A Multi-criteria Decision using the Analytical Hierarchy Process (AHP) for Delineation of Groundwater Potential Zones in Part of the Obudu-Massif, Nigeria

Abstract

Groundwater occurrence in
crystalline basement terrains is strongly
controlled by lithology, structural features,
topography, and climatic conditions. This
study evaluated groundwater potential zones
(GWPZ) in parts of the Obudu Massif,
Southeastern Nigeria, Using an integrated
Geographic Information System (GIS) and
Analytical Hierarchy Process (AHP)
approach. Eight groundwater conditioning
factors, namely lithology, lineament density,
drainage density, precipitation, elevation,
slope, aspect, and curvature, were analyzed
and weighted through pairwise comparison
with the AHP framework. The resulting
consistency ratio (CR) of 0.071 indicated
acceptable consistency in the weighting
process. The analysis revealed that
geology/lithology (42.6%) and lineament
density (18.6%) exert the greatest influence on
groundwater occurrence, followed by drainage
density (12.5%) and slope (10.5%). The
groundwater potential map produced,
delineated the study area into three classes:
low high and very high GWPZs. Raster pixel
interpretation showed that high GWPZ cover
approximately 119 km2
(49.3%) of the study
area, while very high GWPZ occupy about
30km2
(12.3%). Low GWPZ account for 92 km2
(38.4%). Areas with very high groundwater
potential are mainly concentrated within the
central-southern and southeastern portions of
the study area, where favorable lithologic and
structural conditions enhance groundwater
recharge and storage. A strong positive
agreement between intermediate-to-high
transmissivity values obtained from pumpingtest data and the mapped high-to-very-high
groundwater potential zones confirmed the
reliability of the model. The high to very high
GWPZs were considered indicative of the
model accuracy. The study demonstrates that
the integration of GIS, remote sensing, and
AHP provides a reliable and cost-effective
approach for groundwater exploration,
borehole siting, and sustainable groundwater
resource management in crystalline basement
terrains.