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29')'-' k...1 xl to capture such flows when they occur and hold them until such time as they can be used beneficially. , The water supply of the lower South Platte Valley is and will continue to be significantly changed by return flows resulting fro~ operation of the Colorado- Big Thompson Project and by prospective upstream irrigation and sto~ge develop- ments (Blue-2iouth natte Project and City of Denver diversions). It is estimated that \lith the Colorado-Big Thompson in operation an average of 64,000 acre-feet annually of otllernise wasted llater will be made available from storage in Narrows. The Colorado River Compact of November 22, '1922, states that the States of the Upper Division shall not withhold water, and the States of the Lower Division shall not require the delivery of water vh ich cannot reasonably be applied to domestic and agricultural uses. The 2iolicitor of tlw uepartQent of Interior fo~~d in a decision in 1936 that the compact authorizes diversion of Colorado Hiver water into another watershed if such water is to be used within the boundaries of a state through which tl1e Colorado hiver passes and if such use is not in excess of that allowed by the comFBct. The Colorado-Big Thompson Project is a project using Colorado Eiver water out- side of the Colorado l~iver Basin and under the terms of the compact must apply the diverted water to agriculturel or domestic use. After the first use of water, return flows will develop. "'hile the first use of the' water will probably satisfy any legal requirements as to applyinG the water to beneficial use, it is apparent that Colorado's position in regard to use of Colorado !liver water will be enhanced against any claims by lovler basin states if the ::>tate :-,as made an effort to exh"us- tively use the Colorado River \later ,~thin the State. Alternate 2iites Prior to the selection of the most feasible site for a reservoir that would provide flood control and conserv~tion storage for the 10',ier reaches of the ::>outh Platte River, studies were made of six different damsites on the ~outh Platte River, in Weld and Morgan Gounties. Designated in dorulstrea~ order, they are: Hardin, Goodrich, Vleldana, lIarrows, Fort Morgan, and Old Fort i,iorsan sites--the only sites found in the vici::.it;;" that could conceivably be considered as alternates for accomp- lishing the sarr.e purpose as the j';u-rows Dam. First, let ~e explain the operation of a flood control reservoir. As you realize, there are two main conditions which ca~se floods on the South Platte River- the first is the meltinG of snow in the upper reaches of the river; the second, intense rains uhich may occur any place on the l'Iatershed. A snowmelt flood occurred in 1949 and, of course, the jfay 1935 flood on Bijou Creek is a good example of an intense rain flood. Rain-caused floods have occurred simul taneou,sly wi t;l snowmelt floods such as happened in 1921. Althoup:h we can partially ;.;redi<;t the occurrence of a snowmelt flood, we have no basis for rredicting intense rains. Consequently it is necessary to have capac:i.ty available for use at the tir,e a flood mi[;ht occ~. A good flood contr~l reservoir is an empty reservoir.