Hydrology and water quality of the Forest County Potawatomi Indian Reservation, Wisconsin

This report presents data from a study by the U.S. Geological Survey, in cooperation with the Forest County Potawatomi Community of Wisconsin, to document the hydrology and water quality of the Potawatomi Indian Reservation in southern Forest County. Data were collected from October 1981 through September 1987.  

Glacial sand and gravel forms the primary aquifer on the reservation. This aquifer is unconfined, and its saturated thickness ranges from approximately 200 feet to zero feet in areas where the bedrock crops out. Horizontal hydraulic conductivity of the glacial deposits is estimated to range from 0.4 to 48 feet per day.

Three watersheds encompass the Reservation: The Wolf, the North Branch Oconto, and the Peshtigo. Estimates of base-flow discharge that will occur on the average once every 2 years for a 7- day period for Reservation streams range from 7.5 ft3/s (cubic feet per second) for North Branch Oconto at Wabeno to 32 ft3/s for the Rat River near Wabeno.

Ground water in the study area is a calcium magnesium bicarbonate type and is suitable for most uses. The ground water sampled during the study was slightly alkaline and moderately hard to very hard; median hardness was 135 mg/L (milligrams per liter) as calcium carbonate. Alkalinity of ground water ranged from 79 to 318 mg/L; median alkalinity was 123 mg/L as calcium carbonate.

With the exception of nitrate in water from one well sampled, constituent concentrations were less than the U.S. Environmental Protection Agency's Maximum Contaminant Levels (MCL's) for drinking water. Nitrate plus nitrite concentration was 15 mg/L as N, or 50 percent greater than the MCL, in one well located one-half mile northeast of Lake Lucerne.

Secondary Maximum Contaminant Levels (SMCL's) for iron were exceeded in water from two wells. In one of these two well waters, the manganese concentration equaled the SMCL.

Streams on the Reservation also contain a calcium magnesium bicarbonate type water. The stream waters are slightly alkaline and are considered soft to moderately hard; median hardness in stream samples was 56 mg/L as calcium carbonate. The alkalinity in stream samples ranged from 46 to 59 mg/L as calcium carbonate; the median value was 51 mg/L. Stream water is intermediate between hard, alkaline ground water and soft, acidic precipitation and surface runoff. Low but detectable concentrations of chromium, copper, iron, magnesium, mercury, and zinc were detected in most bottom-material samples.

Water quality of three lakes on the Reservation is variable and depends on the degree of connection with the ground-water system. In general, Bug Lake and Devils Lake are in poor hydraulic connection with the ground-water system, and their waters contain low concentrations of dissolved solids and alkalinity and low pH. King Lake is in good hydraulic connection with the ground-water system, and its waters contain higher concentrations of dissolved solids and alkalinity and higher pH than Bug and Devils Lakes.