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<br />~i" , <br />C-l <br />..:; <br />...-4 <br />~; future if new land is brought into production. Within the Basin, salt pick <br />(~) up rates from irrigated lands valY from 0.1 ton per acre per year to as <br />much as 8.5 tons per acre per year. <br /> <br />The annual salt pick up from all irrigation above Hoover Dam averages about <br />two tons per acre. For some areas, especi ally those under1 a in by shales and <br />saline lake bed formations, salt pick up is much higher, with average annual <br />loads ranging between four and eight tons per acre. Below Hoover Dam, the <br />average annual salt pick up from irrigation is about 0.5 ton per acre after <br />the initial leaching period. <br /> <br />Figure 3 shows the relative salt loads from irrigated land by subbasins. <br />Tab 1 e 8 1 is ts the a verage sa It yi e 1 ds and loads fl"om i rri gated areas wi thi n <br />the subbasins. Figure 4 shows the location of potential salt load reduction <br />through irrigation improvements as well as other projects. Information in <br />these three exhibits is taken from the Environmental Protection Agency report. <br /> <br />As a part of its cooperation in the Western U.S. Water Plan Study, USDA has <br />made studies of water conservation and salvage and of erosion and sedimenta- <br />tion. Each of these studies provides some further general inf0l111ation as <br />to the relation of soil and water conservation and management practices to <br />salinity of the Colorado River Basin. <br /> <br />The water conservation and salvage study was undertaken to determine the <br />potential for water savings, better water management, improving use of <br />current water supplies, and increasing quality of return flows for areas <br />currently under irrigation. Information was gathered and compiled at the <br />county and/or subbasin level by SCS field personnel. The material being <br />-compil ed inc1 udes (1) the improvements needed for off-farm water supply, <br />conveyance and return systems, and on-farm application; (2) cost of these <br />improvement measures, and (3) the impact of the improvement program on water <br />supply, water quality, land stability, crop production, and water use effi- <br />ciency. It is hop~d to complete this study this year. <br /> <br />The preliminary data collected for five Upper Colorado River Basin States <br />are sUl1l11arizedin Table 9. These data show about six million acre-feet <br />are withdrawn from the average 15 m.a.f. water supply to irrigate 1.7 <br />million acres in the Upper Colorado Region. Average system efficiency is <br />.28 percent. <br /> <br />The data for on-farm systems show about 17 percent of the irrigated land has <br />adequate irrigation systems with proper water management. The present aver- <br />age on-farm application efficiency ranges between 23 to 50 percent. <br /> <br />The key system treatment impr("l\'e~o~ts shown to be needed are (1) 282,000 <br />acres of irrigation method change, (2) 527,000 acres of land leveling and <br />system layout, (3) 260,000 acres of drainage, (4) 4,500 miles of farm ditch <br />lining or piping together with adequate control structures, and (5) improved <br />management on 80 percent of the land. Total installation cost to improve <br />on-farm systems is estimated to be $208 million or an average cost of $120 <br />per acre for 1.7 million acres. <br /> <br />- 15 - <br />