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<br />l <br /> <br />--") <br /> <br />N <br />-..J <br />Cl') <br />:';1 <br /> <br />i. The channel opening at the AT&SF Railway bridge over the <br />Purgatoire River decreased slightly between the last two resurveys. <br />The opening has decreased by 757 square feet since the original survey <br />of January 1942 but the decrease has not been caused by backwater <br />effects of John Martin Reservoir, The highest reservoir elevation to <br />date has been 3,856.16 feet. This did not cause backwater effects <br />at the bridge section. <br /> <br />j. The computation of volumes by the Constant Factor Method <br />and subsequent computation of areas from these volumes introduces an. <br />error within increments that are compensated for in subsequent incre- <br />ments causing the area curve to oscillate, These erratic incremental <br />areas will be corrected in the next resurvey as indicated in paragraph 42g. <br /> <br />k. The bedload carried into John Martin Reservoir is small. <br />It amounts to about 5 percent of.the total load. <br /> <br />1. The resurvey of degradation ranges below John Martin Dam <br />indicates a total degradation of 205 acre-feet since the original survey <br />of degradation ranges in January 1944, Average degradation has been <br />0.22 foot, This is less than 0,01 foot per foot per year. <br /> <br />42. ConaZusions. <br /> <br />a. The selective sampling program at the two inflow stations <br />to John Martin Reservoir will be continued on the same basis as pres- <br />ently used. <br /> <br />b. Daily sampling of releases will be continued at the out- <br />flow station, <br /> <br />c. Annual corrections of the area-capacity table for the. <br />lower 20,000 acre-feet of storage wi 11 be made through drawdown data <br />or from estimated sediment inflow-outflow data computed at the stations. <br />If necessary, a partial survey of the lower portion of the reservoir <br />will be made. <br /> <br />d. Resurveys of the degradation range system as well as the <br />tributary ranges will be made when determined to be necessary. The <br />changes at these ranges have not been enough to justify resurveys each <br />time the reservoir is resurveyed. . <br /> <br />e.Resurveys will be scheduled when inflow to the reservoir <br />has been 1,250,000 acre-feet or more instead of on the basis of elapsed <br />time. Resurveys on this basis could be only two or three years apart <br />or could be as much as ten years apart, In the event of extended periods <br />between resurveys, a partial resurvey of the lower portion of the reser- <br />voir may be made to adjust the area-capacity tables. <br /> <br />13 <br />