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J ..\ 2,908 acre-feet. The storage loss is 10.07 percent of the original capacity. Depletion of the flood control pool (above elevation 3,851.00) is 1,421 acre-feet or 0.5 percent. Depletion of the conservation pool is 69,233 acre-feet or 16.4 percent. For the first time since construc- tion the reservoir reached flood control storage in 1965. The highest reservoir elevation to date was 3,856.16 feet. This wason 25 August 1965. N --J en - - b. Sediment deposition in the reservoir for the period Octo- ber 1961 through September 1966, computed from suspended sediment samp- ling, was 16,598 acre-feet, as shown in table 8. Density of 75.7 pounds per cubic foot was used in these computations and allowance was made for consolidation . c. The density of the most recent sediment deposits, using the eleven sediment samples taken during the resurvey, varied from 41.5 to 74.4 pounds per cubic foot of soil solids. When the samples and readings from the radioisotope density probe are considered, the unit weights range up to 112.0 pounds per cubic foot. The overall density of the sediment deposits is, as expected, greater than the 75.7 pounds per cubic foot originally assumed as the 1nitial density. The _av~rage ~f_all deposits may be about 85 pounds per cubic foot. Paragraph 42f recommends. systematic .sa.mpling dUrlng the- next resurvey to obtain fur- ther data for density studies. d. The size analysis of the deposited sediment shows an esti- mated 3 percent sand, 63 percent silt, and 34 percent clay. Average size analysis of inflows for the most recent period between resurveys indicates approximately 10 percent sand, 71 percent silt, and 19 percent clay. e. The trap efficiency of the reservoir for the entire period of operation has been 88.8 percent. f. During the period from October 1951 through September 1966, a total of 5,479 days, the reservoir was dry or operated on an inflow equals outflow basis for 1,790 days or 32.7 percent of the time. g. The most recent profile shows a definite change between ranges 8B and II, approximately 9-1/2 miles upstream from the dam. The change in profile occurs vertically at about elevation 3,832. It is noteworthy that the reservoir operated at or above that elevation for 48 percent of the time during the latest period between resurveys. This, very possibly, could be the beginning of a delta formation and could also be caused by a change in materials. h. No indication of adverse sediment deposition is evident at the confluence of the Purgatoire and Arkansas Rivers. The main channel at Range 16 is moving northward and could become a menace to farmlands in the future. 12