Abstract
Sustainable management of groundwater in desert environments dictates better knowledge of the quality status and the controlling processes. To this end, an integrated analysis of hydrochemical and statistical assessment was carried out for 692 groundwater samples collected from the multi-layered aquifer system in Wadi ad-Dawasir area (Saudi Arabia). The four water-bearing formations arranged upwards, namely Lower Wajid, Upper Wajid, Khuff-Kumdah, and Quaternary, were investigated. The prime objective was to delineate the baseline conditions and the dominant process controlling the groundwater evolution that can help make resource management better. We used fifteen indicators, namely the total dissolved solid (TDS), total hardness, Eh, pH, temperature degrees C, turbidity, Fe2+, dissolved oxygen (DO), NH4, HCO3-, NO3-, F, NO2-, PO42-, and SiO2. Descriptive statistics, violation of the international standards, geostatistical modeling, and factorial analyses (FA) were performed. Geologic, soil, topographic, and climatic factors controlling the quality were investigated. The Quaternary aquifer was the most polluted by TDS, total hardness, NO3-, SiO2, Fe2+, F, and HCO3-. Khuff-Kumdah showed largest means of DO and NH4. Upper Wajid was the largest in NO2-. Lower Wajid proved largest in PO42-. Violation of the international standards clarified largest emergence of the pH for the Lower Wajid; Fe2+ and NO3- for the Upper Wajid; and total hardness, TDS, Fluoride, turbidity, and NH4 for the Quaternary aquifer. Rock interaction and evaporation are the dominant processes that contributed largely to the hydrochemical evolution of the groundwater. FA distinguished six main factors that explained for over 60.8% of the total groundwater quality variation lead byF1 (44.23%) that clarified strong positive loads of TDS (0.98), total hardness (0.95), nitrate NO3- (0.84), turbidity (0.78), NH4 (0.67), moderately loaded by fluoride (0.47), and Fe2+ (0.31).