Considerations Related to Equal Monthly Volumes

Home Browse Search

Science Principle: For any given annual volume release of water, sandbar erosion and sediment transport is minimized by reducing both daily /monthly /seasonal variations in volume releases, and by minimizing subsequent daily variations in discharges. (Rubin and others, 2002; Wright and others, 2005; Wright and others, 2008; ASCE, 1975; USDOI, 1995; Topping and others, 2006). Proposed Operating Parameters: • Monthly Release Volumes will be adjusted each month based on the most current forecast of the annual release required by the 2007 Interim Guidelines. • Monthly Release Volumes will vary within a range of +/- 100,000 acre -feet from the Average Monthly Release Volume over the water year (defined in the next bullet). This operational flexibility will be used for existing power production operations under the Modified Low Fluctuating Flow (MLFF) alternative selected by the 1996 ROD and contained in the 1995 FEIS. Modifications of monthly release volumes will be made in consultation with Western Area Power Administration. • Average Monthly Release Volumes will be the amount of remaining water to release for the water year divided by the remaining months in the water year (excluding the September /October steady flows). • Daily peaks will be no greater than 22,000 cfs, with all other flow parameters of the current MLFF in place (including daily range in fluctuating flows up to 8,000 cfs), including the fall steady flows required in the 2008 High Flow Experiment Environmental Assessment (2008 BYE EA). • Steady flows in September and October per the 2008 HFE Environmental Assessment (EA). Expected Resource Results: Under this scenario, loss of recreational camping beaches would be reduced to the extent possible by minimizing sediment transport (Wright and Grams, 2010). Recreational rafting values may benefit from the more limited fluctuations. Terrestrial and aquatic river edge riparian habitats and archaeological sites may continue to degrade, but the amount of loss may be reduced under this recommended flow regime., 4