9676

• UCREFRP Catalog Number: 9676
• Author: U.S. Department of the Interior.
• Title: Preliminary Analysis
• USFW Year: 2001.
• USFW - Doc Type: Wayne N. Aspinall Unit Operations and the Draft Endangered Fish Flow Recommendations for the Gunnison and Colorado Rivers.
• Copyright Material: NO

issue in operating under real conditions. While recommended peaks are not consistently met,
operations would significantly improve habitat conditions for the fish. Base flows for the
endangered fish are met over 95 percent of the time, and minimum flows in the lower 3 miles of
the Gunnison River, recommended for fish passage, are met over 90 percent of the time under
model runs that include recommended flows. Overall, the model runs show changes in Aspinall
Unit operations, while not fully meeting flow recommendations, could meet the recommendations
to a greater degree and would benefit the endangered fish and their habitat. However, as discussed
below, there are significant negative impacts associated with attempting to meet the flow
recommendations.

Model runs show operating to meet the draft recommended fish flows would result in negative
impacts to the operation and purposes of the Aspinall Unit that are inconsistent with the intent of
the authorizing legislation. Operating to meet the flow recommendations does not create
additional water in the river on an annual basis; it redistributes flows, with increased flows at one
time of the year and decreased flows at another. Impacts to purposes such as generation of
hydroelectric power, downstream flood protection, reservoir recreation, Colorado's Compact
entitlement, and reservoir fisheries are discussed in this report. Preliminary analysis shows the
greatest negative impact would be on reliable reservoir yield for use in Colorado and on reservoir
recreation and fisheries. Operating the Aspinall Unit to meet the draft flow recommendations to a
greater extent would increase these negative impacts. This report does not evaluate impacts on
other private and Federal water supplies, water rights, or diversion structures. Negative impacts
of partially meeting the draft recommended fish flows include:

- foregone hydroelectric power averaging 7,000-11,000 megawatt hours (1 megawatt hour =
1,000 kilowatts hours) annually
- reduced ability to response to power system emergencies - This response is limited when
Crystal is spilling. Operating to meet peak flow~recommendations increases the number of
Crystal spills.
- increased operation and maintenance costs due to increased spillway and bypass use
- impacts to reservoir fishery and reservoir recreation due to reduced reservoir levels
- increased risk of downstream flooding - Days exceeding 12,000 cfs increased downstream
flooding from 10 - 13 days; at 15,000 cfs, flooding increased an additional 4 days.
- reduced reservoir yield with possible impacts on Colorado's Compact use (ranging from a
loss of 150,000 to 200,000 acre-feet to no impact depending on hydrologic year) - Existing
agreements governing Taylor Park and Aspinall operations could be impacted.

Operating criteria would need to be further adjusted and storage releases increased to more fully
meet the recommended flows. Structural modifications, including additional outlet works at the
three dams, could also be required to safely operate the Aspinall Unit facilities to meet flow
recommendations at the frequencies recommended for the endangered fish.

Reclamation plans to complete an environmental impact statement on alternative operations to
help meet the endangered fish recommendations when the recommendations are final. The
existing model to analyze the draft fish flows will be upgraded and integrated with State resources
to assess impacts to other water uses in this process. In addition, Reclamation will work with the

IV