Water-resources data were collected in the Bad River Indian Reservation of northern Wisconsin from 1983 through 1987. Some data are interpreted to describe ground-water flow, groundwater quality, streamflow, and surface-water quality. Data also are presented in tables and appendixes for baseline reference.

Precambrian sandstone and basalt underlie varying thicknesses of sandy till, outwash sand and gravel, and clay deposited in glacial meltwater lakes. The thickness of glacial deposits generally ranges from 100 to 300 ft but reaches a known thickness of almost 1,000 ft on the east-central edge of the Reservation. Sand and gravel deposits are generally buried beneath 50 to 150 ft of glacial lake clays and silts throughout most of the Reservation. These buried sand and gravel deposits lie directly on Precambrian sandstone of unknown thickness in the northern half of the Reservation. The sand and gravel deposits and the sandstone form a single aquifer system confined by the overlying clay deposits. In and near the village of Odanah, numerous wells finished in either the sand and gravel or in the sandstone flow above land surface.

Estimates of the horizontal hydraulic conductivity of the sand and gravel based on 30 specific- capacity tests range from about 2 to 700 ft per day with a median value of about 80 ft per day. Horizontal hydraulic conductivity estimates for the sandstone range from about 1 to 360 ft per day with a median of about 2 ft per day. These estimates are based on 42 specific-capacity tests of wells open only to the upper 20 to 60 ft of sandstone. The horizontal hydraulic conductivity of the sandstone appears to decrease with depth; highest estimates were determined for wells open only to the upper 20 ft of sandstone.

Ground water in the confined aquifer system is a calcium magnesium bicarbonate type with relatively low total dissolved solids concentrations. The median total dissolved solids concentration of water from 17 sand and gravel wells is about 150 milligrams per liter and the median for water from 21 sandstone wells is about 244 milligrams per liter. High concentrations of iron and manganese were found in water from 12 of 36 sampled wells. Total recoverable concentrations of iron exceeded 500 micrograms per liter in 5 wells and concentrations of manganese exceeded 50 micrograms per liter in 7 wells.

Streamflow has been continuously measured at a streamflow-gaging station in the Bad River near Odanah for much of the time since 1914. This station monitors drainage from a basin with an area of 597 square miles and the average daily discharge of the Bad River at this gaging station is 622 cubic feet per second. The peak instantaneous flow at the station was 27,700 cubic feet per second on April 24, 1960 and the minimum instantaneous flow was 34 cubic feet per second on November 8,1976.

Analysis of water samples collected at 12 sites at 10 small streams during base-flow conditions indicate that the concentrations of common chemical constituents are similar to but lower than those found in ground water. The median concentration of total dissolved solids was about 110 milligrams per liter as compared to about 155 milligrams per liter in ground-water samples from wells finished in sand and gravel.