Improved stratigraphic modified Lorenz plot and flow zone indicator methods for integrated electrogeohydraulic characterization and delineation of hydrodynamic units in parts of Nsukka, Enugu State

This study investigated the electrogeohydraulic characteristics of hydrogeologic units in parts of Nsukka, Enugu State, using Vertical Electrical Sounding (VES), the Improved Stratigraphic Modified Lorenz Plot (ISMLP), and Flow Zone Indicator (FZI) methods. Fifteen VES stations were interpreted, revealing four geoelectric layers and seven curve types, with H- and K-type curves dominating, indicating favorable groundwater conditions. The third geoelectric layer was identified as the principal aquifer unit, exhibiting resistivity values ranging from 33.7 to 21,987.8 Ωm, which reflect significant lithologic heterogeneity within the Ajali Sandstone Formation. Estimated hydrogeologic parameters showed porosity values of 0.268–0.330, hydraulic conductivity of 0.035–14.55 m/day, and permeability of 13.169–7596.737 μm 2 . Spatial analyses revealed considerable variability in porosity and permeability, indicating a heterogeneous aquifer system controlled by pore connectivity and lithologic variations. ISMLP analysis delineated seven hydraulic flow units (HFUs), grouped into five flow-efficiency classes. HFU2 was identified as the dominant fractured-flow unit, contributing 70.8% of the total aquifer flow capacity, while HFU1, HFU3, and HFU7 represented low-flow baffle zones. The FZI method identified six distinct HFUs, with HFU6 exhibiting the highest permeability and groundwater productivity. Aquifer heterogeneity assessment using the Dykstra–Parsons coefficient yielded a value of 0.833, indicating an extremely heterogeneous aquifer characterized by substantial permeability contrasts and complex groundwater flow behavior. The integrated application of geoelectrical, ISMLP, and FZI techniques successfully characterized aquifer flow units and hydraulic performance, providing valuable information for groundwater exploration, development, and sustainable management in the study area.