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<br />e <br /> <br />c. Reservoir Evaporation <br />Reservoir evaporation in the upstream basin was considered <br />to increase linearly over the years, based on the <br />assumption that 1% of the basin is covered by reservoirs <br />and that a net of 1 ac-ftjacre of surface area would <br />evaporate each year. Based on the above assumptions, total <br />reservoir evaporation for the basin ranged from 15,000 ac- <br />ft in 1940 to 30,000 ac-ft in 1984. <br /> <br />3. <br /> <br />Existing Downstream Demands <br />There are several downstream water rights that have been <br />perfected (made absolute) and have, in the past, called for <br />water. They can be summarized in two general categories. <br />First, there is a senior winter "call" of 800 cfs, equivalent to <br />around 290,OOO ac-ftjyr, for a hydropower right that diverts <br />from the Grand Valley ditch headgate. <br /> <br />e <br /> <br />Second, there is a series of irrigation water rights that have a <br />cumulative practical call of 2,000 cfs, which is equivalent to <br />about 720,000 ac-ft during the six-month irrigation season. <br /> <br />The diversions for municipal and industrial use from the <br />Colorado River between Webster Hi 11 and Grand Junction are not <br />now significant. For their analysis, WWE has assumed the <br />present downstream demand for the above uses to be 5,000 ac- <br />ftjyr. <br /> <br />It has been assumed for the existing conditions that there are <br />no oil-shale diversions, no active federal water rights, and no <br />minimum stream flow calls. <br /> <br />e <br /> <br />D. FUTURE WATER DEVELOPMENT <br />Just as present river development conditions affect the water yield <br />of the Webster Hill Reservoir, so do future water development condi- <br />tions. It is difficult to anticipate the extent of future water <br />resource development in the river bas in. However, WWE establ ished <br /> <br />3686-aj6 <br /> <br />11-4 <br />