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r ~ ) 14 • <br />flooding of roads and fields, and plugging of water intake systems <br />far the mines. <br />The capability of a stream to maintain indigenous fish populations <br />is jeopardized when factors extrinsic to natural degradation are intro- <br />duced. These factors become critical only when the tolerance level for <br />a fish species is exceeded. <br />Excepting flood-producing rainstorms in summer, runoff is dominated <br />by snowmelt which creates high discharges generally between early May <br />and the end of July.. Peak discharge at Stonewall during this period was <br />about 65 and 80 cfs in 1978 and 1979, respectively. Very low flows were <br />recorded from mid-September to mid-April each year, with minimum flows <br />C ) being 4 cfs at Stonewall. These periods of low flow are of most concern ~• <br />when considering welfare of fish. This is because of the reduced <br />capacity for di]ution of any toxic or harmfu] effluents introduced into <br />the stream. <br />Water quality is monitored at a USGS surface water gaging station <br />at Stonewall, Colorado on the Middle Fork approximately 4 miles upstream <br />from the Allen Mine. Measurements of water <br />station were averaged in the Water, lJaste 8 <br />Of the chemical parameters reported, only a <br />welfare of fish populations. Measurements <br />turbidity, which may be of more consequence <br />r are not available from USGS. <br />quality parameters at this <br />Land, Ltd. (1980) report. <br />few can be related to the <br />~f suspended solids and <br />to the production of fish, <br />