Water rights Diversion of Columbia River water for the division will not infringe on any existing water rights, and the effect on downstream power production, navigation, or other uses will be inconsequential.' A notice dated October 5, 1955, has been filed with the Washington State Department of Conservation and acknowledged October 10, 1955, for withdrawal of Columbia River water for the Foster Creek and Greater Wenatchee divisions of the Chief Joseph Dam project. Prior to construction of any unit of the division, application for permits to divert water from the river, up to the capacity of the pumping plants, will be made to the Washington State Department of Conservation. WATER REQUIREMENTS The water requirements determined for the Greater Wenatchee division consist of annual and peak diversion requirements. The annual requirements establish the average amount of irrigation water to be pumped each season, and the peak requirements determine the capacities of the pumping plants and distribution systems. Consumptive use The annual consumptive use of water in the Greater Wenatchee division area was determined to be 3.0 feet for orchards with cover crops and 2.47 feet for alfalfa and general crops. Effective precipitation was deducted from annual consumptive use in arriving at the crop-irrigation requirements. Based on weather records at Wenatchee, Wash., the effective precipitation for the Greater Wenatchee division is about 0.34 foot. Thus, the resulting crop-irrigation requirements for orchards and general crops are 2.7 and 2.1 feet, respectively. Farm-delivery requirements Farm-irrigation eficiency varies with methods of irrigation (such as surface or sprinkler), types of crops, and variations in land characteristics (such as slope, soil depth, permeability, and moisture-holding capacity). On lands that would be sprinkler irrigated, the principal factors affecting irrigation efficiencies are soil depth and moistureholding capacity. These factors determine the moisture available to the crop between irrigations and how often the crop must be irrigated. In addition to those factors affecting sprinkler irrigation efficiencies, slope and topography affect, to considerable extent, the efficiency of surface irrigation. On the basis of the land classification, the lands in the Greater Wenatchee division were grouped into four water-requirement classes according to soil depth, moisture-holding capacities, and topographic deficiencies. Table 2 shows the estimated farm-delivery requirements for each water-requirement class for orchards and general crops. TABLE 2.— Farm-delivery requirements by water-requirement classes The average farm delivery requirement was determined for each unit after consideration of the anticipated land use, the proportion of lands in each water requirement class, and the above per acre requirements. With the exception of the coulee area of the Moses Coulee unit, all irrigable lands are expected to be devoted to fruit production. Tables 3 and 5 show the estimated peak and annual farm delivery requirements for each unit. Peak irrigation requirements Peak irrigation requirements were determined independently of average annual requirements and reflected the higher than normal average peak water use of crops grown on the shallower soils with less moisture-holding capacity. "Table 4 shows the peak farm delivery requirements for each water requirement class and table 5 shows the peak requirements for each unit. 4. 5 4. 2 4.9 5. 4 6. 7 4.2 4. 5 3.3 3.8 4. 26 crops. B |