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<br /> <br />. <br /> <br />drip irrigation facilities, <br />water measurement devi ces, and <br />improvement of conveyance and <br />onfarm management practices. <br />Costs involved in making detailed <br />studies on all of these study <br />areas over a period of 1 to <br />5 years would total approximately <br />$24.7 million. If all indicated <br />water conservation measures were <br />authorized for implementation, the <br />total cost of the measures woul d <br />be approximately $1.1 billion. <br /> <br />It is emphasized that these <br />estimates of potenti al reducti on <br />in di versions, water lost to <br />further use, costs of detailed <br />studies, and costs and benefits of <br />implementation measures are based <br />on subappraisal level studies of <br />limited detail and scope; thus, <br />caution should be exercised in <br />i nterpreti ng them. <br /> <br />Of the 3.1 million acre-feet of <br />reduced diversions estimated to be <br />attainable with implementation of <br />the proposed improvement measures, <br />66 percent would result from <br />improvements in facil ities and <br />operation of irrigation water <br />conveyance and deli very systems, <br />and 34 percent woul d result from <br />improvement of onfann i rri gat ion <br />systems and operation. Project <br />acti ons taken on the storage and <br />conveyance system and thei r <br />estimated annual costs, based on <br />reduction in diversions, would <br />consist of improved management <br />practices at $2 to $10 per <br />acre-foot, seepage reducti on <br />at $20 to $50 per acre-foot, <br />automation at $1 to $5 per <br />acre-foot, and recycli ng of <br />return flow at 1 ess than $10 per <br />acre-foot. Onfarm activities <br />and their estimated annual costs, <br />based on reduction in diversions, <br /> <br />... <br /> <br />. <br /> <br />. <br /> <br />would consist of seepage reduction <br />measures at $10 to $60 per <br />acre-foot, reorienting and <br />1 evel i ng fi el ds at $5 to $80 per <br />acre-foot, onfarm i rri gati on <br />schedul i ng at $4 to $30 per <br />acre-foot, improved water <br />application methods at $60 to $90 <br />per acre-foot, and recycling of <br />irrigation tailwater at $10 to <br />$15 per acre-foot. <br /> <br />Total annual weighted costs for <br />the measures proposed vary <br />substantially among areas, but <br />genera lly fall in the $10 to $40 <br />per acre-foot of reduced <br />diversions. It should be noted <br />that if cost per acre-foot were <br />computed on the basis of water <br />actually sal vaged for new <br />beneficial uses, these costs would <br />be sUbstantially higher, in some <br />cases an order of magni tude <br />hi gher, dependi ng on the specifi c <br />study area. <br /> <br />Annual benefits per acre-foot of <br />reduced diversions were not <br />preci sely estimated, but tend to <br />fall below estimated average costs <br />for about 67 percent of the study <br />areas, indicating that water <br />conservation programs may need to <br />be eval uated on other than stri ct <br />economic efficiency standards <br />if they are to be undertaken. <br />Cauti on shoul d be exerci sed when <br />applyi ng any of these data in <br />benefit-cost comparisons. <br /> <br />Envi ronmental effects of proposed <br />conservation measures within an <br />individual study area can be both <br />positive and negative. Positive <br />effects can arise from such <br />effects as the stabilization of <br />reservoir surface, improved <br />instream flows, and improved water <br />quality. However, the predominant <br /> <br />ix <br />