Determination of fault zone and hydro-geophysical characteristics of the fractured aquifers are complicated, because their fractures are controlled by different factors. Therefore, 60 VESs were carried out as well as 17 productive wells for determining the locations of the fault zones and the characteristics of the carbonate aquifer at the eastern desert, Egypt. The general curve type of the recorded rock units was QKH. These curves were used in delineating the zones of faults according to the application of the new assumptions. The main aquifer was included at end of the K-curve type and front of the H-curve type. The subsurface layers classified into seven different geoelectric layers. The fractured shaly limestone and fractured limestone layers were the main aquifer and their resistivity changed from low to medium (11-93 Ω m). The hydro-geophysical properties of this aquifer such as the areas of very high, high, and intermediate fracture densities of high groundwater accumulations, salinity, shale content, porosity distribution, and recharging and flowing of groundwater were determined. The statistical analysis appeared that depending of aquifer resistivity on the water salinities (T.D.S.) and water resistivities add to the fracture density and shale content. The T.D.S. increasing were controlled by Na + , Cl − , Ca 2+ , Mg 2+ , and then (SO 4 ) 2− , respectively. The porosity was calculated and its average value was 19%. The hydrochemical analysis of groundwater appeared that its type was brackish and the arrangements of cation concentrations were Na + > Ca 2+ > Mg 2+ > K + and anion concentrations were Cl − > (SO 4 ) 2− > HCO 3 − > CO 3 − . The groundwater was characterized by sodium-bicarbonate and sodium-sulfate genetic water types and meteoric in origin. Hence, it can use the DC-resistivity method in delineating the fault zone and determining the hydro-geophysical characteristics of the fractured aquifer with taking into account the quality of measurements and interpretation.

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Discovering, studying and determining the hydrogeoelectrical properties of the aquifer at the new area by using resistivity sounding parameters are difficult and need high accuracy in measurements and interpretation. The hydrogeological settings of the area of northwest Al Hurghada town are not studied on large scale by using the surface geophysical measurements before this study. So, for this aim, 24 vertical electrical soundings (VESs) were measured and interpreted. Discovering of groundwater aquifer along the main wadi called Wadi Om Dehas especially to the Far East, adds to determine the main lithology, shaly sandstone, sandstone and sandstone to limestone, of the aquifer and the complicated structural setting at form of inferred faults by using VESs curves, were the main tenets at this study for studying their effects on the correlation coefficient (R 2) between the electric and hydraulic parameters of the aquifer. Accordingly, the two suggested locations were chosen for drilling and their results were as expected from VESs interpretation. The interpretation results using the true resistivity values assisted in delineating the complicated facies, heterogeneity of aquifer rock units and in expecting the flow direction of groundwater along the area. The relationship between the resistivity with transverse resistance and longitudinal conductance was carried out and assisted strongly in separating aquifer rock units. The heterogeneity and water salinity at different directions affected the strong relationship between the resistivity and transverse resistance where in case of shaly sandstone and sandstone it was weak but strong in case of sandstone to limestone. The hydraulic conductivity of aquifer was calculated using the transverse resistance. The transverse resistance was used in calculating the transmissivity and concluded that there is complicating and changing in its values from depth to others and from location to other due to the effect of structure and heterogeneity. This confirmed that the geological and hydrogeological settings of the area are more complicated. So, according to the relationship between the hydraulic conductivity (K h) and resistivity (ρ t), it can be said that it is strongly controlled by the nature of the aquifer rock units either heterogeneous or homogeneous. Accordingly, it can only use the last creating empirical equation in calculating the expected transmissivity values of the recorded water-bearing sandstone to limestone rocks at this area with taking into account the calculated value of R 2 between both depending on the statistical analysis.

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