Hydrogeology of Confined-Drift Aquifers Near the Pomme de Terre and Chippewa Rivers, Western Minnesota

Confined-drift aquifers in a 1,380-square-mile area of western Minnesota range in thickness from less than 10 feet to 114 feet. Transmissivities range from less than 1,000 square feet per day to over 16,000 square feet per day and theoretical well yields range from less than 100 gallons per minute to more than 1,800 gallons per minute. Regional ground water flow in the confined-drift aquifers is toward the Minnesota River and locally toward smaller streams, lakes, wetlands, and wells. Water levels near high-capacity pumping wells generally fluctuate 5 to 10 feet annually, compared to annual fluctuations of 2 to 3 feet in the surficial aquifers. Water from confined-drift aquifers generally is suitable for most uses. The water is hard to very hard and contains locally elevated concentrations of some chemical constituents. Dissolved-solids concentrations ranged from about 400 to 1,800 milligrams per liter. A ground-water-flow model indicated that increased pumping from two of the confined aquifers simulated, the Appleton and Benson-middle aquifers, would not adversely affect water levels. The addition of 30 hypothetical wells in the Benson-middle aquifer, pumping a total of approximately 792 million gallons per year, resulted in regional water-level declines of as much as 1.4 and 2.7 feet in the surficial and Benson-middle aquifers, respectively. The addition of 28 hypothetical wells in the Appleton aquifer, pumping a total of approximately 756 million gallons per year, lowered water levels as much as 5 feet in the surficial and Appleton aquifers. Simulations of reduced recharge and increased pumping, which could represent a 3-year drought, probably would lower water levels 2 to 6 feet regionally in the surficial and confined aquifers and as much as 11 feet near aquifer boundaries. Ground-water discharge to the Pomme de Terre and Chippewa Rivers in the southern part of the study area probably would be reduced by approximately 15.2 and 7.4 cubic feet per second, respectively, as a result of the simulated drought. Mean discharge of the Pomme de Terre and Chippewa Rivers is 104 and 267 cubic feet per second, respectively.
Date Issued
Number of Pages
U.S. Geological Survey
Main Topic
Body of Water
Rights Holder
Minnesota Water Research Digital Library
Rights Management
Creative Commons