Water sustainability is an important concern for communities that rely on groundwater in fractured rock; yet the complexity of the fracture system and the unknown rate of recharge make quantifying groundwater availability difficult, if not impossible, using conventional water balance calculations. This study provides a new approach for estimating groundwater sustainability in fractured rock that entails synthesis of pre-existing well data into a comprehensive database that permits defining bedrock groundwater drainage basins and flow for use in estimating recharge and usage. The method was tested in the Coventry Quadrangle, Connecticut and entailed the use of more than 2,500 wells. Groundwater recharge and usage were estimated for each drainage basin and the sustainability of each basin was determined by taking the difference between these estimates. Additionally, temporal analysis of well parameters indicated a decrease in well yield by approximately 20% and the depth to water declined. The method demonstrated here provides a means to allow the consideration of groundwater sustainability in land use planning and decision-making.