In hydrogeology, the GPR method is a precious tool for tracking the movements of the water table, because of its very high electromagnetic contrast.

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  Step 1: Detection of the top of a water table
  The example published in 1994 by Van Overmeeren shows that the radar method led to the detection of abrupt variations in the depth of the water table which are caused by steeply dipping clay layers, buried within tills. The top of the water table appears at a time between 120 and 170 ns, which corresponds to a depth between 13 and 15 m. At the abscissa of 285 m, the 30 ns jump corresponds to an abrupt 1.7 m drop of the water table. The observations are controlled by the wells and the radar method permits the tracking of the water table fluctuations. Here, The GPR becomes a monitoring tool.


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  Step 2: Image of a coastal dune
  Figure is an example of a radar section recorded in Seignosse, in the Landes region of France, over a coastal dune using an Ekko 3 pulse-type radar at 100 MHz. The figure shows the dune structure after static corrections. It shows the hydrostatic level (H.L.) in two-way time verified by drilling. We also note dipping horizons showing the successive locations of back flank of the dune. The gain recovery, which is sufficient to correctly image the structure over the hydrostatic level turns out to be ineffective below. That is because of the strong impedance contrast between dry sand and water-saturated sand.

Reference

Van Overmeeren R.A., 1994, Monitoring of a water well field by Georadar, 56th EAGE congress, Vienna, paper I015.