Ground-water availability from surficial aquifers in the Red River of the North Basin, Minnesota

Population growth and commercial and industrial development in the Red River of the North Basin in Minnesota, North Dakota, and South Dakota have prompted the Bureau of Reclamation, U.S. Department of the Interior, to evaluate sources of water to sustain this growth. Nine surficial-glacial (surficial) aquifers (Buffalo, Middle River, Two Rivers, Beach Ridges, Pelican River, Otter Tail, Wadena, Pineland Sands, and Bemidji-Bagley) within the Minnesota part of the basin were identified and evaluated for their ground-water resources. Information was compiled and summarized from published studies to evaluate the availability of ground water. Published information reviewed for each of the aquifers included location and extent, physical characteristics, hydraulic properties, ground-water and surface-water interactions, estimates of water budgets (sources of recharge and discharge) and aquifer storage, theoretical well yields and actual ground-water pumping data, recent (2003) ground-water use data, and baseline ground-water-quality data.

Water-budget estimates for the aquifers were compiled from steady-state aquifer simulations, precipitation data and hydrograph analysis, and recharge and discharge information. Major sources of recharge to the aquifers are areal recharge, flow from surface water, and flow across aquifer boundaries from adjacent geologic units. Losses of water from the aquifers include evapotranspiration, flow to surface water, flow across aquifer boundaries, and withdrawals by pumping wells. The Bemidji-Bagley, Otter Tail, Pineland Sands, and Wadena surficial aquifers have the highest rates of water inflow and outflow of the nine aquifers in the study area, and the Middle River surficial aquifer has the lowest rates of total water inflow and outflow.

Maximum storage volumes of five of the surficial aquifers were calculated using areal extent and published saturated thickness and porosity data. Storage estimates from published studies were included for three of the surficial aquifers. Maximum theoretical well yields for the aquifers generally occur in areas with more abundant, well-sorted, coarse-grained sediment. In 2003, 28 billion gallons of ground water were withdrawn from the aquifers, not including water used for private supply. In 2003, the largest volume of ground water was withdrawn from the Otter Tail surficial aquifer, and the smallest volume was withdrawn from the the Middle River surficial aquifer. Agricultural irrigation and public supply totaled 95 percent of the volume of ground water withdrawn from the aquifers in 2003.

Ground-water-quality data indicate that the Buffalo aquifer contained the largest specific conductance and concentrations of dissolved solids, calcium, magnesium, sodium, sulfate, and iron. Ground water from the Bemidji-Bagley, Otter Tail, Pineland Sands, and Wadena surficial aquifers contained the largest concentrations of nitrate (as nitrogen). In general, the nine aquifers are hydraulically connected to local surface water. Simulations of ground-water development for some of the aquifers describe correlations between increased ground-water withdrawals and declining lake levels and streamflows, lower water-table altitudes, and variations in ground-water quality.

On the basis of data and methods presented to evaluate ground-water availability, the Otter Tail and Pineland Sands surficial aquifers and Pelican River sand-plain aquifer have the greatest potential for additional development of ground-water resources in the study area.