HYDROGEOLOGY, WATER QUALITY, AND EFFECTS OF INCREASED MUNICIPAL PUMPAGE OF THE SACO RIVER VALLEY GLACIAL AQUIFER: BARTLETT, NEW HAMPSHIRE TO FRYEBURG, MAINE By Dorothy H. Tepper, Daniel J. Morrissey, Carole D. Johnson, and Thomas J. Maloney U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 88-4179 Prepared in cooperation with the MAINE DEPARTMENT OF CONSERVATION (GEOLOGICAL SURVEY), the NEW HAMPSHIRE WATER SUPPLY AND POLLUTION CONTROL COMMISSION, the NEW HAMPSHIRE WATER RESOURCES BOARD, and the TOWN OF CONWAY, NEW HAMPSHIRE Augusta, Maine 1990 DEPARTMENT OF THE INTERIOR MANUEL LUJAN, JR., Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information write to: Copies of this report can be purchased from: U.S. Geological Survey Books and Open-File Reports Section Water Resources Division U.S. Geological Survey 26 Ganneston Drive Box 25425, Federal Center Augusta, ME 04330 Denver, CO 80225 CONTENTS Page Abstract ........................................................................................................................................ 1 Introduction................................................................................................................................. 2 Background .......................................................................................................................... 2 Purpose and scope ............................................................................................................. 2 Previous investigations ...................................................................................................... 4 Methods of investigation .................................................................................................. 4 Well- and site-numbering system ................................................................................... 5 Description of study area ................................................................................................. 6 Physiography and climate ........................................................................................... 6 Land use and population ............................................................................................ 6 Geologic setting .................................................................................................................. 7 Bedrock geology ........................................................................................................... 7 Lithology ................................................................................................................. 7 Bedrock-surface topography .............................................................................. 7 Surficial geology............................................................................................................ 7 Acknowledgments .............................................................................................................. 11 Hydrogeology .............................................................................................................................. 14 Saturated thickness ............................................................................................................ 14 Hydraulic conductivity ...................................................................................................... 14 Availability of ground water ............................................................................................ 17 Water-table configuration and generalized directions of ground-water flow .... 17 Water-level fluctuations .................................................................................................... 19 Recharge ............................................................................................................................... 24 Precipitation .................................................................................................................. 24 Upland runoff ................................................................................................................ 24 Tributary-stream infiltration ..................................................................................... 24 Recharge from septic systems ................................................................................... 25 Induced infiltration ...................................................................................................... 25 Discharge .............................................................................................................................. 26 Ground-water discharge to the Saco River ........................................................... 26 Ground-water withdrawals by municipal water-supply systems ....................... 27 Evapotranspiration ...................................................................................................... 27 Water Quality ....................................................... i...................................................................... 27 Ground water ....................................................................................................................... 27 Background water quality .......................................................................................... 28 Effects of agriculture ................................................................................................... 29 Effects of development ............................................................................................... 36 Surface water ....................................................................................................................... 37 Effects of increased municipal pumpage ............................................................................. 38 Description of the numerical model and model construction ................................ 38 Boundary conditions .................................................................................................... 40 Aquifer properties ....................................................................................................... 42 Recharge and discharge .............................................................................................. 42 Model calibration ............................................................................................................... 43 Model sensitivity ................................................................................................................. 44 Model applications ............................................................................................................. 51 Prediction of water-level changes ........................................................................... 52 Analyses of contributing areas to municipal wells .............................................. 62 Summary and Conclusions ....................................................................................................... 70 References Cited ........................................................................................................................ 73 Glossary ........................................................................................................................................ 77 m PLATES (Plates are inside envelope) Plate 1. Map showing ground water and surface water data-collection network in the Saco River valley aquifer, Carroll County, New Hampshire, and Oxford County, Maine. 2. Map showing altitude of the bedrock surface in the Saco River valley aquifer, Carroll County, New Hampshire, and Oxford County, Maine. 3. Map showing saturated thickness of the Saco River valley aquifer, Carroll County, New Hampshire, and Oxford County, Maine. 4. Map showing average hydraulic conductivity of the Saco River valley aquifer, Carroll County, New Hampshire (modeled area). 5. Map showing altitude of the water table and general direction of ground-water flow, December 1985, in the Saco River valley aquifer, Carroll County, New Hampshire, and Oxford County, Maine. 6. Map showing finite-difference grid and boundary conditions used to model the Saco River valley aquifer, Carroll County, New Hampshire (modeled area). ILLUSTRATIONS Page Figure 1. Map showing location of the study area ...................................................................................... 3 2. Sketch showing generalized stratigraphic section and interpreted environments of deposition .............................................................................................;................................ 8 3. Seismic-reflection profile MRA-MRA', with interpretation of record............................... 9 4a. Generalized geologic section along seismic line 000-000' in Fryeburg Harbor area ....... 12 4b. Generalized geologic section along seismic line V-V across west section of valley, west of Pine Hill, in Conway .................................................................................................. 13 5. Sketch showing idealized pattern of ground-water circulation in stratified drift.............. 18 6. Hydrograph showing long-term monthly readings for observation well OW76................. 20 7. Comparison of hydrographs for observation wells OW6 and OW16 from March 1985 through January 1986 ..................................................................................................... 21 8. Graphs showing relations between stage in Lucy Brook, water levels in observation well OW7C, and precipitation