Groundwater Vulnerability Assessment of Bannu Basin (Pakistan): Attaining United Nation Sustainable Development Goal (SDG 6)

Abstract

Groundwater serves as a primary source of drinking and irrigation water in the Bannu Basin, making its protection from pollution a critical concern. This study aims to apply the DRASTIC model, integrated with GIS, to evaluate groundwater vulnerability in the basin. The model considers seven hydrogeological parameters to generate a spatial vulnerability map, which was further validated through nitrate concentration data. Each influencing parameter was weighted on a scale of 1 to 5, with 5 indicating the most critical contamination risk and 1 the least significant. Each sub-parameter was assessed on a scale of 1 to 10 based on its impact on pollution concentration, with higher values indicating more potential for pollution. Finally, all thematic layers were integrated in ArcGIS 10.8 to generate a vulnerability map, which is reclassified into four categories: very low, low, moderate, and high. Very low vulnerability zones, covering 476.72 km² (10.93% of the basin), are concentrated in the central basin. The most significant portion of the basin, 2034.56 km² (46.66%), falls under the low vulnerability class, indicating limited susceptibility to contamination. The moderate zone covers 1593.41 km² (36.54%), while the high-vulnerability zones are relatively small, occupying 255.63 km² (5.86%) of the basin, typically where coarse sediments and shallow groundwater depths favour pollutant migration. Nitrate-based validation showed strong spatial concordance between elevated nitrate concentrations and high-vulnerability zones, reinforcing the model's predictive accuracy and reliability. The findings contribute to sustainable water resource management by providing decision-makers with robust tools to preserve groundwater quality, support land use planning, and formulate targeted mitigation strategies.