Abstract
Due to scarcity of precipitation in Egypt, the groundwater is the basic source of fresh water in the regions located far from the River Nile. This contribution represents an integration between geophysical and hydrogeochemical studies to determine the distribution of groundwater and assess the water quality of the fractured limestone aquifer in the western end of Al Kurimat-Al Zafrana Road, (The east of Al Kurimat area), Eastern Desert, Egypt. To determine the thickness and depth of the water-saturated zone and infer the quality of the groundwater, vertical electrical probing or sounding (VES) and electromagnetic probing in time domain (TDEM) measurements were performed in sites selected based on prepared digital elevation map. The results of the geophysical measurements were confirmed by calibrating the calculated electrical resistance values with design reports and log records of 18 wells have been drilled beside the geophysical sounding sites. VES and TEM data revealed the occurrence of one groundwater layers divides into two parts, which differ in thickness and water quality. The upper part of the aquifer has variable thickness (89–250 m) and resistivity values ranging from 27 to 76 Ωm, reflecting saturation with fresh water, whereas the lower part is thinner (6–20 m) and contain brackish water as indicated by lower resistivity values (8 and 23 Ωm). The geochemical results of eighteen samples of groundwater taken from wells dug in the aquifer of fractured limestone are used to verify the groundwater’s hydrogeochemical characteristics and its suitability for different uses, and to assess the processes controlled its chemistry. The domination of common ions was following the order of Na
+
> Ca
2+
> Mg
2+
> K
+
for cations and Cl
−
> HCO
3
−
> SO
4
2−
> NO
3
−
for anions. Na–Cl is the most prevalent water type, whereas Ca-HCO
3
type is subordinate. Saturation indices of anhydrite, halite and gypsum are observed as undersaturated, while 61% of samples reveal oversaturated respecting to calcite and dolomite minerals. According to the understanding of groundwater geochemical characteristics, ion exchange, silicate and carbonate mineral dissolution, and the evaporation process each have a great influence on aquifer chemistry. The total dissolved solids (TDS) and total hardness (TH) values signify that the most of groundwater samples (88%) are very hard brackish. Various hydrogeochemical indices (PI, RSC, SAR and Na%) indicate that the groundwater of the fractured limestone aquifer is permissible to excellent for poultry farming and irrigational purposes; nevertheless, the high salinity needs cultivation of crops and plants that support such high salinity and arid nature of the region. Additional studies are needed to assess the extent of groundwater pollution using other methods such as Induce Polarization measurements, contaminant transport modelling and isotopic analysis, as well as to successfully manage groundwater in this aquifer.