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The above do not include bedload. These figures are not significantly ~ different from previous periods of observation. The size of suspended sediment at the outflow station below the dam shows the following size r~ distribution: --J en i.~ Percent Suspended Sediment Outflow Sand Silt Clay Reservoir in operation 4 48 48 Riverflow 6 69 25 Initial release after storage 59 35 6 It will be noted that there is a considerable change in size distribu- tion with the initial release after storage. This is evident when irrigation releases are made after winter storage. The suspended sand load with the reservoir in operation is comparable to the sand load in the riverflow but there is a notable change in silt and clay sizes when the storage is depleted and riverflow takes over. 35. Results of sediment deposit sampling are shown in tables 9 and 10. Table 9 shows the size analysis of 11 samples taken through- out the reservoir. The samples from all locations show very little material of sand size except at Range 29 near the mouth of Rule Creek. This sand deficiency is probably attributable to the large sediment inflow during the 1965 flood that carried very little sand. Samples taken on the Arkansas River at Las Animas on 19 June 1965 show 99 percent silt and clay and 1 percent sand. Samples taken on the Purgatoire River at Las Animas on 28 June 1965 show 98 percent silt and clay and 2 percent sand. 36. A steel tub~was forced into the deposits to secure samples of the reservoir deposits for size and density analysis. The depth of the sample depended on the ability of the sampler to penetrate the deposits. At some locations, this was almost to the depth of prior deposition. Samples secured from the reservoir were taken at locations that would indicate trends in size distribution for the most recent deposits. No attempt was made to compare the size dis- tribution of the latest samples with that of prior samples because of the many factors involved in selecting comparative samples and conditions of deposition. Grain size and density of samples at range lines are graphically illustrated on plates 23 and 24. 37. Density and aonso~idation of reservoir deposits. The sedi- ment retention in John Martin Reservoir is presented in table 8. The effects of consolidation on the retained sediment were calculated by using the method described in "Determination of Unit Weight of Sedi- ment for Use in Sediment Volume Computations," by Carl R. Hiller, using the Lane and Koelzer values of initial weight and the coeffi- cient for the type of reservoir having "considerable drawdown." The size distribution was taken from representative samples of the reservoir deposits. Table 13 presents the results of these computations. 10