Groundwater is a critical resource for sustaining domestic, agricultural, and industrial activities in
the Komadugu-Yobe Basin (KYB). However, growing pressures from over-exploitation, rapid
population growth, pollution from geogenic and anthropogenic sources, and climate variability
threaten the long-term sustainability of this vital water source. This thesis employs an integrated
approach which combines geochemical modelling, hydrochemical characterization, Geographic
Information System (GIS)-based techniques, chemometric analysis, index-based models and
environmental stable isotopes analysis to determine the factors influencing groundwater chemistry,
recharge mechanisms, and contamination sources, human health risk of heavy metals in KYB, to
support Integrated Water Resources Management (IWRM) and help in achieving Sustainable
Development Goal 6 (SDG 6) in KYB and the wider Sahel region. Groundwater samples were
collected from 240 water points across the Komadugu-Yobe basin during two sampling campaigns
(120 each) of wet and dry seasons. The pH, temperature, total dissolved solids (TDS), oxidationreduction potential (ORP), and electrical conductivity (EC) were assessed in situ using a handheld
digital electrical conductivity meter in situ while dissolved oxygen (DO) was measured using a
DO meter. Major cations (Na, Ca, Mg, and K) and heavy metals (As, Cd, Cu, Zn, Pb, Ni, Fe, Mn,
Cr and Co), were analyzed using inductively coupled plasma optical emission spectroscopy (ICPOES) while anions (Cl, HCO3, NO3, and SO4) were analyzed using ion chromatography (IC). Total
alkalinity and bicarbonate were measured in situ using a HACH digital alkalinity kit by the
titrimetric method and in Laboratory using KONE equipment. The stable isotopes of δ2H and δ18O were analysed at the IAEA Isotope Laboratory, Vienna and the Isotope Laboratory for the Ministry
of Water in Lilongwe, Malawi using Picaro Stable Isotope Analyser.
Hydrochemical analysis revealed that groundwater in the Komadugu-Yobe basin is predominantly
of Ca-Mg-HCO₃ water type, constituting about 59 % of the samples. Some groundwater quality
parameters exceeded World Health Organization guidelines for drinking water, while Gibbs
diagrams identified rock-water interactions as the primary factor influencing groundwater
chemistry. The groundwater quality index (GWQI) classified 63 % of samples as excellent and
27% as good for drinking. The study showed a strong interaction between geology, hydrochemistry
and groundwater quality during the wet season. A further geochemical and chemometric analysis
revealed that chloride and nitrate originated from anthropogenic sources mainly synthetic
fertilizers and nitrification processes in pit latrines. Principal Component Analysis (PCA) indicated
that groundwater chemistry is primarily influenced by geogenic processes, agricultural activities,
industrial processes and mineral weathering. Additionally, hierarchical cluster analysis (HCA)
identified the impacts of evaporation and ion exchange processes within the aquifer systems.
Groundwater sampled during wet and dry seasons is significantly undersaturated with calcite,
dolomite and fluorite minerals and partial pressure of carbon dioxide (pCO2) exceeded the
atmospheric pCO2 in nearly all samples.
The study also assessed heavy metal pollution and its associated human health risks, highlighting
lead, iron, manganese, and cadmium as the main contaminants and pose significant health risks to
the local communities in the basin. Index-based models revealed that the groundwater is less
polluted in upstream parts and highly polluted in downstream parts of the basin. Human health risk
assessments showed that both adults and children are at risk of both carcinogenic and noncarcinogenic health effects from drinking contaminated groundwater. Chemometric analysis
suggests that physicochemical parameters and heavy metals likely have different geochemical
behaviours and originated from distinct geogenic and anthropogenic sources. Moreover, isotopic analysis of δ¹⁸O and δ²H signatures provided insights into groundwater recharge, indicating that
local precipitation is the primary source of recharge particularly in areas near Hadejia-Nguru
wetland, Hadejia Komadugu Valley, Chalawa George Dam, and Tiga Dam, with seasonal
variations in isotopic signatures due to evaporative enrichment before infiltration. The local
meteoric water line (LMWL) was defined as δ2H = 6.7 (± 0.1) δ18O + 4.1 (±0.4) for the KYB,
while regional analyses of δ¹⁸O and δ²H signatures revealed the influence of the Inter-Tropical
Convergence Zone (ITCZ) on isotopic variability. D-excess results highlighted complex recharge
processes in both sedimentary and basement aquifers, suggesting that recharge occurs primarily
during periods of heavy rainfall with depleted isotopic signatures. D-excess analysis suggests that
average precipitation in the entire Sahel region exhibits a general continental effect until the ITCZ
meets the Congo Basin and that average precipitation in the entire Sahel region occurs under
equilibrium conditions. The findings from this study are essential for policymakers, stakeholders,
government agencies, NGOs, and local communities to implement integrated water resources
management strategies toward achieving SDG 6 in the Komadugu-Yobe basin and the wider Sahel
region.