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~ V. ) ~""",. t.~.,;.~.". ,.,... '. ) n.... . ,-.-~'.' :;..:- ~ -~j INTRODUCTION A number of entities with water rights in Bear Creek have requested various amounts of storage space in Bear Creek Reservoir for various purposes. The Colorado Water Conservation Board (CWCB) is one of these entities and has requested 2,000 acre~feet of storage space over and above the permanent pool. The various entities will store water attributable to "changed" direct flow rights or by vinue of storage rights. The CWCB fits into both of these categories. Most of the filling will normally occur during the high runoff months of May and June for storage rights, and direct flow rights will be stored as a result of a decree granted by the Water Court. For most entities, releases will occur during the non-irrigation season or during dry months when augmentation water is needed. Evaporation losses from the permanent pool and accounts will be debited to each entity according to an agreed upon formula. The current thinking is that CWCB will make up 50 percent of the permanent pool evaporation losses and the remaining 50 percent of the permanent pool evaporation losses will be debited to each entity in proportion to the volume of storage requested and granted. Each entity will cover evaporative losses from its account completely. The filling and releasing of storage water, in addition to evaporation losses, will cause a rise or fall in the reservoir level of Bear Creek Reservoir as the State Engineer administers these decrees. Because the City of Lakewood has an agreement with the State to provide recreation facilities near the lake, it is concerned with fluctuations in the lake. Accordingly, the various entities seeking storage have agreed to participate in a simulated operation study that will model the effect of inflows and releases by the various entities, plus evaporation losses, for the purpose of identifying extremes in the lake level . fluctuations. The years 1949 through 1957 were selected as the period of study. This period includes the wet years of 1949, 1952 and 1957, the drought cycle of 1954 through 1956 and the more average type of years such as 1950, 1951 and 1953. Also, this period encompassed a period when agriculture was the dominant use of water diverted from Bear Creek just prior to the urbanization of the area. PURPOSE AND SCOPE The primary purpose of this report is to quantify the storable flows avai!able to the CWCB's water rights for the 1949.1957 period. Whenever applicable, the Bear Creek Water Rights Computer Model will be used as an aid to quantify CWCB's storable flows. Also taken into account will be the South Plane River calls which have not been inputed into the Model. Storable flows will be calculated on a daily basis and summarized monthly. The CWCB's evaporation losses, releases and other commitments fur its water will not be quantified in this report. The CWCB will do so later. 89-026.00W