| Ground-penetrating radar (GPR) and electrical resistivity surveys were used to monitor three aquifer pump tests conducted at a test site south of Millis, Massachusetts. Measurements of drawdown were made both during and after each pumping test. Distance-drawdown experiments were conducted in which GPR profiles and electrical resistivity pseudo-sections were used in an attempt to image the depth to the water table (or the top of the capillary fringe). Although differences could be observed between the profiles collected during the pump test, we have not been able to uniquely identify the phreatic surface and map the cone of depression. Time-drawdown experiments using both electrical resistivity soundings and stationary GPR measurements have proven to be more effective in directly imaging the depth to the “water table”. In particular, we have been able to use GPR measurements made as a function of time at a fixed location to estimate the hydraulic conductivity of the aquifer. |
