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<br />(- <br /> <br />r.e <br /> <br />b. Sedimentation <br /> <br />The Contractor shall conduct a study of sedimentation in <br />the Colorado River basin at the upstream end of the <br />project site in order to develop an estimate of sediment <br />inflow and deposition in Una Reservoir. In this regard, <br />the Contractor shall: <br /> <br />(1) Collect and review all existing data pertinent to <br />the sediment yield of the basin, including yields <br />at existing reservoirs in the area. <br /> <br />(2) Estimate the sediment yield at the dam site based <br />upon suspended sediment data currently being <br />collected near DeBeque, streamflows, and Soil <br />Conservation Service (SCS) sediment yield maps. <br /> <br />(3) Determine the reservoir trap efficiency by the use <br />of Churchill's and Brune's methods, or such other <br />suitable techniques as the Contractor may elect to <br />use. <br /> <br />(4) Distribute the 50- and 100-year sediment <br />accumulations within the reservoir in order to <br />determine revised reservoir capacity curves and the <br />depth of sediment expected at the dam. The <br />empirical area-reduction method or other suitable <br />method will be used. This study of sedimentation <br />shall be subject to the State's review and approval <br />bef ore it is u sed in subsequent work t a.sks. <br /> <br />Task 8 - Water Rights Evaluation and Storable Water Analysis <br /> <br />The Contractor shall conduct such analyses as are <br />necessary in order to determine the monthly flows physically and <br />legally available for storage at Una Reservoir for a 30-year <br />hydrologic period for each of three scenerios of conditional <br />decree assumptions, and to ascertain the required releases for <br />downstream water rights. The output of this work task will be <br />input to Task 9. The storage rights available to the Una <br />Reservoir shall be assumed to be those storage rights decreed to <br />the Colorado River Water Conservation District for the Una and <br />Placita Reservoirs. <br /> <br />The methodology to be utilized shall include the <br />fo tlowing steps: <br /> <br />a. Generate a 30-year record of monthly virgin flow at Una <br />Reservoir by correlation of the short-term record of the <br />USGS gage "Colorado River near DeBeque" with the <br />long-term gage record for "Colorado River near Cameo," <br />and by appropriate adjustments for transmountain <br /> <br />-7- <br />