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15 • --:- -sharp=-drop in output 1-ate in the afternoon. A_reduction, in flow from, 2500 to 400 cfs within an hour or less is not uncommon. Because Flam- ing Gorge Dam is one unit in the Colorado River Storage Project, power needs--are-variable and operations at the dam are unpredictable. The discharge record at the Greendale station is so variable within any single day that the U. S. Geological Survey uses integration techniques to calculate -mean`dai'ly"flow. `This is not necessary for most other discharge records in the state. Daily fluctuations in flow were most pronounced near the dam and - - -strdden- changes 'in flow were dampened progressively. downstream. Maxi- mum water level fluctuations observed for any given 24-hour period in 1965 were 2.14 feet at Little Hole, 1.47 feet at Carr Ranch, and 0.33 feet 'at "Island -Park.--- Near Jensen 1(93.4 MBD) only -major changes in low • lasting 24 hours or more were detected. The seasonal flow stability imposed on the river above Taylor Flats 'Bridge (16.1 MBD) has statiilized?fhe bottom materials. At Little Hole (7.2 MBD) very little change in the physical nature of the substrate was observed among seasons or between years. Farther downstream, how- ever, the bottom remained unstable, and at Island Park several rubble- bottomed areas were washed clean of sediments during the spring floods but were smothered by thin layers of silt as the waters receded in summer and fall. Erosion of the river bank continued throughout the year at Island Park and, to a lesser extent, at Echo Park. Temperature 0 The general effect of the dam has been an increase in river tempera- ture during the winter and a decrease in the summer. MMean monthly pre-