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• Tables 9, 10 and I 1 present the monthly water balances for Taylor, Nilson and Goodspring <br />Creeks for the average year (October 1974 through September 1970. These data show <br />runoff occurring primarily in the late winter and early spring months of February, March and <br />April. These are the months of highest snowfall and saturated ground conditions which allow <br />for runoff to take Place. It must be stressed that these data are for runoff, i.e., flow over and <br />above the baseflow values. <br />Runoff values for these watersheds are extremely low and range between 1.3% and 4.2% of <br />the precipitation falling on the watersheds. ET ranges from 95.6% to 93.6% of total <br />precipitation indicating that nearly all of the precipitation is evaporated in place. This is <br />particularly true of winter snowfall, when dry winds occurring in the late winter and spring <br />may evaporate significant depths of snow before it begins to melt, resulting in no stream <br />flow. Obviously the amount of water left for infiltration and deep percolation is a minute <br />fraction of the total. <br />The computed runoff figures presented above appear to be reasonable estimates when <br />compared to recorded flows in Table 7. As with all estimates of runoff for semi-arid regions, <br />the probable error in many variables entering into the computations may range from <br />negligible to as large or larger than the predicted runoff values. This is mentioned not to <br />discredit the results, but to remind the reader that these figures are estimates, and wou]d be <br />subject to revision as additional data becomes available. <br />Flow Estimates <br />Another part of the requirements for permit approval with respect to the hydrology of the <br />basins in and adjacent to the mine permit area is an estimation of flow values for the high and <br />low flows in each watershed. These calculations assist the mine operations personnel in <br />designing runoff detention ponds, diversion conveyances and channel stabilization structures. <br />The method used to estimate these flow values for each watershed was the United States <br />Department of Agriculture, Soil Conservation Services' Triangular Unit Hydrograph <br />Procedure. Flow records for <br /> <br />2.04.7-49 <br />