9413

• UCREFRP Catalog Number: 9413
• Author: Osmundson, D. B.
• Title: Flow Regimes for Restoration and Maintenance of Sufficient Habitat to Recover Endangered Razorback Sucker and Colorado Pikeminnow in the Upper Colorado River.
• USFW Year: 2001.
• USFW - Doc Type: Grand Junction.
• Copyright Material: NO

EXECUTIVE SUMMARY
Suitable flow regimes are needed to promote recovery of endangered fishes in the
upper Colorado River (USFWS 1987, USFWS 2000), and legal protection of instream
flows is required before delisting can occur (USFWS 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.
Assuming future Recovery Program activities are successful in repopulating the area
between and above the diversions with Colorado pikeminnow Ptychocheilus lucius and
razorback sucker Xyrauchen texanus, flow regimes suitable for these fish will need to be
provided. This report identifies such flows. In doing so, needs of the fish within these
reaches are considered as well as those of fish downstream, also affected by such flows.
For summer and winter, recommendations are based largely on the determination of
what flow levels maximize the amount of those habitats most used by razorback sucker and
preferred by Colorado pikeminnow. Because these fish are essentially absent upstream of
the diversions, reach-specific habitat-use and habitat preference information is lacking.
Also, habitat mapping of representative reaches at various discharges is required before
flow levels that maximize certain habitats can be determined. To date, such mapping within
the subject reaches at base flows has been very limited. At this time, the only practical
approach for developing summer and winter flow recommendations is to use results from
the Grand Valley as a surrogate for more reach-specific information. Therefore, interim
recommendations presented here are based on the assumption that habitats preferred in
these upstream reaches will be the same as those in the 15-mile reach immediately
downstream and that flow levels that maximize these habitats will be similar among reaches.
In general, the recommendation for summer and winter are for flows to be between 1,600
and 2,500 cfs.
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