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Annualized Beneficial NED Effects 6/ Field Office Technical Guide, Section III, Resource Management Systems was ~sed. This provides an estimate of water used before and after the application of conservation. It determines acceptablility of planned or installed resource management systems. 7/ The acre inches of water applied per acre documentation was multiplied by the ~cres by crop and divided by 12. This analysis is not a water balance study. The intent is to provide a reasonable average per acre effect before and after applying on-farm conservation. Water use documentation was recorded on conservation impacts worksheets by specific fields and crops. This basic data is associated with the Yuma Field Office Technical Guide, Section III. -8/ Considerable effort was devoted by SCS economists from the National f1eadquarters, the W~st National Technical Center and the state to establish the value of water in the Colorado River. It was agreed that the value of water in the Colorado River will not be placed any lower than 555 per acre foot. Therefore, the off-site water benefits are obtained by multiplying the number of acre feet by 555. The unevaluated off-site Colorado River beneficial NED effects resulting from reduced diversions due to increased on-farm irrigation efficiences are (a) pumpage to the Well ton-Mohawk irrigation and drainage District, (b) pumping ground water to lower the water table below crop root zones, and (c) salinity reductions. (a) The:Wellton-Mohawk Irrigation and Drainage District is located upstream on the Gila River from where it joins the Colorado River. Three large pumps along the Wellton-Mohawk canal lift water a total of 170 feet. Smaller relift pumps are also utilized. (b) The improve",ent of the irrigation systems and the application of soil, water and plant management practices result in less water.being applied. This reduces deep percolation. (c) The Wellton-Mohawk Irrigation and Drainage District return flow graph (which was prepared by the United States Bureau of Reclamation) shows drainage pumping required for no change in ground water storage at 216,000 acre feet per year in 1970 and a target of 110,000 acre feet. (d) The United States and Mexico international boundary and water commission developed the ~inute No. 242 agreement. Waters delivered to Mexico will have an annual average salinity of no more than 115 parts per million, plus or minus 30 parts per million, of total dissolved salts over the salinity of Colorado River water at Imperial Dam. The Soil Conservation Service Activities resulted in less water being applied. This means less water is diverted from the Colorado River at Imperial Dam to the Well ton-Mohawk Irrigation and Drainage District. It also means less salts enter the ground water. The pumped drainage increases the salinity of water delivered to Mexico unless desalted or diverted for non use purposes. 2! The estimated irrigation labor cost of four dollars per acre was taken fro~ Table 72 - Wage and Piece Rates, 1987 Arizona Field Crop Budgets for Yuma County which is available through the University of Arizona. The irrigation labor costs were estimated by multipling the number of hours by four dollars per hour. -36-