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 that is available from stratified-drift aquifers. A combined hydrograph-separation and streamflow- duration-curve analysis indicates that 20.8 million cubic feet of water can be withdrawn from the stratified-drift aquifer above the South Acton streamflow-gaging station during a 102-day period of no recharge before streamflow is reduced to a prescribed minimum level. This volume, which equaled 2.85 million cubic feet per square mile of strati- fied drift, was used to estimate volume of available water for the 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 withdrawal rates do not exceed the volume of water available during a 102-day period of no recharge. Results from model simulations of 10- and 65-percent water-table draw- down at existing and hypothetical wells indicate that withdrawn water volumes would exceed the available water in the two aquifer areas.