Prepared in cooperation with the CITY OF RAPID CITY Flow-System Analysis of the Madison and Minnelusa Aquifers in the Rapid City Area, South Dakota—Conceptual Model Water-Resources Investigations Report 02-4185 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior U.S. Geological Survey Flow-System Analysis of the Madison and Minnelusa Aquifers in the Rapid City Area, South Dakota—Conceptual Model By Andrew J. Long and Larry D. Putnam Water-Resources Investigations Report 02-4185 Prepared in cooperation with the CITY OF RAPID CITY U.S. Department of the Interior GALE A. NORTON, Secretary U.S. Geological Survey Charles G. Groat, Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Government. Rapid City, South Dakota: 2002 For additional information write to: District Chief U.S. Geological Survey 1608 Mt. View Road Rapid City, SD 57702 Copies of this report can be purchased from: U.S. Geological Survey Information Services Building 810 Box 25286, Federal Center Denver, CO 80225-0286 CONTENTS Abstract . 1 Introduction . 2 Purpose and Scope. 2 Description of Study Area . 2 Previous Investigations . 5 Acknowledgments . 5 Hydrogeologic Setting. 5 Madison Hydrogeologic Unit . 8 Minnelusa Hydrogeologic Unit . 9 Concepts of the Ground-Water-Flow System . 9 General Concepts. 10 Hydraulic Properties . 12 Transmissivity . 12 Anisotropic Transmissivity . 20 Vertical Hydraulic Conductivity . 21 Specific Yield. 28 Storage Coefficient . 28 Hydraulic Head and Ground-Water Flow . 29 Potentiometric Surfaces. 29 Hydraulic Response to Recharge. 30 Unconfined Areas . 34 Flowpaths. 35 Water-Budget Analysis . 44 General Concepts. 45 Seepage from Deadwood Aquifer . 48 Streamflow Recharge. 50 Methods . 50 Estimation of Streamflow Recharge . 54 Continuously Gaged Streams . 54 Battle Creek . 54 Spring Creek . 54 Rapid Creek . 54 Boxelder Creek . 57 Elk Creek . 57 Ungaged Streams. 58 Areal Recharge . 59 Methods . 59 Estimation of Areal Recharge . 61 Springflow . 64 Estimation of Springflow. 64 Jackson-Cleghorn Springs . 65 City Springs . 65 Deadwood Avenue Springs . 65 Boxelder Springs and Elk Springs. 65 Water Use. 65 Estimation of Water Use . 65 Rapid City Wells . ..