SWSI Environment and Recreation Needs and Priorities TRT Draft

Home Browse Search

The model simulations show that to achieve a firm yield of 4,000 AFY, for example, without minimum reservoir capacity considerations (Alternative A), approximately 8,000 AF of storage is required. Alternatively, for the same system but with a minimum permanent pool requirement of 30 percent (Alternative B), approximately 12,000 AF of storage is required. The additional storage requirement (4,000 AF) for Alternative B would allow for the capture and storage of a greater percentage of the legally available flows, which can then provide the minimum pool. The acquisition of additional water rights may be required for the implementation of Alternative B. Costing of the two reservoir options could then be performed and assessed relative to the recreational benefits gained from maintaining the minimum pool. This analysis assumes that reservoir releases for firm yield are taken out of the river at the reservoir and not released from the reservoir and carried downstream where the releases could help meet instream flow targets. As a second example, Figure 2 shows model simulations for a hypothetical reservoir located on Little Bear Creek in the Yampa River basin. Predicted yield curves are again a function of legally available flows for the location, as predicted by the Yampa River basin CDSS. For this analysis, the two curves shown on the figure correspond to: Alternative A - A management alternative in which no minimum release requirements are maintained. Alternative B - A management alternative that follows the approach outlined by The Nature Conservancy in the paper "How much water does a river need?" This approach maintains average historical monthly flows, minus 1 standard deviation, downstream of the reservoir. 6,000 1,000 -without minimum releases 5,000 - - with minimum releases (TNC) 4,000 >= i:i: ~ :E 3,000 CI) .~ E \t: Average Annual Available Flow = 10,900 AF 2,000 .. .. .. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~- ~-- ~ ~ ~ ~ ~ ~ ~ ~ -- .. .. -- .,. .,. .,. .,. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~, ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .. .. .,. .,. o o 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 reservoir size (AF) Figure 2 Example Storage to Yield Curve for Environmental and Recreational Options: Instream Flow Little Bear Creek Reservoir - Yampa River Basin: Agricultural Use ~5\^ISI S.lal~.....ide WeIer Supply Initiclive DRAFT CDIVI C:\DOCUMENTS AND SETTINGS\ROWANNC\DESKTOP\SWSI\RICKREDREC_ENV WHITE PAPER_1 Q-4-QS.DOC 17