C154141 Feasibility Study - Laserfiche WebLink

Home Browse Search

whether it could do so and still have yield for other uses. The model showed that the smaller reservoir's firm yield was not quite up to 58,300 af; hence no non-irrigation demand was modeled for the small reservoir. 2. Municipal and Industrial Demand AECOM assigned 23 percent of the project yield to M&� demands to determine the approximate proportion of the yield attributable to non-irrigation uses for the large reservoir. The percentage is based on the Clay Report's references to 40,800 af of M&I use, out of a project yield of 178,000 af/yr. Monthly distribution of this annual demand was estimated by blending two sources of information: the CDSS Baseline demand for the City of Grand Junction, and Ute Water Conservancy District's Plateau Creek Pipeline Replacement Project Draft Environmental Impact Statement. The two monthly patterns were averaged. For instance, April use in the Ute EIS is 6.8 percent of total annual use, and CDSS shows that Grand Junction's April use is 7.6 percent of the annual total. Accordingly, AECOM used 7.2 percent of the annual total M&I use occurring in April. 3. Endangered Fish Flow Demand The U.S. Fish & Wildlife Service (USFWS), through the Colorado River Recovery Program, has identified late summer target flows in the 15-Mile Reach, which vary with the hydrologic year type. The late summer target flow in Dry years (100 to 80 percent exceedance years) is 810 cfs, and for Below Average years (50 to 80 percent exceedance years), is 1240 cfs. East Slope and West Slope water providers in the Upper Colorado Basin were obligated to permanently supply 10,825 acre-feet of water per year (10825 Water) to assist with meeting these targets: The USFWS has several sources of augmentation water in other reservoirs and utilizes these sources for current operations which allow the flow recommendations to be met. It is possible that additional augmentation water could allow the flow recommendations to be met at all times, however, no present budget exits for purchase of water for this purpose. It was assumed that 17 percent of Grand Valley Lake yield would be devoted to this use. The percentage was based on the Clay Report's use of 61,100 af (i.e., 400 cfs for the 77 days from July 15 through September 30) in half the years, out of a yield of 178,000 af. Uniform releases were assumed to occur from mid-July through September. Based on the 10825 study information (Grand River, 2007), AECOM assumed that late summer releases from Grand Valley Lake to the 15-Mile Reach would be beneficial in 1 out of 2 years, that is, during the Dry and Below Average years per USFWS target designations. However, the usefulness of flow supplementation from the Grand Valley Lake in relation the Recovery Program goals may not coincide with other options currently under moving forward in the 10825 process. If the Grand Valley Lake Project is studied in more detail in the future, it will likely be necessary to revise 40 � AECOM 2/22/10 '