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<br />in the Gunnison River (measured at USGS gage #09152500 just upstream of
<br />Highway 141 bridge). McAda and Kaeding recommended instantaneous peak flows
<br />of between 2,000-5,000 ft3/s for one year, between 5,000-10,000 ft3/s for one
<br />year, above 12,000 ft3/s for two years, and above 15,000 ft3/s for one year
<br />(essentially, two years of relatively low flows and three years of relatively
<br />high flows). Peaks should be timed to coincide with peaks on the Colorado
<br />River, generally occurring between May 15 and June 15 of each year. As run-
<br />off begins to subside, a gradually descending/declining limb that represents a
<br />more natural hydrograph should follow with lower stable flows the remainder of
<br />the year through summer, fall, and winter. Ramping rates at the dam,
<br />particularly on the descending limb of the hydrograph should not exceed
<br />250 ft3/ S per day.
<br />
<br />McAda and Kaeding also suggested a range of test fl ows for the remainder of
<br />the year as follows:
<br />Jan Feb Mar ADr May June
<br />700. 700 700 900 3,000 2,000
<br />900 900 1,000 1,500 4,000 3,500
<br />1,100 1,100 1,300 3,000 6,000 5,000
<br />1,300 1,300 1,800 5,000 8,000 6,500
<br />1,700 1,700 2,200 7,000 10,000 8,000
<br />Jul AUQ SeD Oct Nov Dec
<br />1,000 1,000 1,000 700 700 700
<br />1,400 1,300 1,000 900 900 900
<br />1,900 1,700 1,300 1,100 1,100 1,100
<br />2,500 2,100 1,600 1,300 1,300 1,300
<br />3,000 2,500 2,000 1,500 1,500 1,500
<br />3,000 2,500 2,000 1,500 1,500 1,500
<br />.
<br />All figures are mean monthly flows in ft3/s, and should not be
<br />confused with instantaneous peak flows previously discussed.
<br />
<br />During the research period, test flow targets should be measured at USGS gage
<br />#09152500 realizing that specific water releases from Aspinall will need to be
<br />coordinated with tributary contributions downstream (e.g., North Fork,
<br />Uncompahgre River, Escalante Creek, etc.).
<br />
<br />Based on hydrology information (attached) prepared by Randy Peterson, Chief of
<br />Operations, for representative dry, average and wet years at several
<br />locations, it appears that test flow targets for the Gunnison River can easily
<br />be accommodated without compromising other resource values.
<br />
<br />Upon conclusion of the study period. the Service. in cooperation with
<br />Reclamation. intends to further refine and make more long-term flow
<br />recommendations for future operations of Aspinall based on the research
<br />results.
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