Laserfiche WebLink
• The annual volume of runoff varies significantly. For example, <br />runoff varied from 285 to 1,217 acre-feet per year during a <br />recent 3-year period (Metcalf s Eddy, 1975). <br />Variations in unit area runoff volumes do occur between Davis <br />and Middle Fork creeks above their confluence. For example, <br />during May and June of 1973, the flow from Middle Fork Creek was <br />over two times the flow from Davis Creek. In all other months <br />during that year and the prior two years, the flows from both <br />creeks were similar. <br />A significant portion of the flows in Davis and Middle Fork <br />creeks enter the alluvium below their confluence. Therefore, <br />the combined flow of these two creeks just prior to their con- <br />fluence will typically be greater than the flow measured in <br />Middle Fork Creek at the south property line (Metcalf S Eddy, <br />1975) . <br />• Tables G-4 and G-5 summarize the runoff volume data for the <br />Parachute Creek drainage basin. <br />The most significant hydrologic factor in relation to stream <br />flow is runoff intensity which varies as a function of surface <br />runoff from both snowmelt and rainfall. Approximately 10 percent <br />(or 1.5 inches) of the average annual precipitation over the <br />mine and plant site leaves the area as runoff. On a volume <br />basis, normal snowmelt will exceed the runoff possible from <br />rainfall events; maximum peak flows for the area, however, <br />are derived from intense rainfalls. The Metcalf & Eddy study <br />(1975) reported the following regarding runoff intensity: <br />• <br />G-9 <br />