DECIPHERING FRACTURED CRYSTALLINE BEDROCK GROUND WATER RECHARGE: DATA INPUT, CONSTRAINTS AND MODELING NEEDS

The growing demand for fractured bedrock ground water necessitates addressing fundamental questions regarding wellhead protection, contamination prevention and aquifer recovery. Accurate sustainability assessments of this water supply are complicated by anisotropic nature of the media. Hydraulic characterizations of bedrock are limited to standard aquifer field methods and borehole logging. Simulating ground water flow in fractured aquifers requires developing models and applying adjustments to accurately depict the flow conditions. University of Connecticut Plant Science Research Farm installed three bedrock pumping wells to sustain turf grass research. Ground water monitoring network at the facility consisting of four bedrock and six shallow overburden wells provides continuous water level readings. Pumping tests reveal that wells are interconnected over a distance of at least 500 meters and individual well contribution areas vary in direction. Recharge to the glacial till overburden at the site is calculated using the Water Table Fluctuation (WTF) method from shallow well hydrographs. Recharge, field test and water level monitoring data during ambient and pumping conditions are utilized to develop an equivalent porous media (EPM) model. The resulting model is used to estimate overburden recharge to bedrock, delineate bedrock contribution area under ambient and pumping conditions and the sustainability of the ground water supply.