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<br />Operations: When Denver Water has filled the surcharge pool at Eleven Mile, which <br />typically occurs in July, bottom releases will be made when possible to meet the <br />temperature target below the dam through September. It is expected to take some <br />experience in blending spill and bottom releases before the target is consistently met. <br />Through experience, Denver Water will develop a system for blending releases so as to <br />minimize operational changes while meeting temperature targets. When possible, Denver <br />Water will provide a temperature gradient of less than lOOP per day when making the <br />transition into and out of bottom releases. In the future, bottom releases for moderating <br />wintertime stream temperatures will be considered. <br /> <br />Bottom releases will be made provided they can be recaptured without loss in Denver <br />Water's downstream facilities, the resulting lost storage in Eleven Mile can be recovered <br />in the next runoff, and there is no impairment of water rights. During years of high <br />streamflow, reservoirs downstream of Eleven Mile may be fullt Under these <br />circumstances, Denver Water may not be able to make bottom releases for temperature <br />moderation. Bottom releases will not be made if it would cause the reservoir to stop <br />spilling. Starting no later than October 1, bottom releases would be discontinued to allow <br />the surcharge pool to fill and complete the cycle4 However, while the surcharge pool is <br />being filled the minimum streamflow will be maintained as described in this Plan. <br />Implementation of these operations will be reviewed at the Annual Operations Meeting. <br /> <br />The limited water available for supplemental bottom releases will first go toward <br />maintaining minimum streamflow and secondarily for temperature moderation. <br /> <br />~ Cheesman Reservoir <br /> <br />Cheesman Reservoir, as the workhorse of Denver Water's South Platte system, usually <br />makes bottom releases except for a few months during wet years. During those spill <br />events., downstream temperature could rise above 600 F. <br /> <br />An experiment was conducted in 1997 to test the reservoir operator's ability to manage <br />temperature downstream of the reservoir during spill operations. Inflows were relatively <br />low) which resulted in a relatively easy-to-manage situation. As a result, daily <br />temperature changes were kept to within a few degrees. A year similar to 1995 presents a <br />much greater challenge where the inflow during spring runoff essentially tripled within <br />three days to a streamflow that nearly exceeded the capacity of the reservoir outlet works. <br />Although managing temperature under such high streamflow is beyond the physical <br />capabilities of the reservoir, temperature can be moderated at other times that the <br />reservoir is spilling. <br /> <br />Tasks: Denver Water will install temperature gages in the spillway, the valve manifold, <br />and the streamflow gage downstream of the dam4 <br /> <br />Operations: When possible, Denver Water will adjust the proportion of spillway <br />discharge and bottom releases to 1) keep the downstream temperature while spilling <br /> <br />N :\Supply\ Waa ge\wiIdscen\attachb. doc <br /> <br />B-12 <br />