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<br />. <br /> <br />. <br /> <br />. <br /> <br />0768 <br /> <br />7.27 inches was computed. The mass rainfall curve and tabulation <br /> <br /> <br />arranged in critical order and the hyetograph are shown on plate 7. <br /> <br /> <br />56. Spillway design flood. - The spillway design flood hydrograh <br /> <br /> <br />for the drainage area above Trinidad dam site was computed by using <br /> <br /> <br />the runoff from the selected storm rainfall, an initial loss of <br /> <br /> <br />1.20 inches, and a minimum infiltration rate of 0.49 inch per hour; <br /> <br /> <br />the rainfall excess was then applied to the adopted unit hydrograph. <br /> <br /> <br />The spillway des!.gn flood would have a peak discharge of 238,000 cubic <br /> <br /> <br />feet per seco~j &~d a volume of 166,800 acre-feet, which is equivalent <br /> <br /> <br />to 4.!r8 inches of rW10ff from the 698 square miles of drainage area <br /> <br /> <br />above the Trinidad dam site. During the summer months, flOl'JS at Trinidad <br /> <br /> <br />gage average about 150 cubic feet per second for long periods of time. <br /> <br /> <br />For this reason base flow has been neglected in computing the spillway <br /> <br /> <br />design flood. The spiU,ray design flood is about 240 percent and 285 per- <br /> <br /> <br />cent of the standard project flood, in peak discharge and volume, respec- <br /> <br /> <br />tively. A comparison of the peak discharge of the spillway design flood <br /> <br /> <br />to the envelope curve of maximum experienced peak discharges in the <br /> <br /> <br />Albuquerque District is shown on plate 6. The spillway design flood <br /> <br /> <br />hydrograph and a tabulation of the average 2-hour ordinates are shown on <br /> <br /> <br />plate 7. <br /> <br /> <br />57. Spillway design flood ro~~~~, - The spillway design flood was <br /> <br /> <br />routed through the reservoir assuming reservoir full to bottom of notch, <br /> <br /> <br />elevation 6,259.0, at beginning of inflow. It was also assumed that the <br /> <br /> <br />conduit gates would be inoperative during the passage of the flood. The <br /> <br /> <br />spillway design flood, when routed through the reservoir, would reach a <br /> <br /> <br />maximum water surface elevation of 6,292.3 or 19.3 feet of surcharge over <br /> <br /> <br />the spillway crest. The peak inflow into the reservoir would be <br /> <br /> <br />238,000 cubic feet per second, and the peak outflow would be 173,500 cubic <br /> <br /> <br />feet per second. The spillway design flood infloVJ, outflow, and pool ele- <br /> <br /> <br />vation hydrographs for this operation are shown on plate 7. <br /> <br />41 <br /> <br />APPENDIX B <br /> <br />. <br /> <br />