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<br />4 <br /> <br />III. Interim Flow "onitoring Results <br /> <br />The interim operating criteria, first tested in August 1991, have been <br />successful in meeting their original objectives. Based on monitoring <br />(Schmidt, 1994; Cluer and Dexter, 1994; Beus and Avery, 1993 Ayers and <br />McKinney, 1995; and Stevens and Ayers, 1994) the results can be separated into <br />the following sections: <br /> <br />A. Physical System <br /> <br />1. The maximum flow criteria of 20,000 cfs was successful in trapping <br />sediment in river pools and eddies. <br /> <br />2. Sediment is moving downstream but at a rate sufficiently slow to <br />allow net accumulation in the channel. <br /> <br />3. The backwaters are in the process of filling, thereby eliminating <br />them as sources of habitat for native and non-native fish. <br /> <br />4. Erosion of the beaches in the Grand Canyon, especially in the <br />critical reaches has slowed but is still going on. In several <br />instances local debris flows and tributary flash floods have <br />buried or eroded the beaches. <br /> <br />Results from monitoring the interim flows confirmed that there is still a need <br />for a high controlled flow to move sediment from the main channel up onto the <br />beaches. <br /> <br />B. Bioloqical System <br /> <br />1. The trout population has begun to rebuild in the Lees Ferry area <br />with increased numbers of naturally produced fish and better fish <br />condition factors. <br /> <br />2. The cladophora beds have expanded in size. <br /> <br />3. The numbers of Gammarus lacustris have increased substantially in <br />the Lees Ferry drift. <br /> <br />4. The riparian areas utilized for nesting by the Southwestern Willow <br />Flycatcher have stabilized in size. <br /> <br />5. The mirshes have filled in with sediment, dried out and are <br />showing an increase in riparian plants. <br /> <br />6. The riparian zone has migrated down to the 20,000 cfs level. <br />