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.~, ,.~. ~~ anu ii. ~~ r.~.~ W W WHEELER SNOWNELT RUNOFF The amount and timing of the spring snowmelt runoff is dependent upon a number of variables including soil moisture conditions, temper- ature, density of vegetation, and exposure (to wind and sun). However, as one might suspect, the most important factor is the actual depth and moisture content of the snowfall. Snowfall in the upper Williams fork basin is reflected in the long term records of the Glen Mar Ranch {1947-1981) and .Ione~; Pass (1957-1981} snow courses. These records include measurements: of snow depth and total moisture content taken on the first day of tiie months February, March, April and May. It should be noted that the runoff is dependent primarily upon the moisture .content of the snowpacl:. At Bones Pass (elevation 10,400), the maximum seasonal moisture content ranged from 9.J inc!-.es (1981) to 24.6 inches (1974). At Glen Mar (elevation 8870), the maximum ranged Trom 4.3 inches (1481) to 15.7 inches (1952). Averaging the values at the two snow courses for the period of concurrent record, the average maximum moisture content ranged from 6.65 inches (1981) to 18.15 inches (1974). A frequency analysis of the annual data was performed to determine the maximum moisture content which could be expected for the ewerage annual and the 50, 100, 200 and 500 year events. Because the mean basin elevation of the Henderson Project area is about elevation 9600±, the average of the data from the two Snow courses was considered most applicable for the analysis. The results are as follows: Recurrence Interval Average Annual 50-year 100-year 200-year 500-year Maximum Seasonal Moisture Content 14.0 inches 20.4 inches 21.2 inches 22.0 inches 22.8 inches -4- 029750 W•W• WHEELER ~ooa RECEIVED TIME NOV. 9. 11~11AM PRINT TIME NOV. 9. 11:18AM