Application of electric resistivity sounding to detect fresh – salt water interface in the fan of wadi watir, gulf of aqaba - egypt

Abstract EN

The vertical electric sounding (VES) is a technique suitable for groundwater exploration in the coastal zone.

Its inherent capability to detect changes in electrical conductivity of pore-water makes it highly sensitive to the fresh water-salt water interface found in coastal and island regions.

This technique was used in this work to detect the fresh–salt water interface in the fan of Wadi Watir, Sinai, Egypt.

This Fan attains 42 Sq.

Km, and has an elliptical shape.

It is bounded from east by the coast of Gulf of Aqaba and high granitic mountains from the west.

This locality represents a typical coastal zone.

The water bearing Formation consists of gravel and sand (alluvial deposits).

The static water level measured through the drilled wells varies from 20 to 40 m.

The salinity of groundwater ranges from 1500 to 4500 ppm.

In this area eighteen electric soundings using Schlumberger array were measured with current electrode spacing (AB) ranging from 400 to 1000 m according to required depth of investigation.

Based on the parametric soundings measured beside the drilled wells, the true resistivity ranges of the various formations were deduced.

This helped the construction of the geoelectric subsurface sections, which reveal three units: The surface layer that reflects very high resistivity values (900-12400 Ohm m), The Wadi deposit unit (204-2360 and The alluvial deposit unit, which in turn is- separated according to resistivity values into two zones.

The upper zone of moderate values (12–55 ohm m) represents the fresh water zone.

The lower zone of low resistivity values (1.1 - 6.1 ohm m) is interpreted as saline water zone.

The study of resistivity and salinity distribution in the fan of Wadi Watir locality indicates that the main recharge of the fresh water aquifer would come from NE and SW sides of the fan.