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,~~~l(t~ 'tru_vvv Affected Environment & Consequences 3-23 ~ , 3.5.2.2 Development Alternatives Because hydropower diversions during the summer irrigation season will be relatively small, their effect on water temperatures during that season should be minimal. During the winters, when hydropower diversions are greatest, water temperatures would be reduced between 1 and 2 oC, which could lead to icing in some areas. This would result in somewhat greater icing than has occurred in the past (though significant icing is still not expected). See the PElS for a detailed discussion. Alternatives E-2 and E-3 would have somewhat less impact than the previously approved Alternative E-l. 3.5.3 Impacts of Alternatives - Uncompahgre River 3.5.3.1 Alternative A (No Action) River temperatures in the Uncompahgre River would remain unchanged under the No Action alternative. Temperatures would be affected by the amount of water withdrawn for irrigation during summer, therefore, average summer temperatures would continue to increase as one moves downstream. During winter, low flows would most likely cause ice cover in slow-moving areas (toward Delta). 3.5.3.2 Development Alternatives Higher water temperatures during the summer between the South Canal and Montrose would result due to reduced flows. Because flows would still be high between the South and Loutzenhizer Canals, this change would not be significant except in the reach between the Loutzenhizer Diversion and the proposed tailrace where summer water temperatures would likely increase. Temperature would not change between the South Canal and the tailrace during the winter because flow profiles would not change. Water temperatures would be expected to decrease during the summer downstream from the tailrace due to relatively cooler Gunnison River water flowing through the powerplant. Project refinements since 1991 would have little impact on temperature conclusions reached in the PElS. Winter water temperatures would be warmer. Reduced-flow alternatives E-2 and E-3 would, however, have slightly less effect than the previously approved Alternative E. 3.6 Water Quality 3.6.1 Existing Conditions 3.6.1.1 Gunnison River Data indicates that water quality within the upper portion of the Gunnison River immediately below Crystal Reservoir is a function of the limnology of and releases from AS Lateral Hydropower Project July 2000 , . .. , ,<- - ~ -~ .<< t .-' "'i'-'-~ .;he ,;,~"Y~'k~,:il~~i