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<br />Arkansas River Water Needs Assessment - Section 1. Executive Summary <br /> <br />via releases thtough the Mt. Elbert Conduit and <br />from Twin Lakes Dam, before the spring <br />snowmelt. Releases would be in a quantity suffi- <br />cient to allow refIlling of the two reservoirs with <br />water imported from the west slope by mid-July. <br /> <br />- Water would not be evacuated from the upper <br />reservoirs before March because an accurate <br />forecast of spring runoff cannot be made until a <br />significant portion of the high elevarion <br />snowpack has accumulated. <br /> <br />- Water would be evacuated from Turquoise Lake <br />before the runoff due to the limited capacity of <br />the Mt. Elbert Conduit. The capacity of the <br />Mt. Elbert Conduit, which carries water from <br />Turquoise Lake to Twin Lakes, is significantly <br />less than the combined spring inflow of the <br />transmountain tunnels and native Lake Fork <br />flows during the runoff. If sufficient space in <br />Turquoise Lake has not been evacuated, then <br />releases from Sugarloaf Dam to Lake Fork would <br />be necessary. Releases in excess of the minimum <br />required releases would be necessary to avoid <br />foregoing west slope imports after the lake fills. <br />Any water released to Lake Fork in excess of the <br />minimum requirement is a loss of energy genera- <br />tion at the Mt. Elbert Power Plant. <br /> <br />In a year of normal spring runoff, releases from <br />the upper reservoirs would be made in March <br />and April such that the entire Project storage <br />capacity of Turquoise Lake is evacuated. Releases <br />in May and June, at the height of the spring <br />runoff, would be avoided because the entire safe <br />channel capacity of Lake Creek below Twin <br />Lakes Dam is quite often needed during that <br />time period for the required bypass of the native <br />inflow to Twin Lakes. The native inflow to Twin <br />Lakes includes native flows of Lake Fork and <br />Halfmoon Creek diverted through the Mt. <br />Elbert Conduit, in addition to the native flow of <br />Lake Creek. If the safe channel capacity below <br />Twin Lakes Dam is reached, then diversions of <br />native water from Lake Fork and Halfmoon <br />Creek would be reduced or discontinued and <br />energy generation would be foregone. <br /> <br />In a year of heavy spring runoff, releases from <br />upper basin reservoirs would start in March and <br />continue through May in order to evacuate the <br />Project storage capacity ofT win Lakes in <br />addition to that of Turquoise Lake. After all <br />Project storage space is filled in the upper reser- <br />voirs, releases from Twin Lakes Dam and, if <br />necessary, Sugarloaf Dam would be made to <br />avoid foregoing imports of Project water from <br />the west slope. An unavoidable bypass of the <br />Mt. Elbert Power Plant would occur in such <br />years. <br /> <br />In a year of below average spring runoff, releases <br />from the uppet basin reservoirs would be discon- <br />tinued before the end of April to avoid storing <br />more water in Pueblo Reservoir than is necessary. <br />Any unnecessary storage of water in Pueblo <br />Reservoir represents a risk of foregoing winter <br />water storage in the reservoir in the following <br />winter and spring. Unnecessary storage of <br />Project water in Pueblo Reservoir also causes <br />greater losses of Project water to evaporation. <br />The evaporation from Pueblo Reservoir is greater <br />than from the uppet reservoirs. <br /> <br />The evacuation of water from the upper reser- <br />voirs could be limited, in any kind of runoff <br />year, by the lack of Project storage space in <br />Pueblo Reservoir. The available space in Pueblo <br />Reservoir does not correlate to the runoff in any <br />single year because Pueblo Reservoir is designed <br />to hold multiple years of water supply. <br />Consecutive dty years draw the reservoir down <br />and consecutive wet years fill it up. <br /> <br />- After the upper reservoirs fill in July, no release <br />of Project water would be made until the <br />following March. The only exceptions would be <br />direct releases of imported water in a heavy <br />runoff year, and releases for Project water <br />demands downstream of Pueblo Reservoir in the <br />event that all Project water is depleted from <br />Pueblo Reservoir. Delaying any further releases <br />unci March allows the upper reservoits to <br />remain as full as possible. This reduces evapora- <br />tion losses and, as a side benefit, enhances <br />flatwater recreation at the reservoirs. <br /> <br />Operation of the Fryingpan-Arkansas Project -1-9 <br />