OCR Text |
Show __2__ consumptive use of water and consumptive-water requirements. Consumptive use (evapo-transpiration) is denned as the sum of the volume of water used by the vegetative growth of a given area in transpiration of building or plant tissue and that evaporated from adjacent soil, snow, or intercepted precipitation on the area in any specified time.1 It may be expressed in acre-inches per acre (depth in inches) or acre-feet per acre (depth in feet). For a 12-month year, consumptive use is usually expressed in acre-feet per acre (or feet). Considered from a valley-wide standpoint, consumptive use includes all transpiration and evaporation losses from lands on which there is growth of vegetation of any kind, whether agricultural crops or native vegetation, plus evaporation from bare land and from water surfaces. Various methods have been used to determine the amount of water consumed by agricultural crops and native vegetation. Regardless of the method, the problems encountered are numerous. The source of water used by plant life, whether from precipitation alone, irrigation plus rainfall or ground water plus precipitation, is a factor in selecting a method. The principal methods used for small plots are: tank experiments, soil-moisture studies and ground-water fluctuations; and for large areas, inflow-outflow and integration methods.2 1Blaney, Harry F.; Ewing, P. A.; Israelsen, O. W.; Rohwer, C.; and Sobey, Fred C.; Regional Planning, Part VI-Upper Rio Grande Basin, (Part III) National Resources Committee, 1938. 2Blaney, Harry F., "Field Methods of Determining Consumptive Use of Water." Division of Irrigation, U. S. Department of Agriculture Mimeo., 1938. |
Source |
Original book: [State of Arizona, complainant v. State of California, Palo Verde Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of Los Angeles, California, City of San Diego, California, and County of San Diego, California, defendants, United States of America, State of Nevada, State of New Mexico, State of Utah, interveners] : California exhibits. |