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EXECUTIVE SUMMARY The Bureau of Land Management (BLM) is responsible for managing lands and resources adjacent to the Dolores River in southwestern Colorado. The BLM recently completed the Dolores River Corridor Management Plan, which prescribes a la-year management program. Values associated with riverine resources include recreational boating, aquatic and riparian habitat, and other stream channel characteristics related to proper channel maintenance. Since the completion of McPhee Dam and Reservoir, located upstream of BLM managed areas, availability and quantity of instream flows to support resource uses have not been determined. In addition to BLM's typical management responsibilities along the Dolores River, certain portions of the river have been recommended for wilderness and wild, scenic, and recreational designations, under the Wilderness and National Wild and Scenic Rivers Acts. The purpose of this report is to document the existing post-dam streamflow regime, present flow dependent resource values found in the Dolores River corridor, analyze water management options for securing in stream flow protection, and identify the water conditions required to support resource management planning objectives. This report summarizes an instream flow assessment conducted on portions of the river that include the area covered by the Dolores River Corridor Management Plan. Specifically, the study reach of the river extends from Bradfield Bridge downstream to Bedrock. In 1987, the Bureau of Reclamation completed construction and filling of McPhee Dam and Reser- voir as part of the agency's Dolores Project, a participating project of the overall Colorado River Storage Project. Streamflows have historically been reduced by diversions that transport water for irrigation out of the Dolores River Basin. McPhee Dam was built to augment the diversions by captur- ing and storing water that is available at times other than the irrigation season. The historical diversions have reduced the average annual flow of the D~lores River by approximately 39 percent. According! to the U.S. Bureau of Reclamation Dolores River Definite Plan Report, when McPhee Reservoir is fully developed, it will further deplete Dolores River flows by an additional 30 percent. Thus, 69 percent of the flow of the Dolores River above the dam has been depleted. Flow dependent resource values identified and analyzed in this report are related to: 1) recreation, 2) fish and wildlife, and 3) channel morphology. Flow dependent attributes analyzed under the recreation category were floatability and quality of whitewater to provide for a variety of experiences in kayaks, canoes, and rafts. Streamflow determinations for fish included an analysis of weighted usable habitat to support four life stages of brown and rainbow trout. Maintaining channel form, function, and sediment transport were studied as flow dependent characteris- tics under the channel morphology category. In order to manage instream flows on the Dolores River, an analysis of institutional, market, and legal options was initiated. The Dolores River is fully appropriated. Therefore, opportunities for increasing streamflows within the study area depend on finding ways to reallocate existing uses of the river. Legal options only address ways in which existing or reallocated releases may be protected from future water depletions. This analysis of options did not include an in-depth study of alterna- tive water reallocation costs and feasibility. Further analysis of this sort is planned for the Dolores River. Flow requirements for boating, fish habitat, and channel maintenance are presented in the report. This report does not recommend annual flow require- ments due to the need for further evaluation of water availability and river management objectives. It is noted that the flow requirements, presented in cubic feet per second (ft3/s), involve resource tradeoffs, such as boating flows versus fishery flows). Annual flow scenarios will vary, depending on water availability. Five possible flow scenarios for management to consider are detailed in the summary of this document. Scenarios are provided to help management gain insight about differences in the flow scenarios relative to water availability and resource tradeoffs. Flow scenarios are examples of annual requirements, and not management alterna- tives. Flows required for recreation values are sorted according to type of craft and floating ex~rience . desired. For canoeing experiences, 125 ft3 Is is required for float/fishing while scenic canoeing requires 300 ft3 Is. Rafting and kayaking experiences include scenic boating, minimum whitewater, and optimum whitewater, and the flow requirements for 1