Groundwater Vulnerability Assessment in Osubi Metropolis, Niger Delta, Nigeria using DRASTIC and GIS Techniques

The vulnerability to contamination of the aquifer at Osubi, Niger Delta, was assessed in order to develop a foundation strategy for safeguarding its groundwater resources using the DRASTIC model and geographic information system (GIS). Using GIS, data corresponding to the seven DRASTIC model parameters were collected and translated into seven thematic maps. The DRASTIC map was created using these maps, which describe the depth to water level (D), net recharge (R), aquifer media (A), soil media (S), topography (T), influence of the vadose zone (I), and hydraulic conductivity (C). The results obtained from this study showed that 7% of the area was classified as very-high vulnerability to pollution, 18% was classified as high vulnerability, 60% was classified as moderate vulnerability and 15% as low vulnerability. The most vulnerable areas occur around waste dumpsites, and some septic systems in residential areas. Policies should be put in place to make it easier to close possible pollution sources in high-vulnerability areas, such as open dump sites, leaking underground storage tanks at fuel stations, effluent discharge from industries, and pit latrines/sewage disposal units.