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<br />Fine sediment on and within spawning gravels reduce egg suvival. Although there are <br /> <br />no known Colorado pikeminnow spawning areas in the White River, some aquatic <br /> <br />invertebrates use open interstices in cobbles and gravel, and accumulated fine sediment <br /> <br />can eliminate this habitat characteristic. Another purpose of high flows is to restore or <br /> <br />enhance pool habitat by preventing the accumulation of fine sediment in pools. Deep <br /> <br />pools provide cover and adequately cool water which permit survival of some species <br /> <br />during warm, low-flow months. <br /> <br />Another objective of including high flows as part of an in-stream flow <br /> <br />recommendation is to maintain active channel width and topographic diversity of the <br /> <br />channel. Ecological diversity and productivity of river channels and flood plains are <br /> <br />directly related to the areal extent, complexity, and variety of available physical habitats. <br /> <br />Hesse and Sheets (1993) pointed out that "we must be careful not to assume that the <br /> <br />.minimum flow necessary to move sediment is the correct flow to achieve a dynamic <br /> <br /> <br />channel morphology." To accomplish this purpose of maintaining channel width and <br /> <br /> <br />channel diversity, it is often necessary to prevent vegetation from encroaching on the <br /> <br /> <br />active channel. This necessitates that seedlings of riparian plants be scoured at least <br /> <br />biennially. Kondolf and Wilcock (1996) suggested that the 2 year flood accomplishes <br />this objective. <br /> <br />Background -- Channel and habitat maintenance in Relation to the Geomorphic <br /> <br />Concepts of Effective and Banlifull Discharge <br />There are two approaches to determining the discharges necessary to maintain the <br />diversity of the channel. One approach is to directly measure habitat movement and <br />2 <br />