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<br />.-) ,.. """"' (i <br />J \; i (, <br /> <br />. <br /> <br />hydrology studies. Under future "with" project conditions, the total <br />service provided these lands is equal to that provided the historically <br />irrigated land. No supplemental water is provided for the 6w lands. <br /> <br />Narrows Dam and Reservoir will serve the lower South Platte <br />Valley in a multiple-purpose capacity by providing flood control, <br />conservation storage for irrigation water, sediment control, fish <br />and wildlife enhancement, and recreational facilities. Long-term <br />records of South Platte River Flow show an average annual discharge <br />at the Colorado-Nebraska State Line of about 315,000 acre-feet. Only <br />a small part of this outflow is needed to comply with the South Platte <br />River Compact with Nebraska. This excessive outflow suggests that <br />water requirements in Colorado are being met. However, this is not <br />the case. Shortages have actually been experienced during years \olhen <br />excessive flows escape into Nebraska. This situation clearly indicates <br />the need for storage of irrigation supplies in Colorado. <br /> <br />This appendix summarizes hydrologic analyses made during the <br />feasibility investigations for the Narrows Unit. Included are <br />studies of water supply, water requirements, water utilization, <br />quality of water, flood control, and sediment control. <br /> <br />. <br /> <br />WATER RESOURCES <br /> <br />Surface Water Supplies <br /> <br />The only significant surface water source for irrigation use <br />comes from the South Platte River. During the period of study, <br />19l+7 through 1961, the average annual flow of the South Platte <br />River at Kersey,Colorado, was 537,200 acre-feet. At the Narro\ols <br />Damsite, the average annual flow was about 365,200 acre-feet per <br />year. Of the 365,200 total flow at Narrows, an average of 187,700 <br />acre-feet per year was surplus and flowed out of the state unused. <br />It is from this surplus flow that the project supply could be <br />developed. Because the surplus flow OCC,ITS either during the <br />nonirrigation season when there is no need for diversions under <br />direct flow rights, or during periods of high flow caused by <br />snow-melt or rainfall runoff \olhen the flow exceeds the direct <br />diversion needs or capabilities, an on-stream storage reservoir is <br />required to develop the new supply. The need for storage is also <br />demonstrated by the variation in annualstorable "low - 5,100 acre-feet <br />in 1953 to 485,000 acre-feet in 1958. The analysis of surplus flow <br />takes into account recorded flows at the gaging stations along the <br /> <br />. <br /> <br />2 <br />