An understanding of water availability in the Concord River Basin for public and private supply requires an understanding of the interaction between surface-water and ground-water systems. This understanding is needed because excessive ground-water withdrawals may reduce streamflows to unacceptable levels. The U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Management, Office of Water Resources, studied the Concord River Basin to estimate the volume of water available from stratified-drift aquifers.
A combined hydrograph-separation and streamflow-duration-curve analysis indicates that 20.8 million cubic feet of water could be withdrawn from the stratified-drift aquifer above the South Acton streamflow-gaging station during a 102-day period of no recharge before streamflow would be reduced to a prescribed minimum level. This volume, which equals 2.85 million cubic feet per square mile of stratified drift, was used to estimate volume of available water in 17 aquifer areas in the Concord River Basin. The total volume of available water in the Concord River Basin is estimated to be 561 million cubic feet.
Finite-difference ground-water-flow models for the River Meadow Brook aquifer area and the Sudbury and Concord aquifer area quantified the current and potential water availability. The results of three withdrawal simulations for each aquifer area indicate that the 1989 ground-water withdrawal rates would not exceed the volume of water that would be available during a 102-day period of no recharge if water-table drawdowns were not considered. However, results do indicate that volumes of withdrawn water would exceed the available water in the two aquifer areas if maximum lowering of the water table as a percentage of total saturated thickness were 10 and 65 percent at existing and hypothetical wells.
