PROBLEMS - Hydrogeology: Objectives, Methods, Applications - page 354

Answer 1:
Figure 23 Geologic cross-sections, considering that the high resistivities measured at depth
correspond to the roof of the rocky substratum.
Answer 2:
The location of a reconnaissance well is dictated by the following factors:
• a maximum thickness of alluvial deposits in order to draw on the entire
thickness of the aquifer. The search must focus on the more deeply
channeled axis revealed by the cross-sections (E4 in AA'; E7-E8 in BB';
E12 in CC');
• mostly gravelly terrain, in order to benefi t from the highest permeability.
Under the rocky surface silt, the high resistivities probably correspond
to unsaturated terrain. Further on and in the meander of the river, the
alluvium offers distinctly higher resistivities along the deeper channel