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measurements of reservoir contents reflect the original elevation-capacity relationship <br />shown in Table 1. <br />Enlargement History: Prewitt Reservoir has never been enlarged. <br />Reservoir Storage Measurement: Storage levels in Prewitt Reservoir are measured using a <br />stilling well within the embankment. Because the stilling well is connected to the <br />reservoir outlet pipes, measurement is only possible when water is not being released. <br />Measurements are made using elevation marks on the concrete face of the dam during <br />periods of reservoir release. <br />Releases from the reservoir into the outlet canal are measured at a double V-notch weir <br />with a clock recording device located below the embankment. Releases are measured by <br />the District Manager and reported to the State. Releases to the river and deliveries to the <br />South Platte Ditch via the Highline Canal are reported separately. Releases to the <br />Highline Canal are measured by a Parshall flume. Flow measurements are not made on a <br />seepage ditch that is located below the embankment to collect reservoir seepage loss. <br />Reservoir Seepage/Evaporation Information: No studies have been conducted to quantify <br />seepage losses from Prewitt Reservoir, although large seepage losses have been reported. <br />A constant inflow of 35 cfs is reportedly required to offset these losses. Prewitt Seep <br />Ditch, a seepage ditch located below the reservoir embankment, collects reservoir <br />seepage and conveys the seepage water over the South Platte Ditch and under Prewitt <br />Outlet Canal, discharging the collected seepage to the South Platte River. <br />Evaporation losses from the reservoir are estimated to be approximately 4 feet per year. <br />Evaporation is not measured at the site. <br />HydroBase Data: End-of--month contents are available in HydroBase under the Prewitt <br />Reservoir structure for the 1950 to 2003 time period. Additional end-of--month contents <br />are also available under the Prewitt Reservoir structure in Water District 1. Paper records <br />of storage contents were provided by the Prewitt Reservoir Manager for the period of <br />1913 through 1989. Due to the completeness of the paper records, Figure 4 displays the <br />paper records for the period of 1950 through 1989, and then Hydrobase records from <br />Prewitt Reservoir in Water District 1 from 1990 to 2002. <br />Prewitt Reservoir.doc Page 10 of 15 <br />