Integrated Assessment of Aquifer Contamination Risk Using GOD, GODL, and GLSI Models in Southern Okigwe, Southeastern Nigeria.

Abstract:

This study assesses aquifer contamination across fifty VES locations in Okigwe South, Southeastern Nigeria, using the GOD, GODL, and GLSI models. The GOD Index classifies vulnerability based on geological setting, overlying soil, and depth to groundwater. Results show that EHUME falls within the extreme vulnerability category, while locations like UMUOKE and UMUDIMIRE are highly vulnerable, requiring urgent protective measures. Moderate to low vulnerability was observed in several other locations, indicating varying degrees of natural protection. The GODL Index, an extension of the GOD model incorporating resistivity, depth, longitudinal conductance, and location, provided a more detailed classification. Sites such as UMUAWUCHI II and UMUARIAM II recorded high GODL values, suggesting thick, resistive formations, while areas like IKPEREJERE II showed low values, reflecting more conductive and potentially vulnerable subsurface conditions. Comparative analysis shows that GODL values were consistently higher than GOD values, emphasizing the role of human activity and land use in increasing groundwater contamination risk. The GLSI model, based on resistivity and layer thickness, further refined the classification. Locations such as UMUARIAM and AMANZE demonstrated strong natural protection (low vulnerability), while UMUOKE and UMUAWUCHI II were flagged as highly vulnerable zones due to weak protective layers. The integration of these models offers a robust approach for identifying contamination risks and guiding groundwater protection strategies. It highlights the need for targeted monitoring, land-use regulation, and sustainable groundwater development in vulnerable areas.