i o l o g y , e n c l o s u r e e f f e c t s a r e t h e s ame a t e a c h s i t e . Q u i c k - w e i g h i n g m e t h o d . I n t h i s m e t h o d , a p a r t o f t h e p l a n t i s c u t o f f , w e i g h e d i m m e d i a t e l y , a n d w e i g h e d a g a i n a f t e r a s h o r t t i m e i n t e r v a l . A n a t t e m p t i s made t o k e e p t h e p l a n t i n i t s n a t u r a l p o s i t i o n a n d e n v i r o n m e n t b y s u s p e n d i n g i t b e f o r e e x c i s i n g . C u t t i n g t h e p l a n t p a r t a l s o c u t s o f f i t s w a t e r s u p p l y s o t h a t t r a n s p i r a t i o n w o u l d s o o n s t o p . T h e c u t t i n g a l s o r e l e a s e s t h e t e n s i o n b y w h i c h t h e w a t e r i s h e l d b a c k f r o m t h e t r a n s p i r i n g p a r t s o f t h e p l a n t . T h i s may c a u s e a t r a n s -p i r a t i o n i n c r e a s e . 42 Rutter (1959) found that severed Scotch pine branches underwent a transpiration decrease of 12 per cent in the first 10 minutes after cutting, but that the transpiration rate of detached needles was not reduced during the same period. He reported that evapotranspiratlon rates determined by the weighing method agreed closely with those estimated by soil moisture measurements. However, as Swanson and Lee (I966) conclude, extrapolation from the part to the whole plant is the most difficult problem with this method. Sap velocity method. Estimating evapotranspiratlon with this method depends on the relation of sap velocity and rate of evapotrans-piratlon. Skau and Swanson (I963) reported that field tests showed that sap velocity is closely correlated with the rate of transpiration from entire trees as determined by the tent method. Two factors complicate the use of sap velocity to estiraate trans-pirations (1) The area through which the sap moves may vary with time. If this area decreases, for example, less water would be available for transpiration even though the sap velocity remained the same. (2) The amount of water within the sapwood may change^ i.e., even i f the con-ducting area remains the same, the moisture content of a given unit within that area may change. The result i s the same as in (l)o These problems could be resolved by making simultaneous measurements of the velocity profile across the sapwood and radial moisture content across the same area. The sap velocity profiles can be obtained but Swanson and Lee (1966) pointed out that a non-destructive method of obtaining the moisture content is lacking. 43 A l t h o u g h e a c h o f t h e t h r e e m e t h o d s d e s c r i b e d a b o v e h a s s e v e r e l i m i t a t i o n s , a c o m b i n a t i o n o f m e t h o d s may p r o v e m o r e u s e f u l t h a n a n y s i n g l e m e t h o d . F o r e x a m p l e , t h e s a p v e l o c i t y m e t h o d may b e u s e d i n c o n j u n c t i o n w i t h t h e w e i g h i n g m e t h o d . T h i s w o u l d p r o v i d e i n f o r m a t i o n o n t h e c h a n g e i n t r a n s p i r a t i o n r a t e i m m e d i a t e l y a f t e r c u t t i n g . E n e r g y b u d g e t m e t h o d . E v a p o t r a n s p i r a t i o n c a n b e e s t i m a t e d i n d i -r e c t l y b y t h e e n e r g y b u d g e t m e t h o d . M u n n (1961) d i s c u s s e d t h e t h e o r y o f e v a p o r a t i o n d e t e r m i n a t i o n b y t h e e n e r g y b u d g e t a n d F o w l e r (1964) a n d G o o d e l l (1965) d e s c r i b e d i t s u s e i n e s t i m a t i n g e v a p o t r a n s p i r a t i o n . T h i s m e t h o d i s a n a c c o u n t i n g o f t h e e n e r g y g a i n , l o s s , a n d s t o r a g e a t a p a r t i c u l a r l o c a -t i o n a n d p e r i o d o f t i m e . I f t h e e n e r g y l o s s d u e t o r a d i a t i o n a n d r e -f l e c t i o n f r o m t h e e a r t h ' s s u r f a c e i s d e d u c t e d f r o m t h e e n e r g y i n p u t , t h e d i f f e r e n c e may b e a t t r i b u t e d t o h e a t s t o r e d i n c r o p s a n d s o i l a n d t h e e n e r g y u s e d i n h e a t i n g t h e a i r a n d t r a n s f o r m i n g w a t e r f r o m t h e l i q u i d t o t h e v a p o r s t a t e . T o o b t a i n a v a l u e f o r t h e l a s t m e n t i o n e d t e r m , e v a p o -t r a n s p i r a t i o n , a l l o t h e r e n e r g y i n p u t s , o u t p u t s , a n d u s e m u s t b e m e a s u r e d . T h e d e v e l o p m e n t o f t h e n e t r a d i o m e t e r h a s s i m p l i f i e d t h e m e a s u r e -m e n t s r e q u i r e d a n d p e r m i t s t h e m e a s u r e m e n t o f t h a t p a r t o f t h e e n e r g y b u d g e t t h a t i s p r o c e s s e d a t t h e e a r t h ' s s u r f a c e , i . e . , n e t r a d i a t i o n . N e t r a d i a t i o n may b e d e s c r i b e d b y t h e e q u a t i o n ( G r a y e t a l . I965)! NR = S + V + K + E w h e r e NR = n e t r a d i a t i o n S = h e a t f l u x i n t o t h e s o i l V = h e a t s t o r a g e i n v e g e t a t i o n K - h e a t u s e d i n h e a t i n g t h e a i r E = l a t e n t h e a t f l u x o f e v a p o -t r a n s p i r a t i o n ii4 T h e a b o v e e q u a t i o n a s s u m e s t h a t p h o t o s y n t h e t i c u s e o f e n e r g y i s s m a l l , a l t h o u g h t h e v a l u e may b e h i g h e r t h a n g e n e r a l l y s u p p o s e d ( T a n n e r a n d L e m o n 1962)<> I t a l s o a s s u m e s a z e r o v a l u e f o r t h e e n e r g y r e l e a s e d b y c o n d e n s a t i o n . H e a t s t o r a g e i n a g r i c u l t u r a l c r o p s i s n o t u s u a l l y a n i m p o r t a n t p a r t o f t h e h e a t b a l a n c e ( G r a y e t a l . 1965), h u t i n f o r e s t s t a n d s may b e c o n s i d e r a b l y g r e a t e r ( J e f f r e y 1964). O n a d a i l y b a s i s , t h e f l u x o f h e a t i n t o t h e s o i l s u r f a c e i s r e l a t i v e l y s m a l l d u r i n g m o s t o f t h e y e a r ( G r a y e t a l . I965), e s p e c i a l l y u n d e r f o r e s t . A l i n e a r r e l a t i o n h a s b e e n s h o w n t o e x i s t b e t w e e n n e t r a d i a t i o n a n d p o t e n t i a l e v a p o t r a n s p i r a t l o n o n a d a l l y b a s i s w h e n s o i l m o i s t u r e a v a i l a b i l i t y i s n o t l i m i t e d ( F o w l e r 1964, T a n n e r a n d P e l t o n i960). H o w -e v e r , e s t i m a t e s o f a c t u a l e v a p o t r a n s p i r a t l o n w h e r e m o i s t u r e i s p e r i o d -i c a l l y l i m i t i n g c a n n o t b e e x p e c t e d t o b e a s r e l i a b l e a s e s t i m a t e s o f p o t e n t i a l e v a p o t r a n s p i r a t l o n , b u t a s F o w l e r (1964) p o i n t e d o u t , s u c h e s t i m a t e s m a y b e i n v a l u a b l e w h e r e o t h e r i n f o r m a t i o n i s n o t a v a i l a b l e . E d d y f l u c t u a t i o n m e t h o d . T h i s m e t h o d c o m b i n e s d a t a o n f l u c t u a t i o n s i n v e r t i c a l a i r m o t i o n a n d h u m i d i t y w i t h n e t r a d i a t i o n t o e s t i m a t e e v a p o -t r a n s p i r a t l o n . M a i n p r o b l e m s a r e a s s o c i a t e d w i t h i n s t r u m e n t d i f f i c u l t i e s c o n c e r n i n g r e s p o n s e t i m e s o f w i n d a n d h u m i d i t y s e n s o r s . H o w e v e r , w i t h i m p r o v e d i n s t r u m e n t a t i o n , t h i s m e t h o d i s l i k e l y t o p r o v e v a l u a b l e i n e s t i m a t i n g e v a p o t r a n s p i r a t l o n w h e r e m o i s t u r e a v a i l a b i l i t y i s l i m i t e d ( B r u c e a n d C l a r k I966). S o i l m o i s t u r e b u d g e t . C h a n g e s i n s o i l m o i s t u r e s t o r a g e h a v e b e e n u s e d i n c o n j u n c t i o n w i t h m o i s t u r e i n p u t b y p r e c i p i t a t i o n a n d o u t g o b y 45 r u n o f f , t o e v a l u a t e e v a p o t r a n s p i r a t i o n . I n s u c h e v a l u a t i o n , s e e p a g e i n t o a n d l e a k a g e o u t o f t h e a r e a b e i n g s t u d i e d a r e u s u a l l y i g n o r e d ( B u r r o u g h s a n d S h u l t z 1964). E x c e p t i n t h o s e r a r e c a s e s w h e r e s e e p a g e a n d l e a k a g e a r e e q u a l , o m i t t i n g t h e s e t e r m s i n t r o d u c e s a n e r r o r o W i l l a r d s o n a n d P o p e (I963) s u g g e s t e d a m e t h o d b y w h i c h t h e a m o u n t o f m o i s t u r e l o s t d u e t o d e e p s e e p a g e may b e s e p a r a t e d f r o m t h e e v a p o t r a n s -p i r a t i o n e s t i m a t e . T h i s i n v o l v e s t h e m e a s u r e m e n t o f d e e p s e e p a g e a t t h e same s i t e b u t o n p l o t s s t r i p p e d o f v e g e t a t i o n a n d c o v e r e d t o p r e v e n t e v a p o t r a n s p i r a t i o n . H o w e v e r , a s J e f f r e y (1964) p o i n t e d o u t , t h i s a s s u m e s t h a t p e r c o l a t i o n o n t h e d e n u d e d p l o t w i l l b e t h e same a s t h a t o n t h e v e g e t a t e d p l o t , w h i c h i s n o t n e c e s s a r i l y t r u e . I f p e r c o l a t i o n l o s s e s a r e i g n o r e d i n t h e e s t i m a t i o n o f 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 , w h e n u s e d , m u s t b e a d d e d s p a r i n g l y t o m i n i m i z e p e r c o l a t i o n l o s s . W a t e r t a b l e l e v e l s m u s t b e d e e p e n o u g h t h a t p l a n t s d e r i v e n o w a t e r f r o m t h i s s o u r c e . T h e m a i n a d v a n t a g e o f t h i s m e t h o d i s t h a t e v a p o t r a n s p i r a t i o n i s d e t e r m i n e d u n d e r f i e l d c o n d i t i o n s . G r a v i m e t r i c s a m p l i n g o f s o i l m o i s t u r e a t p e r i o d i c i n t e r v a l s h a s b e e n u s e d f o r m a n y y e a r s i n e s t i m a t i n g e v a p o t r a n s p i r a t i o n . E l e c t r i c a l r e s i s t a n c e b l o c k s p e r m i t s o i l m o i s t u r e m e a s u r e m e n t w i t h l e s s s i t e d i s -t u r b a n c e t h a n d o e s g r a v i m e t r i c m e a s u r e m e n t . A c c e s s t u b e s f o r m o i s t u r e d e t e r m i n a t i o n w i t h t h e n e u t r o n p r o b e , w h i c h h a s b e c o m e w i d e l y u s e d i n t h e p a s t 10 y e a r s , u s u a l l y c a u s e l i t t l e s i t e d i s t u r b a n c e . H o w e v e r , p r o b l e m s a r e e n c o u n t e r e d i n i n s t a l l i n g a c c e s s t u b e s i n s t o n y s o i l s w h e r e 46 access with tractor-mounted equipment i s not practical. With hand-bored access holes, problems include trampling of s o i l and vegetation at the site and maintaining close contact of the access tube with the adjacent s o i l * Potted plant methodo A simple method which has been used widely i n the past to estimate transpiration i s weighing a potted plant, allowing i t to transpire for a period, and reweighing i t . The difference i n weight i s due to loss of water and change i n weight of the planto The plant weight changes are so small relative to the loss i n weight by trans-piration that they may be ignored and the total weight change attributed to transpiration (Bonner and Galston 1959)° Lysimeters. The use of lysimeters to measure evapotranspiratlon i s described comprehensively by Pelton (1961). With this method plants are grown i n tanks, and water loss from the tanks i s determined period-i c a l l y . Metal or plastic tanks are used having surface areas of several hundreds of square feet and depths of eight feet or more. Lysimeters were i n use i n the 17th century for water percolation studies, but i t was not un t i l the 18th century that they were used for measuring evapotranspiratlon (Gray et a l 0 1966). In 1906 the f i r s t lysimeters with weighing devices were installed i n Germany, and i n 1923 the f i r s t self-recording weighing lysimeters were constructed i n the United States (Pelton 1961). More recently 5, lysimeters have been equipped to record rates and amounts of runoff and percolation automatically (Dreibelbis 1963). 47 L y s i m e t e r s a r e o f t h r e e m a i n t y p e s , c l a s s i f i e d a c c o r d i n g t o t h e p r i n c i p l e s o f c o n s t r u c t i o n : (1) E b e r m a y e r , (2) f i l l e d - i n , a n d (3) m o n o -l i t h , o r u n d i s t u r b e d s o i l b l o c k . P e l t o n (1961) d e s c r i b e d t h e t y p e s a s f o l l o w s » I n t h e E b e r m a y e r t y p e , a p e r c o l a t e f u n n e l i s p l a c e d u n d e r a b l o c k o f s o i l l e f t i n s i t u . T h e l y s i m e t e r h a s n o s i d e w a l l s a n d c a n n o t , i n i t s e l f , b e u s e d t o d e t e r m i n e e v a p o t r a n s p i r a t i o n . T h e f i l l e d - i n l y s i m e t e r c o n s i s t s o f a c o n t a i n e r w i t h v e r t i c a l s i d e w a l l s , a n o p e n t o p , a n d a b o t t o m t h a t p r o v i d e s f o r p e r c o l a t i o n . T h e s e l y s i m e t e r s a r e u s u a l l y f i l l e d w i t h s o i l t h a t h a s b e e n s t r i p p e d f r o m t h e a r e a i n s t r u c t u r a l l a y e r s . T h e y a r e f i l l e d i n s u c h a m a n n e r t h a t t h e y a p p r o a c h n a t u r a l c o n d i t i o n s a s n e a r l y a s p o s s i b l e . T h e m o n o l i t h l y s i m e t e r i s c o m p o s e d o f a c a s i n g b u i l t a r o u n d a n a t u r a l b l o c k o f s o i l a n d p r o v i d e d w i t h a p a r t l y o p e n b o t t o m . M e a s u r e m e n t s o f w a t e r a p p l i e d , o u t f l o w , a n d c h a n g e s i n s o i l m o i s -t u r e a r e u s e d t o d e t e r m i n e e v a p o t r a n s p i r a t i o n . S o i l m o i s t u r e may b e m e a s u r e d b y d i r e c t m o i s t u r e s a m p l i n g ( e . g . , g r a v i m e t r i c s a m p l e s o r n e u t r o n p r o b e ) , o r b y u s i n g w e i g h i n g o r h y d r a u l i c m e t h o d s . I n t h e h y d r a u l i c m e t h o d , t h e t a n k i s f l o a t e d a n d c h a n g e s i n w e i g h t a r e r e c o r d e d a s p r e s s u r e c h a n g e s o n a m a n o m e t e r ( G r a y e t a l . 1966). T h e c h i e f a r g u m e n t a g a i n s t t h e u s e o f t h e l y s i m e t r i c m e t h o d o f e v a p o t r a n s p i r a t i o n d e t e r m i n a t i o n i s t h a t t h e r e may b e d i f f e r e n c e s b e -t w e e n t h e l y s i m e t e r a n d n a t u r a l c o n d i t i o n s . T h e s c o p e f o r s u c h d i f f e r e n c e s i s l a r g e , e . g . , s o i l p r o f i l e a n d m o i s t u r e r e g i m e n , p l a n t r o o t i n g 48 character! sties j, methods of water application, and the net energy ex-changes However, i f the installations satisfy certain minimum standardsB they will provide reasonably reliable estimates of evapotranspiration over short time periods (Linsley et al. 1949 9 Pelton 1961). The minimum standards that should pertain are? (1) the lysimeter should contain soil that has been disturbed as l i t t l e as practicable*) . (2) uniform conditions around the lysimeter should be maintained 9 and (3) the ratio of the area of surface occupied by lysimeter walls to the enclosed area should be made small. Results of Investigations The Tennessee Valley Authority determined that total transpiration from a forest of pine, oak9 and other shrubss from May 19 to October 1 9 was 420 mm0 (16,5 in°) (Rothacher 1949). The method used was the placing against the growing leaf strips of f i l t e r paper that had been soaked in a solution of cobalt chlorideo The time required for colour changes to take place as moisture was absorbed by the f i l t e r paper was compared to a standard to obtain an estimate of transpiration. Oelkers (19^Q8 cited by Penman 1963) 9 in Germany, used lysimeters to determine transpiration for a growing season of 153 days on a. medium pine site. He reported the following values: pine9 80 mm. (3<>2 in.); f i r 9 66 mm. (2.6 in.); bireh 9 74 mm0 (2<>9 in.); larch (Larix sp 0) B 147 mm. (5°79 in.)? and spruce, 323 mm. (12.7 in.). Using a set of large lysimeters at Gas tricum* Holland 9 Dei j (195^9 cited in Penman 1963) determined that conifers had a mean annual 49 evapotranspiratlon for the period 1948-1953 of 538 mm. (21.2 in.) compared to 417 nwo (16.4 in.) for deciduous, and 448 mm. (17»6 in.) for low vegetation. Smirnov and Odinovkova (195^), working on aspen in the Tellerman Forest in Russia, reported transpiration of 203 mm* (7»99 in.) for eight-year old aspen; 230 mm. (9«06 in.) for 25-year old aspen; 201 mm. (7«91 in.) for 36-year old aspen; and I85 mm. (7«28 in.) for 63-year old aspen. These figures were arrived at by calculating a water balance using evaporimeter measurements, throughfall, soil moisture, runoff, and infiltration. Straight-line relations were found between the amount of transpiration and the current annual volume increment of the stand. Holstener-Jorgensen (1959) reported water use by 65-year old beech and 45-year old spruce on the Danish Forest Experiment Station. The author used ground-water levels, which, i f they reach the zone of root activity, may be used to give a measure of water use. For the period April 19 - December 14, 1956, beech transpired 48lmm0 (18.94 i n c . ) ; spruce transpired 471 mm. (18.5^ in.) for the period April 15 - December 13» 1956; and for April 10 - December 28, 1957, beech 417 mm. (16.42 in,) and spruce, February 28 - December 28, 1957, 469 mm. (18.46 in.). The order is reversed for the two years which might be accounted for by a difference in response of the two species to changed availability of water in the two years, but more likely i t is that because of the mild spring or late winter the spruce began transpiration several weeks before the beech in 1957= Molchanov ( 1 9 5 5 » cited by Penman I963) used soil moisture deter-mination to estimate water use in an area where mean annual rainfall was 500 mm. ( 1 9 c ? in,)« The maximum values of evapotranspiratlon were as follows % Scotch pine (Pinus sylvestris L,), 40-80 years, 420-467 mra, (I60 5-18,4 in,) oak, 40-100 years, 443-469 mm. (17 = 4-18 ,5 tn„) ash, 40 yearst 416 mm= (16,4 in,) aspeng 20 years9 392 mm, (15<>4 in,) Molohanov ( i 9 6 0 ) concluded that evapotranspiratlon was greatest in larch, followed by f i r , pine, oak, aspen, ash, and birch standsc Wtihin a given species the water use varied with age, the highest use being observed in the period of culmination of current annual volume increment.. Kittredge (1948) also indicated that there i s evidence that transpir-ation is greatest for dense stands on the best sites at the culmination of current annual increment. Brown and 'Thomson (I965) measured soil moisture in spring and f a l l of 1955* 195?9 1958 s in Colorado to determine water use. The study indicated that water use per day was greatest on aspen sites, intermediate on Engelmann spruce sites, arid least on grassland sites. There is reason to believe that in aspen and spruce types the water use would be similar under conditions of similar soil moisture* since the moisture with.dra.wn by aspen exceeded that of spruce by almost the same amount as the differ-ences in spring soil moisture under the two types. 51 The evapotranspiration from spruce-subalpine f i r forest in the eastern Rocky Mountains of Alberta» was estimated by the eddy-flux method (Munn and Storr 196?)«, Measurements of net radiation above the canopy and of gradients of wind and temperature from an 80-foot tower were taken. Fast-speed runs of the fluctuations of temperatures, humidity9 and vertical wind were taken using dry and wet bulb thermocouples and a vertical anemometer. Evapotranspiration was estimated to be about 0o3 grams/cm. or Q013 inches/day. Rutter (1959) related evapotranspiration to solar radiation. The trends over time of both variables were quite similar. In 1928s Meyer constructed a graph from which the depth of trans-piration could be read directly from mean monthly air temperature. Al-though factors other than air temperature were neglected^ the results were not dissimilar to those obtained by other methods. - Considering the important influences of meteorology and soil mois-ture as well as the influence of vegetative factors such as the type9 colour^ density;, and shape of the plant on evapotranspiratdong, few detailed conclusions seem warranted regarding the amount of water use by trees. There i s evidences, however9 which seems to indicate that in both conifer and deciduous stands there i s an increase in water use until about age 60, with a gradual dropping off after that age. The range of evapotranspiration for most species i s about 300 to 500 mm./year (roughly 10 to 20 in./year). 52 4„ STREAM FLOW Annual Disoharge Investigation of the hydrologic role of forests has often been directed toward streamflow measurements, Of the elements of the hydro-logic cycle, surface runoff in channels is the easiest to measure. This, along with the importance of quantity and timing of runoff9 has been responsible for the accent on stream gaugingo Streamflow is the integrator of a l l the variables on a watershed. Because of this, water= shed treatment has been assessed by it s influence on streamflow,, Of the factors of the water balance that might be amenable to influence by man, evapotranspiratlon seems to be the most readily altered. Rakhmanov (1959)» reviewing the literature of the past 100 years, con-cluded that forest cover does not accelerate evapotranspiratlon, and that there is no substantial difference between forest and other culti-vated land areas in similar environments. However, this view is not widely accepted, as a review of the literature will indicate. In Japan, clearing of broad-leaved trees, 30-feet t a l l , caused greater streamflow surges immediately after rain, and a reduction in annual water use, the increase in quantity of runoff being similar to the estimated interception before cutting (Hirata 1929)o One watershed of a paired-watershed experiment in Kamabuchi, Japan, containing mixed conifer and broad-leaved deciduous trees, was clear cut, grass and brush regrowth being removed in each subsequent year. Runoff during the succeeding three years averaged 1790 mm. (70<>47 in.) from the 53 f o r e s t e d w a t e r s h e d a n d 1955 rom* (76.9? i n . ) f r o m t h e b a r e o n e . T h e d i f f e r e n c e , 165 mm. (6.50 i n . ) was a t t r i b u t e d t o r e d u c e d e v a p o t r a n s -p i r a t i o n o n t h e b a r e s i t e ( M a r u y a m a a n d I n o s e 1956). I n t h e S p e r b e l g r a b e n a n d R a p p e n g r a b e n w a t e r s h e d s t u d i e s i n S w i t z e r l a n d , B u r g e r (195*+) r e p o r t e d g r e a t e r r u n o f f f r o m t h e l e a s t f o r e s t e d w a t e r s h e d a n d t h a t e v a p o t r a n s p i r a t i o n was g r e a t e r f r o m w o o d l a n d t h a n g r a s s l a n d . P e n m a n (1963) s u g g e s t e d t h a t t h e d a t a f r o m t h i s s tudy-m u s t b e a p p r o a c h e d w i t h c a u t i o n b e c a u s e o f d o u b t s a b o u t t h e a c c u r a c y o f t h e r a i n g a u g i n g a n d s t r e a m g a u g i n g . D e l f s e t a l . (1958) r e p o r t e d 10 p e r c e n t g r e a t e r e v a p o t r a n s p i r a t i o n f r o m t h e h e a v i l y - f o r e s t e d W i n t e r t a l w a t e r s h e d t h a n t h e c l e a r - c u t , g r a s s -c o v e r e d L a n g e B r a m k e w a t e r s h e d i n G e r m a n y . P r e c i p i t a t i o n a n d r u n o f f f r o m t h e f o r e s t e d w a t e r s h e d f o r t h e p e r i o d 1948-1953 w e r e 49 a n d 23 i n . r e s p e c t i v e l y , a n d 48 a n d 28 i n . r e s p e c t i v e l y f o r t h e g r a s s - c o v e r e d w a t e r -s h e d . A t W a g o n W h e e l Gap i n C o l o r a d o , o n e o f two s i m i l a r w a t e r s h e d s was c l e a r e d a n d s l a s h - b u r n e d , w i t h a s p e n q u i c k l y i n v a d i n g t h e a r e a . A n n u a l p r e c i p i t a t i o n was a b o u t 21 i n . a n d r u n o f f was a b o u t 6 i n . a n n u a l l y . F o r t h e f i r s t t h r e e y e a r s a f t e r c u t t i n g , t h e t r e a t e d w a t e r s h e d h a d 23 p e r c e n t g r e a t e r r u n o f f t h a n t h e u n t r e a t e d w a t e r s h e d ; f o r t h e s e c o n d t h r e e -y e a r p e r i o d r u n o f f was o n l y 18 p e r c e n t g r e a t e r . T h e a s s u m p t i o n i s t h a t t h e d e c r e a s i n g d i f f e r e n c e i n r u n o f f , f r o m 23 t o 18 p e r c e n t , was d u e t o t h e v e g e t a t i v e r e c o v e r y o f t h e t r e a t e d a r e a ( B a t e s a n d H e n r y 1928). A t t h e C o w e e t a E x p e r i m e n t a l F o r e s t i n N o r t h C a r o l i n a , t h e c u t t i n g o f o n e w a t e r s h e d r e s u l t e d i n a r u n o f f i n c r e a s e o f 16 i n . w h e r e p r e - t r e a t m e n t 54 yield averaged about 30 in« (Hoover 1944), Removal of vegetation from 30 per cent of a 250-acre watershed on the H UJ. Andrews Experimental Forest, in Oregon, caused a 12-28 per cent increase in minimum streamflow. Removal of timber on 40 per cent of another watershed increased low flows by 45 per cent, and by 85 per cent after 80 per cent of the watershed had been logged. Annual water yields before treatment were from 50 to 60 in. and annual precipitation averaged 94 in. (Rothacher 1965a). Twenty years of before-and-after records on the Pine Tree Branch watershed in Tennessee indicated that total runoff decreased from three to six inches per year while ground-water runoff volumes remained un-changed after reforestation r Mean annual runoff for the 20-year period was 10 in. Peak discharges in both summer and winter floods were reduced by ?0 to 90 per cent for moderate to large storms (T.V.A. 1962). Up to five inches of increased runoff (increasing the annual yield to 26 in.) resulted from clear cutting watersheds in the Fernow Experimental Forest. Evidence indicated that fully-stocked stands were a benefit to flood control during the growing season (Reinhart et al. I963). Evidence reported by Rich (19&5) indicated that the type of cut, not just the basal area removed, influenced the runoff from Workman Creek watersheds in Arizona. No significant increase in water yield resulted from a riparian cut on the North Fork, but only 0,6 per cent of the total basal, area was removed. A later clear cut of moist-site vegetation along the streams, amounting to 32 per cent of the area, did result in increased water yields. However, removal of 24 per cent of total basal area by 55. s i n g l e - t r e e s e l e c t i o n a n d a n o t h e r 21 p e r c e n t by r o a d c o n s t r u c t i o n a n d f i r e o n t h e S o u t h F o r k w a t e r s h e d , h a s n o t s i g n i f i c a n t l y i n c r e a s e d w a t e r y i e l d d u r i n g t h e 11 y e a r s s i n c e t h e c u t . , S c h n e i d e r a n d A y e r (1961) r e p o r t e d t h a t i n c r e a s i n g f o r e s t c o v e r f r o m 26 t o 8 4 p e r c e n t o n S h a c k h a m B r o o k w a t e r s h e d , i n c e n t r a l New Y o r k s t a t e , s i g n i f i c a n t l y r e d u c e d i t s m e a n f l o w o v e r t h e 26 y e a r s f o l l o w i n g t r e a t m e n t . H e w l e t t a n d H i b b e r t (1961) r e v i e w e d t h e w a t e r s h e d s t u d i e s c a r r i e d o u t o v e r t h e p a s t 30 y e a r s a t t h e C o w e e t a H y d r o l o g i c L a b o r a t o r y , N o r t h C a r o l i n a . F o l l o w i n g a r e s o m e o f t h e c o n c l u s i o n s t h a t h a v e b e e n r e a c h e d a t C o w e e t a : (1) F i v e t o 16 i n . o f i n c r e a s e d r u n o f f h a v e b e e n m e a s u r e d i n t h e f i r s t y e a r a f t e r c l e a r - c u t t i n g . (2) S o u t h s l o p e s h a v e y i e l d e d o n l y h a l f t h e f i r s t y e a r i n c r e a s e s o b -t a i n e d o n n o r t h s l o p e s a f t e r t r e a t m e n t . (3) When t r e a t m e n t e f f e c t s h a v e b e e n l a r g e , t h e r e h a s b e e n c o n s i d e r a b l e d e l a y i n t h e t i m i n g o f p a r t o f t h e i n c r e a s e d r u n o f f . When e f f e c t s h a v e b e e n s m a l l , t h e i n c r e a s e t e n d s t o b e d u r i n g t h a t s e a s o n i n w h i c h t h e a c t u a l s a v i n g s i n t e r m s o f r e d u c e d e v a p o t r a n s p i r a t i o n w o u l d b e e x p e c t e d . ( 4 ) When i n c r e a s e s a r e l a r g e , t h e y e x t e n d o v e r a p e r i o d o f 35-^ 0 y e a r s , b u t m o s t o f t h e i n c r e a s e c o m e s d u r i n g t h e w i n t e r ( h i g h - f l o w ) s e a s o n . 56 (5) F i r s t - y e a r i n c r e a s e s i n y i e l d s e e m t o b e r e l a t e d t o t h e p e r c e n t o f t h e f u l l y - d e v e l o p e d s t a n d t h a t i s r e m o v e d o T h e p a t t e r n o f c u t t i n g a t C o w e e t a s h o w e d l i t t l e r e l a t i o n t o t h e y i e l d i n c r e a s e , (6) A r i p a r i a n - s t r i p c u t , r e m o v i n g 12 p e r c e n t o f t h e b a s a l a r e a o f o n e w a t e r s h e d d i d n o t p r o d u c e a s i g n i f i c a n t i n c r e a s e i n a n n u a l y i e l d . A n i n t e r e s t i n g p o i n t i s t h a t t h e r a t i o o f f i r s t » y e a r i n c r e a s e t o p e r c e n t b a s a l a r e a c u t i s a p p r o x i m a t e l y t h e s a m e f o r t h e f o u r n o r t h e r l y s l o p e s , i , e . , 0,15 ( r a n g i n g f r o m 0.13 t o 0.17), e x c l u d i n g t h e r i p a r i a n - s t r i p c u t w h i c h w a s a l s o c o n d u c t e d o n a n o r t h e r l y s l o p e . T h e r a t i o f o r s o u t h s l o p e c u t s r a n g e f r o m 0.00 t o 0.07. Some R u s s i a n i n v e s t i g a t o r s r e p o r t s m a l l e r a n n u a l r u n o f f f r o m f o r -e s t e d w a t e r s h e d s t h a n f r o m n o n - f o r e s t e d w a t e r s h e d s . T h e f o l l o w i n g e x a m p l e s a r e f r o m S o k o l o v s k y (1959)* T a j e s h n y w a t e r s h e d , 98 p e r c e n t f o r e s t e d , h a d a r u n o f f c o e f f i c i e n t o f 0.27, ( i » e . , 27 p e r c e n t o f t h e p r e c i p i t a t i o n was r u n o f f ) w h i l e t h e n e a r e s t f i e l d w a t e r s h e d , U s a d j e v s k y j , h a d a c o e f f i c i e n t o f 0,54; V o r o n y w a t e r s h e d , 90 p e r c e n t f o r e s t e d , h a d a c o e f f i c i e n t o f s p r i n g r u n o f f o f 0,29 c o m p a r e d t o O.56 f o r t h e f i e l d w a t e r s h e d , P e t r u s h i n o . T h e . r e a s o n g e n e r a l l y a c c e p t e d f o r l e s s r u n o f f f r o m f o r e s t e d w a t e r -s h e d s i s t h e l o s s o f m o i s t u r e d u e t o t r a n s p i r a t i o n o f t h e t r e e s . H o w e v e r , o b s e r v a t i o n s o n m e d i u m a n d l a r g e w a t e r s h e d s (116 t o 77,000 s q . m i . ) i n R u s s i a s e e m t o i n d i c a t e t h a t r u n o f f i n c r e a s e s a s t h e f o r e s t e d p r o p o r t i o n o f t h e w a t e r s h e d I n c r e a s e s ( S o k o l o v s k y 1959)« T h e r e a s o n f o r t h i s s e e m i n g c o n t r a d i c t i o n o f m o s t w a t e r s h e d r e s u l t s may b e t h a t t h e i n c r e a s e i n p r o p o r t i o n f o r e s t e d i s d i r e c t l y r e l a t e d t o e l e v a t i o n , p r e c i p i t a t i o n , o r s o m e o t h e r f a c t o r s . W h a t e v e r f a c t o r s may e x p l a i n t h e c o n c l u s i o n r e a c h e d by Sokolovosky, much evidence indicates the opposite to be true. In summary, runoff is greater from grassland than forest, and annual runoff has usually increased after clear cutting, increases commonly being about 25 per cent with extremes of nine and 85 per cent being recorded. Flow Regime The effect of cover changes on streamflow would not be expected to be constant throughout the year but to vary with season as other factors vary (e.g., transpiration). Studies have shown that cover changes do alter the regime as well as total flow of streams. Wagon Wheel Gapt Colorado. At Wagon Wheel Gap in Colorado, partial cutting of a 200-acre watershed resulted in spring runoff beginning earlier and higher peak flows (Bates and Henry 1928). o San Gabriel River. California. On the San Gabriel River in south-ern California fire burned over the Fish Creek watershed but missed the adjacent, and. similar, Santa Anita Creek watershed. Peak discharges from the Fish Creek watershed were much greater in the first year after the fire, but f e l l progressively in succeeding years (335» 292, 145, 15» 11, and 11 c.f.s./sq. mile) as vegetation regrew on the watershed. With-in six years, runoff from the watershed was back to normal (Hoyt and Troxell 1934). Coweeta, North Carolina. At Coweeta, North Carolina, a 33-acre watershed was cut over in 1941. The average monthly streamflows for the following 15 years was higher than predicted, with the September-December 53 p e r i o d ( n o r m a l l y t h e p e r i o d o f l o w e s t f l o w ) b e i n g i n c r e a s e d b y o v e r 90 p e r c e n t ( M e g i n n i s 1959)• P i n e T r e e B r a n c h * T e n n e s s e e . O n t h e P i n e T r e e B r a n c h w a t e r s h e d i n T e n n e s s e e , r e f o r e s t a t i o n r e s u l t e d i n m a r k e d l y r e d u c e d w i n t e r a n d s u m m e r p e a k d i s c h a r g e s ( T . V . A . 1962), H . J . A n d r e w s E x p e r i m e n t a l F o r e s t . O r e g o n . R o t h a c h e r (1965a) r e -p o r t e d o n w a t e r s h e d s t u d i e s a t t h e H . J . A n d r e w s E x p e r i m e n t a l F o r e s t , o n t h e w e s t e r n s l o p e s o f t h e C a s c a d e R a n g e i n w e s t e r n O r e g o n . A f t e r s e v e n y e a r s o f c a l i b r a t i o n w i t h a n a d j a c e n t w a t e r s h e d , a 250-acre w a t e r s h e d i n t h e D o u g l a s f i r r e g i o n , b e t w e e n 1,500 a n d 3,500 f t . e l e v a t i o n , was t r e a t e d . I n 1959, e i g h t p e r c e n t o f t h e w a t e r s h e d w a s c l e a r e d i n t h e p r o c e s s o f r o a d c o n s t r u c t i o n . T h e e f f e c t o n s t r e a m f l o w was s t u d i e d f o r t h r e e y e a r s , t h e n 25 p e r c e n t o f t h e a r e a was c l e a r c u t . T h e n e x t y e a r t h e c l e a r - c u t a r e a was b r o a d c a s t b u r n e d . No i n c r e a s e i n max imum f l o w s f r o m t h e t r e a t e d w a t e r s h e d was r e c o r d e d , b u t f o r t h e f i r s t s i x y e a r s a f t e r t h e b e g i n n i n g o f t h e t r e a t m e n t t h e r e was a 12 t o 2 8 p e r c e n t i n -c r e a s e i n m i n i m u m f l o w s . O n a s e c o n d w a t e r s h e d i n t h e H . J . A n d r e w s E x p e r i m e n t a l F o r e s t c u t t i n g b e g a n i n 1963 w h e n 4 0 p e r c e n t o f t h e a r e a was c u t , a n d c o n t i n u e d i n 1964 u n t i l 80 p e r c e n t o f t h e a r e a was c u t . I n I963, l o w f l o w s i n -c r e a s e d 45 p e r c e n t a n d i n 1964, 85 p e r c e n t . T h e i n c r e a s e s w e r e s m a l l i n a b s o l u t e t e r m s b u t t h e h i g h p e r c e n t a g e s a r e d u e t o t h e e x t r e m e l y l o w f l o w s n o r m a l f o r t h e l a t e s u m m e r m o n t h s . 59 Fernow Experimental Forests West Virginia. On the Fernow Experi-mental Forest in West Virginia, studies were carried out on watersheds supporting stands of deciduous species, vizo, oak,, maple (Acer sp0) beech9 cherry (Prunus spo) s and poplar. Significant increases in stream-flow during the growing season were recorded for three watershedsa one clear cut a one cut to diameter limit 9 and one cut on an extensive selection basis (harvesting and killing of culls larger than 11 in. dsboh.)o The increase in discharge appeared to be greater with the more severe cut. Large increases in flow were not recorded during the dormant season (November-April). Instantaneous peaks on the clearcut watershed were increased9 on the average, by ZL per cent in the growing season and reduced by four per cent in the dormant season (Reinhart at al. 1963)o Fraser Experimental Forests Coloradoo At the Fraser Experimental Forest in Colorado9 streamflow records were kept for 12 years before cutting the 714-aere Fool Creek watershed in 1954 (Goodell 1958). The 25O- to 30Q-year-old stands of lodgepole pine and Engelmann spruce-subalpine f i r were logged in clear-cut strips so that 278 of the - 550 ,. forested acres were cleared (Love 1960)o In the eight years since the cut, average annual streamflow has increased by 2.7 area-inchess or 25 per cent (Goodell 1964)0 Howevers> nearly all of the increased flow occurred during the spring runoff period and low flows were increased l i t t l e (Hoover and Shaw 1962). It i s estimated that increased yield will continue for 35 to 50 years before regrowth reduces i t to zero (Goodell 1964)o 6o Spring flood peak was greater the f i r s t year and 23 per cent less the second year than predicted values. The author suggested that the effect of clearing may be to decrease or increase peak flow depending on weather conditions (Goodell 1958). Shackham Brook, Central Mew York. Reforestation of three water-sheds in central New York state resulted in dormant-season runoff being reduced 0.17 to 0.29 in. per year, averaged over the 26 years since treatment. For Shackham Brook watershed, runoff was reduced by 0.14 in. for the growing season, 0.23 in. for the dormant season, and O.36 in. for the year, and peak discharges by 41 per cent for the dormant season. No significant change in peak flows for the growing season nor annual low flows were recorded for any of the watersheds (Schneider and Ayer I96I). In summary, the effects of clear cutting on flow regime vary with climate, soils, etc. The literature reviewed indicates that peak flows increased l i t t l e to as much as 21 per cent and low flows l i t t l e to as much as 90 per cent. Snowmelt and' Water Yield Snow accumulation and melt have an important influence on water yield and regime but less attention has been paid to this aspect than to accumulation itself. In 1935» Gonnaughton concluded from a study carried out in ponderosa pine in southern Idaho that forest-cover conditions affected snowmelt and that retarding the rate of melt by forest management could, increase the duration of runoff and distribute the peak flow over a longer time. 1 In the White River drainage basin in Colorado, 226 sq. mio( of i Engelmann spruce and lodgepole pine were killed by the Engelmann spruce beetle. The resulting increase in snow accumulation increased streamflow by 22 per cent with peak flows coming in June instead of May as they had before (Love 1955). i Other studies on snow accumulation and melt have been reported in a preceding section on sriow, and Colraan (1953) has summarized the litera-ture on the subject to 1953* The results of most of these studies indicate that forest-cover reduction usually increases snow accumulation as well as melt rate. This, in turn, produces greater water yield and higher peak flows. Reinhart et al. (1963), however, reported from limited observations that daily snowmelt runoff from a clear-cut watershed in West Virginia was for one 14-day period more uniform than from the forested, control water-shed. The period was March 18-30, i960, during which flow from the clear-cut watershed was only 92 per cent of the control. On March 30, peak flows were recorded on each watershed and the flow from the clear-cut watershed was 71 per cent of control. The explanation suggested by the authors i s that, snow cover disappeared near the end of the 14-day period and that i t was gone on the clear-cut watershed before the control. Appar-ently, exposure of the snow cover resulted in a much lower peak. Eschner and Satterlund (I963) stated that timber harvesting may increase or decrease, depending on weather conditions, not only peak flows, 62 as suggested by Goodell (1958 ) 9 but the entire period of high winter-spring runoff. A study by Satterlund and Eschner (1965) indicated that the average rate of concentrated runoff during snowmelt appeared to be faster after reforestation of Shackham Brook watershed in New York state. The reason given i s that runoff from the forested watershed, though reduced in quantity was even more concentrated in time. "If we accept the well-demonstrated fact that the rate of snowmelt per degree day i s less in the forest than in the open" (Satterlund and Eschner 1965» p» kOk), the con-centration in time can be explained. As spring days pass the number of degree-days increases rapidly. Before this rapid increase, snowmelt has been slower9 i . e 0 , the snow in the open, which melts before that in the forest, has melted at a slow rate due to the slow increase in degree-days. The snow in the forest is then subjected to the greater amount of heat per day causing? faster melt rates than occurred in the open. Along with this is the greater possibil-ity of a rain on snow event the longer the snow remains. The authors suggested that the relation between forest and snowmelt under the climatic conditions of the north-eastern United States may be • i different where a uniformly cold winter climate prevails. \ \ 5« EROSION The terms normal and geological erosion refer to natural erosion which includes the processes of soil formation and soil erosion, and 63 w h i c h o c c u r s t h r o u g h t h e a c t i o n o f w a t e r s , w i n d , g r a v i t y , a n d g l a c i e r s o S o i l l o s s i n e x c e s s o f g e o l o g i c a l e r o s i o n , t e r m e d a c c e l e r a t e d e r o s i o n , i s u s u a l l y c o n s i d e r e d t h e r e s u l t o f c h a n g e s i n n a t u r a l c o v e r o r s o i l c o n d i t i o n s a n d i s c a u s e d b y w a t e r a n d w i n d ( F r e v e r t e t aLo 1955)° T h e e r o s i o n o f i n t e r e s t h e r e i s a c c e l e r a t e d e r o s i o n b e c a u s e i t i s t h i s t y p e t h a t i s a m e n a b l e t o m a n ' s c o n t r o l e f f o r t s » T h e d e s i r e t o c o n t r o l e r o s i o n i s t h e r e s u l t o f t h e l o s s e s i n c u r r e d b y man b e c a u s e o f e r o s i o n . T h e s e l o s s e s i n c l u d e , f i r s t o f a l l , p r o d u c t i v e l a n d t h a t h a s e r o d e d o r u p o n w h i c h e r o d e d m a t e r i a l h a s b e e n d e p o s i t e d , . E r o d e d m a t e r i a l a l s o c a u s e s d a m a g e , a s i t m o v e s , t o e n g i n e e r i n g s t r u c t u r e s a n d h o m e s . S e c o n d l y a r e t h e l o s s e s c a u s e d b y s e d i m e n t , w h i c h i s t h e .. p r o d u c t o f e r o s i o n . T h e s e l o s s e s t a k e t h e f o r m o f l o w e r w a t e r q u a l i t y , d a m a g e t o a q u a t i c h a b i t a t , s i l t i n g u p o f r e s e r v o i r s a n d i r r i g a t i o n . c a n a l s , d a m a g e t o p u m p s , t u r b i n e s , a n d p i p e l i n e s , a n d r a i s e d s t r e a m b o t t o m s w h i c h o f t e n c a u s e i n c r e a s e d f l o o d d a m a g e . L o s s e s a l s o i n c l u d e t h e p l a n t n u t -r i e n t s a n d t h e f i n e r s o i l p a r t i c l e s w a s h e d o f f t h e s o i l . F a l l i n g r a i n i m p a r t s t r e m e n d o u s e n e r g y t o t h e s u r f a c e o n w h i c h i t l a n d s . F o r e x a m p l e , a t w o - i n c h r a i n f a l l i n g i n o n e h o u r i m p a r t s s u f f i c -i e n t e n e r g y t o l i f t t h e s e v e n - i n c h t o p - s o i l l a y e r two f e e t ( R o b i n s a n d N e f f 1963)9 t h e d r o p s r e a c h i n g s p e e d s o f u p t o 20 m i l e s p e r h o u r ( L a w s 1940)o T h e f o l i a g e a n d b r a n c h e s o f t h e v e g e t a t i o n o f f e r t h e f i r s t o b s t a c l e t o f a l l i n g r a i n . R a i n w h i c h i s n o t h e l d a n d e v a p o r a t e d b y t h i s c o v e r r e a c h e s t h e g r o u n d w i t h c o n s i d e r a b l y l e s s d r i v i n g f o r c e . L e a f l i t t e r f u r t h e r r e d u c e s t h e f o r c e o f i m p a c t a n d a b s o r b s w a t e r . 64 R o o t s a n d t h e b i o l o g i c a l a c t i v i t y a s s o c i a t e d v d t h v e g e t a t i o n i n c r e a s e s o i l p o r o s i t y a l l o w i n g f a s t e r i n f i l t r a t i o n * L i t t e r , t w i g s , a n d p l a n t s t e m s r e d u c e t h e v e l o c i t y a n d c u t t i n g a c t i o n o f t h a t w a t e r t h a t d o e s n o t i n f i l t r a t e t h e s o i l b u t f l o w s o v e r l a n d o T h i s i s a n i m p o r t a n t p a r t o f t h e i n f l u e n c e o f v e g e t a t i o n o n e r o s i o n b e c a u s e f l o w i n g w a t e r i s a p r e -r e q u i s i t e t o s i g n i f i c a n t s o i l e r o s i o n ( R o b i n s a n d N e f f 1 9 6 3 ) 0 B l a m e f o r t h e d e c l i n e o f N e a r E a s t e r n a n d N o r t h A f r i c a n c i v i l i z a -t i o n s h a s o f t e n b e e n l a i d t o d e f o r e s t a t i o n o f t h e h i l l s i d e s b y c u t t i n g a n d g r a z i n g , a l t h o u g h c l i m a t i c c h a n g e s h a v e o f t e n b e e n s u g g e s t e d a s t h e c a u s e o L o w d e r m i l k (1953) c i t e d e v i d e n c e t h a t t h e c l i m a t e h a s n o t b e c o m e n o t i c e a b l y d r i e r i n t h o s e r e g i o n s s i n c e t h e e x i s t e n c e o f t h o s e c i v i l i z a -t i o n s , a n d t h a t h u m a n a c t i v i t y was r e s p o n s i b l e f o r t h e d e n u d a t i o n o f t h e h i l l s i d e s . T h e r e s u l t i n g e r o s i o n c e r t a i n l y p l a y e d a p a r t i n t h e d e c a d e n c e o f t h o s e c i v i l i z a t i o n s , b u t t o s u g g e s t t h i s a s t h e c a u s e i s p r o b a b l y n o t w a r r a n t e d . E r o s i o n S t u d i e s T h e f i r s t s o i l - e r o s i o n s t u d y i n w h i c h d a t a w e r e o b t a i n e d w i t h w h i c h t o c o m p a r e v e g e t a t i o n a l i n f l u e n c e s o n e r o s i o n was c a r r i e d o u t i n C h i n a i n t h e 1920" s . R u n o f f a n d e r o s i o n r a t e s w e r e m a n y t i m e s g r e a t e r o n c u l t i v a t e d l a n d t h a n o n f o r e s t l a n d ( L o w d e r m i l k 1953)« I n t h e S w i s s w a t e r s h e d s t u d y i n E m m e n t a l , a v e r a g e s e d i m e n t l o a d f r o m t h e a l m o s t w h o l l y -f o r e s t e d w a t e r s h e d w a s 85 m 0 ^ / k m 0 2 / y e a r (12.1 c u . f t . / a c r e / y e a r ) a n d 145 m . 2 / k m . 2 / y e a r (20.7 c u . f t . / a c r e / y e a r ) f r o m t h e w a t e r s h e d o f o n e -t h i r d f o r e s t a n d t w o - t h i r d s p a s t u r e ( B u r g e r 1943; c i t e d i n P e n m a n 1963). 65 T h e s e d i m e n t p r o d u c t i o n f r o m t h e p a s t u r e w a t e r s h e d was a l m o s t d o u b l e t h a t f r o m t h e f o r e s t e d w a t e r s h e d b u t t h e a b s o l u t e a m o u n t was s t i l l v e r y s m a l l . I n M i c h i g a n , S m i t h a n d C r a b b e (1952) f o u n d t h a t e r o s i o n f r o m a r a b l e l a n d w a s f r o m 500 t o 1,000 t i m e s t h a t f r o m f o r e s t . I n a n o t h e r M i c h i g a n s t u d y t h e f o l l o w i n g s e d i m e n t d i s c h a r g e r a t e s w e r e m e a s u r e d ( S t r i f f l e r 1964): F o r e s t — — — — — . — 360 l b . / d a y / s q . m i . W i l d l a n d — 7 4 1 1 1 " P a s t u r e 1 , 800 " " C u l t i v a t e d — 2,200 " " L o w d e r n d l k (1953) r e p o r t e d t h e r e s u l t s o f a s t u d y a t t h e S t a t e s v i l l e , N o r t h C a r o l i n a , E r o s i o n E x p e r i m e n t S t a t i o n i n t e r m s o f t h e n u m b e r o f y e a r s i t w o u l d t a k e t o e r o d e a s e v e n - i n c h l a y e r o f t o p s o i l u n d e r d i f f e r e n t c r o p s . L a n d i n f a l l o w w i t h o u t c r o p p i n g w o u l d t a k e 1 8 y e a r s ; u n d e r c o n -t i n u o u s c r o p p i n g o f c o t t o n , 44 y e a r s ; n a t u r a l c o v e r o f t r e e s b u r n e d o v e r a n n u a l l y , 1 , 800 y e a r s ; g r a s s l a n d , 96.000 y e a r s ; a n d u n d e r u n b u r a e d f o r e s t , 500,000 y e a r s . T h e c o n v e r s i o n o f f o r e s t l a n d t o r a n g e l a n d i n n o r t h e r n C a l i f o r n i a h a s r e s u l t e d i n b a d l y g u l l i e d a n d s l u m p i n g g r a s s l a n d s ( W a l l i s 1965)* W a t e r s h e d a c t i v i t i e s t h a t d e c r e a s e t h e s o i l - h o l d i n g i n f l u e n c e o f v e g e t a -t i o n r e s u l t i n a c c e l e r a t e d e r o s i o n t o some d e g r e e . GELeason e t a l . (1955) i n c l u d e d a m o n g t h e c a u s e s o f s u c h e r o s i o n , c a r e l e s s l o g g i n g , f i r e , o v e r - g r a z i n g , a n d p o o r r o a d c o n s t r u c t i o n m e t h o d s . S i x t e e n w a t e r s h e d s w e r e s e l e c t e d i n n o r t h e r n M i s s i s s i p p i t o r e p r e s e n t p r e v a i l i n g c o n d i t i o n s o f s o i l s , s l o p e s , e r o s i o n , l a n d u s e , a n d p l a n t c o v e r i n a s t u d y o f s e d i m e n t a n d s u r f a c e w a t e r y i e l d s ( U r s i c a n d D e n d y 1965)» M e a n a n n u a l p r e c i p i t a t i o n v a r i e d b e t w e e n 51 a n d 5^  i n . f o r t h e 66 d i f f e r e n t w a t e r s h e d s b u t a v e r a g e a n n u a l r u n o f f i n i n c h e s w a s : c u l t i -v a t e d l a n d , 16; p a s t u r e , 15; a b a n d o n e d f i e l d s , 75 d e p l e t e d h a r d w o o d s , 5; p i n e p l a n t a t i o n , 1; m a t u r e p i n e - h a r d w o o d o n s h a l l o w s o i l s , 9° S e d i m e n t y i e l d s a v e r a g e d i n t o n s p e r y e a r : c u l t i v a t e d l a n d , 21.75; p a s t u r e , 1.61; a b a n d o n e d f i e l d s , 0.13; d e p l e t e d h a r d w o o d s , 0.10; p i n e p l a n t a t i o n , 0.02; m a t u r e p i n e - h a r d w o o d o n s h a l l o w s o i l s , 0.02. T h e d a t a a r e a v e r a g e s f o r t h e t h r e e y e a r s 1959-1961, e x c e p t f o r t h e m a t u r e p i n e - h a r d w o o d s w h i c h was f o r t h e two y e a r s 1960-1961. T h e r e s u l t s o f many s t u d i e s h a v e s h o w n t h e r e l a t i o n s h i p b e t w e e n e r o s i o n a n d f o r e s t c o v e r : a s f o r e s t s t a n d d e n s i t y d e c r e a s e s , e r o s i o n i n c r e a s e s ( A n d e r s o n 19*+9» A n d e r s o n a n d T r o b i t z 19^ 9» A n d e r s o n 195^ » T . V . A . 1962). E r o s i o n H a z a r d R a t i n g s E r o s i o n r e s u l t s f r o m t h e i n f l u e n c e o f c l i m a t e o n s o i l , m o d i f i e d b y t h e f a c t o r s o f t o p o g r a p h y a n d v e g e t a t i o n . A c h a n g e i n a n y o f t h e s e f a c t o r s w i l l c h a n g e t h e e r o s i o n h a z a r d a n d , u n l e s s c o m p e n s a t i n g c h a n g e s o c c u r i n t h e o t h e r f a c t o r s , t h e a m o u n t o f s e d i m e n t p r o d u c e d . M e a n s o f e s t i m a t i n g t h e e r o s i o n h a z a r d h a v e b e e n t h e o b j e c t i v e s o f m a n y s t u d i e s . T h e h o p e h a s b e e n t h a t s u c h a h a z a r d r a t i n g w o u l d b e h e l p f u l i n m a n a g i n g l a n d t o m i n i m i z e e r o s i o n . S o i l s d i f f e r i n t h e i r p r o p e n s i t y t o e r o d e , i . e . , t h e i r e r o d i b i l i t y o A m e t h o d b y w h i c h s o i l c h a r a c t e r i s t i c s a s t h e y r e l a t e t o e r o d i b i l i t y m i g h t b e e v a l u a t e d was p r o p o s e d b y M i d d l e t o n (1930). H e d e v e l o p e d t w o i n d i c e s o f e r o s i o n , t h e d i s p e r s i o n r a t i o a n d t h e e r o s i o n r a t i o . 6? The dispersion ratio i s the ratio of the amount of s i l t plus clay-in the soil, determined without chemical or mechanical dispersion, to the amount of s i l t and clay determined after standard dispersiono The erosion ratio is the dispersion ratio divided by the ratio of colloid percent to moisture equivalent,. Middle ton classified erodible soils as those whose dispersion ratios were greater than 10 and whose erosion ratios were greater than 15° Non-erodible soils had ratios below these values, Anderson (1951) used the erosion ratio and the dispersion ratio , in conjunction with other soil characteristics and forest cover density to estimate sediment in streams. He reported that both ratios were useful indices of soil credibility, but that the dispersion ratio was the better index. His study also showed that forest cover density had a highly significant influence on erosion, Andre and Anderson (1961) related the surface-aggregation ratio and dispersion ratio, as indices of erodibility, to geology, vegetation and elevation. The surface<=aggregation ratio i s (the amount of surface in square cm,/gm, on particles larger than silt) divided by (the total percentage of s i l t and clay in dispersed soil minus the percentage of s i l t and clay in an undispersed soil), i,e», the ratio of the amount of surface in the non-binding fraction to the amount of clay in the,soil. The study indicated that the surface-aggregation ratio was more signi-ficantly related to soil erodibility than was the dispersion ratio. Also shown by the study were, (1) soils developed from acid igneous 68 rook were about Zj times as erodible as s o i l developed on basalt, (2) erodibility was highest for soils under brush, next under trees, and least under grass, and (3) no definite relation of erodibility to elevation was shown. Analyses of texture and potential erodibility were made on samples of forest soils from 6,500 to 8,000 feet i n the southern Sierra Nevada, i n California (Willen I965). Texture and erodibility were related by regression analysis, to rock type, cover type, elevation, aspect, and slope. Soil texture was found to vary widely with rock type, as did aggregated s i l t and clay. Soil texture was less s i g n i f i -cantly related to vegetative cover but aggregated s i l t and clay was highly significantly related to cover type. Middleton's dispersion ratio and Anderson's surface aggregation ratio were used as indices of potential erodibility i n Willen*s study. The dispersion ratio was significantly related only to parent rock type. Soils developed from granodiorite were, based on the dispersion ratio, more erodible than those from basalt, and those developed from quartzite were least erodible. Based on the surface-aggregate ratio, the sequence was granodiorite with the highest potential erodibility, followed by quartzite and basalt. Potential s o i l erodibility was greatest for soils under grass, followed by brush, pine, and f i r . West slopes were more erodible than south slopes, followed by north and east slopes. Soils at high eleva-tions were more erodible than soils of the same derivation at low elevations. 69 Wooldridge (1965) used mean aggregate size as an index of erosion on basaltic soilso He found this index a good guide i n assessing erosion hazard, due to i t s sensitivity to changes i n vegetative cover and i t s strong relation to organic matter content, bulk density^ and porosityg, s o i l properties known to be related to s o i l t i l t h and struetureo Anderson (1949) derived an equation to predict annual erosion from California watersheds, i n which erosion was related to the maxi-mum yearly peak discharge, the area of the main channel of the water-shed,, and the cover density of the watershed. In a later study 9 he reported a more comprehensive equation which included as independent variables 9 information on the slope of the channels, the s o i l s 9 roads 9 land-use pattern, and the character of the hydrograph (Anderson 19609 1965)o The estimating of sediment production on the basis of soi l s , top-ographys and forest cover i s a form of erosion hazard rating. The equations constructed by Anderson (194-9» I960, I965) estimated the volume of sediment from watersheds given the values of the above variables. A proposed change i n land management, e 0go 9 clear cutting part of the watershed or building roads, could be used i n the equation to predict the sediment production l i k e l y to result; i n reality, an erosion hazard rating. Bullard (1962) carried out a study to estimate sediment produc-tion on the Umpqua River basin i n Oregon. Two watersheds were chosen as standards, one given a very high rating with regard to erosion and 70 sediment production, the other given a low rating. Other watersheds were rated by comparison to these standards according to observations on channel, slope, and road conditions checked against available sediment sampling data. Geologic maps and aerial photos were used to extend the rating to areas not visited. The author stated that though the sediment production ratings were guided to some extent by sediment sampling data, good correlation did not exist between them. The total sediment of all the rated water-sheds was calculated on a. per square mile basis. However, as sediment sampling data did not exist for the whole basin, a comparison of actual and calculated sediment production could not be made. The author con-cluded that the calculated production should not be considered as within less than - 30 per cento The rating method was highly subjective and. does not seem capable of producing figures on sediment production in which confidence could be justified. Regression theory states that predicted values will be more precise when derived from independent variables than when derived directly from correlated variables. Because of this, estimates of erosion hazard ba,sed on independent variables are more precise than those based on related variables such as soil topography, climate, and vegetation, according to Alvis (1961). He presented a theory to attempt "to reduce soil erosion into its fundamental forces" (p. 3 2 ) , stability capacity of soil and moving capacity of an external agent. The fi r s t expresses the capacity of the soil to resist movement, its components being cohesion 71 of the i n d i v i d u a l s o i l aggregates, f r i c t i o n between the surface aggre-gates s and the mass of the average surface aggregate,, The second concerns the erosive agent, and its components are mass and velocity,: Stability capacity and moving capacity are independent o f each othor and. their relation to e r o s i o n i s fixed., A l v i s s t a t e d that this method, of rating erosion hazard has advantages in a d d i t i o n to its being based on regression theoryc If each of the two parts is reduced to its components, f a c t o r s affecting erosion could then be related to the individual components on a rational rather than empirical basis: An example of the type of equation d e r i v e d from t h i s theory i s one for water erosion hazard during the most intense probable rainfall period: Bea = 1/2 MV 2 = 1/2 (Mr x V r 2 ) + 1/2 (>,p x Vp 2) where Eea = the k i n e t i c energy o f the erosive agent M mass V = velocity Mr = peak r e s u l t a n t r u n o f f m a s s Vr = peak resultant r u n o f f v e l o c i t y Mp - peak r a i n f a l l mass Vp = r a i n f a l l v e l o c i t y The author concluded, t h a t equations such as t h i s could be r e f i n e d as kmwledge of er o s i o n grows, and th a t a t any stage of knowledge, hazard ratings based on the fundamental elements of erosion will theoretically be the most accurate, Ero si on ...Con trol As shown by many studies of er o s i o n and streamflow, a strong re-lationship e x i s t s between plant cover, streamflow, and soil stability,. 72 Control of vegetation i s a natural and usually very efficient way to maintain or restore soil stability. In some cases, however, revegetation is not sufficient by itsel f to re-establish the hydrologic norm of a watershed but must be supplemented by engineering structures. The rehabilitation of damaged watersheds is often an expensive job. On forest areas i t will require reforesting understocked areasj, protecting against fire, and improving roads that are in unsatisfactory condition. Soil disturbance that has resulted in a concentration of overland flow must be stabilized by vegetation, aided where necessary9 by mechanical structures. In I960, wildfire burned over part of the San Dimas experimental forest. Rice et al. (1965)conducted studies on the areas burned to obtain a quantitative evaluation of several mechanical and vegetative land treatments. Watersheds seeded to low density perennials had higher sediment production than did watersheds treated in other ways. Planting annual grasses, the report stated, may be justified as an emergency erosion control measure because of i t s low cost and the speed with which i t can be applied. Of the mechanical treatments to reduce erosion, side-slope stab-ilization and contour trenching were found to be superior to channel stabilization. This supports the view that measures that prevent the concentration of water are more effective than those aimed at reducing the erosive effect of channel flow. j In June, 1959» the Three Bar experimental watersheds in Arizona were swept by fire. Pase and Ingebo (1965) described the early results 73 o n s e d i m e n t a n d w a t e r y i e l d s o f s e e d i n g b y h e l i c o p t e r t o g r a s s e s a n d s w e e t - c l o v e r . T h e c o n t r o l a r e a was a l l o w e d t o r e t u r n t o t h e n a t u r a l s h r u b c o v e r o f c h a p a r r a l , l i v e o a k ( Q u e r c u s t u r b i n e l l a G r e e n e ) , a n d b i r c h - l e a f m o u n t a i n m a h o g a n y ( C e r o c a r p u s b e t u l o i d e s N u t t . ) . T h e s e e d e d a r e a w a s s p r a y e d f o r f o u r s u c c e s s i v e y e a r s , b e g i n n i n g i n I960, t o d e s t r o y t h e r e s p r o u t i n g n a t u r a l s h r u b s . S p r a y was a p p l i e d o n l y t o t h e s h r u b a r e a s o t h a t l i t t l e d a m a g e was d o n e t o t h e s t a n d o f g r a s s . R u n o f f was h i g h e s t f r o m b o t h w a t e r s h e d s i n t h e f i r s t y e a r a f t e r t h e f i r e . R u n o f f f r o m t h e c o n t r o l w a t e r s h e d h a d d e c r e a s e d t o p r e - f i r e r a t e s b y t h e e n d o f t h e f o u r t h y e a r . R u n o f f f r o m t h e s e e d e d w a t e r s h e d h a s b e e n s i g n i f i c a n t l y i n c r e a s e d f o r t h e l a s t t h r e e y e a r s , c o m p a r e d t o t h e c o n t r o l . S e d i m e n t y i e l d s f r o m b o t h w a t e r s h e d s i n c r e a s e d g r e a t l y i m m e d i a t e l y a f t e r t h e f i r e , b u t h a v e s i n c e d e c l i n e d t o a b o u t p r e - f i r e l e v e l s . S e d i m e n t p r o d u c t i o n i s g r e a t e r a t p r e s e n t , h o w e v e r , f r o m t h e w a t e r s h e d i n n a t u r a l c o v e r t h a n f r o m t h e s e e d e d w a t e r s h e d . I n M i c h i g a n , 1 1 5 a r e a s w e r e t r e a t e d t o s t a b i l i z e s t r e a m b a n k s a n d t h e e f f e c t was c o m p a r e d t o 1 1 3 u n t r e a t e d a r e a s ( S t r i f f l e r I 9 6 0 ) . B a n k t r e a t m e n t c o n s i s t e d o f r o c k r i p r a p , s e e d i n g , a n d f e r t i l i z a t i o n . T h e s t u d y s h o w e d t h a t t r e a t m e n t r e d u c e d b a n k e r o s i o n b y 4 0 p e r c e n t a n d s t a b i l i z e d w a t e r l i n e s . T h e k e y t o s u o c e s s a p p e a r e d t o b e s t a b i l i z a t i o n o f t h e w a t e r l i n e b y r o c k r i p r a p o r o t h e r m e c h a n i c a l m e a n s . T h e m e c h a n i c a l m e a s u r e s w h i c h may b e u s e d t o s u p p l e m e n t v e g e t a -t i v e m e a s u r e s a r e o u t l i n e d b y B a i l e y a n d C o p e l a n d ( 1 9 6 1 ) . D e b r i s b a s i n s r e d u c e t h e v e l o c i t y o f c h a n n e l f l o w a l l o w i n g d e b r i s a n d s e d i m e n t t o s e t t l e o u t . C o n t o u r t e r r a c i n g r e t a i n s r a i n f a l l o n t h e l a n d w h e r e 74 i t falls, thus preventing overland flow and erosion, and creates favor-able moisture conditions for the re-establishment of vegetation* Small check dams are sometimes constructed across the trenches, A modification of contour terracing is pitting the soil surface with short, V-shaped trenches, at regular intervals. Seeding with grasses or legumes must follow pitting or terracing, otherwise the trenches would soon f i l l with sediment and lose their valueo In disturbed stream channels, check dams or precast cribbing are often used to control channel flow. Sections of interlocking cribbing are placed across the channels and because of their open structure permit water flow but retain sediment. Design and construction of prefabricated concrete were described by Heede (1965) and of rock check dams by the same author (1966), Bailey and Copeland (1961) discussed vegetation and engineering structures in erosion control and concluded that three kinds of action were needed: (l) wider public understanding of the importance of for-ested watersheds, (2) a speeded up and more vigorous application of known and tested measures of watershed protection and rehabilitation^, and (3) more basic and applied research to f i l l the gaps in our know-ledge, 6, WATER QUALITY Eschner and Larmoyeux (I963) defined water quality as the sum of the measurable characteristics of the water. By this definition any change in the character of water which is not measurable does not affect 75 t h e q u a l i t y * T h e c h a r a c t e r i s t i c s o f w a t e r t h a t a r e u s u a l l y m e a s u r e d a r e c o l o r , t u r b i d i t y , t e m p e r a t u r e , p H , a n d s p e c i f i c c o n d u c t a n c e . A s i n t e r e s t i n o t h e r c h a r a c t e r i s t i c s d e v e l o p , b e c a u s e o f n e w u s e s f o r t h e w a t e r f o r e x a m p l e , t e c h n i q u e s w i l l b e d e v e l o p e d t o m e a s u r e t h e s e c h a r a c t e r i s t i c s . T h a t i s , t h e s t a n d a r d s b y w h i c h w a t e r q u a l i t y i s m e a s u r e d c h a n g e a s u s e s a n d t e c h n i q u e s d e v e l o p . P e r h a p s a b e t t e r d e f i n i t i o n o f w a t e r q u a l i t y f o r t h e p u r p o s e o f t h i s d i s c u s s i o n i s t h e sum o f t h e c h a r a c t e r i s t i c s o f w a t e r t h a t d e s c r i b e i t s u s e f u l n e s s f o r a s p e c i f i c p u r p o s e ( B u l l a r d 1963)* C o n s i d e r t h e e x a m p l e o f m u d d y w a t e r . I t s v a l u e i s r e d u c e d b e c a u s e s o m e i n d u s t r i e s c a n n o t u s e i t , p e o p l e w i l l n o t d r i n k i t , r e s e r v o i r s f i l l u p w i t h s e d i m e n t a s t h e r e s u l t o f i t , a n d i t h a s a d e t r i m e n t a l e f f e o t o n f i s h . ( T h e f i s h e r y a s p e o t w i l l b e d i s c u s s e d i n t h e n e x t s e c t i o n ) * B u l l a r d a t t e m p t e d t o d e f i n e q u a l i t y a s t h e d e g r e e o f e x c e l l e n c e t h e w a t e r p o s s e s s e s * H o w e v e r , t h e sum o f t h e m e a s u r a b l e c h a r a c t e r i s t i c s i s g e n e r a l l y a c c e p t e d a s d e f i n i n g w a t e r q u a l i t y , a n d i s t h e m o r e u s e f u l d e f i n i t i o n * T h e i n f l u e n c e o f t h e f o r e s t o n w a t e r q u a l i t y c a n b e s u m m a r i z e d b y f o u r s t a t e m e n t s : (1) T h e a m o u n t o f s e d i m e n t i n s t r e a m f l o w i s a f f e c t e d b y f o r e s t c o v e r , (2) T h e c o l o r a n d t a s t e o f w a t e r i s a f f e c t e d b y l o g g i n g d e b r i s i n s t r e a m c h a n n e l s , (3) W a t e r t e m p e r a t u r e i s a f f e c t e d b y t h e r e m o v a l o f t r e e s a l o n g 76 streambanks and by forest-cover changes that alter the proportion of water that reaches stream channels by surface flow, (4) Timing of runoff i s affected by forest-cover changes. Timing i s included i n water quality by the second definition given above. Changes i n water temperatures brought about by logging are not l i k e l y to affect the quality of water for human use but are important i n fisheries, and w i l l be discussed i n the section on forests and f i s h . Timing has been discussed i n the section on streamflow and w i l l be con-sidered further i n the section on forests and fis h . The influence of vegetation on erosion was discussed i n the pre-vious section. Conversion of forests to other land uses generally favors faster erosion rates, higher sediment loads i n streams, and im-pairment of water quality. The turbidity of water i s i t s capacity for absorbing or scatter-ing l i g h t and i s measured by the concentration of fine s i l i c a which produces an equivalent effect (Camp 1963) <> Another method of determin-ing turbidity i s the Jackson candle method by which the depth of water through which the flame of a candle disappears i s converted to an index number. For example, i f the flame disappears when viewed through 72.9 cm. of the sampled water, the turbidity i s 25; through 10.8 cm. the turbidity i s 200. These units were originally intended to be equivalent to p.p.m. (parts per million) of standard s i l i c a suspensions, and there-fore turbidities are often expressed i n p.p.m. Numerically these are the same as turbidity units (Nordell 1961). 77 Turbidity may result from living or dead algae or other organisms, but i t i s generally caused by s i l t or clay, Th6 amount and character of turbidity depend on the type of soil over which the water has run and the velocity of the water (Steel I960), AS the velocity decreases, the heavier particles settle out, but the finest clay particles may require months to settle out of s t i l l water. For drinking water, the United States Public Health Service standards are widely used. These specify that the turbidity shall not exceed 10 units for culinary and drinking purposes (Nordell 1961), Turbidity tolerances for industrial purposes run from as low as two for carbonated beverages to 50 for paper produced from groundwood pulp, A turbidity of 20900Q or more can be tolerated for fish propagation. The effect is an indirect one in that turbidity reduces light penetration and this limits photosynthesis and algal growth, the lower links in the food chain on which the fish depend (Camp 1963)° Soms rivers have turbidities as high as 60,000, and extremes of over 100,000 have been measured (Nordell 1961), Effect of Logging on Water Quality Loggings Logging greatly affects water quality not so much be-cause of the conversion of forested areas but because of the methods employed. The use of heavy machinery in areas formerly inaccessible because of steep slopes and rugged terrain disturbs soms of the soil surface to varying depths and degree. The result i s greatly increased sediment discharge. Studies in Oregon have shown that 10 years of 78 l o g g i n g i n o n e w a t e r s h e d p r o d u c e d 80 p e r c e n t g r e a t e r s e d i m e n t d i s c h a r g e t h a n a n u n l o g g e d a d j a c e n t w a t e r s h e d ( A n d e r s o n a n d W a l l i s 1 9 6 5)0 I n t h e S i e r r a N e v a d a t h e s e d i m e n t d i s c h a r g e o n e y e a r a f t e r l o g g i n g was 17 t i m e s t h e p r e - l o g g i n g r a t e ; t w o y e a r s a f t e r , 5 t i m e s ( R i c e a n d W a l l i s 1 9 6 2 ) . S o i l d i s t u r b a n c e a n d t h e r e s u l t i n g e r o s i o n v a r y c o n s i d e r a b l y f o r d i f f e r e n t l o g g i n g m e t h o d s . G a r r i s o n a n d R u m m e l l (1951) , i n e a s t e r n O r e g o n , f o u n d t h a t e x p o s u r e o f m i n e r a l s o i l a v e r a g e d 2 0 . 9 p e r c e n t o f a r e a s l o g g e d w i t h t r a c t o r , 1 5 . 2 p e r c e n t o f a r e a s l o g g e d w i t h c a b l e s , a n d 11 .8 p e r c e n t o f a r e a s l o g g e d w i t h h o r s e s . I n t h e C a l i f o r n i a p i n e z o n e 22 p e r c e n t o f t h e a r e a was b a r e g r o u n d a f t e r l o g g i n g b y c r a w l e r t r a c t o r ( F o w e l l s a n d S c h u b e r t 1951 ) . W o o l d r i d g e ( i 9 6 0 ) r e p o r t e d a c o m p a r i s o n o f l o g g i n g b y t r a c t o r a n d b y t h e W y s s e n S k y l i n e C r a n e i n W a s h i n g t o n . M i n e r a l s o i l was e x p o s e d o n 22 .2 p e r c e n t o f t h e a r e a l o g g e d b y t r a c t o r a n d o n l y 5»k p e r c e n t o f t h e a r e a l o g g e d b y S k y l i n e C r a n e . D y r n e s s (I965) r e p o r t e d a s t u d y w h i c h was c a r r i e d o u t i n t h e H . J . A n d r e w s E x p e r i m e n t a l F o r e s t i n O r e g o n t o a s s e s s t h e e f f e c t s o f h i g h - l e a d a n d t r a c t o r l o g g i n g o n s o i l s w i t h s i m i l a r u n d i s t u r b e d s u r f a c e c o n d i t i o n s . S u r f a c e a r e a o f f o u r d e a r c u t u n i t s was c l a s s i f i e d b y f o u r d e g r e e s o f d i s t u r b a n c e : u n d i s t u r b e d , s l i g h t l y d i s t u r b e d , d e e p l y d i s -t u r b e d , a n d c o m p a c t e d . T h e t r a c t o r l o g g e d a r e a h a d a b o u t t h r e e t i m e s m o r e a r e a w i t h i n t h e c o m p a c t e d c l a s s t h a n d i d t h e h i g h l e a d a r e a (27 p e r c e n t a g a i n s t n i n e p e r c e n t ) , a n d a c o r r e s p o n d i n g d e c r e a s e i n t h e a m o u n t i n t h e u n d i s t u r b e d c l a s s . D e e p l y d i s t u r b e d a n d c o m p a c t e d c l a s s e s 79 had higher bulk densities, i,e,, decreased soil porosity. The author con-cluded that tractor use results in increased runoff and erosion., but this i s minimized i f slopes do not exceed 20-30 per cent, A study in Russia showed that after a shower of 63 mm, (2,5 in,), lasting two days, erosion was 5° 3 kg,/ha, (4,7 lbso/acre) in forest stands of 60-70 per cent density, 15<>1 kg,/ha, (13»5 lbs,/acre) in stands of 20-30 per cent density, and 32°1 kg,/ha, (28,7 lbs,/acre) in cut-over area (Molchanov 1963), In the northern Caucasus and in the Urals, hauling with horses caused soil erosion of 200 cu,m,/ha, (106 cu, yd,/acre) on slopes of 10° or less, but as much as 550 cu0 m,/ha, (291 cu0 yd,/acre) on 0 0 . slopes of 10 - 20 5 and with tractors the values were 550 cu,m,/ha, (291 cu, yd,/acre) and 780 cu, m,/ha, (413 cu, yd,/acre) (Molchanov 1963)o The cutting of timber in itself does not seem to affect water quality 9 although there i s some evidence that increased streamflow re-sulting from timber cutting may cause stream-bank erosion and thus increase sediment production (Packer 1965)0 Log skidding, particularly where equipment i s used that deeply disturbs the soil mantle, often increases sediment production, however. The degree of increase depends on many factors such as the location of skidways in relation to stream courses, the adequacy of drainage facilities, the size of storms, and the nature of the terrain and soil. Logging, even when carried out on steep terrain 8 does not nec~ essarily reduce water quality as was shown by experiments carried 80 out on the Fernow Experimental Forest in the mountains of West Virginia (Hornbeck and Reinhart 1964)o It was pointed out in these studies that most of the damage to water quality occurs during and immediately after logging. Where skidways become revegetated slowlyhowever9 impairment of water quality can continue for many years. Stream channels. Logging debris in stream channels can discolour water and cause a disagreeable taste. This is relatively unimportant where the proportion of the watershed that has been logged is small9 and where the dilution effect of large reservoirs occurs. Where the opposite is the case9 usually confined to small communities where the water supply is taken directly from the stream, the quality of water for drinking purposes is definitely impaired. The hazard associated with debris in stream channels i s the log jam that sometimes occurs during runoff. During high water the jams often break up sending a mass of logsj, rocks9 muds and water downstream causing damage to property and changing channel alignment. The question arises as to the size of stream from which i t is necessary to remove logging debris. Rothacher (1959) pointed out that to answer the question information is needed on maximum flow from the stream and the size of stream that can move logs. He suggested that any stream fed by a watershed greater than 40 acres should have logging debris removed. Roads. Road-building associated with logging is largely respon-sible for the increased sediment discharge of logged areas. Modem equip= ment has made road building easy enough that often roads are built piece-meal I 81 without an overall plan. This may result in more miles of road than other-wise needed, and often the location i s poor, Silen and Gratkowski (1953) reported that 12,4 per cent of the total area logged in a study conducted in Oregon was disturbed by road building and landing construetiono Building of 1,65 miles of logging road on one of the watersheds of the H 0J 0 Andrews Experimental Forest in Oregon caused sediment discharge from the f i r s t rainstorms after con-struction 250 times that of an adjacent undisturbed watershed. Dis-charge during the following two years was about twice that before road construction (Frederickson 1965), The reasons for increased sediment after road building include; (l) roads often intercept seepage and concentrate the flow9 and (2) road surfaces often have lower infiltration rates due to the disturbance and compaction of the soil, A logging system requiring fewer miles of road would be expected to contribute a smaller amount to stream sediment. In the comparison of tractor and Skyline Crane logging i t was shown that the truck road , system needed for logging by Crane was about 10 per cent of that needed by standard methods (Wooldridge I960), In the same study i t was reported that transporting logs across a stream channel caused l i t t l e disturbance with Skyline Crane but even well-planned crossings produced s i l t and • debris during runoff periods after tractor logging. Eight l/lOO ac, plots were set up on the f i l l slope of a newly-constructed highway in Idaho to determine the effect of various treat-ments on erosion from side slopes (Bethlahmy and Kidd 1966), Those 82 plots that were seeded and fertilized produced the greatest amount of erosiong, an average of 97 lbs, during the 322 days in which the research was in progress. This figure is larger by 13 lbso than that for the control plot on which no control measures were taken<> The addition of straw mulch to the seeded and fertilized plots was responsible for a reduction of erosion to 24 lbso Seeding, fertilizing, straw mulching, and netting reduced erosion to 0 o5 lbs. In many parts of North America, especially in mountainous regions, secondary roads are "put-to-bed" after harvesting of timber has been completedo This usually involves removing temporary culverts, out-sloping the road surface, installing earthen cross drains at prescribed intervals y and perhaps seeding the road surface and cut bankso In resent years, the outsloping of road surfaces and removal of berms or curbs have been questioned, especially on "incurved1" sections of road in steep terrain. In such locations surplus road material is usually caste ver and comes to rest in long unstable f i l l s extending for 100 f t , or more down the ravine. Such f i l l s are usually shorter on side slopes below "outcurved" sections of road. In a study carried out on a newly-built, secondary logging road in Idaho, both concepts were evaluated (Haupt et al, 1963)0 Observa-tions indicated that insloping the road surface was more desirable than outsloping as an erosion-control measure. The inslope should be designed 83 t o l e a d away a s m u c h w a t e r a s p o s s i b l e f r o m t h e l o n g f i l l o n t h e i n c u r v e o f t h e r o a d . I n W e s t V i r g i n i a , o n a c l e a r c u t w a t e r s h e d w i t h u n p l a n n e d s k i d r o a d s a n d n o p r o v i s i o n f o r d r a i n a g e , t u r b i d i t y was 56.000 p . p . m . ( p a r t s p e r m i l l i o n ) . P a r t i a l c u t t i n g o f a n a d j a c e n t w a t e r s h e d w i t h w e l l p l a n n e d s k i d r o a d s r e s u l t e d i n t u r b i d i t y o f o n l y 25 p . p . m . ( R e i n h a r t e t a l . 1963). A s t u d y i n c e n t r a l I d a h o r e l a t i n g s e d i m e n t a t i o n t o l o g g i n g i n -d i c a t e d t h a t h a u l r o a d s w e r e t h e m a j o r c o n t r i b u t o r s o f s e d i m e n t ( H a u p t a n d K i d d 1965). T h e a m o u n t o f s e d i m e n t a t i o n was n o t r e l a t e d t o t o t a l a r e a b a r e d b y r o a d s b u t t o t h e s e v e r i t y o f d i s t u r b a n c e . S e d i m e n t a t i o n r e a c h i n g s t r e a m s o r i g i n a t e d p r i m a r i l y o n h a u l r o a d s a n d n o t s k i d r o a d s , a n d t h e p r o x i m i t y o f t h e r o a d t o t h e s t r e a m a f f e c t e d t h e f r e q u e n c y w i t h w h i c h s e d i m e n t r e a c h e d t h a t s t r e a m . W h e r e b u f f e r s t r i p s b e t w e e n r o a d s a n d s t r e a m s w e r e g r e a t e r t h a n 30 f t . w i d e , s e d i m e n t a t i o n d i d n o t r e a c h t h e s t r e a m . T r i m b l e a n d S a r t z (1957) s t u d i e d t h e w i d t h o f s t r i p b e t w e e n s t r e a m a n d r o a d i n New H a m p s h i r e b y m e a s u r i n g t h e d i s t a n c e t h a t s e d i m e n t t r a v e l l e d f r o m t h e r o a d a n d r e l a t i n g t h i s t o s l o p e . T h e y d e v i s e d a r u l e - o f - t h u m b f o r t h e g e n e r a l s i t u a t i o n w h e r e i t i s a c c e p t e d t h a t s o m e s e d i m e n t w i l l o c c a s i o n a l l y r e a c h t h e s t r e a m : t h e w i d t h o f s t r i p s h o u l d b e 2( s l o p e p e r c e n t ) + 25 f t . F o r m u n i c i p a l w a t e r s h e d s t h e s t r i p s h o u l d b e 4 ( s l o p e p e r c e n t ) + 5 0 . 84 A s t u d y w a s c o n d u c t e d i n I d a h o r e l a t i n g s e d i m e n t - f l o w d i s t a n c e t o t h e f o u r s i g n i f i c a n t r o a d a n d d o w n s l o p e c h a r a c t e r i s t i c s : s l o p e o b s t r u c t i o n i n d e x ( a f u n c t i o n o f s e d i m e n t f l o w d i s t a n c e , s l o p e o b s t r u c t i o n s , a n d p l a n t c o v e r ) , c r o s s - d i t c h i n t e r v a l , e m b a n k m e n t s l o p e l e n g t h , a n d r o a d g r a d i e n t ( H a u p t 1959)* A m u l t i p l e r e g r e s s i o n e q u a t i o n w a s d e v e l o p e d w h i c h , w i t h s u b s t i t u t i o n f o r t h e d e p e n d e n t v a r i a b l e s , w o u l d e s t i m a t e t h e w i d t h o f p r o t e c t i v e s t r i p n e e d e d t o d i s s i p a t e s e d i m e n t m o v e m e n t t h a t may o c c u r f r o m a p r o p o s e d r o a d . G u i d e s w e r e d e v e l o p e d f r o m t h e p r e d i c t i o n e q u a t i o n g i v i n g : (1) T h e m i n i m u m s l o p e d i s t a n c e t o t h e c e n t r e l i n e o f t h e p r o p o s e d r o a d , g i v e n r o a d a n d s i d e s l o p e g r a d i e n t a n d a s p e c t . T h i s s h o u l d p r o v e u s e f u l i n l o c a t i n g r o a d s f a r e n o u g h a w a y f r o m s t r e a m s s o t h a t s e d i m e n t f l o w i n g f r o m t h e r o a d d o e s n o t r e a c h t h e c h a n n e l , (2) t h e max imum p e r m i s s i b l e c r o s s - d i t c h i n t e r v a l f o r r o a d s h a v i n g p r o t e c t i v e s t r i p s n a r r o w e r t h a n 200 f t . , g i v e n s l o p e e x p o s u r e , e m b a n k m e n t s l o p e l e n g t h , w i d t h o f p r o -t e c t i v e s t r i p , a n d r o a d g r a d i e n t , (3) t h e m i n i m u m n u m b e r o f s l o p e o b s t r u c t i o n s n e e d e d b e l o w c r o s s d i t c h e s s p a c e d 30 f t . a p a r t , g i v e n r o a d g r a d i e n t , e m b a n k m e n t s l o p e l e n g t h , a n d w i d t h o f p r o t e c t i v e s t r i p . K i d d (1963), w o r k i n g i n I d a h o , c o n d u c t e d a s t u d y t o d e t e r m i n e t h e o p t i m u m s p a c i n g o f w a t e r b a r s o n s k i d t r a i l s a n d t h e m o s t e f f e c t i v e s t r u c t u r e s f o r c o n t r o l l e d d i s p o s a l o f s e d i m e n t - l a d e n w a t e r t h a t o r i g i -n a t e s o n s k i d t r a i l s . T h e r e s u l t s o f h i s s t u d y i n d i c a t e d t h a t e r o s i o n w a s g r e a t e r f r o m s k i d t r a i l s l o c a t e d i n r a v i n e s t h a n f r o m t h o s e o n s i d e -h i l l s . O p t i m u m s p a c i n g o f c o n t r o l s t r u c t u r e s , s u c h a s l o g w a t e r b a r s a n d c r o s s d i t c h i n g , d e p e n d s o n t h e s l o p e a n d l o c a t i o n o f t h e s k i d t r a i l 85 a s w e l l a s s o i l p a r e n t m a t e r i a l . S t r u c t u r e s t h a t d i v e r t w a t e r o f f t h e s k i d t r a i l o n t o u n d i s t u r b e d f o r e s t f l o o r s a r e s u p e r i o r t o t h o s e t h a t o n l y r e t a r d w a t e r m o v e m e n t a n d f i l t e r o u t s e d i m e n t a l o n g t h e s k i d t r a i l . W a l l i s (1963)» i n p r e s c r i b i n g l o g g i n g m e t h o d s t o p r o t e c t w a t e r q u a l i t y f c a u t i o n e d t h a t e a c h a r e a i s d i f f e r e n t a n d t h a t m a n y v a r i a b l e s b e s i d e s l o g g i n g m e t h o d i n f l u e n c e s e d i m e n t d i s c h a r g e . H i s w a r n i n g c a n b e a p p l i e d t o a l l a s p e c t s o f e r o s i o n c o n t r o l . T h e r e s u l t s o f s t u d i e s c o n d u c t e d i n a p a r t i c u l a r l o c a t i o n c a n n o t b e a s s u m e d t o a p p l y i n e v e r y s i t u a t i o n . H o w e v e r , s u c h s t u d i e s s h o u l d b e c o n s i d e r e d a n d m e t h o d s o f e r o s i o n c o n t r o l s u g g e s t e d b y t h o s e s t u d i e s s h o u l d b e a p p l i e d w h e r e t h e y s e e m a p p l i c a b l e . F o r e x a m p l e , t h e s t u d y b y H a u p t e t a l . (1963). c o n c e r n -i n g i n s l o p e d r o a d s u r f a c e s , w a r r a n t s c o n s i d e r a t i o n i n r o a d c o n s t r u c t i o n e v e n t h o u g h i t c a n n o t b e a s s u m e d t h a t t h e m e t h o d a p p l i e s i n a l l s i t u -a t i o n s . A c t u a l p r e s c r i p t i o n s f o r r o a d b u i l d i n g , a s w e l l a s f o r o t h e r a s p e c t s o f l o g g i n g , w i l l b e c o v e r e d i n C h a p t e r V w h i c h d e a l s w i t h w a t e r -s h e d m a n a g e m e n t i n B r i t i s h C o l u m b i a . F i r e . S l a s h i s o f t e n b u r n e d a f t e r l o g g i n g t o r e d u c e f i r e h a z a r d , t o f a c i l i t a t e r e g e n e r a t i o n , o r t o m a k e t h e a r e a a m e n a b l e t o p l a n t i n g . T h e d e g r e e t o w h i c h t h e s e o b j e c t i v e s a r e m e t b y s l a s h b u r n i n g w i l l n o t b e d i s c u s s e d i n t h i s s e c t i o n , b u t t h e e f f e c t o n e r o s i o n w i l l b e c o n -s i d e r e d . ( F o r a c o m p r e h e n s i v e d i s c u s s i o n o f t h e e f f e c t s o f f o r e s t f i r e s s e e A h l g r e n a n d A h l g r e n i960, D a v i s 1959» a n d J a b l a n c z y 1963)» 86 E v i d e n c e t h a t b u r n i n g d e c r e a s e s t h e i n f i l t r a t i o n c a p a c i t y o f t h e s o i l w a s r e p o r t e d b y Rowe (1941). A n i n c r e a s e i n i n f i l t r a t i o n r a t e was r e p o r t e d b y S c o t t (1956) a n d B u r g y a n d S c o t t (1952) who a t t r i b u t e d t h i s t o f o r m a t i o n o f l a r g e r - s i z e d a g g r e g a t e s i n t h e s o i l s u r f a c e . D i f f e r e n c e s i n t h e s e v e r i t y o f t h e b u r n a r e p r o b a b l y l a r g e l y r e s p o n s i b l e f o r w h a t a p p e a r s t o b e c o n f l i c t i n g e v i d e n c e . O t h e r v a r i a b l e s i n f l u e n c i n g t h e e v i d e n c e m a y b e d i f f e r e n c e s i n t h e c h a r a c t e r i s t i c s o f t h e s o i l s u n d e r i n v e s t i g a t i o n a n d t h e m o i s t u r e c o n t e n t o f t h e s o i l s a n d t h e s u r f a c e f u e l s a t t h e t i m e o f b u r n i n g ( D y r n e s s I963). A u s t i n a n d B a i s i n g e r (1955) r e p o r t e d t h a t m o i s t u r e - h o l d i n g c a p a c i t y o f t h e t o p o n e - h a l f i n c h o f s o i l s i g n i f i c a n t l y a f f e c t e d b y t h e f i r e was r e d u c e d b y 33»7 p e r c e n t a f t e r s l a s h b u r n i n g . D y r n e s s e t a l . (1957) r e p o r t e d s i m i l a r e v i d e n o e a n d c o n c l u d e d t h a t i t was d u e t o l e s s o r g a n i c m a t t e r i n t h e s o i l a f t e r b u r n i n g . T a r r a n t (1956) r e p o r t e d t h a t s e v e r e b u r n s r e d u c e d p e r c o l a t i o n r a t e s b y o v e r 70 p e r c e n t w h e r e a s l i g h t b u r n s i n c r e a s e d t h e r a t e s . I n t h e a r e a s e x a m i n e d i n T a r r a n t ' s s t u d y l e s s t h a n f i v e p e r c e n t o f t h e b u r n e d a r e a w a s s e v e r e l y b u r n e d . D y r n e s s e t . a l . (1957) r e p o r t e d o n l y e i g h t p e r c e n t o f a s l a s h - b u r n e d a r e a s e v e r e l y b u r n e d . B e t h l a h m y (I960) p o i n t e d o u t , h o w e v e r , t h a t t h e e f f e c t o n e r o s i o n o f t h e s e s e v e r e l y b u r n e d a r e a s m a y b e f a r i n e x c e s s o f t h e i r i n s i g n i f i c a n t a r e a ! e x t e n t . C r o f t (1946) r e p o r t e d t h a t e x t r e m e f l o o d s i n U t a h w e r e t r a c e d t o s e v e r e f i r e s a n d o v e r g r a z i n g o n o n l y 2 t o 10 p e r c e n t o f t h e h e a d w a t e r a r e a . 87 M o s t o f t h e e v i d e n c e i n d i c a t e s t h a t l i g h t b u r n i n g h a s l i t t l e e f f e c t o n w a t e r m o v e m e n t t h r o u g h t h e s o i l p r o f i l e . I f t h e l i t t e r h a s b e e n b u r n e d , h o w e v e r , i n f i l t r a t i o n c a p a c i t y c a n b e e x p e c t e d t o d e c r e a s e w i t h t i m e a s t h e s u r f a c e s t r u c t u r e o f t h e m i n e r a l s o i l i s b r o k e n d o w n b y r a i n d r o p s a n d t h e p o r e s c l o g g e d b y s e d i m e n t . T h e r e s u l t m a y b e i n -c r e a s e d p e a k f l o w s a s r e p o r t e d b y R i c h (19&5) * o r a w i l d f i r e i n p o n d e r o s a p i n e o n W o r k m a n C r e e k , A r i z o n a . E r o s i o n w o u l d b e e x p e c t e d t o i n c r e a s e a f t e r f i r e d u e t o g r e a t e r s u r f a c e r u n o f f c a u s e d b y r e d u c e d i n f i l t r a t i o n r a t e s a n d d u e t o t h e l o o s e n e s s o f s o i l p a r t i c l e s c a u s e d b y d e c r e a s e d c l a y ( D y r n e s s a n d Y o u n g b e r g 19 5? > S r e e n i v a s a n a n d A u r a n g a b a d k a r 1940) a n d o r g a n i c m a t t e r c o n t e n t ( A u s t i n a n d B a l s i n g e r 1955» D y r n e s s a n d Y o u n g b e r g 1957» Y o u n g b e r g 1953)* A c c e l e r a t e d e r o s i o n a f t e r b u r n i n g h a s b e e n r e p o r t e d b y m a n y i n -v e s t i g a t o r s a m o n g whom a r e A n d e r s o n (1955)» A n d e r s o n a n d T r o b i t z (1949)» C o n n a u g h t o n (1935)» H e n d r i c k s a n d J o h n s o n ( 1 9 4 4 ) , P i l l s b u r y (1953)» a n d S a r t z (1953)* T h e i n c r e a s e d s e d i m e n t i n w a t e r s u p p l i e s r e s u l t i n g f r o m f i r e s , t h e n , a f f e c t s w a t e r q u a l i t y , a n d o f t e n t o a n e x t r e m e d e g r e e . 7, F O R E S T S AND F I S H T h e v a l u e o f t h e f i s h e r i e s m u s t i n c l u d e t h e r e c r e a t i o n a l b e n e f i t d e r i v e d b y man a s w e l l a s t h e e c o n o m i c b e n e f i t s a n d c o s t s . I m p o r t a n t i n B r i t i s h C o l u m b i a a r e s a l m o n ( s o c k e y e , p i n k , c o h o , s p r i n g , a n d c h u m ) a n d s t e e l h e a d t r o u t ( F r a s e r R i v e r B o a r d 1958)• T h e s e m i g r a t e f r o m s t r e a m t o s e a , r e t u r n i n g t o s p a w n i n s t r e a m g r a v e l s a f t e r o n e o r m o r e y e a r s i n t h e o c e a n . A f t e r e m e r g e n c e f r o m t h e g r a v e l a s f r y t h e f i s h s p e n d 88 different lengths of time in fresh water depending on the speciess so that the freshwater environment has greater importance for some species0 Water Yield and Regime Discussion of the forest and fish mainly concerns the influence of logging on the yield, regimea and water quality of streamflow, The effect of logging on water yield was discussed in the section on stream-flow,, Most studies have shown that clear cutting increases yields by four to eight inches, but the effect on regime i s not as well defined , (Jeffrey I965). Some studies indicate that cutting causes greater low flows (Eschner and Larmoyeux 1963a Kittredge 1948, Meginnis 1959s Rothaeher 1 9 6 3 % and Shirai et alo 1954)* This may be explained by precipitation being well distributed through the year so that low flows are probably due not to a lack of precipitation but to high evapotranspiratlon.drain (Esehner and Larmoyeux 1963)0 Greater minimum flows, where low flows are critical,, would improve the survival of fish during this period and favor higher fish populations0 Greater flows in summer would provide greater water surface for catching terrestrial insects, greater algae and insect-producing bottom area, and more room for the fish (Chapman 1963)o The results of some studies indicate that removal of the forest causes higher peak flows (Bates and Henry 1928, Hirata I 9 2 9 2 Hoyt and Troxell 1934, and Tennessee Valley Authority 1962)0 Higher flows may 89 r e s u l t i n c h a n n e l s c o u r a n d c u t t i n g , m o v e m e n t o f s t r e a m - b o t t o m g r a v e l s , a n d h i g h e r s e d i m e n t l o a d s . E r o s i o n a n d s e d i m e n t d i s c h a r g e c a u s e d by-l o g g i n g a n d r o a d b u i l d i n g was d i s c u s s e d i n t h e s e c t i o n s o n e r o s i o n a n d w a t e r q u a l i t y . C h a n n e l s c o u r a n d c u t t i n g c a n r e m o v e e s t a b l i s h e d s p a w n i n g b e d s , i s o l a t e o t h e r s , a n d a d d t o t h e d e b r i s t r a n s p o r t e d b y t h e s t r e a m a n d d u m p e d i n o t h e r l o c a t i o n s . G r a v e l d e p o s i t i o n o n i n c u b a t i n g e m b r y o s may b e s o d e e p t h a t t h e h a t c h e d f r y s u f f e r h i g h m o r t a l i t y i n e m e r g i n g f r o m t h e g r a v e l ( C h a p m a n 1963). G r a v e l m o v e m e n t may k i l l f i s h e m b r y o s , a l g a e , a n d a q u a t i c i n s e c t s , t h u s d e c r e a s i n g f u t u r e p o p u l a t i o n s o f f i s h w h i l e r e d u c i n g p r e s e n t f o o d s u p p l i e s . S e d i m e n t may c o v e r s t r e a m - b o t t o m f a u n a a n d f i s h e g g s , r e d u c e t h e s i z e a n d n u m b e r o f g r a v e l i n t e r s t i c e s i n w h i c h s m a l l f i s h h i d e , a n d l o w e r t h e d e p t h , i . e . , d e c r e a s e t h e l i v i n g s p a c e , f o r l a r g e f i s h . H i g h s e d i m e n t l o a d s may c a u s e i n f l a m m a t i o n o f t h e g i l l m e m b r a n e s o f y o u n g f i s h a n d t h e i r e v e n t u a l d e a t h . T h e g r o w t h o f g r e e n p l a n t s d e -c r e a s e s a s s u n l i g h t i s f i l t e r e d o u t o f t h e w a t e r b y s e d i m e n t . F i s h e m b r y o s i n s p a w n i n g g r a v e l s n e e d d i s s o l v e d o x y g e n a n d a v e l o c i t y o f i n t r a - g r a v e l w a t e r s u f f i c i e n t t o m a i n t a i n t h e o x y g e n s u p p l y a n d t o c a r r y a w a y m e t a b o l i c w a s t e p r o d u c t s . S e d i m e n t s r e d u c e t h e v e l o c i t y o f i n t r a - g r a v e l w a t e r t h u s r e d u c i n g t h e o x y g e n a v a i l a b l e ( P e t e r s 1962). T h e d e c o m p o s i t i o n o f o r g a n i c s e d i m e n t s d e c r e a s e s t h e o x y g e n c o n t e n t e v e n m o r e 0 90 D e b r i s i n C h a n n e l s L o g g i n g d e b r i s l e f t i n s t r e a m c h a n n e l s was d i s c u s s e d i n t h e s e c t i o n o n s t r e a m c h a n n e l s . S u c h d e b r i s , w h e t h e r i t b e n o r m a l d e b r i s o r t h e r e s u l t o f l o g g i n g , o f t e n r e s u l t s i n l o g j a m s . T h e s e o f t e n a c t a s b a r r i e r s t o m i g r a t i o n b u t c a n a l s o p r o v i d e p o o l s f o r r e s i d e n t f i s h . When l o g j a m s b r e a k , t h e s t o r e d u p w a t e r a n d d e b r i s r u s h i n g d o w n s t r e a m o f t e n c h a n g e t h e c h a n n e l a l i g n m e n t . T h e e f f e c t s o f t h i s a c t i o n a r e d i s -c u s s e d i n t h e p r e v i o u s s e c t i o n . P r o b a b l y t h e m a i n h a z a r d t o f i s h r e s u l t i n g f r o m o r g a n i c m a t t e r i n s t r e a m c h a n n e l s i s t h e r e d u c t i o n o f d i s s o l v e d o x y g e n c a u s e d b y i t s d e c o m p o s i t i o n . W a t e r T e m p e r a t u r e s H i g h w a t e r t e m p e r a t u r e s i n s u m m e r a r e o f t e n t h e f a c t o r l i m i t i n g d i s t r i b u t i o n a n d s u r v i v a l o f t r o u t . L i m i t i n g h i g h t e m p e r a t u r e s o f f r o m 75° t o 83° F . f o r b r o o k , b r o w n , a n d r a i n b o w t r o u t a r e c i t e d b y E s c h n e r a n d L a r m o y e u x (19^3) b u t t h e s e v a r y w i t h t h e p H , d i s s o l v e d o x y g e n , a n d c o n d i t i o n o f t h e f i s h . d e a r c u t t i n g o n t h e F e r n o w E x p e r i m e n t a l F o r e s t i n c r e a s e d max imum s u m m e r w a t e r t e m p e r a t u r e s b y 8° F . a n d d e c r e a s e d m i n i m u m w i n t e r w a t e r t e m p e r a t u r e s b y 3°5° F . ( E s c h n e r a n d L a r m o y e u x 1963). R e m o v a l o f r i p a r i a n v e g e t a t i o n m a y a l s o c a u s e i n c r e a s e d max imum s u m m e r w a t e r t e m p e r -a t u r e s ( C h a p m a n 1962). L o w e r w i n t e r t e m p e r a t u r e m i n i m a may r e s u l t f r o m t h e l o s s o f i n s u l a t i o n p r o v i d e d b y s t r e a m s i d e v e g e t a t i o n ( G r e e n 1950)° T h i s c o u l d e x t e n d t h e i n c u b a t i o n p e r i o d f o r f a l l - a n d w i n t e r - s p a w n i n g s p e c i e s , t h u s i n c r e a s i n g t h e p e r i o d o f v u l n e r a b i l i t y o f e m b r y o s t o u n f a v o r a b l e c o n d i t i o n s . 91 C h a p m a n (I963) s u g g e s t e d t h e p o s s i b i l i t y o f i n c r e a s e d s p r i n g a n d s u m m e r t e m p e r a t u r e s c a u s i n g a c c e l e r a t e d a l g a l p r o d u c t i o n a n d f i s h m e t a b o l i s m . W h e r e s t r e a m s a r e c o l d t h e e f f e c t o f i n c r e a s e d t e m p e r a t u r e m i g h t b e a d v a n t a g e o u s , b u t a n i n c r e a s e i n t h e t e m p e r a t u r e o f a l r e a d y w a r m s t r e a m s w o u l d l i k e l y p r o v e d e t r i m e n t a l i n n e t e f f e c t ( J e f f r e y 1965 ). R e m o v a l o f r i p a r i a n v e g e t a t i o n a l s o c u t s d o w n o n t h e f o o d s u p p l y o f a q u a t i c i n s e c t s p r o v i d e d b y t e r r e s t r i a l p l a n t s . I t w o u l d a l s o t e n d t o r e d u c e t h e n u m b e r o f t e r r e s t r i a l i n s e c t s r e a c h i n g t h e w a t e r s u r f a c e . C h a p m a n (1963) e s t i m a t e d t h a t o v e r 60 p e r c e n t o f t h e e n e r g y r e a c h i n g c o h o s a l m o n o r i g i n a t e d w i t h t e r r e s t r i a l p l a n t s . T h i s i s e s t i m a t e d i n t h e f o l l o w i n g m a n n e r . T h i r t y p e r c e n t o f t h e c o h o s ' d i e t i s t e r r e s t r i a l i n s e c t s . T h e o t h e r 70 p e r c e n t i s a q u a t i c i n s e c t s , 50 p e r c e n t o f w h o s e d i e t i s t e r r e s t r i a l p l a n t m a t e r l a l o O n t h e o t h e r h a n d , h o w e v e r , v e g e t a -t i o n r e m o v a l s h o u l d s t i m u l a t e a l g a l p r o d u c t i o n b y i n c r e a s i n g t h e l i g h t r e a c h i n g t h e s t r e a m . 92 CHAPTER III. ADMINISTRATION OF WATER RESOURCES 1. JURISDICTION Bri t i s h North America Act An act for the union of Canada. Nova Scotia, and New Brunswick, and the government thereof; and for purposes connected therewith; otherwise known as the British North America Act, 186?, i s often blamed for many of the problems involving the federal and provincial governments (Information about the B.N.A. act i s from Sirois 1940). With specific regard to the water resource, "the Bri t i s h North America Act i s the root of today's dilemma" (C.A.A.E. 1966, p. 10). This statement brings forth the following questions: (1) Are there jurisdictional problems with the water resource? (2) I f so, how do they manifest themselves? (3) Is the B.N.A. act responsible? (4) What solutions can be proposed? Relevant sections of the act. The sections of the B.N.A. act relevant to the water resource are Sections 91» 92, and 95« Section 91 l i s t s the classes of subject that are the exclusive legislative responsibility of the parliament of Canada. Provincial legislative responsibility i s l i s t e d i n section 92, as well as section 95 which includes laws related to agri-culture. Section 91 of the B.N.A. act includes navigation and shipping (para. 10), sea-coast and inland fisheries (para. 12), and peace, order, and good 93 g o v e r n m e n t i n C a n a d a . S e c t i o n 92 i n c l u d e s a s p r o v i n c i a l p o w e r s , l e g i s l a t i o n r e g a r d i n g t h e m a n a g e m e n t a n d s a l e o f p u b l i c l a n d s b e l o n g i n g t o t h e p r o v i n c e a n d t h e t i m b e r o n t h e m ( p a r a . 5)» l o c a l w o r k s a n d u n d e r t a k i n g s o t h e r t h a n t r a n s p o r t a t i o n l i n e s c o n n e c t i n g p r o v i n c e s o r b e t w e e n t h e p r o v i n c e a n d a n o t h e r c o u n t r y ( p a r a . 10), a n d g e n e r a l l y a l l m a t t e r s o f a l o c a l o r p r i v a t e n a t u r e i n t h e p r o v i n c e ( p a r a . 16) ( S i r o i s 19^0). I n t e r p r e t a t i o n . T h e a d m i n i s t r a t i o n o f w a t e r r e s o u r c e s i n C a n a d a h a s b e e n t h e r e s u l t o f t h e p r o v i s i o n s o f t h e B . N . A . a c t a n d t h e i r s u b s e q u e n t i n t e r p r e t a t i o n . T h e a d m i n i s t r a t i o n , c o n t r o l , a n d d e v e l o p m e n t o f w a t e r r e s o u r c e s w i t h i n a p r o v i n c e a r e t h e r e s p o n s i b i l i t y o f t h e p r o v i n c e . H o w -e v e r , t h e f e d e r a l p a r l i a m e n t h a s j u r i s d i c t i o n o v e r w a t e r w h e r e n a v i g a t i o n a n d f i s h e r i e s a r e c o n c e r n e d j , a s w e l l a s w a t e r i n n a t i o n a l p a r k s n I n d i a n r e s e r v e s p a l o n g o r c r o s s i n g t h e i n t e r n a t i o n a l b o u n d a r y , a n d , i n s o m e c a s e s $ o v e r i n t e r - p r o v i n c i a l w a t e r s . O b v i o u s l y t h e e x p r e s s i o n o f t h e p o w e r s o f t h e t w o l e v e l s o f g o v e r n m e n t i s i n g e n e r a l t e r m s e v e n y e t o p e n t o i n t e r p r e t a t i o n i n many c a s e s . T h i s was c o n s i d e r e d n e c e s s a r y i n a f e d e r a t i o n t o a l l o w f l e x i b i l i t y t o t h e c o n s t i t u t i o n ( L e d e r m a n 1962). T h e p r i c e o f t h i s f l e x i b i l i t y i s s o m e t i m e s d u p l i c a t i o n a n d o m i s s i o n , a s w e l l a s c o n f l i c t b e t w e e n t h e l e v e l s o f g o v e r n m e n t . 2. E V O L U T I O N O F WATER P O L I C Y C a n a d a E v o l u t i o n o f w a t e r p o l i c y i n C a n a d a came a b o u t b y r e s t a t e m e n t o f p o l i c y o b j e c t i v e s a s t h e n e e d b e c a m e a p p a r e n t . T h e n e e d s w e r e o f t e n b r o u g h t t o l i g h t b y f o r e s t r y a n d c o n s e r v a t i o n c o n f e r e n c e s w h i c h h a d g r e a t i n f l u e n c e o n 94 w a t e r p o l i c y a t t h e f e d e r a l l e v e l . E a r l y c o n f e r e n c e s . T h e f i r s t C a n a d i a n F o r e s t r y C o n v e n t i o n was h e l d i n 1906, p r e s i d e d o v e r b y t h e P r i m e M i n i s t e r , S i r W i l f r i d L a u r i e r . Among t h e t o p i c s d i s c u s s e d was t h e r e l a t i o n o f f o r e s t s a n d w a t e r . T h e r e c o m m e n d a t i o n s m a d e b y t h e c o n f e r e n c e i n c l u d e d : (1) F o r e s t s s h o u l d r e m a i n u n d e r c r o w n o w n e r s h i p . (2) G r e a t e r e m p h a s i s s h o u l d b e p l a c e d o n p r o t e c t i o n o f t h e f o r e s t f r o m f i r e , d i s e a s e , a n d i n s e c t s . R e p r e s e n t a t i v e s f r o m C a n a d a a t t e n d e d t h e N o r t h A m e r i c a n C o n s e r v a t i o n C o n f e r e n c e h e l d i n W a s h i n g t o n i n F e b r u a r y , 1909<> F r o m t h i s c o n f e r e n c e c a m e a d e c l a r a t i o n o f p r i n c i p l e s w h i c h w e r e a n i m p o r t a n t i n f l u e n c e o n a g e n c i e s l a t e r e s t a b l i s h e d i n C a n a d a t o d e a l w i t h n a t u r a l r e s o u r c e s . O n e o f t h e r e c o m m e n d a t i o n s w a s t h a t a s t u d y o f m u l t i p l e u s e o f t h e w a t e r r e s o u r c e b e u n d e r t a k e n . A n o t h e r was t h a t a c o n s e r v a t i o n c o m m i s s i o n s i m i l a r t o t h o s e i n t h e U n i t e d S t a t e s b e s e t u p i n e a c h o f t h e c o u n t r i e s r e p r e s e n t e d . C o n s e r v a t i o n C o m m i s s i o n . I n M a y , 1909, t h r e e m o n t h s a f t e r t h e N o r t h A m e r i c a n C o n s e r v a t i o n C o n f e r e n c e , t h e C a n a d i a n c a b i n e t a p p r o v e d t h e p r i n c i p l e o f e s t a b l i s h i n g a c o m m i s s i o n o f r e p r e s e n t a t i v e s f r o m f e d e r a l a n d p r o v i n c i a l g o v e r n m e n t s a n d u n i v e r s i t i e s . T h e c o m m i s s i o n h a d s i x m a i n c o m m i t t e e s : f o r e s t r y , l a n d s , f i s h a n d w i l d l i f e , w a t e r , m i n e r a l s a n d f u e l , a n d p u b l i c h e a l t h o T h e c o m m i t t e e o n f o r e s t r y i n c l u d e d l a n d u s e a n d w a t e r s h e d s t u d i e s i n t h e i r p r o g r a m . T h e w a t e r c o m m i t t e e d e a l t m a i n l y w i t h w a t e r p o w e r a n d d o m e s t i c w a t e r s u p p l i e s . D u r i n g t h e p e r i o d 1909-1921 t h e C o n s e r v a t i o n C o m m i s s i o n s t i m u l a t e d i n t e r e s t i n n a t u r a l r e s o u r c e t o p i c s a n d p r o v i d e d a p u b l i c f o r u m f o r d i s c u s s i o n . 95 T h e c o m m i s s i o n g r a d u a l l y b e c a m e m o r e o r i e n t e d t o w a r d r e s e a r c h , a f u n c t i o n n o t i n t e n d e d b y i t s c h a r t e r . . T h i s c r e a t e d f r i c t i o n w i t h f e d e r a l a g e n c i e s s e t u p t o c a r r y o u t r e s e a r c h r e s p o n s i b i l i t i e s a n d was o n e o f t h e r e a s o n s f o r a b o l i s h -i n g t h e c o m m i s s i o n i n 1921. R e c o n s t r u c t i o n C o n f e r e n c e . M u c h o f t h e w o r k w h i c h h a d b e e n c a r r i e d o u t b y t h e C o n s e r v a t i o n C o m m i s s i o n b e c a m e t h e r e s p o n s i b i l i t y o f f e d e r a l a g e n c i e s . T h e c o o r d i n a t i n g f u n c t i o n was n e g l e c t e d , h o w e v e r , a n d t h e e f f e c t o n C a n a d i a n w a t e r p o l i c y i s s t i l l a p p a r e n t . N a t u r a l r e s o u r c e s t u d i e s o n t h e s c a l e c a r r i e d o u t b y t h e C o n s e r v a t i o n C o m m i s s i o n w e r e n o t r e v i v e d u n t i l t h e R e c o n s t r u c t i o n C o n f e r e n c e o f 194-5. I n 194-3, t h e f e d e r a l g o v e r n m e n t , a w a r e o f t h e g r e a t c h a n g e s i n C a n a d a ' s e c o n o m y b r o u g h t a b o u t b y t h e w a r , s e t u p t h e A d v i s o r y C o m m i t t e e o n R e c o n s t r u c t i o n t o s t u d y e c o n o m i c a n d s o c i a l l i f e o f t h e c o u n t r y . Among t h e r e c o m m e n d a t i o n s m a d e b y t h i s c o m m i t t e e t o t h e N a t i o n a l R e c o n s t r u c t i o n C o n f e r e n c e w e r e : (1) D e v e l o p c o n s e r v a t i o n m e a s u r e s t o p r o t e c t r e n e w a b l e r e s o u r c e s . (2) C a r r y o u t s u r v e y s o f r e s o u r c e s . (3) E n a c t a d o m i n i o n f o r e s t a c t t o d i v i d e f o r e s t r y w o r k b e t w e e n t h e f e d e r a l a n d p r o v i n c i a l g o v e r n m e n t s . (4) C a r r y o u t s t u d i e s o f w a t e r r e s o u r c e s . T h e N a t i o n a l C o n f e r e n c e a d o p t e d i n l a r g e p a r t t h e r e c o m m e n d a t i o n s o f t h e a d v i s o r y c o m m i t t e e . T h i s l e d t o a s t a t e m e n t o f p o l i c y o n t h e p a r t o f t h e f e d e r a l g o v e r n m e n t a c c e p t i n g a s i t s r e s p o n s i b i l i t y t h e b a s i c s u r v e y s a n d r e s e a r c h e s s e n t i a l f o r t h e d e v e l o p m e n t a n d m a n a g e m e n t o f n a t u r a l r e s o u r c e s a n d f o r t h e d e v e l o p m e n t a n d c o n s e r v a t i o n o f r e s o u r c e s t h a t a r e i n t e r p r o v i n -c i a l i n n a t u r e ( e . g . , t h e p r o t e c t i o n o f r e g i o n a l w a t e r s h e d s ) . T h e f e d e r a l 96 g o v e r n m e n t w o u l d p r o v i d e a s s i s t a n c e , b y s p e c i f i c a g r e e m e n t , t o p r o v i n c e s f o r r e s o u r c e d e v e l o p m e n t ( T h o r p e 1962). R e s o u r c e s f o r T o m o r r o w C o n f e r e n c e . T h e m o s t a m b i t i o u s o f r e s o u r c e c o n f e r e n c e s h e l d i n C a n a d a was t h e R e s o u r c e s f o r T o m o r r o w C o n f e r e n c e o f 1961. T h e P r i m e M i n i s t e r , t h e R t . H o n . J o h n G . D i e f e n b a k e r , a n n o u n c e d i n F e b r u a r y , I958, t h a t a n a t i o n a l c o n f e r e n c e o n c o n s e r v a t i o n w o u l d b e c a l l e d . T h e s t e e r -i n g c o m m i t t e e m e t i n t h e s ame y e a r t o p l a n f o r t h e c o n f e r e n c e w h o s e o b j e c t i v e s e v o l v e d d u r i n g t h e n e x t t h r e e y e a r s e n d i n g u p w i t h t h e f o l l o w i n g . (1) I d e n t i f i c a t i o n o f t h e m a j o r p r o b l e m s r e q u i r i n g a t t e n t i o n i n t h e r e n e w a b l e r e s o u r c e s f i e l d . (2) E x a m i n a t i o n o f w h a t i s b e i n g d o n e t o s o l v e t h e s e p r o b l e m s . (3) C l a r i f i c a t i o n o f t h e i m p e d i m e n t s t o f u r t h e r p r o g r e s s a n d p o s s i b l e c o u r s e s t o a c h i e v i n g s o l u t i o n s t o t h e s e p r o b l e m s ( K r i s t j a n s o n 1962). T h e w a t e r r e s o u r c e was e x a m i n e d i n d e t a i l a t t h i s c o n f e r e n c e . P r o b l e m s i n t h e m a n a g e m e n t o f t h e r e s o u r c e w e r e i s o l a t e d a n d r e c o m m e n d a t i o n s d e s i g n e d t o a l l e v i a t e t h e s e w e r e s e t o u t . T h e c o n f e r e n c e a g r e e d t h a t a r e g u l a r e x -c h a n g e o f v i e w s o n r e s o u r c e m a n a g e m e n t was n e c e s s a r y . C a n a d i a n C o u n c i l o f R e s o u r c e M i n i s t e r s . T o m e e t t h i s n e e d t h e C a n a d i a n C o u n c i l o f R e s o u r c e M i n i s t e r s was f o r m e d i n F e b r u a r y , 1962, t o a l l o w t h e r e s o u r c e m i n i s t e r s o f t h e 11 s e n i o r g o v e r n m e n t s t o m e e t s e v e r a l t i m e s a y e a r t o d i s c u s s r e s o u r c e p o l i c y . T h e c o u n c i l i s n o t a n e x e c u t i v e a g e n c y b u t p r o v i d e s a f o r u m w i t h i n w h i c h t h e r e s o u r c e p o l i c i e s o f m e m b e r g o v e r n m e n t s a r e e x a m i n e d a n d c o o r d i n a t e d . T h e 11 g o v e r n m e n t s a g r e e d a l s o t o e s t a b l i s h t h e n e c e s s a r y c o o r d i n a t i n g m a c h i n e r y t o a l l o w c o o p e r a t i o n b e t w e e n 97 t h e v a r i o u s d e p a r t m e n t s i n v o l v e d i n r e s o u r c e m a n a g e m e n t ( C a n . C o u n . R e s . M i n i s t e r s 1965). T h e f i r s t p r o j e c t o f t h e c o u n c i l was a s t u d y o f 69 f e d e r a l - p r o v i n c i a l s h a r e d - c o s t r e s o u r c e a g r e e m e n t s . D e f i c i e n c i e s w e r e e x a m i n e d a n d a s e t o f g u i d e l i n e s d r a w n u p f o r u s e i n f u t u r e r e s o u r c e a g r e e m e n t s . C o n c e r n i n g w a t e r , t h e c o u n c i l b e l i e v e d t h a t a s e r i o u s s t u d y o f t h i s r e s o u r c e r e q u i r e d , f i r s t , a n u n d e r s t a n d i n g o f p r e s e n t m a n a g e m e n t . T h e c o u n c i l s p o n s o r e d t h e n a t i o n a l c o n f e r e n c e " P o l l u t i o n a n d o u r E n v i r o n m e n t " , h e l d i n M o n t r e a l i n O c t o b e r - N o v e m b e r , I966. T h e a i m o f t h i s c o n f e r e n c e was t o a s s i s t g o v e r n m e n t a l a n d i n d u s t r i a l a g e n c i e s i n e s t a b l i s h i n g c o o r d i n a t e d p r o g r a m s f o r p o l l u t i o n c o n t r o l . T h e c o u n c i l was i n s t r u m e n t a l i n h a v i n g t h e U N E S C O - s p o n s o r e d I n t e r -n a t i o n a l H y d r o l o g i c D e c a d e ( I H D ) b a c k e d b y t h e f e d e r a l a n d p r o v i n c i a l g o v e r n -m e n t s . T h e o b j e c t o f t h i s d e c a d e , 1965-1974, i s " t o a c c e l e r a t e t h e s t u d y o f w a t e r r e s o u r c e s a n d t h e r e g i m e n o f w a t e r s w i t h a v i e w t o t h e i r r a t i o n a l m a n -a g e m e n t i n t h e i n t e r e s t o f m a n k i n d ; a n d t o i m p r o v e o u r a b i l i t y t o e v a l u a t e r e s o u r c e s a n d t o u s e t h e m t o t h e b e s t a d v a n t a g e " ( I H D 1965a, p«3)» F e d e r a l - P r o v i n c i a l P r e m i e r s ' C o n f e r e n c e . T h e f e d e r a l g o v e r n m e n t ' s g r a d u a l l y - e v o l v e d w a t e r p r o g r a m was s e t o u t a t t h e F e d e r a l - P r o v i n c i a l P r e m i e r s C o n f e r e n c e i n O t t a w a , J u l y , 1965° T h e s t a t e m e n t , a c k n o w l e d g i n g t h a t w a t e r i s v i t a l t o C a n a d a ' s d e v e l o p m e n t a n d t h a t t h e r e a r e r e g i o n a l d i f f e r e n c e s i n w a t e r e n d o w m e n t , d e s c r i b e d t h e p o l i c y a s e n d e a v o r i n g " t o f o s t e r b o t h a w i s e m a n a g e -m e n t a n d o p t i m u m u s e o f w a t e r t h r o u g h o u t a l l o f C a n a d a a n d o n b e h a l f o f a l l C a n a d a ' s p e o p l e " ( F e d e r a l - P r o v . P r e m i e r s " C o n f . 1965, a s q u o t e d b y C.A.A.E. 1966). 98 A t t h e F e d e r a l - P r o v i n c i a l P r e m i e r s " C o n f e r e n c e o f 1965» t h e f e d e r a l g o v e r n m e n t ' s w a t e r p r o g r a m was d e s c r i b e d a s c o n s i s t i n g o f i n v e n t o r y , b a s i c a n d a p p l i e d r e s e a r c h , d e v e l o p m e n t o f p r o t e c t i v e r e g u l a t i o n s ( e . g . , p o l l u t i o n c o n t r o l m e a s u r e s ) , d e v e l o p m e n t o f s p e c i f i c p r o j e c t s ( e . g . , w a t e r d i v e r s i o n f o r i r r i g a t i o n ) , c o n s u l t a t i o n w i t h t h e p r o v i n c e s a n d t h e U n i t e d S t a t e s , a n d p u b l i c a t i o n o f s c i e n t i f i c a n d t e c h n i c a l m a t e r i a l . B r i t i s h C o l u m b i a B r i t i s h C o l u m b i a b e c a m e t h e s i x t h p r o v i n c e o f t h e D o m i n i o n o f C a n a d a i n I87I, M a n i t o b a h a v i n g j o i n e d t h e o r i g i n a l f o u r i n 1 8 ? 0 . F i v e y e a r s p r e v i o u s t o e n t e r i n g t h e c o n f e d e r a t i o n t h e c r o w n c o l o n y o f B r i t i s h C o l u m b i a h a d b e e n e s t a b l i s h e d b y u n i o n o f V a n c o u v e r I s l a n d , Q u e e n C h a r l o t t e I s l a n d s , m a i n l a n d B r i t i s h C o l u m b i a , a n d S t i c k e e n T e r r i t o r y . W a t e r p o l i c y i n B r i t i s h C o l u m b i a d i d n o t e v o l v e a s a t t h e f e d e r a l l e v e l b u t b e c a u s e t h e p r o v i n c e s a d m i n i s t e r t h e w a t e r r e s o u r c e , e v o l u t i o n t o o k t h e f o r m o f a s e r i e s o f a d d i t i o n s a n d a m e n d m e n t s t o w a t e r l e g i s l a t i o n . G o l d F i e l d s A c t . L e g i s l a t i o n r e g a r d i n g w a t e r a d m i n i s t r a t i o n i n B r i t i s h C o l u m b i a b e g a n w i t h t h e G o l d F i e l d s A c t o f I859. T h i s a c t g a v e p o w e r t o t h e G o l d C o m m i s s i o n e r t o g r a n t e x c l u s i v e r i g h t s t o t h e u s e o f d e f i n e d q u a n t i t i e s o f w a t e r , n o t n e c e s s a r i l y t o a r i p a r i a n o w n e r . T h i s d e n i a l o f r i p a r i a n r i g h t s i s a n i m p o r t a n t f e a t u r e o f B r i t i s h C o l u m b i a l a w . T h e a c t s t i p u l a t e d t h a t t h e w a t e r u s e r p a y r e n t a l t o t h e c r o w n , a n d t h a t c a n c e l l a t i o n o f h i s r i g h t w o u l d r e s u l t f r o