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Description of Alternatives Although an occasional floodflow (greater than 33,200 cfs) may rebuild high elevation beaches and re-form backwaters, frequent floodflows would likely transport more sand than could be supplied by the tributaries-resulting in long-term sandbar erosion. Therefore, habitat maintenance flows are included in this alternative to re-form backwaters, which are important for fish habitat. Habitat maintenance flows are high, steady releases within powerplant capacity for 1 to 2 weeks in the spring. The exact month would be determined under the Adaptive Management Program and the Annual Operating Plan. March was assumed for evaluating impacts for the following reasons: Backwater channels could be re-formed prior to the humpback chub spawning period. More sediment is likely to be supplied by tributary flow in March than later in the spring. • March is prior to the peak recreation use season. Habitat maintenance flows would not be scheduled when the projected storage in Lake Powell on January 1 is greater than 19 maf. Annual release volumes under such conditions are typically greater than the minimum annual release volume (8.23 maf), and such flows already may be near or exceed powerplant capacity. Although habitat maintenance flows are defined as steady, minor fluctu- ations of up to plus or minus 1,000 cfs would be permitted to regulate voltage within the power grid. Maintenance flows would begin by increasing flows at a rate no greater than 4,000 cfs/hour and would conclude by decreasing flows back to the normal operating range at a rate no greater than 1,500 cfs/hour. The limit on daily change in flow would not apply during these transitions. Habitat maintenance flows differ from beach/habitat-building flows because they would be within powerplant capacity and would occur nearly every year when the reservoir is low. Habitat maintenance flows would not occur in years when a beach/habitat-building flow is scheduled. Neither of these special releases would be scheduled in a year when there is corcem for a sensitive resource-such as sediment or an endangered species. Increasing the flow to 30,000 cfs for 10 days would result in the release of an additional 412,000 acre-feet of water in March, which would require adjusting the release volumes in the other months. This scheduling adjustment would be determined during the Annual Operating Plan preparation and may vary from year to year. 26 Glen Canyon Dam EIS Summary