Water resources of the Lac Du Flambeau Indian Reservation, Wisconsin, 1981-86

Unconsolidated glacial sand and gravel deposits provide virtually all water used by residents of the Lac du Flambeau Indian Reservation.  Well yields of 10 to 20 gallons per minutecan be obtained from these deposits throughoutthe reservation. Yields of 1,200 gallons perminute are obtained from wells for a fish-rearingfacility near the village of Lac du Flambeau. Thesaturated thickness of glacial deposits rangesfrom 100 to just less than 200 feet throughout thereservation. Domestic water-supply wells aretypically 50 to 150 feet deep.

Estimates of the horizontal hydraulic conductivity of glacial deposits generally range from about 1 to 50 feet per day and average about 20 feet per day. However, a horizontal hydraulicconductivity of about 950 feet per day and atransmissivity of about 71,000 feet squared perday were calculated from aquifer-test data at thefish-rearing facility.

Lakes cover about 20 percent of the reservation. Many of these lakes are smallseepage lakes or drainage lakes with surfaceareas less than 100 acres. Depth profiles oftemperature, dissolved oxygen, pH, and specificconductance show that all lakes more than25 feet deep are thermally stratified duringsummer months. The median alkalinity andhardness for 34 lake-water samples were 30 and31 milligrams per liter as calcium carbonate,respectively. The median dissolved-solids concentration was only 50 milligrams per liter.  Total phosphorus concentrations in water samples are high enough to classify some lakes as eutrophic.

Calcium, magnesium, bicarbonate and, to a lesser extent, chloride and sulfate are the major dissolved ions in ground water and surface water.Concentrations of these ions in ground water aretwice those in lake water. Nitrate and chloride concentrations in ground-water samples from 25 wells in the reservation were less than the maximum concentrations allowed by Wisconsin drinking-water standards. Iron and, to a lesserextent, manganese seem to be the only constituentspresent at high enough concentrations tosignificantly affect drinking-water supplies onthe reservation. The maximum concentration of dissolved solids found in ground water on the reservation was 198 milligrams per liter, the median was 86 milligrams per liter. The relatively small amount of dissolved solids in ground water and surface water on the reservation is typical of water quality in northeastern Wisconsin.