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<br />.~ <br /> <br />::-) <br /> <br />N 34. Gradation of reservoir deposits. The grain size of the deposited <br />00 <br />~.) sediment in the reservoir is dependent on the grain size of the inflow. <br />o <br /> <br />Once the inflow enters the reservoir, the sediment particles are segregated <br /> <br />. I <br />and distributed 1n the reserVOIr area and the original size distribution <br /> <br />is lost. Very few samples were taken at the inflow stations during the <br /> <br />period October 1966 to ~larch 1973 and none of these were analyzed for size <br /> <br />of particles. Samples taken and analyzed prior to this period indicate <br /> <br />the suspended sediment entering the reservoir is approximately 10 percent <br /> <br />sand, 70 percent silt, and 20 percent clay. These do not include bed load <br /> <br />"hich is estimated to be 5 percent of the total load. The size of suspended <br /> <br />sediment at the out flow stat ion below the dam varies \d th operational <br /> <br />conditions but averages about 5 percent sand, 58 percent silt, and 37 percent <br /> <br />clay. TIle suspended sand load with the reservoir in operation is comparable <br /> <br />to the sand load in the riverflow but there is a notable change in silt and <br /> <br />clay sizes as storage is depleted and riverflow takes over. <br /> <br />35. Results of sediment deposit sampling are shown in table 9. Samples <br /> <br />arc listed in upstream order from the dam. Averages for the entire reservoir <br /> <br />area show a gradation of approximatel,}' 36 percent clay, 44 percent silt, and <br /> <br />20 percent sand. Irrigation storage during the winter usually creates a <br /> <br />pool that extends upstream to range 5. Dividing the reservoir into two <br /> <br />segments from the dam to range 5 and from range 5 to range 13 shows a better <br /> <br />picture of the sediment sizes deposited in the reservoir reaches. Average <br /> <br />size analysis of the 24 samples taken between the dam and range 5 shows <br /> <br />approximately 47 percent clay, 47 percent silt, and 6 percent sand. The <br /> <br />16 <br />