10825 Water Supply Alternative Summary Phase 2 Assessment January 2008 Draft

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Reservoir, along with the release of an additional 2,700 acre feet to compensate Denver Water for past releases from Williams Fork Reservoir. While this alternative meets all of the primary objectives of the study, it does not meet secondary considerations. In below average and dry years, Ruedi Reservoir would release 13,525 acre -feet of water. These increased releases will have the most adverse impacts to the Fryingpan River of any alternative studied. Further, water currently released from Williams Fork Reservoir would be released from Ruedi Reservoir in these drier than average years, resulting in lower stream flows in the upper Colorado River than would otherwise exist. This alternative is not recommended for further consideration. 7.3 SULPHUR GULCH PAIRED WITH WILLIAMS FORK RESERVOIR (Alternative C4) This alternative would provide different amounts of water from Sulphur Gulch and Williams Fork Reservoirs from year to year, depending upon whether it was a drier than average, or wetter than average year. It would operate the same as Alternative C3, only with Sulphur Gulch releases instead of Ruedi Reservoir releases. While this alternative meets all of the primary objectives of the study, it does not meet secondary considerations. This alternative would decrease the amount of water in the Colorado River below the confluence with the Williams Fork by 2,700 acre feet in below average and dry years, when releases would instead be made from Sulphur Gulch. This coincides with the years that Williams Fork does not fill. This alternative is not recommended for further consideration because changes below Williams Fork Reservoir would either have neutral or negative impacts to aquatic conditions when compared to other proposed alternatives. It may also require the construction of a larger Sulphur Gulch Reservoir, in order to meet the increased dry year release demands. 7.4 WOLFORD RESERVOIR EXPANSION & PUMPBACK WITH RUEDI (Alternative C5) This alternative would supply 5,412 acre -feet from an enlarged Wolford Mountain Reservoir and Ruedi Reservoir would supply the other 5,412 acre -feet in each and every year. The Wolford Mountain Reservoir enlargement would be filled by a pump station from the Colorado River. This alternative is not recommended for further consideration for several reasons. First, the alternative cannot supply 5,412 acre feet in dry years such as 1977, without impacting the marketable yield of the reservoir. Second, this alternative is not recommended for further study because of the more significant wetland impacts of Wolford Mountain Reservoir when compared to other structural alternatives. As a result, this alternative does meet the primary objectives of the study. Any alternative that utilizes a Wolford Mountain enlargement would not likely be the Least Environmentally Damaging Practicable Alternative (LEDPA) when compared to Sulphur Gulch Reservoir or to non - structural alternatives. 1 825 Water SupplyStudly Phase 2 Alternatives Assessment January 2008 ?raft 14