GIS-Based Groundwater Vulnerability Assessment and Hadrochemical Validation of Borehole Exposure to Waste Contamination Risks in Kaduna Polytechnic, Nigeria

Groundwater is the primary source of potable water for many tertiary institutions in sub Saharan Africa, yet increasing anthropogenic pressures from inadequate waste management threaten groundwater quality and long-term water security. This study assessed groundwater vulnerability to waste contamination within Kaduna Polytechnic, Nigeria, using an integrated Geographic Information System (GIS) and hydro chemical validation framework. Geographic coordinates of 58 boreholes and 61 waste disposal points were extracted from geotagged field photographs using Python-based metadata processing and incorporated into a GIS database. Spatial analyses, including nearest-hub assessment, proximity modelling, and vulnerability classification, were conducted in QGIS. Boreholes were classified into critical (≤15 m), high (>15–30 m), moderate (>30–100 m), and low (>100 m) vulnerability zones based on their proximity to waste disposal points. Twenty-five boreholes located within critical and high-risk zones were identified for investigation, of which fifteen operational boreholes were subjected to hydro chemical analysis. Parameters analyzed included pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, nitrate, sulphate, chemical oxygen demand (COD), and total organic carbon (TOC). A Groundwater Exposure Index (GEI) was developed by integrating spatial and hydro chemical indicators. Results revealed a mean borehole–waste point distance of 49.89 m, while correlation analysis showed moderate inverse relationships between distance and EC (r = −0.431) and TDS (r = −0.424). The GEI identified BH42, BH27, BH04, and BH02 as the most vulnerable boreholes. The study demonstrates that integrating GIS-based vulnerability assessment with hydro chemical validation provides an effective decision-support framework for groundwater protection in institutional environments.