Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, Massachusetts By Carl S. Carlson and Forest P. Lyford In cooperation with the Drinking Water Program, Massachusetts Department of Environmental Protection Scientific Investigations Report 2004-5269 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director U.S. Geological Survey, Reston, Virginia: 2005 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. 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Suggested citation: Carlson, C.S., and Lyford, F.P., 2005, Simulated ground-water flow for a pond-dominated aquifer system near Great Sandy Bottom Pond, Pembroke, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2004-5269, 43 p. iii Contents Abstract .......................................................................................................................................................... 1 Introduction ................................................................................................................................................... 2 Description of Study Area ........................................................................................................................... 2 Geology and Hydraulic Properties .................................................................................................... 5 Bedrock ........................................................................................................................................ 5 Till .................................................................................................................................................. 5 Stratified Sediments ................................................................................................................... 5 Alluvium and Swamp Deposits ................................................................................................. 6 Characteristics of Ponds ................................................................................................................... 6 Water Use and Wastewater Disposal .............................................................................................. 6 Runoff, Recharge, and Evapotranspiration ..................................................................................... 7 Data Collection and Compilation ................................................................................................................ 9 Simulation of Ground-Water Flow ........................................................................................................... 11 Model Extent, Boundary Conditions, and Discretization ........................................................... 12 Model-Simulated Streams ............................................................................................................... 15 Model-Simulated Stresses ............................................................................................................. 15 Hydraulic-Property Zones ................................................................................................................ 18 1998–2003 Transient Model ............................................................................................................. 19 Regional Hydrologic Context of 1998–2003 Transient Model ..................................................... 24 Sensitivity and Limitations for the 1998–2003 Transient Model ................................................. 25 Steady-State Model ......................................................................................................................... 27 Simulated Water Budgets and Pond Stages for Average Conditions and Various Water-Use Scenarios ................................................................................................................... 27 Changes in Water Withdrawals under Average Conditions ...................................................... 27 Changes in Climatic Conditions ....................................................................................................... 30 Summary ..................................................................................................................................................... 32 Acknowledgments ...................................................................................................................................... 34 References Cited ........................................................................................................................................ 34 iv Figures 1–4. Maps showing: 1. Ponds, streams, production wells, pond diversion and export points, and pumping rates in 2002 for the study area around Great Sandy Bottom Pond, Pembroke, southeastern Massachusetts ...........................................................3 2. General distribution of geologic materials at the land surface and bedrock-surface contours in the study area around Great Sandy Bottom Pond, Pembroke ....................................................................................................4 3. Data-collection sites in the study area around Great Sandy Bottom Pond, Pembroke, 2002–03. ..........................................................................................................10 4. Model boundary conditions, stream cells, ponds, and hydraulic conductivity zones for model layers 1 and 2 (surficial materials), Pembroke area ..................................................................................................................13 5. Generalized north-south cross section through the model area showing model layers and hydraulic-conductivity zones in the study area around Great Sandy Bottom Pond, near Pembroke .................................................................................................. 14 6. Map showing average yearly recharge (1998–2002), in inches per year, representative of recharge applied to the transient 1998–2003 model and Year 2000 census tracts, near Pembroke .............................................................................. 17 7. Graph showing model-simulated and measured ground-water levels, pond and lake levels, and stream discharge and simulated monthly base recharge, near Pembroke ........................................................................................................................... 20 8. Map showing water-table altitudes near Pembroke ........................................................... 21 9–15. Graphs showing: 9. Measured streamflow and model-simulated monthly streamflow for variations in model hydraulic characteristics for Herring Brook at Route 36 in Pembroke, October 1, 2002–September 30, 2003. ...................................22 10. Monthly outflow for model stream nodes and constant-head nodes and measured streamflow for the Indian Head, Jones, and Taunton Rivers .................24 11. Measured water levels for the model period January 1998–September 2003 in well MA-HGW 76 (well depth = 26.6 ft) near Wampatuck Pond, Hanson ................................................................................................................................25 12. Simulated and measured water level of Great Sandy Bottom Pond in Pembroke, October 1, 2002–September 30, 2003. ........................................................26 13. Simulated average monthly water levels in Great Sandy Bottom Pond for five water-use scenarios based on average monthly recharge from the period 1949–2002, Pembroke ...........................................................................................29 14. Simulated monthly water-level altitude in Great Sandy Bottom Pond for average recharge conditions and for two periods of reduced recharge resulting from the historical droughts of 1979–82 and 1963–66 ...............................31 15. Simulated water-level altitude of Great Sandy Bottom Pond, near Pembroke, with average 2002 pumping, diversion, and export rates (scenario 1) and the 180-day simulation with no recharge (scenario 8) .................32 v Tables 1. Summary of average daily water use near Pembroke, southeastern Massachusetts, for average 1998–2002 and average 2002 .................................................. 7 2. Cranberry bog water-use schedule and rates, Pembroke area .......................................... 8 3. Precipitation, streamflow, pond-stage measurement sites, and summary of data collection near Pembroke ............................................................................................... 11 4. Summary of properties for the Pembroke-area model ........................................................ 16 5. Average monthly and monthly recharge rates used for model calibration and model simulations of average and drought seasonal conditions near Pembroke ......... 18 6. Summary of results for sensitivity model runs by the 1998–2003 model for simulated yearly streamflow for Herring