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<br />These targets came from weighted area curves of fish habitat at different life stages (see <br />Chadwick, Appendix B). They are not based on the native or historical streamflows and <br />do not reflect the capability of the water facilities to manage streamflow ~ <br /> <br />a. Minimum Streamflows <br /> <br />Low streamflows result in low habitat levels for trout. Natural streamflows in many <br />Colorado streams can fall below levels necessary to maintain healthy trout streams. Since <br />the majority of South Platte River streamflow comes from snowmelt, the streamflows are <br />naturally very low in the wintertime. These natural streamflows can be lower than the <br />habitat needs of trout~ hnportation of water into the basin and reservoirs provides <br />opportunities to augment natural streamflows with streamflows more suitable for troutt <br />The goal is to provide minimum levels of streamflow to maintain or enhance habitat for <br />trout. <br /> <br />~ Spinney Mountain Reservoir <br /> <br />Background: Low streamflow (particularly less than 20 cfs) drastically reduces <br />streamflow habitat for all trout life stages in the reach between Spinney and Eleven Mile. <br />With the creation of the reservoir, streamflow in this river segment has improvedt <br />particularly the otherwise low winter flows. Spinney has a minimum release requirement <br />of 32 efs or native inflow whichever is less. <br /> <br />Target: The minimum desired release is 20 efs with 50 to 150 cfs being optimum <br />(Table 2). Future improvements (in-stream, habitat structures and modifying or reducing <br />width-to-depth ratios in areas that are currently wide and shallow) in stream geometry and <br />habitat may allow for lower minimum streamflows needed to maintain or enhance trout <br />population dynamics and structure. <br /> <br />Operations: Aurora has already committed to a minimum release of 32 cfs or the native <br />inflow, whichever is less as designated in the 1980 agreement between Aurora and <br />CDOW. Aurora will strive to keep the release above 50 cfs (optimum) recognizing this <br />will not always be achieved. <br /> <br />Storage releases may be made to meet the desired 32 cfs minimum provided it can be <br />recaptured without loss in Aurora's downstream reservoir and there are no impainnents to <br />water rights. When Aurorats downstream storage is full but there is space available in <br />Cheesman Reservoir, reservoir operations will be coordinated between Aurora and <br />Denver Water to allow water released from Spinney Mountain to be stored in Cheesman <br />to meet the desired 32 efs release. <br /> <br />N :\Supply\ Waage\wild scen\attachb. doc <br /> <br />B..7 <br />