WSP11913

• File Number: 8220.101.08
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 8/29/2000
• Title: Summary & Discussion of Recent Research Findings Related to Dam Operations & Sand Bar Resources of the Colorado River Ecosystem
• Water Supply Pro - Doc Type: Report/Study

Figure 2. Calculated time to export one-half of a 500,000 metric ton input of tributary sand
past the Grand Canyon gage, Calculations are based on sediment-transport data collected at the
Grand Canyon and above LCR gages during the 1990's, The upper limit of the shaded area
(slowest expon) is calculated using the average suspended-sediment concentration for each
specified discharge; the lower limit of the shaded area (most rapid export) is calculated for high
concentrations of suspended sediment at each discharge; the solid line in the center of the
shaded band is calculated using concentrations that decrease through time from high values
(during and immediately following tributary inputs) to mean concentrations (after half of the
tributary sand has been exported), At the upper range of dam operations, half of the sediment
is exported within a few days; multi-year accumulation is only likely to occur if discharge is
restricted to less than 8,000-10,000 cfs, To maximize the benefit of sand supplied by
tributaries, releases above peak power-plant discharge should be implemented as soon as
possible after tributary input events.

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