Bohling, Geoffrey C. / A ground penetrating radar study of water table elevation in a portion of Wisconsin's central sand plain
I. Introduction: motivation and objectives, pp. 1-9 PDF (2.5 MB)
system in a discharge area. Therefore, use of an agricultural chemical on a field in a discharge area should have a less detrimental effect on the groundwater system than its use on a field in a recharge area. B. Objectives The primary objective of this study is to test the reliability of ground penetrating radar (GPR) as a tool for obtaining high-resolution maps of water table elevation. GPR surveys were performed in the sum- mer and fall of 1987 in a portion of the Central Sand Plain with a fairly dense set of existing water table observation wells. GPR is a geophysical instrument which transmits an electromagnetic pulse into the ground and records the return times of pulses reflected from subsurface interfaces, pro- ducing a profile of return time versus horizontal distance as the radar is pulled along the ground. In order to test the reliability of GPR as a water table reconnaissance tool, sparse subsets of wells in the area are used to calibrate the radar and water table depths obtained from these calibra- tions are compared to known water table depths in the remaining wells. Water table elevation maps produced from observation well data and from the GPR data are also compared. Thus, the study tests whether GPR can be used to help produce an accurate water table map when only a few observation wells exist. The results of these comparisons are presented in Chapter V.