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<br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />1960, 1964 and 1973 appreciable precipitation over widespread areas was recorded up- <br /> <br /> <br />stream of this study reach. Further, these years did not produce high frequency peak run- <br /> <br /> <br />off at Gunnison River near Gunnison and Tomichi Creek at Gunnison gaging stations. <br /> <br />I <br />I <br />I <br /> <br />To check the accuracy of the precipitation data obtained from N. O. A. A., <br />Atlas 2 and T. P. 40, hourly precipitation data were analyzed for the Gunnison station. <br />The data WClS selected as the peak 24 hour precipitations from the month of maximum cumu- <br />lative precipitation. Months of similor quantities of precipitation were all checked for <br />peak daily amounts. From the hourly precipitation data peak precipitation for one, two, <br />three, six, twelve and twenty-four hour periods were determined for the period 1949- <br />1974. Hourly data for years 1952, 1954, 1956 and 1972 were not available. This data <br />is presented in Table 5. Precipitation data for one hour was then distributed according <br />to log normal procedure and plotted on log - normal paper. This procedure was repeated <br />for two, three, six, twelve and twenty-four hour durations. The precipitation frequencies <br />and depths for various durations were then compared with those obtained from N. O. A. A. <br />Atlas 2 and T. P. 40. The results showed a resonable agreement between the two sets of <br />values. <br /> <br />I <br /> <br />I <br /> <br />The design storms uti lized to determine the design discharges were based on the <br />precipitation data developed from the data published in N. O. A. A. Atlas 2 and T. P. 40. <br />Depth-duration-frequency curves for sub-basin T-l through T-5 of Tomichi Creek <br />basin were developed. This data was utilized for design storm to determine the design dis- <br />charges from these individual sub-basins. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Generally speaking the more productive streams of Wesl'ern Colorado have exper- <br />ienced lorge peak runoff rates during years of high temperatures in combination with snow <br />packs of high wal'er content. An exception to l'his has been the San Juan Mountains area <br />where rainsl"orms have also been known to produce peak flows. <br /> <br />To analyze the impact of these rainstorms in San Juan basin on Gunnison River <br />basin, correlations of precipitation data from the two basins were performed. Table 6 <br />shows the data used in these correlations. The basis for the selection of this data was <br /> <br />I <br /> <br />-3- <br />