The Accuracy of Water Table Elevation Estimates Determined from Ground Penetrating Radar Data

Water table elevations measured at sparsely distributed monitoring wells are used to interpolate the water table surface. Ground-penetrating radar (GPR) is a non-invasive technique that has been used to estimate water table elevations between monitoring wells. GPR can be used to estimate the elevation of the top of the capillary fringe. The water table elevation is obtained by subtracting an estimate of the height of the capillary fringe from the capillary fringe elevation. The accuracy of these estimates is affected by numerous sources of error including surface elevation, GPR wave velocity, spatial velocity variations, capillary rise estimates and the time sampling interval. The main sources of uncertainty are due to GPR velocity estimates and predicting the height above the water table of the capillary fringe reflection. Theoretical analysis and field experiments indicate that, under favorable circumstances, the elevation of shallow water tables can be estimated with an accuracy on the order of 0.20m.