Monitoring pumping test response in a fractured aquifer using ground-penetrating radar

Fractured aquifers present a number of problems when attempting to characte rize flow on the well scale (less than 100 m). Standard hydraulic testing m ethods are expensive because of the need for installation of monitoring wel ls. Geophysical methods may suffer from a lack of resolution and nonunique solutions to data interpretation. We used ground-penetrating radar (GPR) su rveying during a pumping test in a well-characterized, fractured, carbonate aquifer to monitor the response of a permeable subhorizontal fracture plan e. We observed radar signal amplitude and waveform variations along a fract ure reflector and correlated the radar signal response to changes in the wa ter saturation of the fracture. Combining hydraulic measurements with GPR d ata and electromagnetic modeling, we identified an asymmetric fracture drai nage pattern, provided accurate spatial information about the saturation of the fracture, and detected the presence of hydraulic boundaries. This stud y demonstrates that GPR surveying can be used successfully for real-time mo nitoring of pumping tests in fractured carbonate aquifers.