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Ground-Water Recharge to and Storage in the Regolith-Fractured Crystalline Rock Aquifer System, Guilford County, North Carolina

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Ground-Water Recharge to and Storage in the Regolith-Fractured Crystalline Rock Aquifer System, Guilford County, North Carolina Ground-Water Recharge to and Storage in the Regolith-Fractured Crystalline Rock Aquifer System, Guilford County, North Carolina By Charles C. Daniel, III, and Douglas A. Harned U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 97-4140 Prepared in cooperation with Guilford County Health Department and Guilford Soil and Water Conservation District Raleigh, North Carolina 1998 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Thomas J. Casadevall, Acting 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. Geological Survey. For additional information write to: Copies of this report can be purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Information Services 3916 Sunset Ridge Road Box 25286, Federal Center Raleigh, NC 27607 Denver, CO 80225 CONTENTS Abstract.............................................................................................................................................. ^ 1 Introduction ......................................................................................................................................................................^ 2 Location and background ............................................................................................................................................ 4 Purpose and scope ....................................................................................................................................................... 4 Previous investigations ................................................................................................................................................ 6 Description of the study area....................................................................................................................................... 6 Acknowledgments....................................................................................................................................................... 7 Hydrogeologic setting of Guilford County............................................................................................................................ 7 Rivers, streams, and drainage basins ........................................................................................................................... 7 The regolith-fractured crystalline rock aquifer system................................................................................................ 8 Hydrogeologic units .................................................................................................................................................... 10 Ground-water source and occurrence.......................................................................................................................... 10 Recharge to and discharge from the ground-water system................................................................................ 13 Ground-water storage ........................................................................................................................................ 14 Hydrograph separation methods and estimation of recharge ................................................................................................ 16 Comparison of methods............................................................................................................................................... 17 The recharge hydrograph............................................................................................................................................. 18 The duration table........................................................................................................................................................ 18 Ground-water recharge in selected drainage basins .............................................................................................................. 18 Dan River subbasin...................................................................................................................................................... 20 Haw River Basin upstream from Benaja, N.C............................................................................................................. 22 Upper Haw River subbasin.......................................................................................................................................... 24 Lower Haw River subbasin.......................................................................................................................................... 26 Reedy Fork Basin upstream from Oak Ridge, N.C..................................................................................................... 28 Horsepen Creek Basin ................................................................................................................................................. 30 Reedy Fork subbasin.................................................................................................................................................... 32 North Buffalo Creek Basin .......................................................................................................................................... 34 South Buffalo Creek Basin.......................................................................................................................................... 36 Big Alamance Creek Basin ......................................................................................................................................... 38 West Fork Deep River Basin........................................................................................................................................ 40 East Fork Deep River Basin......................................................................................................................................... 42 Upper Deep River subbasin......................................................................................................................................... 44 Lower Deep River subbasin......................................................................................................................................... 46 Abbotts Creek Basin.................................................................................................................................................... 48 Comparison of basins .................................................................................................................................................. 50 Determination of the quantity of ground water available from storage................................................................................. 53 Use of recharge and storage data for ground-water management planning .......................................................................... 54 Example 1: Using estimated mean annual recharge to determine recharge area........................................................ 55 Example 2: Using recharge-duration statistics and ground-water storage to determine recharge area ..................... 57 Potential effects of ground-water withdrawals on streamflow .............................................................................................. 59 Summary and conclusions..................................................................................................................................................... 60 References ............................................................................................................................................................................. 63 Contents FIGURES 1. Map showing the regional setting of the Guilford County study area in the Piedmont physiographic province of North Carolina, selected drainage basins, and locations of gaging stations used in the ground-water recharge analysis..............................................................................................................................................................^ 3 2. Principal components of the ground-water system in the Piedmont physiographic province of North Carolina.................................................................................................................................................^ 8 3. The reservoir-pipeline conceptual model of the Piedmont ground-water system and the relative volume of ground-water storage within the system..................................................................................................................... 9 4. Hydrogeologic unit map of Guilford County, N.C..................................................................................................... 12 5. Water level in observation well NC-126, Orange County, N.C. (A) Decade hydrograph for the period 1978-87; (B) Annual hydrograph for the year 1987 .................................................................................................................. 14 6. Relation of porosity and specific yield to total ground-water storage and available water in the regolith. (A) Variation of porosity and specific yield with depth in the regolith; (B) Total ground water in storage below the water table and water available by gravity drainage.................................................................................. 16 7-21. Hydrographs showing variation of monthly mean ground-water recharge in the: 7. Dan River subbasin
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