Groundwater is a vital natural resource for the inhabitants of Afghanistan and is widely used for irrigation, drinking, and industrial purposes, making it crucial for public health. This study investigates the dominant hydro-geochemical processes and assesses the suitability of groundwater of Herat for drinking and irrigation. The study employed Entropy Water Quality Index (EWQI) and multivariate statistical techniques to evaluate groundwater quality. Results reveal that nearly 81% of water samples belong to the Na-HCO3 water facies, indicating that silicate weathering and cation exchange are the primary processes controlling groundwater chemistry. Based on EWQI, the water samples were classified as medium to excellent quality. Nitrate (NO3) was identified as the major contaminant in the area, with approximately 25% of water samples exceeding the maximum permissible limit of 50 mg L--(1), suggesting contamination likely from anthropogenic sources. Elevated levels of fluoride (F) were also observed, reaching up to 8 mg L--(1), significantly surpassing the recommended safety threshold (1.5 mg L--(1)). Moreover, the Wilcox diagram indicated that 44.72% of irrigated areas are vulnerable to soil salinization, potentially affecting agricultural sustainability. These findings highlight the urgent need to develop integrated groundwater management strategies that consider influencing factors to safeguard water resources in the Herat Plain aquifer.