Data were collected on the hydrology of the Copper-Nickel study region, to identify the location and nature of groundwater resources, determine the flow characteristics and general quality of the major streams, and determine the potential effects of mining copper and nickel on the hydrologic system. Groundwater investigations indicate that water generally occurs in local flow systems within surficial deposits and in fractures in the upper few hundred feet of bedrock. Availability of ground water is highly variable. Yields commonly range from only 1 to 5 gallons per minute from wells in surficial materials and bedrock, but can be as much as 1,000 gallons per minute from wells in the sand and gravel aquifer underlying the Hnbarrass River valley. Except over the mineralized zone, ground water in the surficial deposits is a mixed calcium magnesium bicarbonate type. Ground water over the mineralized zone generally has both a greater percentage of sulfate, compared to bicarbonate, and concentrations of copper and nickel greater than 5 micrograms per liter. Surface-water investigations indicate that the average annual runoff from streams is about 10 inches. Plow characteristics of streams unregulated by industry are similar, with about 60 percent of the annual runoff occurring during snowmelt in April, May, and June. Flood peaks are reduced in the Kawishiwi River and other streams that have surface storage available in onchannel lakes and wetlands. These lakes and wetlands also trap part of the suspended-sediment load. Specific conductance in streams can exceed 250 micromhos per centimeter at 25° Celsius where mine dewatering supplements natural discharge. Between 85 and 95 percent of the surface water used is for hydroelectric power generation at Winton and thermo-electric power generation at Colby Lakes. Mine dewatering accounts for about 95 percent of the groundwater used. Estimated groundwater discharge to projected copper-nickel mines ranges from less than 25 to about 2,000 gallons per minute, depending on the location and type of mining activity. The introduction of trace metals from future mining to the groundwater system can be reduced if tailings basins and stockpiles are located on material of low permeability, such as till, peat, or bedrock.
Flood data from gaging stations on Wisconsin rivers and streams are listed in this report. From these data, composite frequency curves were defined which express the ratio of floods of various recurrence intervals to the mean annual flood. Multiple correlation techniques were used to obtain formulas that relate the basin parameters of drainage area, main channel slope, and lake and reservoir surface area to the mean annual flood. By combining the results from the mean annual flood formulas with the regional frequency curves, the flood-frequency relationship can be determined for most sites in the State where the drainage basin exceeds 20 square miles. The curves and formulas are not applicable to: main stem of several of the larger rivers, highly regulated streams where it is possible for man to alter flood peaks, and drainage basins under 70 square miles in a part of west-central Wisconsin. Irainage area ]sq mi)
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