This report presents the results of a study by the U.S. Geological Survey, done in cooperation with the Red Lake Indian Reservation Tribal Council, to evaluate the water resources of the contiguous Red Lake Indian Reservation. Water resources of the contiguous Red Lake Indian Reservation meet the present (1989) needs for potable supply and other household uses. In addition, they provide ecological, recreational, and aesthetic benefits.

Mean annual precipitation in the study area is 22.7 inches. Approximately 90 percent of this precipitation returns to the atmosphere by evapotranspiration; the remainder becomes runoff. Some of the precipitation that contributes to evapotranspiration and runoff initially infiltrates the land surface and recharges the ground-water reservoir. The net recharge to ground water generally ranges from roughly 0.5 to 1.35 inches per year. Assuming negligible long-term changes in the amount of ground water in storage, the recharge to and discharge from the ground-water reservoir balance each other over time.

Glacial-drift aquifers are the source of ground water in the Red Lake Indian Reservation. The most significant sources of ground-water supply are confined glacial-drift aquifers, which are discontinuous lenses of sand and gravel 50 to 150 feet below land surface. Estimated yields of wells completed in these aquifers range from approximately 20 to 240 gallons per minute.

Lower and Upper Red Lakes, which extend over one fourth of the study area, are the largest surface-water bodies. The study area also includes streams and many smaller lakes. Most of the streams drain into Lower and Upper Red Lakes, and the lakes discharge into the Red Lake River. Spring snowmelt generally causes peak flows in the streams. Low-flow conditions commonly occur during midsummer to early fall and winter.

The quality of ground water is suitable for drinking and other household uses, and the quality of the surface water generally meets U.S. Environmental Protection Agency criteria necessary for the maintenance of aquatic life. The major ions in both ground and surface water are calcium, magnesium, and bicarbonate. Lower and Upper Red Lakes are eutrophic to mesotrophic on the basis of their summer Secchi disk-transparency readings, which ranged from 2.6 to 8.2 feet. The concentration of total organic carbon in samples from Lower and Upper Red Lakes and four streams were below or, in the case of one stream, about equal to 30 milligrams per liter, which is indicative of water little affected by human activities. The sample with the highest organic carbon content was collected from a stream that drained peatlands, which were probably sources of organic matter in the runoff. The concentration of nitrite plus nitrate in samples collected from Lower and Upper Red Lakes in late summer was below 0.01 milligrams per liter, which is characteristic of water uncontaminated by animal wastes. Total phosphorus in these samples ranged from 0.01 to 0.02 milligrams per liter. Most of this phosphorus was in the particulate organic fraction because of the abundance of phytoplankton.