8221 - Laserfiche WebLink

Home Browse Search

10 I J (Kondolf et aI., 1987; Reiser and Ramey, 1985). Flows for channel maintenance in one region may be very different than those in another region. For example, Wolman and Miller (1960) argued that channel morphology is controlled by flows of moderate magni~de which recur frequently, rather than by rare events of high magnitude. In contrast, Baker (1977) argued that large floods determined the channel morphology on many rivers, and that the conclusions of Wolman and Miller (1960) apply well to humid areas with low relief and deep soils, but may not be applicable to rivers in arid regions where the rainfall/ runoff characteristics result in very large floods relative to mean flow. Therefore, it is clear that regional topography, geology and climate are essential to determining the individual characteristics of a river, and broad generalizations for prescribing flushing flows are not very useful. It is unknown what discharges are necessary for the maintenance and/ or creation of natural channel features on the upper Colorado River, but periodic high flows are thought to be beneficial. Osmundson and Kaeding (1991) observed that the mouths of many backwaters and pools of the Colorado River near Grand Junction, Colorado silted in during years with low peak flows, and vegetation became established in these areas. To remedy this and other problems, Osmundson et al. (1995) proposed flow recommendations for the Colorado River above Gran~ Junction. In general, they recommended that the current flow regime be changed to more closely mimic flows which occurred before major water development in the basin. This calls for increasing spring and summer flows, and slightly decreasing winter flows. Since Colorado squawfish show a preference for habitats of complex channel (Osmundson and Kaeding, 1991), it is important to determine I -~ 1 :,"] J J 1 1 J J I .1 j