Laserfiche WebLink
The reservoir is normally operated to draw down storage during the winter months by the <br />diversion of water through the Adams Tunnel to storage in the East Slope reservoirs of the CBT <br />Project (Horsetooth and Carter Reservoirs). The reservoir is then filled during the following <br />spring runoff. Historic EOM storage contents for the reservoir were obtained from the USBR and <br />are incorporated into HydroBase. Pursuant to the requirements of Senate Document 80, releases <br />are made from Granby Reservoir to ensure a minimum streamflow in the Upper Colorado River <br />below the dam. During the non-irrigation season, October 1 through Apri130, the required <br />release is 20 cfs, measured at the stream gage below Granby Dam (Gage ID 09019500). During <br />the irrigation season, the minimum release is measured below the headgate of the Coffee- <br />McQuery Ditch (about two miles downstream of the dam) and is 75 cfs from May 1 through July <br />31, 40 cfs during August, and 20 cfs during September. <br />Granby Pumping Plant and Pump Canal (WDID 510678). This facility is used to transfer <br />water from Granby Reservoir to Shadow Mountain Reservoir for delivery to the Adams Tunnel. <br />The plant has three pump units but normally only uses two. The pumping capacity is a function <br />of the number of pumps being used and the water levels in Granby Reservoir and is estimated to <br />range from 340 cfs to 620 cfs. <br />Willow Creek Reservoir (WDID 513710). This reservoir is used to collect and store surplus <br />water in the Willow Creek drainage and transfer that water to Granby Reservoir via the Willow <br />Creek Pump Canal and Willow Creek Pumping Plant. The reservoir commands a drainage area <br />of about 134 square miles. Inflows to the reservoir are calculated by the USBR using storage <br />content and release data. These calculated inflows were obtained from the USBR and are <br />incorporated into HydroBase. Average annual inflow is approximately 33,700 acre-feet. <br />Willow Creek Reservoir has a total storage capacity of 10,553 acre-feet of which 1,486 acre-feet <br />is dead storage and 9,067 acre-feet comprises the live storage (inactive storage of 5,738 acre-feet <br />and active storage of 3,329 acre-feet). Operation of the reservoir is normally only within the <br />active capacity of 3,329 acre-feet (above elevation 8,117). In general the reservoir is operated to <br />draw down storage to elevation 8,116 (equivalent to a total capacity of about 7,015 acre-feet) by <br />late October or early November by pumping to Granby Reservoir. This provides capacity for <br />storage of the winter inflows and the following spring runoff. In the spring, the available inflows <br />are pumped to Granby Reservoir and the water in the active storage capacity above elevation <br />8,117 (equivalent to a total capacity of 7,224 acre-feet) is pumped to Granby as soon as possible. <br />After pumping commences, when the active capacity is drawn back down to elevation 8,117, <br />pumping is curtailed. After this drawdown in the spring, the pumps are operated as necessary to <br />maintain the minimum elevation at 8,117. <br />When inflows (minus required releases) exceed pumping capacity, the active pool is filled to <br />elevation 8,129, at which time the outlet gates are opened to release excess flows to Willow <br />Creek. <br />Willow Creek Reservoir is designed to store that portion of the Willow Creek streamflow above <br />the quantity required for downstream fishery flows and to meet the vested water rights of <br />downstream water users. Criteria for the fishery flows require that during the non-irrigation <br />Upper Colorado River Basin Information 2-4 <br />