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Last modified
7/14/2009 5:02:37 PM
Creation date
5/20/2009 2:54:16 PM
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Template:
UCREFRP
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
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<br />the Colorado pikeminnow and the razorback sucker. In general, the endangered fish flow <br />recommendations call for mimicry of a natural hydrograph. <br /> <br />The flow recommendations provide criteria to define the annual hydro graph for any year based on <br />the April through July runoff at the Whitewater gage. Runoff years are classified into six <br />categories: dry, moderately dry, average dry, average wet, moderately wet, and wet. The annual <br />hydro graph consists of minimum flows for: 1) a spring peak with appropriate ramping rates, 2) a <br />variable base flow for the Gunnison River at the Whitewater gage, and 3) variable flows below <br />the Redlands Diversion Dam for fish passage. The suggested peaks for the modeled period range <br />from 4,000 cubic feet per second (cfs ) in an extremely dry year such as 1977 to 18,000 cfs2 in a <br />very wet year such as 1984. According to the flow recommendations, peaks should occur <br />between May 15 and June 15. Table B-3 in the attachments includes the suggested peaks for the <br />years 1975 through 2000. <br /> <br />Model Runs and Results <br /> <br />Four model operation runs (A through D) were developed for this analysis, including a baseline <br />and three operational alternatives as described below. The model reflects operations of the <br />Aspinall Unit that attempt to meet flow recommendations subject to certain limitations. <br />Reclamation modeled a combination of tributary flows downstream of Blue Mesa Reservoir and <br />storage releases to attempt to meet the flow recommendations. The legal availability of water and <br />water rights are not included in the model. <br /> <br />To determine the amount of water the Aspinall Unit must release for flow recommendations, the <br />estimated daily contributions oftributaries downstream of the Aspinall Unit were subtracted from <br />the daily recommended flow hydro graph at the Whitewater gage for each year. (Further described <br />in Attachment A). The difference is referred to as the-FWS demand hydro graph. <br /> <br />Model Run <br />A <br /> <br />Description <br />This model run reflects current operations without attempts to provide <br />peaks for a reserved right or for endangered fish (Baseline). <br /> <br />B <br /> <br />Morrow Point* releases for flow recommendations limited to powerplant <br />capacity of 5,000 cfs (FWS_5000). <br /> <br />c <br /> <br />Morrow Point* releases for flow recommendations limited to powerplant <br />and bypass capacities totaling 6,500 cfs (FWS_6500). <br /> <br />D Morrow Point* releases for flow recommendations from powerplant, <br />bypass, and spillway (FWS _ UNL TD). <br />*Morrow Point is the furthest downstream dam of the Aspinall Unit that uses regulated gates to control releases. <br /> <br />2For the purposes of this report, Reclamation used 18,000 cfs versus 20,000 cfs, identified <br />in the draft recommendations, based upon discussion with the FWS: <br /> <br />3 <br />
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