AZ vs. CA:11 California Exhibits, Vol. XI; Nos. 1001-1011; 1101-1109; 1201-1251; 1301-13431301-1343

page 3

__3__ Consumptive use was defined in the Report of the Duty of Water Committee of the Irrigation-Division of the American Society of Civil Engineers, presented July 14, 1927 (Trans. Amer. Soc. Civ. Eng., vol. 94, 1930 [California Exhibit No. 27], p. 1351), as: "Consumptive use in a basic sense is here denned as the quantity of water, in acre-feet per cropped acre per year, absorbed by the crop and transpired or used directly in the building of plant-tissue, together with that evaporated from the crop-producing soil." Since it is impracticable to confine water-loss to crop-producing area, the term is not ordinarily used in the sense in which that Committee defined. The more common use is more properly defined as "valley consumptive use." "Valley consumptive use" is the difference between valley inflow, consisting of the runoff of streams entering the valley, either on the surface or as underflow, together with precipitation, and outflow from the valley, in the form of water either in surface-streams or an underflow, with suitable adjustment for changes in ground-water storage. It represents the total water-loss from the valley-area by evaporation and transpiration, except for water contributed by dew, frost, or fog, together with the small amount retained by the plant-structure. Applied to many western valleys where agriculture is dependent upon irrigation and the irrigated area is the economic unit, it may well be stated in terms of acre-feet per year per irrigated acre.