WSP09372 - Laserfiche WebLink

Home Browse Search

'001276 . . Draft Task 7 Technical Memorandum Significant shortages occur in the Yampa River basin under future demand conditions when the Juniper instream flow right is in place unless additional storage is available. All three of the modeled new storage projects mitigate these future shortages to some degree but only Scenario IV (Elkhead Reservoir and Stagecoach Reservoir enlargement) eliminates them entirely. Conversion of the Juniper Project water right to an instream flow would be based on the contemplated draft of the project if it had been built. The instream flow water right would reflect the pattern of use that the Juniper Project would have had if in place. The priority of the Juniper instream flow right has an important affect on the amount of shortages which occur in the basin. As currently represented in the model, the instream flow right has a 1954 priority date. A more senior right would probably result in more shortages to demands in the basin. The Juniper Reservoir decree includes a subordination to 65,000 af of consumption by in-basin junior users. Had the project been built, the reservoir would not have placed a call on the upstream users until the upstream consumption under junior rights had reached a total of 65,000 af per year. Analysis of the current water usage of those rights junior to 1954 indicated that a maximum of approximately 36,663 afof water use junior to 1954 currently occurs in the Yampa Basin, approximately 28,480 af of which occurs on the Yampa and its tributaries above the confluence with the Little Snake River. This 28,480 af comprises 6,617 af of storage depletion and 21,863 af of direet flow depletions. As discussed in a previous section of this memorandum, approximately 24,200 af of the total junior depletions were explicitly represented in the model. Considering demand projections utilized in this study, it is unlikely that the entire 65,000 af subordination would be exhausted even under the long-term (2040-level) demand scenario. The effect of the subordination on an instream flow would be to permit junior users to divert physically available water as they needed it, if the Juniper Project were ever built or its associated water rights were converted to other uses, until the Division Engineer had determined the 65,000 af had been consumed. Water users would continue to realize shortages that they now experience due to lack of supply on tributaries and possible mainstem calls by the Maybell Canal. The undesirable situation of the reduced flows in the Yampa River during the late irrigation season would continue and, ultimately, grow worse. The modeling performed for this study, i.e. the scenario with no new storage but with the instream flow right in place, indicates that, should the instream flow water right have a 1954 priority date and the 65,000 af subordination exercised, additional storage is still required to satisfy projected demands in the Yampa River Basin. This follows from the fact that the subordination can only benefit water users if there is a sufficient physical water supply in the basin. In addition to providing water to projected demands, new storage in the basin will provide opportunities to help late season flow in the Yampa River. Currently, many segment 1> of the Yampa River, including those important to the endangered fish, realize less than desired stream flows at certain times of the year. For the past several years, the Division Engineer has utilized water "borrowed" from existing storage facilities to prevent river flows in the lower sections of the river from being completely cut off by diversions. This praetice has provided two benefits: 1) it has prevented the need to place a mainstem call on the Yampa River and 2) it has provided a minimum amount of flow for utilization by aquatic life in the river. 21