Influence of natural and anthropogenic factors on the hydrogeology and hydrogeochemistry of Wadi Itwad Aquifer, Saudi Arabia: Assessment using multivariate statistics and PMWIN simulation

Abstract

The quantity and quality of the aquifers have been depleted by human activities such as industrialization, the use of fertilizers, excessive pumping, and the discharge of domestic wastewater. The government of Saudi Arabia (SA) built three dams in the Wadi Itwad so that Abha city could get 15,000 m3/d of water. Ten groundwater samples have been collected from ten wells (Well 1 – Well 10) located in Wadi Itwad. The samples were analyzed for total dissolved solids (TDS), electrical conductivity (EC), pH, turbidity, temperature, chloride (Cl-), potassium (K), sulphate (SO42-), nitrate (NO3–), nitrite (NO2–), fluoride (F-), ammonia (NH4), radium (Ra)-226, 228, and 234, total uranium (TU), and total faecal coliforms to evaluate the aquifer quality and quantity and to preserve it by isolating it during dry periods. Geographic Information System (GIS)–Inverse Distance Weighting (IDW) contour maps were utilized to collect and display the aquifer's hydrogeological parameters. The southeast of the downstream area shows the highest, whereas the lowest drawdown was in the northeastern and southwest parts of the downstream area. The TDS concentration was consistently within a narrow range of 573 to 606 ppm, and the anomalies in the SO42- and NO3– concentrations were consistent with and representative of runoff from agricultural areas. The low levels of NO2–, F-, and NH4 indicated negligible pollution. The concentration of radioactive elements was below the maximum contaminant level. Different hydrogeochemical processes within the aquifer system were distinguished using multivariate statistical analyses, including correlation analysis (CA), principal component analysis (PCA), hierarchical cluster analysis (HCA), and one-way analysis of variance (ANOVA). The Processing Modflow Windows (PMWIN) groundwater modeling explains that the abstraction rate needs to be lowered during the first few days of pumping and then raised again afterwards. This could aid in decreasing withdrawals and enhancing aquifer hydrogeological properties.