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<br />Records of peak flow on Purgatoire River at Highland Dam, a short dis- <br />tance upstream, are available for the years 1932-55. The period of <br />comparable record is 1949-55. A correlation study of the records at <br />both sites disclosed that the two records are markedly similar. Fur- <br />ther, the two drainage areas differ in size by less than four percent. <br />Therefore, it was decided to use the record at Highland Dam for the <br />period 1932-48, without adjustment, as the record for that period at <br />Las Animas. Flow data for the entire 1922-65 period were subjected <br />to analysis as described in "Statistical Methods in Hydrology." Peak <br />frequency curves on Purgatoire River at Las Animas for conditions with <br />and without the authorized Trinidad Reservoir in operation are shown <br />on plates 15 and 16. Data used in the development of these curves are <br />shown in table 14. <br /> <br />VI - PROJECT DESIGN FLOOD <br /> <br />6-01. GeneraZ.- The June 1921 flood had an estimated peak dis- <br />charge of 187,000 c.f.s. at Las Animas. After that flood, the Pueblo <br />Conservancy District constructed a flood control project at Pueblo. <br />The project included Barrier Dam on the Arkansas River. This dam is <br />located about 6 miles upstream from Pueblo at about the same location <br />as the recommended site for the authorized Pueblo Dam. Studies indi- <br />cate that with Barrier Dam in operation the June 1921 flood peak at <br />Las Animas would have been reduced to 140,000 c.i.s. With the author- <br />ized Pueblo Dam in, operation, the June 1921 flood peak at Las Animas <br />would have been reduced to 108,000 c.f.s. <br /> <br />6-02. Project design fZood.- Project document studies indicated <br />that a project that would provide protection against discharges greater <br />than 155,000 c.f.s. would not be economically justified and that pro- <br />tection against 140,000 c.f.s. would be the most economical and would <br />provide a high degree of protection. As a result of those studies a <br />peak discharge of 140,000 c.f.s. was selected as the project design <br />flood. The project design flood is approximately 70 percent of the <br />standard project flood and 30 percent greater than the flood of record <br />regulated by the authorized Pueblo Dam. However, as mentioned in <br />paragraph 5-06, the change in discharge-frequency will necessitate <br />additional economic studies. These studies will include further con- <br />siderations for the project design flood. Recommendations will be <br />presented in the general design memorandum. <br /> <br />6-03. A comparison of the magnitude of the standard project <br />flood and project design flood of 140,000 c.f.s. with the envelope <br />curve of maximum peak discharges of record for areas within the Albu- <br />querque District is shown on plate 17. The plots of the standard <br />project and project design floods appear somewhat low in comparison <br />with the maximum experienced peak curve. An explanation for this is <br />that the peak flow data that controls the large drainage area portion <br />of the curve were obtained mainly from the lower reaches of the Pecos <br /> <br />23 <br />