Assessing Aquifer Vulnerability to Contamination in the Vicinity of Osubi Dumpsite through the Application of DRASTIC Method

Abstract

In the Niger Delta region of Nigeria, rapid population growth in areas like Osubi, due to the construction of the Warri airport, has raised concerns about aquifer contamination. Factors such as wastewater, borrow pits, dumping sites, and agricultural activities contribute to this risk. This study assesses the vulnerability of the aquifer near the Osubi dumpsite to contamination using the DRASTIC method, integrating Geographic Information System (GIS) technology. Seven environmental parameters—Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity—are considered. Geophysical techniques, including vertical electrical sounding (VES), were used to gather data on depth to water table (D), hydraulic conductivity (C), and aquifer media (A) at ten points. Other data, including soil media (S), vadose zone impact (I), and topography (T), were obtained from previous studies and NASA's Shuttle Radar Topographic Mission (SRTM). Rainfall data were sourced from the PERSIANN system developed by the University of California. Using ArcGIS Pro 10.3, raster maps for each DRASTIC parameter were overlaid to generate a regional-scale aquifer vulnerability map. The resulting map highlights heightened vulnerability in the northwest and southwest regions, potentially linked to historical land usage shifts from the proposed Osubi airport site to the Osubi dumpsite. Additionally, an average depth to the water table ranging from 14m to 22m suggests a shorter contamination travel time, exacerbated by predominantly sandy soil media facilitating infiltration and increasing contamination risk to the aquifer.