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<br />16 <br /> <br />ANALYSIS OF GAGING STATION RECORDS <br /> <br />Gaging station records were used in the analysis to <br /> <br />predict the design discharge for DeBeque Canyon. The Log <br /> <br />Pearson Type III procedure was used to determine the re- <br /> <br />currence interval curve for each station. The observed <br />d' l' N+l <br />lscharges were potted, uSlng the ~ recurrence interval, <br /> <br />along with the Log Pearson Type III curve. See figures 7 <br /> <br />thru 11 in the appendix. <br /> <br />Two periods of time were studied; records before and <br /> <br />after 1934. The year 1934 was picked for two reasons. <br /> <br />One, that was about the time the first retention structure <br />(Williams Fork Reservoir) was built. Secondly, that year <br />was the approximate time there was a break in the principal <br />gaging station records. Gage 9-1060 records stopped in <br />1933 and gage 9-0955 records started in 1934. <br />Gage 9-0725 at G1enwood Springs is the only gage on the <br /> <br />Colorado River near the study reach that had many years of <br />records in both periods of time; 34 years before 1934 and <br />33 years after 1933. There was a difference of 11,500 cfs <br />(33%) between the 50 year floods calculated for the two time <br />periods. See figure 7 in the appendix for the recurrence <br />interval plot. A graph of the peak flows for gage 9-0725, <br />figure 12, readily illustrates a trend of lower annual peak <br />flows in recent years. <br />The two periods of gage records were plotted in figure <br /> <br />5 to form a Discharge vs. Drainage Area Curve. A straight <br />