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Description of Alternatives Beach/Habitat-Building Flows Sandbars above the normal peak river stage would continue to erode, and backwater habitat within normal stage would tend to fill with sediment under any EIS alternative. To alleviate this, beach/habitat-building flows have been incorporated in all restricted fluctuating and steady flow alternatives. Beach/habitat-building flows would be scheduled high releases of short duration designed to rebuild high elevation sandbars, deposit nutrients, restore backwater channels, and provide some of the dynamics of a natural system. A frequency of 1 in 5 years (when the reservoir is low) was assumed for analyzing the environmental consequences. These flows would be avoided during high reservoir conditions because of the increased risk of unscheduled flows greater than powerplant capacity. Magnitudes would be at least 10,000 cfs greater than the allowable peak discharge in a minimum release year for a given alternative. Releases would be increased at no more than 4,000 cfs/hour and decreased at a maximum of 1,500 cfs/hour. As part of adaptive management, a test of a beach/habitat-building flow would be conducted prior to long-term implementation of this element to test the predictions made about its impacts. Scheduled flows exceeding powerplant capacity (33,200 cfs) may require legislation to implement. Beach/habitat-building flows could be scheduled in the spring (to coincide with the May/June peak in the natural hydrologic cycle) or in late summer when, due to local thunderstorms, tributaries are expected to supply large quantities of sediment and nutrients. Initially, these flows would be scheduled for a duration of 1 to 2 weeks. Additional water would be scheduled in the spring to support this flow. Beach/habitat-building flows would be recommended under the Adaptive Management Program and scheduled as part of the Annual Operating Plan. Such flows would be recommended during years when sufficient quantities of sediment are available, but not following a year in which a large population of young humpback chub is produced. New Population of Humpback Chub The Grand Canyon population of humpback chub (an endangered species) uses habitats in both the Colorado River mainstem and the Little Colorado River (LCR). Conditions in the mainstem (principally water temperatures) are not conducive to humpback chub spawning or survival of eggs and young. The only confirmed successful spawning habitat for that population is in the LCR, with individuals moving between that tributary and the mainstem. 14 Glen Canyon Dam EIS Summary