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'::I N -..J e11 (Xl change was determined by the end-area method assuming the change on each range was representative of the change halfway to the adjacent ranges. The range system was almost destroyed by the June 1965 flood but was reestablished during the fall of 1966. Additions to the range system will be made when necessary. SAMPLING 18. sus~ended sediment s~ting. Daily suspended sediment sampling at t e inflow stations or John Martin Reservoir was dis- continued on 1 October 1962. Since then sampling at these stations has been done on an intermittent selective basis by the U.S. Geo- logical Survey. The outflow below John ~Iartin Dam is sampled daily when releases are being made from the reservoir. 19. Riverbed and lake deposit sampling. Riverbed samples were not taken outside the boundary of John Martin Reservoir during the period 1962-1966. During the October 1966 resurvey 11 samples of deposited material were secured from selected locations in the reservoir. The reservoir pool elevation at the time of sampling was 3,831.5 and samples were secured from the bottom of the reservoir by a drop-tube type sampler. The reservoir deposits have been exposed to alternate wetting and drying, and deep penetration with this type of sampler was not possible. Therefore, only the top of the deposits was sampled. A radioisotope sediment densitometer was used at 16 locations in the reservoir to obtain 31 density readings to depths of 7 feet in the deposits. 20. Density flows. Density flows were observed entering the res- ervoir several times during the summer of 1966. Samples were taken below the dam during periods- when these flows were observed passing through the outlet works. The density flows are discussed in para- graphs 31 and 32. RESULTS OF SURVEYS AND SAMPLING 21. Reservoir sediment range survey. The results of the 1966 resurvey are presented on the Sediment Data Summary, ENG Form 1787, which is presented as table 3 of this report. The 1966 area-capacity is presented in tabular form on table 4 and in graphic form on plate 4. Longitudinal profiles of the reservoir are shown on plate 5. Profiles of representative sediment ranges are shown on plates 6 through 15. 22. The longitudinal profiles of the reservoir, presented on plate 5, were drawn using the average bed elevation at each sedi- ment range as indicated by the original survey and the 1962 and 1966 resurveys. The distance between ranges is measured along the axis of the reservoir. These profiles clearly indicate comparative changes as produced by sediment deposition at each range line. 6