Research about Prairie Island Indian Community

USGS2002

Simulation of ground-water flow and delineation of areas contributing recharge within the Mt. Simon-Hinckley aquifer to well fields in the Prairie Island Indian Community, Minnesota

The Prairie Island Indian Community in east-central Minnesota uses ground water from the Mt. Simon-Hinckley aquifer as its source of water supply. Tribal officials implemented a Source Water Protection Program to protect the quality of this water. Areas of contributing recharge were delineated for two community well fields. At well field A are two wells 325 m apart, and at well field B are two wells 25 m apart. A steady state single layer, two-dimensional ground-water flow model constructed with the computer program MODFLOW,combined with the particle-tracking computer program MODPATH, was used to track water particles (upgradient) from the two well fields. A withdrawal rate of 625 m 3 /d was simulated for each well field. The ground-water flow paths delineated areas of contributing recharge that are 0.38 and 0.65 km 2 based on 10- and 50-year travel times, respectively. The flow paths that define these areas extend for maximum distances of about 350 and 450 m, respectively, from the wells. At well field A the area of contributing recharge was delineated for each well as separate withdrawal points. At well field B the area of contributing recharge was delineated for the two wells as a single withdrawal point. Delineation of areas of contributing recharge to the well fields from land surface would require construction of a multi-layer ground-water flow model.

Minnesota, Wisconsin↗

USGS2002

Hydraulic properties of Mt. Simon aquifer, Prairie Island Indian community, southeastern Minnesota, 2001

An aquifer test of the Mt. Simon aquifer was conducted at the northern end of the Prairie Island Indian Com-munity, in cooperation with the Prairie Island Indian Community, September 10-11, 2001 to determine hydraulic properties. Two wells at the northern end of Prairie Island were used in the aquifer test. A production well, Water-Supply Well No. 3, completed in the Mt. Simon aquifer, was pumped for 24 hours at 1,530 gal/min. Draw-down and recovery water levels were measured in the pumped well and in an observation well located 458 ft from the pumped well that was open to the Mt. Simon aquifer. Recovery water levels were measured in both wells for 10 hours after pumping ceased at Water-Supply Well No. 3. Hantush and Theis methods type curves were fitted to the measured drawdown and recovery curves in the observation well. The results of matching the type curves to the measured data indicate that leakage is negligible from the overlying Eau Claire confining unit into the Mt. Simon aquifer. The transmissivity and storage coeffi-cients for the Mt. Simon aquifer, determined by both methods, are 3, 000 ft 2 /d and 3 x 10 -4 , respectively. The average hydraulic conductivity, assuming an aquifer thickness of 233 ft, is 10 ft/d.

Minnesota, Wisconsin↗