WSP07589 - Laserfiche WebLink

Home Browse Search

I\) 0:>, -.l tJ~ Project, the Department of the Interior assured Congress that there would be a water supply adequate to deliver an annual average of 1,200,000 ac ft to the potential Central Arizona Project service area during the 50-year project cost repayment period. However, In any year in which there should be too little water available to deliver the minimum aUotments to ' California, Nevada, and Arizona, it is agreed that the shortage will be borne first by the Central Arizona Prpject. By the same token. Central Arizona Pr~ect will share in any surplus above these ntinlmums. The Arizona Water Commission estimates that by the year 2000 municipal and industrial users will take at least 400,000 ac ft. leaving approximately 800,000 for agriculture. This will faU far short of meeting present requests. One large irrigation district alone has asked for more than 500,000 ac ft of Central Arizona Project water. Thus, It is clear that if only the established Irrigation districts are considered in the aUocation of water, few can expect to receive as much as half of what they have asked for. Exceptions might be such districts as the Salt River and San Carlos projects. These projects have surface water supplies, storage facilities, and distribution systems in opera- tion that could be greatly enhanced by aUotments of Central Amona Project water. Conversely, it is doubtful if comparable areas which depend entirely, upon groundwater could sustain the capital invest- ment necessary to construct distribution systems. Since agricultural lands are dispersed over a rather large area, It was decided to divide the potential Central Arizona Project service area Into several subgroups or areas as outlined in a previous section. In recapitulation. these areas were: Salt River Project, Lands Supplemental to Salt River Project, Roosevelt Water Conservation District, Roosevelt Irrigation District, San Carlos Project (Non-Indian), and San Carlos Project (Indian). In addition, due to the fact that many possible aUocations of Central Arizona Project water still exist, certain assumptions had to be made concerning representa- tive conditions of each respective area. Delineation of the circumscribed. areas, Central Arizona Project impacts on present agricultural water supplies, and model results corresponding to the respective sub- areas foUow. Salt River Project The Salt River Project irrigation system serves approximately 261,246 acres of land in the Salt River VaUey of Central Arizona (Map 3.9); It supplies fuU service to the Salt River VaUey Water Users Association (238,264 acres), supplemental service to special contractors (22,982 acres). and 5.6 percent of the surface water diverted at Granite Reef Dam to the Roosevelt Water Conservation District (Arizona Water Commission files, Annual Crop Production, Reports, Roosevelt Water Conservation District and Salt River Project). 1Lower Basin allotments: California, 4,400,000 '""" f..t: Nevada. 800,000 acre feet: Arizona, 2,800,000 acre feet. In 1973 the acreage under fun supplemental irrigation (not including Roosevelt Water Conserva. tion District) consisted of 101,370 acres of urban and suburban residential, commercial, and industrial lands, 9,414 acres of farmsteads, roads, ditches, and drains, and 150,462 acres of cultivated cropland. Of the cropland 136,385 acres were irrigated (Annual Crop Production Reports, Salt River Project). In general, the Salt River Project includes: 1) the Verde River with its two reservoirs above Horseshoe Dam and Bartlett Dam, 2) the Salt River and its reservoirs above Stewart Mountain Dam, Mormon Flat Dam, Horse Mesa Dam, 3) Granite Reef Diversion Dam at the confluence of the Verde and Salt Rivers, 4) the distribution system which includes the Arizona Canal, Grand Canal, Tempe Canal, Western Canal, Consolidated Canal, Eastern Canal, and their laterals, and 5) drainage and pumping works with 252 active weUs. Electrical power is also generated from the Salt River Project with the releases or flows from the dams on the Salt and Verde Rivers. These hydroelectric plants are not necessarily a part of this report except as they affect the quality of water which reaches the farms and cities. This effect may not be of great Importance because of the relatively low salt content of the combined rivers. However, water quality varies between the rivers and with the amount of natural flow. Operation of the power generating plants helps determine which water source Is released or stored at anY,given time and, therefore, is a factor to consider. This will be especlaUy true if Orme Dam Is built and different proportions of Salt River Project and Central Arizona Project waters are stored there at different times of the year. There are other possibilities that could affect the quality of water that might be delivered to the Salt River Project as weU as to other contractors for Central Arizona Project water: 1. Orme Dam mayor may not be built. This would affectthe water quality for any user below this point in the Central Arizona Project system. 2. The Salt River Project may have to make exchanges with other Central Arizona Project water contractors. The amount of Salt River Project water involved would affect the mixture of Central Arizona Project and Salt River Project waters. 3. The quantities of water aUocations to the Indians. 4. The aUocation between various contractors for Central Arizona Project water and their diversion point locations. For the purposes of this report, the fonowing assumptions are made: 1) continued surface water supply based on a 10-year average; 2) possible Central Arizona Project aUocations; 3) groundwater pumpage to maintain the ntinlmum balance required to meet Salt River Project obligat10ns; and 4) uniform mixing of all water sources. Water quality stations for which records are ,published on the surface water of the project are downstream from Bartlett Damon the Verde River and the Stewart Mountain Dam on the Salt River. The 9-year average flow (1964.1972) of the Verde River 178