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Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MassachusettsBy Carl S. Carlson and Forest P. Lyford
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The citation for this report, in USGS format, is as follows:
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.
A ground-water flow simulation for a 66.4-square-mile area around Great Sandy Bottom (GSB) Pond (105 acres) near Pembroke, Massachusetts, was developed for use by local and State water managers to assess the yields for public water supply of local ponds and wells for average climatic and drought conditions and the effects of water withdrawals on nearby water levels and streamflows. Wetlands and ponds cover about 30 percent of the study area and the aquifer system is dominated by interactions between ground water and the ponds. The three largest surface-water bodies in the study area are Silver Lake (640 acres), Monponsett Pond (590 acres), and Oldham Pond (236 acres). The study area is drained by tributaries of the Taunton River to the southwest, the South and North Rivers to the northeast, and the Jones River to the southeast. In 2002, 10.8 million gallons per day of water was exported from ponds and 3.5 million gallons per day from wells was used locally for public supply.
A transient ground-water-flow model with 69 monthly stress periods spanning the period from January 1998 through September 2003 was calibrated to stage at GSB Pond and nearby Silver Lake and streamflow and water levels collected from September 2002 through September 2003. The calibrated model was used to assess hydrologic responses to a variety of water-use and climatic conditions. Simulation of predevelopment (no pumping or export) average monthly (1949-2002) water-level conditions caused the GSB Pond level to increase by 6.3 feet from the results of a simulation using average 2002 pumping for all wells, withdrawals, and exports. Most of this decline can be attributed to pumping, withdrawals, and exports of water from sites away from GSB Pond. The effects of increasing the export rate from GSB Pond by 1.25 and 1.5 times the 2002 rate were a lowering of pond levels by a maximum of 1.6 and 2.8 feet, respectively. Simulated results for two different drought conditions, one mild drought similar to that of 1979-82 and a more severe drought similar to that of 1963-66, but with current (2002) pumping, were compared to results for average monthly recharge conditions (1949-2002). Simulated mild drought conditions showed a reduction of GSB Pond level of about 1.3 feet and a lower streamflow of about 1.7 percent in the nearby stream. Simulated severe drought conditions reduced the pond level at GSB Pond by almost 7 feet and lowered streamflow by about 37 percent. Varying cranberry-irrigation practices had little effect on simulated GSB Pond water levels, but may be important in other ponds. The model was most sensitive to changes in areal recharge. An increase and decrease of 22 percent in recharge produced changes in the GSB Pond water level of +1.4 feet and -2.4 feet, respectively.
The accuracy of simulation results was best in the central portion of the study area in the immediate location of GSB Pond. The model was developed with the study-area boundary far enough away from the GSB Pond area that the boundary would have minimal effect on the water levels in GSB Pond, nearby ponds, and the underlying aquifer system. The model is best suited for use by local and State water managers to assess the effects of different withdrawal scenarios for wells and ponds near GSB Pond and for general delineation of areas contributing recharge to wells and ponds in the vicinity of GSB Pond. The model in its current form may not be well suited to detailed analyses of water budgets and flow patterns for parts of the study area farther from GSB Pond without further investigation, calibration, and data collection.
Abstract
Introduction
Description of Study Area
Geology and Hydraulic Properties
Bedrock
Till
Stratified Sediments
Alluvium and Swamp Deposits
Characteristics of Ponds
Water Use and Wastewater Disposal
Runoff, Recharge, and Evapotranspiration
Data Collection and Compilation
Simulation of Ground-Water Flow
Model Extent, Boundary Conditions, and Discretization
Model-Simulated Streams
Model-Simulated Stresses
Hydraulic-Property Zones
1998–2003 Transient Model
Regional Hydrologic Context of 1998–2003 Transient Mode
Sensitivity and Limitations for the 1998–2003 Transient Model
Steady-State Model
Simulated Water Budgets and Pond Stages for Average Conditions and Various Water-Use Scenarios
Changes in Water Withdrawals under Average Conditions
Changes in Climatic Conditions
Summary
Acknowledgments
References Cited
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
2. General distribution of geologic materials at the land surface and bedrock-surface contours in the study area around Great Sandy Bottom Pond, Pembroke
3. Data-collection sites in the study area around Great Sandy Bottom Pond, Pembroke, 2002–03
4. Model boundary conditions, stream cells, ponds, and hydraulic conductivity zones for model layers 1 and 2 (surficial materials), Pembroke area
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
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
7. Graph showing model-simulated and measured ground-water levels, pond and lake levels, and stream discharge and simulated monthly base recharge, near Pembroke
8. Map showing water-table altitudes near Pembroke
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
10. Monthly outflow for model stream nodes and constant-head nodes and measured streamflow for the Indian Head, Jones, and Taunton Rivers
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
12. Simulated and measured water level of Great Sandy Bottom Pond in Pembroke, October 1, 2002–September 30, 2003
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
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
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)
1. Summary of average daily water use near Pembroke, southeastern Massachusetts, for average 1998–2002 and average 2002
2. Cranberry bog water-use schedule and rates, Pembroke area
3. Precipitation, streamflow, pond-stage measurement sites, and summary of data collection near Pembroke
4. Summary of properties for the Pembroke-area model
5. Average monthly and monthly recharge rates used for model calibration and model simulations of average and drought seasonal conditions near Pembroke
6. Summary of results for sensitivity model runs by the 1998–2003 model for simulated yearly streamflow for Herring Brook at Route 36 and Herring Brook at Mountain Avenue, Pembroke, October 1, 2002 through September 30, 2003
7. Cumulative budgets for simulations of average transient (water-use scenario 1) and steady-state conditions for model simulation in the Pembroke area
8. Record for selected wells near Pembroke
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