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f ~ _ Creek Ditch. This relocation is subject to U. S. Forest Service appro- val. The new location will measure flows above the permit boundary ' and will also provide more accurate measurements than the present location on Upper Dry Fork. Analysis Plan The method for dei:errnining potential impacts on stream flows resu~,ting from mining is baked on the paired watershed concept. A control (unaffected) watershed is used as barometer for detecting possible changes in the affected basin. A calibration period of about fivE~ to ten years is normally sufficient to establish a streamflow relation- ship bet;reen the paired basins. Once one of the basins has been affected, the calibration relation is used as a basis to detect tr.e magnitude and statistical significance of any impact on streamflow resulting from the change in the basin. The choice of a control - watershed is an important consideration. formally a control which has characteristics similar to the affected watershed is selected. lJhen . more than one possible control watershed is available, the basin pro- viding the best calibration relationship is preferable as a control. Four gaged watersheds are possible candidates as control watersheds for the Dry Fork at tlinnesota Creek - they are Lick Creek, South Prong, Horse Creek and East Fork. Collection of five to ten years of baseline calibrati~m period/data will be necessary to narrow the list of possible control watersheds. The accuracy of the rela- tionship between flows from the control and affected basin is the important consideration in the selection of the control watershed. Several questions arise when considering this approach for detecting possible impacts of mining on•streainflow: (1) liow do we account for tyre slo~vly changing effects on strewn flo,v response that may occur should the basin be affected? • (lo)