A GIS-Based Transmissivity-Constrained Frequency Ratio Approach for Groundwater Potential Assessment in Basement Terrain

Authors

  • O. O. Oso Department of Mineral and Petroleum Resources Engineering, The Federal Polytechnic, Ado-Ekiti, Nigeria. 2. Department of Geology, Afe Babalola University, Ado Ekiti, Nigeria https://orcid.org/0009-0001-1312-2870
  • O. S. Ogungbemi Department of Geology, Afe Babalola University, Ado-Ekiti, Ekiti State, Nigeria
  • O. O. Afolabi Department of Geology, Afe Babalola University, Ado-Ekiti, Ekiti State, Nigeria https://orcid.org/0000-0003-2156-1475
  • H. O. Aliu Department of Contract/Project Management, AUGJ Services Limited, Bonny Island, Rivers State, Nigeria.

DOI:

https://doi.org/10.63746/njtd.v23i2.4103

Keywords:

Frequency Ratio model, Transmissivity, Groundwater potential, GIS, Basement complex

Abstract

: Groundwater potential assessment in crystalline basement terrains is challenging due to heterogeneous subsurface conditions and limited recharge pathways. This study applied a transmissivity-constrained Frequency Ratio (FR) model within a Geographic Information System (GIS) framework to delineate groundwater potential zones (GPZs) in southwestern Nigeria. A total of 150 Vertical Electrical Sounding (VES) datasets were analyzed, of which 88 points with transmissivity >15 m²/d were considered hydraulically effective and used for model calibration. Twelve thematic layers—elevation, lithology, slope, drainage density, surface and subsurface lineament densities, geomorphology, curvature, topographic wetness index, soil texture, land use/land cover, and depth to fracture—were integrated to evaluate their influence on transmissivity. The FR analysis revealed that subsurface lineament density, lithology, and drainage density exerted the strongest control on transmissivity (FR > 2.5), indicating a high likelihood of groundwater occurrence in these classes. In contrast, steep slopes and high drainage density areas (FR < 1.0) showed limited groundwater potential. The resulting groundwater potential prediction map (GwPPM) classifies about 11.35% of the zone as very low potential, while 30.17%, 45.40% and 13.08% are categorized as low, moderate and high potential zones, respectively.  Moderate-to-high potential zones, mainly around Igede-Ekiti and Iyin-Ekiti, correspond to highly fractured granitic terrains with gentle slopes and low drainage density. Validation with borehole yield data yielded ~80% accuracy, confirming model reliability. These results demonstrate that integrating transmissivity with FR-based GIS modeling provides an effective approach for groundwater assessment and supports sustainable exploration in basement terrains.

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Published

2026-06-30