Reports
Effects of projected (2086) groundwater withdrawals on management water levels and domestic wells in Anne Arundel County, Maryland
2017, Andreasen, D.C.
Open File Report 17-02-01
Key Results
Well fields operated by Anne Arundel County Department of Public Works withdrew ~34 million gallons per day (average day) in 2016. That amount is projected to increase to ~67 million gallons per day (average day) by 2086 at build-out. Current permitted groundwater allocations for Anne Arundel County Department of Public Works total ~51 million gallons per day (average day) from the Upper Patapsco, Lower Patapsco, and Patuxent aquifer systems. The projected withdrawals will require additional allocations totaling ~16 million gallons per day (average day). Total average-day build-out withdrawals will increase by 2.7, 12.1, and 1.4 million gallons per day over current permitted allocations in the Upper Patapsco, Lower Patapsco, and Patuxent aquifer systems respectively. To determine if the increased withdrawals are sustainable (do not fall below the 80-percent management level) and to assess the potential effects on water levels and domestic-well operation, a groundwater-flow model simulation was run. The model is a revised version of a previously developed model used for water-supply planning in Anne Arundel County. The model was updated and re-calibrated using more recent water-level and pumpage data. Model simulations indicate that projected withdrawals will not cause water levels to fall below the 80-percent management level in all well fields with the exception of the Upper Patapsco aquifer system at Severndale. Sufficient supply capacity is available in the Lower Patapsco aquifer system at Severndale, however, to shift the Upper Patapsco withdrawals (0.4 million gallons per day by 2086) to the Lower Patapsco. Simulated water levels by 2086 are as low as approximately 100, 170, and 228 feet below sea level in the Upper Patapsco, Lower Patapsco, and Patuxent aquifer systems respectively. Drawdown from current water levels is as great as ~80, 130, and 200 feet in the Upper Patapsco, Lower Patapsco, and Patuxent aquifer systems respectively. Seasonal variations in withdrawals at build-out have a negligible effect on water levels. The simulated drawdown at the projected build-out amount does not adversely affect domestic-well operation. Simulated water levels remain above well screens and casing-diameter reductions (telescoping wells) in the 3,154 domestic wells estimated to be screened in the Upper Patapsco, Lower Patapsco, and Patuxent aquifer systems. Of the total number of domestic wells only ~3 percent are telescoping. Simulated water levels remain at least 20 ft above well screens and casing-diameter reductions in all but six wells.
