Ground-Water Resources of the Uppermost Confined Aquifers, Southern Wadena County and Parts of Ottertail, Todd, and Cass Counties, Central Minnesota, 1997-2000 By R.J. Lindgren Water-Resources Investigations Report 02–4023 Prepared in cooperation with the Minnesota Department of Natural Resources and the Wadena Soil and Water Conservation District U.S. DEPARTMENT OF THE INTERIOR Gale A. Norton, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Use of brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. Mound View, Minnesota, 2002 For additional information write to: U.S. Geological Survey District Chief 2280 Woodale Drive Mounds View, MN 55112 Copies of this report can be purchased from: U.S. Geological Survey Branch of Information Services Box 25286, MS 517 Federal Center Denver, CO 80225 For more information on the USGS in Minnesota, you may connect to the Minnesota District home page at http://mn.water.usgs.gov For more information on all USGS reports and products (including maps, images, and computerized data), call 1-888-ASK-USGS Water-Resources Investigations Report 02–4023 CONTENTS Abstract.................................................................................................................................................................................................... 1 Introduction ............................................................................................................................................................................................. 2 Description of study area.................................................................................................................................................................. 2 Methods of investigation.................................................................................................................................................................. 4 Log data, test drilling, and well installation.............................................................................................................................. 4 Water levels and stream discharge ............................................................................................................................................ 4 Theoretical maximum well yields............................................................................................................................................. 4 Modeling of ground-water flow................................................................................................................................................ 8 Acknowledgments............................................................................................................................................................................ 8 Hydrogeology.......................................................................................................................................................................................... 8 Hydrogeologic units ......................................................................................................................................................................... 9 Hydraulic properties....................................................................................................................................................................... 14 Hydrology....................................................................................................................................................................................... 14 Ground-water withdrawals............................................................................................................................................................. 14 Vertical hydraulic connection between aquifers............................................................................................................................. 16 Stream-aquifer leakage................................................................................................................................................................... 19 Theoretical maximum well yields in uppermost confined aquifers ............................................................................................... 19 Simulation of ground-water flow .......................................................................................................................................................... 19 Numerical model description ......................................................................................................................................................... 19 Numerical model calibration.......................................................................................................................................................... 29 Steady-state simulation ........................................................................................................................................................... 30 Transient simulation................................................................................................................................................................ 35 Effects of ground-water withdrawals .................................................................................................................................................... 37 Historical withdrawals.................................................................................................................................................................... 40 Anticipated increases in withdrawals............................................................................................................................................. 41 Anticipated increases in withdrawals during a drought ................................................................................................................. 41 Greater than anticipated increases in withdrawals ......................................................................................................................... 46 Greater than anticipated increases in withdrawals during a drought ............................................................................................. 46 Model limitations and accuracy of results............................................................................................................................................. 46 Summary................................................................................................................................................................................................ 47 References ............................................................................................................................................................................................. 48 Glossary................................................................................................................................................................................................. 50 ILLUSTRATIONS Figures 1-8. Maps showing: 1. Location of study area, observation wells, and extent of surficial aquifer, southern Wadena County and parts of surrounding counties, Minnesota........................................................................................................................................ 3 2. Location of stream-stage and stream-discharge measurement sites, and extent of surficial aquifer, southern Wadena County and parts of surrounding counties, Minnesota.............................................................................................. 5 3. Location of high-capacity water-supply wells and dug pits, and extent of surficial aquifer, southern Wadena County and parts of surrounding counties, Minnesota ..................................................................................................................... 10 4. Thickness of composite zone and uppermost confined aquifers, southern Wadena County and parts of surrounding counties, Minnesota ...............................................................................................................................................................11 5. Depth to top of uppermost confined aquifers and extent of surficial aquifer, southern Wadena County and parts of surrounding counties, Minnesota ......................................................................................................................................... 12 6. Thickness of uppermost confining units and extent of surficial aquifer, southern Wadena County and parts of surrounding counties, Minnesota .......................................................................................................................................... 13 iii ILLUSTRATIONS--CONTINUED 7. Altitude of potentiometric surface of surficial aquifer, December 1998, and extent of surficial aquifer, southern Wadena County and parts of surrounding counties, Minnesota ........................................................................................... 17 8. Altitude of potentiometric surface of uppermost confined aquifers, December 1998, southern Wadena County and parts of surrounding counties, Minnesota................................................................................................................................ 17 Figure 9. Hydrographs showing measured and simulated hydraulic heads for selected observation wells completed in