Deciphering Flow Conditions and Evaluating Sustainability of Groundwater in Fractured Crystalline Bedrock

The crystalline bedrock is a critical water resource for the state of Connecticut, as well as many other mountainous areas. Characterizing the hydrogeology of the fractured rock is difficult given the complex nature of fracture systems. Thus, groundwater basins are assumed to be the same as drainage basins derived from surface topography and the estimated rate of recharge to the bedrock is typically unknown. This research 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 2500 wells integrated into a geographic information system. Results indicate that groundwater drainage basins of the fractured rock do not correspond to drainage basins derived from surface topography, and groundwater recharge estimates for delineated groundwater fractured rock basins are lower than those reported in other studies. Additionally, groundwater recharge and usage for each drainage basin were estimated and the sustainability of each basin was determined by taking the difference between these estimates. Temporal analysis of well parameters indicated a decrease in well yield by approximately 20% and the depth to water declined.