Hydrogeophysical and hydrochemical characteristics of Pliocene groundwater aquifer at the area northwest El Sadat city, West Nile Delta, Egypt

摘要

Due to the overpopulation in the main cities and shortage of water in Egypt, finding new possible reclamation areas becomes an urgent necessity. The area northwest of El Sadat city can be considered one of the most promising new reclamation areas. This study focuses on detecting the groundwater aquifers, delineating the best localities to drill groundwater boreholes, and evaluation of the groundwater quality. To achieve these goals, an integrated study of vertical electric sounding (VES), time domain electromagnetic (TEM) sounding, and hydrochemical analyses has been executed. The results show that the Pliocene aquifer is the main groundwater aquifer in the survey area where it is divided into two sub-aquifers. The first aquifer is encountered at depth ranging from 30 m to 70 m, where it's thickness range is 20-60 m and its resistivity is varying from 28 to 70 Omega m. The second aquifer is recorded at depth range from 95 m to 135 m with resistivity values of 33-57 Omega m.Moreover, the suitability of 57 groundwater boreholes for drinking and irrigation purposes was assessed as they were compared with the known standard guidelines values. Piper's tri-linear diagram shows the dominance of Alkaline earth (Ca2+ + Mg2+) and strong acids (SO42- + Cl-) in most of the water samples. According to the concentrations of major ions, the water types in the area are: Ca-HCO3 (22.8%), Ca-SO4 (17.5%), Na-SO4 (15.8%), Na-Cl (14.0%), Ca-Cl (14.0%), Na-HCO3 (10.5%), Mg-HCO3 (3.5%), and Mg-SO4 (1.8%). The electric conductivity (EC) and the total dissolved solids (TDS) values suggest fresh to brackish water. The groundwater is classified according to its total hardness (TH) based on the calcium carbonate concentration into moderately hard, hard and very hard water. Water quality indices such sodium adsorption ratio (SAR), sodium content (SC), permeability index (PI), and residual sodium carbonate (RSC) were considered to evaluate the groundwater quality for agricultural activities. These parameters suggest a safe and suitable groundwater for agricultural activities. Before exploitation further studies are however essential in order to establish a sustainable level of abstraction from the aquifer, as well as assessing the vulnerability to protect it from pollution.