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• Water yielded from the lease area streams comes mainly as surface runoff in direct response to <br />thunderstorms and/or snowmelt originating at higher elevations. Groundwater discharge may contribute a <br />small amount on a local basis during the snowmelt season. During 1979, no runoff events were noted in <br />Scullion Gulch. However, during 1980, three runoff events were detected and sampled. An event durino <br />the 1979-80 winter had a peak flow of about 185 cubic feet per second, during the late summer of 1980 a <br />flow of 135 cubic feet per second was recorded, and during the late fall a flow of 45 cubic feet per second <br />was recorded. Three runoff events occurred during 1979 in Red Wash at a crest gage station located near <br />the mouth of the basin. An event during the first part of April was the result of snowmelt runoff, producing <br />an estimated peak flow of 94 cubic feet per second (based on flow depth, channel geometry, and Manning's <br />open channel flow equation; see Figure II.C-5) and presumably lasting several days. Flows near the end of <br />August and near the end of October resulted from thunderstorrn activity. The peak flows from the <br />thunderstorm events were both lower than that resulting from the snowmelt event (8 and 42 cubic feet per <br />second, respectively) as was the duration (less than 24 hours in both thunderstorm cases). Because of the <br />general proportional relationship between peak flow and runoff volume in ephemeral watersheds (see <br />Renard and Keppel, 1966 among others) it is assumed that the flow volume was also greater from the <br />snowmelt event than the thunderstorm events. During 1980 three runoff events (corresponding with the <br />three runoff events detected on Scullion Gulch) were detected in Red Wash. As measured by the crest <br />gage at SW1-1, the measured peak flows were well over 240 cubic feet per second which is the upper limit <br />of the calibration curve, except for the late summer event which had a peak flow of about 240 cubic feet per <br />second. <br />• It is expected that there is runoff in a normal year in Scullion Gulch and that 1979 was abnormal in that <br />respect. The data from these gages on these two streams are presumably indicative of general seasonal <br />and spatial runoff variations in Scullion Gulch and Red Wash. Scullion Gulch probably experiences little <br />runoff at its mouth because of the presence of twice the number of stock-watering ponds per unit drainage <br />area relative to the Red Wash Basin (an average of 0.4 as opposed to 0.2 ponds per square mile) and the <br />lower snowpack accumulation created by its lower relief (i.e., approximately 25 percent of the Red Wash <br />lies at elevations above 6400 feet, the approximate upper elevation in the Scullion Gulch Basin). Red <br />Wash, on the other hand, likely contributes to the flow of the White River during the early spring as a result <br />of high elevation snowmelt runoff, except during drought years. Summer runoff from the Red Wash Basin <br />is probably highly variable, occurring only when a thunderstonn of sufficient intensity and duration occurs to <br />produce a sufficient amount of overland flow at the source to overcome transmission losses in the stream <br />channel. <br />• Permit Renewal #3 (Rev. 8/99) II.C-10 <br />