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<br />An element of the ROD, which was also emphasized in the biological opinion, was the
<br />formulation of an Adaptive Management Program, Based on information presented at a
<br />September 10-\ 1, \997 meeting, the AMWG decided to recommend a 1997 fall test flow to~the
<br />Secretary through his designee, The additional power that will be produced by a peak powefplant
<br />release at this time of year is valuable on the market, availability of water is not a restriction, and
<br />impacts to sport fishermen and the non-native trout resource will be low,
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<br />Decision to Implement Test Flow:
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<br />Because of current reservoir storage levels throughout the Colorado River system, and because of
<br />high levels of eastern Pacific Ocean warming since March 1997 (El N"1iI.o), there is a potential for
<br />above normal inflow to Lake Powell during spring 1998, Based on the similarity of present
<br />conditions with those that occurred in 1982/83, there is also some potential for a spill to occur at
<br />GCD (releases above power plant capacity),
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<br />In light of the present sediment conditions, the Glen Canyon Dam Adaptive Management .
<br />Workgroup (Workgroup) recommended on September 11, 1997, that the Bureau of Reclamation
<br />conduct a peak-powerplant test flow, GCMRC would be responsible for insuring scientim
<br />working in the canyon monitor the results of the flow,
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<br />The goal of this experiment is to determine whether or not sediment conservation in the _
<br />sediment-poor reaches of the system can be enhanced by a test flow at other release rates t1uln the
<br />45,000 cfs (release that was tested in March, 1996), Information on the October test flow will
<br />provide an additional data point which the Workgroup could use to determine ifpeak-powerplant
<br />releases can be used in the future as a management tool to promote sediment deposition and
<br />conservation in sediment-limited reaches,
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<br />The timing of the test flow was constrained, in part, by operations and scheduled maintenance of
<br />the powerplant, the need to conduct environmental compliance on the proposed action, and a
<br />storm related event which resulted in reduced release capacity, The probability of scouring
<br />existing sediment deposits is also considered minor in light oflast winter, spring and summer's
<br />high clearwater flows, The 48-hour duration of the test flow was established based on 1996 study
<br />results, antecedent sediment-storage conditions, and data collectionllogistical requirements.
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<br />Recent flood peaks as high as 4,000 cfs from the Paria River, combined with powerplant highs,
<br />have resulted in short-duration river flows as high as about 28,000 cfs in Marble Canyon, It is
<br />unclear whether these naturaJ high flows were responsible for significant levels of fine-sediment
<br />deposition and storage along shorelines,
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<br />Science Planned to Support the 31,000 as Test Flow:
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<br />Stream gaging for sediment monitoring purposes and limited monitoring of sandbar changes will
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