WSP03293 - Laserfiche WebLink

Home Browse Search

2 Base Case The STATEMOD Base Flow Module creates a set of "base stream flows" which have the impact of historic diversions, return flows, and reservoir storage, release, evaporation and seepage removed. The Service requested that base streamflows be prepared for two locations, (1) the Cameo gage, and (2) at the top of the l5-Mile Reach. The Service defmes the base case streamflow at the top of the l5-Mile Reach as baseline flow for purposes of discussion in the biological opinion. !:j Scenario The C, scenario includes all depletions as of September 30,1995. The C, scenario is a modification of the C, or Calculated scenario (the C scenario is one of the standard STATEMOD data sets; it reflects historic gage conditions, with the main exception that the irrigation demands are calculated from average irrigation efficiencies for the study period, 1975 to 1991). The C, scenario expands on the C scenario by taking the major diversions and operations in the basin, and backcasting their current (as of the end of water year 1995) level of demand throughout the study period. For example, Windy Gap started operating in water year 1985. With data from the Northern Colorado Water Conservancy District, CWCB has implemented a 1995 level of demand for Windy Gap in the model for 1975 to 1991. Other major diversions that have been backcasted are shown below. Existing projects with backcasted demands (for their 1995 demand level) in Cj scenario, with their minimum, maximum and average annual depletion (acre-feet) in the Cj run (1975-91) Minimum Maximum Average >Roberts Tunnel 8,594 127,570 59,154 >Moffat Tunnel 27,948 78,107 58,389 >Colorado Big-Thompson Project 175,800 281,839 236,489 diversions through the Adams Tunnel >Windy Gap diversions through 2,498 32,568 18,779 the Adams Tunnel >Homestake Project 6,439 51,997 29,538 >lndependence Pass Tunnel 16,934 82,687 49,527