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INTRODUCTION The goal for recovery of the endangered fishes of the Colorado River is to achieve naturally self-sustaining populations and to protect the habitat on which they depend (USFWS 1987, USFWS 2000, USFWS 2001). Identification and protection of instream flows for the endangered fish is required before delisting can occur (USFWS 2001) and is one of seven elements of the Recovery Implementation Program Recovery Action Plan (RIPRAP). Section 2.1 of the RIPRAP (USFWS 2000) discusses this element as follows: "Recovery cannot be accomplished without protecting and managing sufficient habitat to support self-sustaining populations of the endangered fishes. Protecting instream flows is key to protecting the habitat of these fishes. The first step in instream flow protection is to identify the flow regimes needed by the fish. In the Recovery Program, determining flow needs is primarily the responsibility of the Fish and Wildlife Service (in cooperation with other participants). Factors considered in determining flow needs include: flow effects on reproduction and recruitment; flow effects on food supplies and nonnative fishes; and interrelationships between flow and other habitat parameters believed to be important to the fish, such as channel structure, sediment transport, substrate characteristics, vegetative encroachment, and water temperature. Flow recommendations (for all or certain seasons) have been or are being developed for most river reaches targeted for recovery in the upper basin. Flow recommendations often are made in stages, with initial flow recommendations based on the best available scientific information, historic conditions, and extrapolation from similar reaches. Recommendations then are refined following additional field research. " To date, flow regimes needed to assist recovery of Colorado River populations of Colorado pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus) have been identified for a 15-mile reach between the Grand Valley diversion dam at Palisade, Colorado and the Gunnison River confluence, hereinafter referred to as the `15- mile reach' (Osmundson et al. 1995). In addition, recommendations for the Gunnison River downstream of Delta, Colorado and the Colorado River downstream of the Gunnison River confluence are currently being developed as part of the Aspinall Unit biological opinion process (McAda 2001). In addition to improving adult habitat by providing more optimum flows in areas currently occupied by the endangered fish, the Recovery Program seeks to increase the extent of adult habitat by providing passage facilities at diversion structures that have historically prevented access to once occupied reaches. One such reach is the Colorado River upstream of Palisade, Colorado. Three diversion dams occur within a 13-km (8-mile) stretch just upstream of Palisade and have prevented upstream movement of fish