3D multicomponent GPR to characterize shallow subsurface flow paths in an epikarst limestone Edwards Plateau, Texas
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We acquired and analyzed 3-D multicomponent ground-penetrating radar (GPR) data to better understand the subsurface flow conduits at a hydrologic experimentation site. Previous workers conducted a set of shallow (< 2.5 m) subsurface hydrology experiments during simulated rainfall events within fractured and karsted limestone of the Edwards Aquifer region near San Antonio, Texas. They observed at an observation trench located on the down slope side of the site that lateral subsurface flow is guided by open joints, bedding planes and karst features. They also utilized tracer experiments, which showed a high degree of variability in tracer recovery, advection speed, and concentration depending on the location of the application of the tracer. We utilized the 3-D multicomponent GPR data in an attempt to identify the main conduits of flow within the experimentation site in order to explain the observed tracer experiments. The GPR revealed that the most obvious conduits run nearly parallel with the observation trench, with some conduits able to quickly move water away from the trench. This information helps explain the high spatiotemporal variability in the tracer data. Our study demonstrates that multicomponent GPR provides a technique that can improve future subsurface hydrologic experimentation. 2007 Society of Exploration Geophysicists.
