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<br />3.8 <br /> <br />.':,.' <br /> <br />The average annual yield of the Colorado Rivei~asin <br /> <br /> <br />above the Cameo gaging station from 1948 to 1980 is approximately 2,665,000 <br /> <br />acre-feet. Table 3.4 gives mean monthly flows for the Colorado River at the <br /> <br /> <br />Cameo gaging station for probable wet, probable dry and probable average <br /> <br />years. Flows in the Colorado River are depleted by transmountain diversions, <br /> <br />on the colorQdQ ~iier. <br /> <br />including the City of Denver's Roberts Tunnel, the Colorado-Big Thompson <br /> <br /> <br />Project, the Homestake project and the Fryingpan-Arkansas Project. <br /> <br /> <br />Whenever the flow in the Colorado River is insufficient to meet the <br /> <br /> <br />senior rights in the Grand Valley, a shortage of water is indicated. The <br /> <br /> <br />Ruedi Reservoir storage rights and Fryingpan-Arkansas diversion rights are <br /> <br /> <br />junior relative to the Grand Valley rights, therefore when the diversion <br /> <br /> <br />system is operating, a replacement release would be required. All water <br /> <br />rights decreed for irrigation and power, active or inactive, total about 2.98 <br /> <br /> <br />million acre-feet for the Grand Valley area (4,110 cfs). Over the years, some <br /> <br />of these rights have been abandoned and others transferred as water delivery <br /> <br /> <br />systems were combined and improved. The present maximum demand for irrigation <br /> <br /> <br />and power under all active decrees is about 1.74 million acre-feet per year <br /> <br /> <br />(2,410 cfs),. This includes 524,000 acre-feet per year (725 cfs) for the Grand <br /> <br /> <br />Valley Project pumping plant and the Orchard Mesa power plant (Grand Valley <br /> <br /> <br />Project, Historical and operational Information, c. 1980), Review of the <br /> <br />historic operation of Green Mountain Reservoir has shown that the flow at the <br /> <br /> <br />Cameo gage has averaged 1.61 million acre-feet per year (2,230 cfs) when a <br /> <br />call for water from Green Mountain Reservoir has been imposed to meet natural <br /> <br /> <br />flow shortages (Colorado River Accounting Sheets, unpublished, USBR). This <br /> <br /> <br />flow has ranged from a low of 1.21 million acre-feet per year (1,680 cfs) to a <br /> <br />high of 1.94 million acre-feet per year (2,680 cfs). For the operation stu- <br /> <br /> <br />dies of Ruedi Reservoir, it was assumed that a call for water from the reser- <br /> <br /> <br />voir for replacement purposes would occur whenever the flow at Cameo fell <br /> <br /> <br />below 1.62 million acre-feet per year (2,240 cfs). <br /> <br />Releases are made from Green Mountain Reservoir primarily for senior <br /> <br /> <br />water rights associated with the Shoshone Power Plant and secondarily for the <br /> <br /> <br />same purposes as releases from Ruedi Reservoir. Pursuant to Senate Document <br /> <br />80, releases are made from Green Mountain to make up natural flow shortages in <br /> <br /> <br />the Colorado River. The shortage is determined at the Dotsero gaging station <br /> <br /> <br />under the assumption that if shortages are met at that location then water <br /> <br /> <br />rights downstream will be met with the addition of flows from the Roaring Fork <br /> <br />River. <br />