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CHAPTER IV - EFr"ECT OF PROJEq:rS 25. Effect of joi~t use space at existing projects. - The Corps of Engineers has no flood control projects wittdn the Upper Colorado Basin. Four storage units constructed by the Bureau of Reclamation with joint use space (conservation and flood control) as a specif- ically designated function were instrumental in reducing floodflot,s resulting from the storm. Joint use space at the reservoirs is available only during the snowmelt runoff season on a forecast basis (normally February thru June). Pertinent data on these projects are shown in the foll~wing tabulation: o Project StrflaIn Joint usp. space ac-ft Agency Gunnison River Florida River Sa.'l Juan Ri ve ~ Los Pinos (Pine) River 748,500 Bureau of Reclamation 39,030 Bureau of Reclamation 1,036,100 Bureau of Reclamation 125,1(00 Bureau of Reclamation Blue Mesa Reservoir Lemon Reservoir Navajo Reservoir Vallecito Reservoir Taylor Park Reservoir on Taylor River, also a Bureau of Reclamation reservoir, has no specific reservation for flood control but provides significant flood control benefits as an incidental function depending on available space at the time of flood. '-- 26. Although joint use space provided in the above reservoirs is for regulation of snowmelt floods (February-June) on a forecast basis, no dedicated space is provided during other times of the year. These reservoirs were designed and built primarily for conservation use with flood control of secondary importance. Because the 5-7 September flood occurred immediately after the irrigation season when reservoir storage was low, complete regulation of flows to non-damaging rates downstream by the storage of floodwater in these reservoirs was possible. The following tabulation shows how the operation of three reservoirs reduced computed peak inflows to non- damaging flows by regulating reservoir releases to the values shown, and storing the 3-day storm volumes shown at each of the reservoirs. 23