Water table detection by GPR in Sardon, Salamanca, Spain

GPR was applied in the semi-arid Sardon catchment (Salamanca, Spain) in order to analyze the distribution of the water table depth with a high spatial resolution to serve as input in the parameterization of a hydrological model. We used a pulse radar with a single 200 MHz bowtie antenna combined with a differential GPS and a survey wheel for accurate positioning. Measurements were performed following a series of transects crossing perpendicularly the bed of the Sardon streams, which were dry during that period (September 2009). We measured the depth of the water table in several observation wells to interpret and validate the GPR data. A time domain reflectometry probe was used to estimate the shallow soil dielectric permittivity and corresponding wave propagation velocity along the transects. In general, the water table was visible in the GPR data, with depths ranging from about 2 to 3 meters.