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I I I I I I I I I I I I I I I I I I I 4.4 4.5 Such a high rate of seepage loss indicates that very little water supply increase will result from storing water in Hourglass Reservoir up to its full capacity, although available capacity can facilitate short term operation of the raw water system. It Is clear that the annual fill and draw operation of Hourglass Reservoir should be conIinued, A11y signiflcant hold-over storage atl~e end of the year would apparently be lost to reservoir seepage, SEDIMENT Sediment yield above Hourglass Reservoir is estimated from the Colorado Land Use Commission sediment yield map of 1974, This informalion is based on surveys of reservoir sediment accumulations of 25 years and longer. Much of the information was obtained from small reservoirs with small drainage basins. The Hourglass Reservoir drainage basin sediment yield is low, as tt is wtth many high mountain reservoirs, Such drainage areas have rock outcrops and dense vegetation. The sediment yieid is estimated to be less than 0.1 acre-feel per square mile per year. This low rate equates to only 7.4 acre-feet of sediment In 100 years. a negligible amount. Very little sediment is expected to be carried Into Hourglass Reservoir from Comanche Reservoir, WATER QUALITY Water released from Hourglass Reservoir flows into Beaver Creek, the South Fork of the Cache la Poudre River, and the Cache la Poudre River on to Ihe City of Fort Collins, The water quality analysis station on the Cache la Poudre River near Fort Collins was used as an appropriate station to compare river waler quality with municipal water standards in the Comanche Dam rehabilitation study that was done by Morrison-Knudsen Engineers, Inc. It is appropriate to use this station for HoUJglass Reservoir releases, parameters currently available from the STORET computer system are following table. Table 4,5, The water quality summarized in the 4-8