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<br />Reservoir Operation Adjustments <br /> <br />There was a policy change in 1983-1984 regarding the operation of Green Mountain Reservoir. <br />Prior to 1983, Green Mountain was operating with a 100,000 afpool for West Slope users and a <br />52,000 af pool for the Colorado - Big Thompson Project ( CBT ) replacements. Prior to 1983 <br />releases for West Slope users were limited to the period April 15 to October 15, with the primary <br />purpose of maintaining 1,250 cfs at the Shoshone Power Plant. Since the policy change there is no <br />season limitation and only 66,000 af of supplemental water is available for senior water rights <br />perfected prior to 1977. The 66,000 af of water attempts to quantify the Cameo call needs of historic <br />Green Mountain Reservoir beneficiaries and leaves the balance for future water sales. <br /> <br />There are many unknowns to consider, including the operation of the Orchard Mesa Check, when <br />adjusting the historic downstream gaged flows to reflect the current operation of Green Mountain <br />Reservoir. Therefore, a simplified approach was selected. The approach is that during the summer <br />months Green Mountain Reservoir will make releases to maintain the Colorado River Cameo gaged <br />flow at 2,260 cfs. This release is made in conjunction with limiting transmountain diversions. <br /> <br />The 2260 cfs is the total decreed amount for the water rights associated with the "Cameo call" and is <br />the amount the Division Engineer administers the river. Sensitivity runs were made at the 1950 cfs <br />and 1720 cfs demands levels to see if streamflow amounts at the 15 Mile Reach would change <br />significantly. No significant change was noted except in the month of August where differences <br />were seen during low flows periods. These differences were not considered significant to change the <br />demand to a reduced amount. Based on the sensitivity runs and the fact that the Division Engineer <br />currently administers the river at the 2260 cfs level, the physical supply study as done using a <br />"Cameo call" at 2260 cfs. <br /> <br />If the Cameo gage shows less than 2260 cfs, then lransbasin diversions were reduced to zero. If this <br />curtailment still does not increase the flow at the Cameo gage to 2260 cfs, then releases would be <br />made from Green Mountain Reservoir. Since the Orchard Mesa Check is currently being operated <br />differently then it was in 1977, this study shows more than 66,000 af water being released from <br />Green Mountain Reservoir <br /> <br />9 <br />