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<br />."."',-",,,-,'-' <br /> <br />WATER SALVAGE RY.l'Em'IALITIES <br /> <br />General <br /> <br />The reconnaissance-grade water salvage studies for this report <br />were based on data collected during previous investigations and from <br />continuing programs of observation of shallow ground water wells. The <br />amount of shallow ground water available for salvage was estimated from <br />analyses of the monthly f'luctuations of the shallow ground water table <br />f'or areas for which such data were available. Where shallow ground <br />water data were not available, the potential salvage was estimated by <br />comparison with other areas.. The spacing and discharge of pumped wells <br />required to salvage shallow ground water were estimated from well pump <br />tests and studies made in the feasibility grade analyses to determine <br />the plan of development for ,the Closed Basin Division of' the San Luis <br />Valley Project. <br /> <br />The discharges of existing free-flowing artesian wells, and <br />potential artesian wells, within selected salvage areas were estimated <br />f'rom the general chamcteristics of' the numerous other a.rtesian wells <br />within the Valley. The expected chemical quality of' the salvaged water <br />was estimated from the data available f'rom previous investigations. <br /> <br />Data on costs and benefits were obtained f'rom the more detailed <br />f'easibility studies of the Closed Basin Division. All data and analyses <br />presented in this report are, of' course, subject to verification or modifi- <br />cation by the collection of' additional basic data and by additional and <br />more detailed analyses. <br /> <br />Wi th the pervious soils common to the Valley and the uncontrolled <br />water supplies available for irrigation, subirrigation is generally prac- <br />ticed. Indiscriminate pumping in and adjacent to irrigated areas would <br />be incompatible with the system of subirrigation. However in the potential <br />salvage areas ground water is being withdrawn, and nonbeneficially coni;lumed <br />by native phreatic vegetation, which is analogous to a myriad of small ' <br />natural pumps. By lowering the shallow ground water table a minimum of <br />8 feet within the salvage area, the ground water table would be at a depth <br />that would essentially preclude the withdrawal and nonbenef'icial use of' <br />water by the native vegetation and the same amount of' water f'ormerly con- <br />sumed by the plants could be removed by pumped wells without disturbing <br />the hydrologic balance of the area or adversely affecting the subirrigation <br />practices in contiguous irrigated areas. The reaction of' the shallow <br />ground water table to pumping is readily definable by observation wells <br />in and around the perimeter of' a salvage area, and artificial wells are <br />instantaneously controllable, in direct contrast to the uncontrolled pump- <br />ing ef'fect of native vegetation. All proposals f'or water salvage contem- <br />plate that the amount of water salvaged f'rom an area will be limited to <br />that now being removed by native vegetation and that the ef'f'ect of pumping <br />would be continuously observed and rigidly controlled to preclude any <br />adverse eff'ect on irrigation in contiguous areas. <br /> <br />" ~ <br />j , <br />v,. <br /> <br />"', ','I <br />^ . :.., <br />.v'.i,; <br /> <br />8 <br />