An application of true resistivity contour sections in groundwater exploration : a case history

الملخص EN

A resistivity survey was conductcd in the vicinity of El Sadal City in the Western Desert of Egypt as a part of an exploration program for groundwater resources in this district.

The survey consisted of 12 vertical electrical soundings (VES) distributed along three profiles.

The Schlum-berger probe configuration was used with a maximum electrode spacing of about 2 km and density of measurements of 7 per decade.

The resistivity measurements of each sounding were subjected to automatic reduction and analysis using modern software of two methods which allow the calculation of a layering model as well as an n-laycrs model.

Three subsurface true resistivity contour sections were constructed along the profiles using the n-layers models of the soundings located on each profile.

Meanwhile, subsurface resistivity bar sections were also constructed along the same profiles using the layering models of the respective soundings.

The subsurface true resistivity contour sections were successfully employed to obtain more precise interpretation of the corresponding subsurface geological layers and the water-bearing formation compared with that provided by the traditional bar sections.

In addition, the contour sections provided valuable information about the lithological variations within the subsurface geological and hydrological units.

In this respect, it was possible to map a number of clay lenses as well as gravel rich zones in the discovered water bearing formations.

The conclusions reached from this interpretation, were confirmed by the subsequent drilling, based on the present study.

A heavy duty water well field was constructed in the investigated area to supply El Sadat City with most of the present water needs for domestic uses (about 4(),(X)0 m/day).