Mapping Groundwater Potential Zones in the Widyan Basin, Al Qassim, KSA: Analytical Hierarchy Process-Based Analysis Using Sentinel-2, ASTER-DEM, and Conventional Data

Groundwater availability in semi-arid regions like the Widyan Basin, the Kingdom of Saudi Arabia (KSA), is a critical challenge due to climatic, topographic, and hydrological variations. The accurate identification of groundwater zones is essential for sustainable development. Therefore, this study combines remote-sensing datasets (Sentinel-2 and ASTER-DEM) with conventional data using Geographic Information System (GIS) and analytical hierarchy process (AHP) techniques to delineate groundwater potential zones (GWPZs). The basin’s geology includes Pre-Cambrian rock units of the Arabian Shield in the southwest and Cambrian–Ordovician units in the northeast, with the Saq Formation serving as the main groundwater aquifer. Six soil types were identified: Haplic and Calcic Yermosols, Calcaric Regosols, Cambic Arenosols, Orthic Solonchaks, and Lithosols. The topography varies from steep areas in the southwest and northwest to nearly flat terrain in the northeast. Hydrologically, the basin is divided into 28 sub-basins with four stream orders. Using GIS-based AHP and weighted overlay methods, the GWPZs were mapped, achieving a model consistency ratio of 0.0956. The zones were categorized as excellent (15.21%), good (40.85%), fair (43.94%), and poor (0%). The GWPZ model was validated by analyzing data from 48 water wells distributed in the study area. These wells range from fresh water to primary saline water, with water depths varying between 13.98 and 130 m. Nine wells—with an average total dissolved solids (TDS) value of 597.2 mg/L—fall within the excellent zone, twenty-one wells are categorized in the good zone, fifteen wells are classified in the fair zone, and the remaining wells fall into the poor zone, with TDS values reaching up to 2177 mg/L. The results indicate that the central zone of the study area is suitable for drilling new water wells.