WSP08813 - Laserfiche WebLink

Home Browse Search

o U tl3 :1 5 (1) During the winter months, the reservoir is operated to draw its storage down by approximately 50,000 acre-feet, with the lowest point of storage generally occurring in April. This drawdown is accomplished by a release (bypass) to maintain a minimum flow in the Blue River below the dam at 50 cfs and by winter diversions through the Roberts Tunnel at a rate of about 100 cfs. The tunnel diversion is used to help minimize icing problems in the North Fork of the South Platte. (2) Beginning in May, Dillon Reservo,ir bllgins to fill. INote that there is genellllly sufficient Inflow to Dhvsicallv fill Dillon Reservoir in most years; the inflow exceeds 100,000 acre- feet even in dry IUnoff yearsl. Denver monitors the filling of its east slope reservoirs (using the east slope storage rights) and evaluates the potential need to divert water from the Blue River too ensure a fill of the South Platte reservoirs. If it is projected that the east slope reservoirs will need additional water, diversions through the Roberts Tunnel are initiated. The majority of these diversions occur in June and July. (3) The water rights for Dillon Reservoir and the Roberts Tunnel are junior to the downstream Green Mountain Reservoir and technically would not be allowed to store/divert until Green Mountain fills. However, in accordance with a number of decrees and agreements (see following discussionl, Denver is allowed to temporarily store water in Dillon Reservoir, out- of-priority with respect to storaae in Green Mountain, if there is a reasonable likelihood that the latter will fill using inflows between Dillon and Green Mountain (including all required bypasses at Dillon). Denver accounts for this "Green Mountain Account" in its operation of Dillon Reservoir. If Green Mountain, fails to achieve a "Blue River Decree Fill", Denver must release the water it stored and/or diverted out of priority. In determining the Blue River fill entitlement, all water diverted pursuant to the United States' direct flow water right at Green Mountain for power generation (1,726 cfs) is not included. Denver has separately negotiated to repay out-of-priority storage with respect to these hydro diversions on the basis of power interference using other sources of power. In accordance with the provisions of the Blue River Decree and agreements with the USBR, Denver can also repay Green Mountain by substituting water from Williams Fork Reservoir and/or Wolford Mountain Reservoir. In fact, this is the normal method of replacement. (4) According to Denver, Dillon Reservoir generally fills by June 30. If and when it is determined that Green Mountain and Dillon will fill and spill, it is Denver's policy to divert as much water as possible through the Roberts Tunnel, providing that there is an east slope need: la) to complete the fill of Denver's east slope reservoirs; or (b) the Roberts Tunnel water can be used directly to meet municipal demands. (5) When Dillon stops filling because of decreasing inflows or because of a senior downstream call, Denver stops direct flow diversions through the Roberts Tunnel and begins to deliver storage water' from the reservoir through the tunnel. In accordance with the terms of the Blue River Decree and other operating policies of Denver, the Blue River supply is generally the last source of water used by Denver to meet its municipal demands (after use of native South Platte sources and transmountain diversions through the Moffat system. (6) Denver has agreed to maintain a minimum flow in the Blue River below Dillon Dam of 50 cfs or the reservoir inflow, whichever is less. In 1987, Denver constructed a hydroelectric 0-9