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• The water yield for East Pyeatt gulch was determined at the flume site S-3 (East Pyeatt drainage). As <br />mentioned previously, East Pyeatt runoff is monitored continuously with a Stevens type F recorder. <br />Figure 2.7-15a is a plot of the runoff for the period of April 1, 1985 to October 31, 1986. The volume of <br />runoff from August, 1985 to July 31, 1988 was approximately 260 acre -ft. The drainage area above the <br />East Pyeatt flume site (S-3) is 1,346 acres. Baseflow is estimated to be approximately 125 gallons per <br />minute (Figure 2.7-15a). The baseflow, therefore, accounts for approximately 200 acre -ft of flow per <br />year. Runoff from precipitation would, therefore, total 60 acre ft/yr or a depth of 0.5 inches for the period <br />analyzed. This value is lower than the estimated mean annual runoff yield from the basin due to the <br />wanner temperatures in earty 1986. <br />During the months of January, February, March and April, the average daily high temperature was above <br />freezing at 33.1, 38.0, 52.9 and 54.3 degrees F, respectively. The significance of these mean daily highs <br />is that the snowpack melted during a longer span of time, thereby allowing for more infiltration and less <br />runoff. It is evident from Figure 2.7-15a that a much higher rate of runoff occurred during the spring of <br />1985 when temperatures were more normal than during the spring of 1986. <br />Some over -estimation of the flow in the analysis occurs for the winter months. Due to the remoteness of <br />• the sites, the stilling wells were often frozen. During these months, occasional warts temperatures would <br />allow the stilling well to thaw. The measurements obtained on the wanner days were averaged and <br />assumed to be representative of the monthly flow rate. The runoff value obtained by this method is <br />higher than the actual average flow. <br />2-41aa <br />MAY -L-3�9$----- <br />