Groundwater Recharge Zone Delineation and Vulnerability Mapping Using GIS and Geophysical Data in Aguata, Anambra State

Effective groundwater management in Aguata Local Government Area of Anambra State requires accurate identification of recharge zones and an assessment of aquifer vulnerability to contamination from overlying land uses. This study delineates groundwater recharge zones and maps aquifer vulnerability in Aguata using an integrated approach combining GIS analysis and vertical electrical sounding data. Forty VES stations were established across the LGA using the Schlumberger array, and one-dimensional resistivity models were derived from IPI2Win inversion. GIS analysis integrated thematic layers for geology, lineament density, land use, slope, drainage, and soil type derived from satellite data and existing maps. The analytic hierarchy process was used to assign weights to each parameter for recharge zone mapping. DRASTIC vulnerability index values were computed at all VES locations using parameters derived from the VES models combined with GIS-derived inputs. Recharge zone maps identify three classes (high, moderate, and low), with the high recharge zones concentrated in the elevated quartzite and granite terrain of the Aguata ridge system where high drainage density and fractured rock promote infiltration. DRASTIC vulnerability indices range from 72 to 148, with values exceeding 110 flagging 35 percent of the study area as highly vulnerable. High-vulnerability zones are predominantly associated with shallow water table conditions, highly permeable soils, and active agricultural land use. The integrated recharge-vulnerability map provides a practical tool for groundwater protection zone designation and regulatory land use planning in Aguata.

Keywords: recharge zone, DRASTIC, aquifer vulnerability, GIS, Aguata