Scientific Investigations Report 2010–5142
ABSTRACT A study of the groundwater and stream-aquifer interaction in the Pootatuck River Basin, Newtown, Connecticut, was conducted to analyze the effect of production wells on the groundwater levels and streamflow in the Pootatuck River as part of a cooperative program between the U.S. Geological Survey and Newtown, Connecticut. This study will help address concerns about the increasing competition for water for human uses and protection of aquatic habitat. The groundwater-flow model developed in the study was designed for use as a tool to assist planners in assessing the effects of potential future development, which will change the amount and distribution of recharge available to the groundwater system.
Several different techniques were used to investigate the interconnection between the stream and the aquifer. Temperature, groundwater levels, stream stage, and stable-isotope data collected during aquifer tests at the principal production wells in the Pootatuck River Basin, as well as groundwater-flow simulations of the system, indicate that more than half of the water pumped from the wells comes from the Pootatuck River. This finding potentially has a large effect on approaches for protecting the water quality of the pumped water. Increases in the amount of impervious surface from future development will reduce and redistribute recharge to the groundwater system. The simulation of future development scenarios showed a decrease in the simulated base flow in the main stem of the Pootatuck River and in all of the 26 simulated subbasins, with some of the subbasins showing a decrease of more than 20 percent when new development had 85 percent impervious area. The groundwater-flow model and particle tracking were used to determine areas that contribute recharge to the five production wells available for use in the Pootatuck River Basin. These areas included narrow portions of the aquifer that extended beyond the immediate upgradient areas, probably because of deeper groundwater-flow paths. |
First posted July 2010 For additional information contact: Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge. |
Carlson, C.S., Mondazzi, R.A., Bjerklie, D.M., and Brown, C.J., 2010, Hydrogeology and numerical simulation of the unconsolidated glacial aquifer in the Pootatuck River Basin, Newtown, Connecticut: U.S. Geological Survey Scientific Investigations Report 2010–5142, 84 p., available at http://pubs.usgs.gov/sir/2010/5142/.
Abstract
Introduction
Purpose and Scope
Location and Description
Previous Investigations
Hydrogeology of the Pootatuck River Valley
Physiography and Geology
Description of Hydrologic Units
Data Collection and Analysis
Methods of Data Collection
Streamflow
Observation Wells and Streambed Piezometers
Groundwater-Level Monitoring
Temperature Monitoring
Aquifer Test
Water-Quality and Stable-Isotope Analysis
Fairfield Hills Well Field
Site Description
Pumping Information
Aquifer Tests at Fairfield Hills Well Field
Groundwater-Level Monitoring
Surface-Water Monitoring
Temperature Monitoring
Water-Quality and Isotope Analysis
Analysis of Aquifer Tests at Fairfield Hills Well Field
United Water Well Field
Site Description
Pumping Information
Induced Infiltration Test at United Water Well Field
Groundwater and Surface-Water-Level Monitoring
Temperature Monitoring
Historical Aquifer Tests
Analysis of Historical Aquifer Test at United Water Well Field
Development of the Groundwater-Flow Models
Development of a Conceptual Model of the Pootatuck River Basin
Development of Numerical Models
Model Discretization and Boundaries
Model Calibration
Well-Field-Scale Models
Fairfield Hills Well-Field-Scale Model
Simulation of Aquifer Test
Model Calibration and Hydraulic Properties
Steady-State Model
United Water Well-Field-Scale Model
Simulation of Reverse Aquifer Test
Model Calibration and Hydraulic Properties
Limitations of Well-Field-Scale Models
Basin-Scale Model
Layer Distribution
Hydrologic Boundaries
Hydrologic Stresses
Recharge
Pumping
Hydraulic Properties
Basin-Scale, Steady-State Model Calibration
Water-Level Data
Streamflow Data
Model Limitations
Sensitivity Analysis of Groundwater-Flow Models
Streambed Conductance
Hydraulic Conductivity
Recharge
Delineation of Areas Contributing Recharge to Production Wells
Simulated Groundwater Levels and Drawdown
Delineation of Groundwater-Recharge Areas
Sensitivity Analysis of Groundwater Recharge Areas
Streambed Conductance
Hydraulic Conductivity
Recharge
Simulation of the Interaction between Groundwater and Surface Water
Sensitivity Analysis of Simulated Groundwater Levels
Sensitivity Analysis of Stream Base Flow in the Pootatuck Rive
Simulated Water Budgets
Simulated Effect of Future Recharge Conditions
Base Flows in the Main Stem Pootatuck River—Future Scenarios
Water Budgets in Subbasins of Pootatuck River—Future Scenarios
Summary
Acknowledgments
References Cited
Appendix. Spatially-Distributed Recharge
U.S. Department of the Interior |
U.S. Geological Survey
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