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Dallas Creek Project, Colorado (BR) -11- the two forks of Dallas Creek about 12 miles above the confluence of Dallas Creek with the Uncompahgre River. The diversions will be in the most productive segments of these streams. Biological productivity below these points will be depressed by the reduction in stream flow. A tabulation of project impacts on fishery resources is shown in Table II. Current project planning does not provide for any diversion of flows of Cow Creek. The fishery value of Cow Creek will not change. Flows of Pleasant Valley Creek will be impounded by Dallas Divide Reservoir. High runoff flows of Pleasant Valley Creek and the two forks of Dallas Creek will be stored for release from June to September. A large part of this stored water will be transported to the point of use by ~he Log Hill Mesa Conduit. Flows in Pleasant Valley Creek will not be excessive and should not alter the quality of this stream fishery. Stream fishing use on the Uncompahgre River in the Ridgway Reservoir basin will be lost. The water quality of the river below the reservoir, however should improve due to the settling action of the reservoir coupled with the use of a dual-level outlet for water releases. The project incorporates the minimum flow regimen recommended by the Colorado Division of Wildlife and the Fish and Wildlife Service for the river below the mouth of Cow Creek. The benefit of the flow regimen, however will occur only to the point where these flows are diverted for project uses. Water sample analysis of the Uncompahgre River and other contributing flows have shown the presence of arsenic and selenium. Arsenic levels recorded for one point source exceed those listed by water quality regulations as permissable for fish and wildlife. Selenium levels recorded were low. However, this chemical accumulates in submerged vegetation and aquatic invertebrates and when these fish foods are ingested, the selenium accumulates in the liver of the fish until toxic levels are reached. Therefore, potential problems exist with the future of the fishery in the Uncompahgre River and Ridgway Reservoir. These problems need detailed study to determine the extent of possible impact of project water quality upon fishery resources.