Groundwater flow, quality evaluation, and contamination zone mapping in a shallow aquifer, Western Saudi Arabia

Groundwater is a vital resource in Saudi Arabia (KSA). The primary objectives are to explore the water quality status and its application for drinking, agriculture, livestock, and poultry and map the contamination zones (CZ) in the Khulais region, western KSA. Groundwater quality data (n = 53) depicts Ca-Mg-Cl (75%) and Na-Cl water types. The electrical conductivity (EC) and groundwater flow (GF) nexus indicate that EC and major ions increase from upstream to downstream along with GF. In the central region, groundwater is less mineralized with elevated HCO₃⁻ due to geogenic sources. NO₃⁻ and F⁻ distributions pose low values in the northern region. Further, 90% of groundwater samples surpassed the drinking water standards and are unfit for drinking. Irrigation suitability assessment explains that EC (38% of samples), SAR (58%), KR (77%), Na% (94%), PI (100%) and MH (81%) are recommended for irrigation applications. USSL classification suggests that groundwater is usable only for coarse textured (high permeability) soil and salt-tolerant plants. Based on salinity, 68% of samples are usable for livestock and poultry whereas multiple parameters (EC, NO₃⁻, Mg^2+, and F⁻) ensure that only 47% of samples are recommended to use for livestock and poultry. CZ mapping illustrates that groundwater is unsuitable in most of the area except for a few pockets in the southern and northern regions. CZ mapping can aid in locating freshwater zones for groundwater development for future needs in the study site. This study implies that groundwater quality monitoring and CZ mapping are inevitable for sustainable aquifer management in any region.