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<br />..~ <br />t- <br />(:J <br />o <br />C) <br /> <br />r. <br />--' <br /> <br />SUMMARY (Continued) <br /> <br />Water supply <br /> <br />Under the no-action alternative, some changes would be expected in <br />the surface water supplies in the valley. Upstream developments would <br />continue to deplete the Colorado River, but present irrigation supplies <br />would be protected by water right laws. No significant changes would <br />occur in ground water levels. <br /> <br />Canal and lateral improvements under both alternatives A and B would <br />be designed to provide the historical water carrying capacity available. <br />This would in turn permit irrigation districts to divert the same amount <br />of water as in the past; therefore, maximum diversions would remain un- <br />changed. <br /> <br />With alternative B, reduced seepage losses and the elimination of <br />administrative wastewater at the end of laterals could increase adminis- <br />trative waste spills from the canals, which would be expected to result <br />in an increase in wash flows during the irrigation season. <br /> <br />Ground water levels would be expected to decline near improved <br />canals and laterals, a reduction that would decrease winter flows in <br />washes and drains. Seepage from canals and laterals would be reduced by <br />approximately 39,500 acre-feet with alternative A and approximately <br />41,100 acre-feet with alternative B. <br /> <br />Water quality <br /> <br />Under any of the alternatives, a significant change is not expected <br />in salt loading to the Colorado River from surface sources. On-farm im- <br />provements would continue and salt loading due to seepage from farm <br />ditches and deep percolation from irrigated fields would decline. <br /> <br />Implementing alternatives A or B would be expected to decrease the <br />salinity of the Colorado River above the Dolores River by about 138,000 <br />and 143,500 tons annually and about 23 and 24 mg/L, respectively. <br /> <br />Fishery and aquatic environment <br /> <br />Colorado River <br /> <br />Under the no-action alternative and under alternatives A and B, <br />flows in the Colorado River will continue to decrease as the Upper Colo- <br />rado River Basin States develop their share of the Colorado River. These <br />flow changes may affect fish populations, but accurate predictions of <br />these changes are not possible. Local fisherman use may increase <br />slightly as the Grand Valley population grows. <br /> <br />Salinity reductions in the river under alternative A or B would have <br />no measurable impact on the existing fishery in the Colorado River down- <br />stream of the Grand Valley Unit. The water possibly gained during the <br />irrigation season and lost during the nonirrigation season would also <br />have no impact on the existing fishery. <br /> <br />S-6 <br />