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l!:i .-l C"j CHAPTEH III WATER SUPPLY _..> Reservoir Losses About 300 acre-feet is lost from Harvey Gap Reservoir through evap- oration each year. About 600 acre-feet annually would evaporate from Rifle Gap Reservoir. Seepage losses through ooth dams during the irri- gation season could be recovered downstream and used for irrigation. Sedimentation From studies made of gaged stream flow and suspended sediment samples, it was determined that an average of about 30 acre-feet of sediment would settle in the Rifle Gap Reservoir each year. For 100 years of operation about 3,000 acre-feet of capacity would be required for sediment deposition. About 2,000 acre-feet of the sediment would be deposited in the active storage section of the reservoir and 1,000 acre-feet in the dead storage pool. A negligible amount of sediment has been deposited in Harvey Gap Reservoir during its 40 years of operation. Water fed to the reservoir by Grass Valley Canal is relatively free from suspended sediment, and the reservoir has almost no drainage area of its own from which it could receive sediment. Water Rights Existing Water Rights Decreed water rights on streams that would contribute to the proj- ect water supply are summarized in the following tabulation. Domestic Source of use Irrigation Storage Power supply sec.-ft,) (se~,-ft.~ (acre-ft.) ~(sec,-ft.) Rifle Creek below Rifle Gap Dam site 10.0 93.9 6S0 -- West Rifle Creek -- 13.5 296 -- Middle Rifle Creek -- 11.661/ 1.90(JJ i.~: oY East Rifle Creek 17,0 122.1 Total 27.0 2L..l.16 1..876 45.0 SUMMARY OF DECRE:ED WATER RIGHTS 11 Includes existing water rights of Grass Valley Canal (100 second- feet) and Davie ditch (8.66 second-feet). 21 Storage rights for Harvey Gap Reservoir. 21 Public Service Company of Colorado; does not control nor diminish natural stream flow, 25