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Water Deficits Stream flows have been below minimum instream flow standards during the late sum- mer and winter during dry years. The fre- quency and duration of minimum instream flow deficits (depending on the location on the Eagle River) varies from once every 1 to 5 years. It is estimated by the Eagle River Assembly (1994) that to increase stream flow to mini- mum instream flow levels, an additional 3,300 to 4,000 acre feet of water needs to be stored and released into the Eagle River during dry times of the year, typically late summer and early winter. The same report estimates that 5,200 to 6,500 acre feet may be needed to increase stream flow ensure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 2. Instream Flow Deficits Section of Eagle River Instream Flow Estimated Frequency Estimated Frequency Standard- of Flow shortage- of Flow shortage- SummerlWmter Summer Winter Cross Creek to Gore Creek 50/20 cfs I in 5-10 years I in 10 years Gore Creek to Beaver Creek 85/35 cfs I in 5-10 years I in 5-10 years Beaver Creek to Lake Creek 85/35 cfs I in 2 years I in 5-10 years Lake Creek to Brush Creek 110/45 cfs I in 5-10 years I in 5-10 years Brush Creek to Colorado River 130/50 cfs I in 5-10 years May not occur NOTE:. A shortage is assu~ed to occur when stream flow is less than the instream flow standard for a period exceedmg several consecutive days. (Source: Eagle River Assembly, Phase I Report, 1994) Fish "kills" have been recorded by the Colorado Division of Wildlife when flows have been above instream flows perhaps indicating that minimum flows may not be adequate to protect trout populations throughout the length of the Eagle River. It should also be noted that historic flows dropped below minimum instream flow stan- dards on portions of the Eagle River before there were either in-basin or trans-basin diversions. This would suggest that there may have always been stress on trout populations during natural low flow periods. Additional biological monitoring is needed to determine the relationship between water quantity/ quality and biological indicators. ~~ .". 22 IMIII minimum instream flow as the County approaches "build out" of developments approved as of 1994. A separate report commissioned by Eagle County estimates that in July 1995 there are approximately 11,000 units unbuilt but approved indicated that the demand for water is sure to increase.