Investigation of groundwater recharge in the transboundary Komadugu–Yobe basin Nigeria via stable isotopes of δ18O and δ2H and comparison with the wider Sahel, Africa

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Shuaibu, Abdulrahman and Kalin, Robert M. and Phoenix, Vernon and Banda, Limbikani C. and Hinton, Rebekah G.K. (2025) Investigation of groundwater recharge in the transboundary Komadugu–Yobe basin Nigeria via stable isotopes of δ18O and δ2H and comparison with the wider Sahel, Africa. Science of the Total Environment, 994. 180043. ISSN 1879-1026 (https://doi.org/10.1016/j.scitotenv.2025.180043)

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Abstract

The transboundary Komadugu–Yobe basin is critical for food security in northern Nigeria and the southern Niger Republic. Groundwater and surface water resources in the basin are prone to pollution and are becoming scarce. Stable isotopes of δ18O and δ2H were used to investigate the source of groundwater recharge to inform integrated water resource management. The local meteoric water line (LMWL) for the Komadugu–Yobe basin is δ2H = 6.7 (±0.1) δ18O + 4.1 (±0.4) for stable isotope datasets from 3 local and 4 regional stations. The regional meteoric water line for the Sahel region is δ2H = 6.2 (±0.1) δ18O + 2.9 (±0.6). The variability in isotopic composition of local and regional precipitation in the transboundary Komadugu-Yobe basin is attributed to the impact of the Inter–Tropical Convergence Zone (ITCZ) and changes in regional orography. The isotopic composition of wet and dry season groundwater samples suggests that groundwater undergoes evaporative enrichment before infiltration. Deuterium excess suggests a complex recharge process in the Precambrian basement and sedimentary Quaternary formation aquifers of the basin with respect to rainfall. Moreover, groundwater recharge in the Sahel mostly occurs when rainfall isotopic signatures are most depleted. Deuterium excess variation suggests the average rainfall across the Sahel region exhibits a general continental effect until air masses mix due to the ITCZ at the Congo Basin. Results provide insight for integrated water resources management in the context of climate change, an ever-growing population, over-exploitation of groundwater, and pollution from geogenic and anthropogenic sources.

ORCID iDs

Shuaibu, Abdulrahman ORCID logoORCID: https://orcid.org/0000-0003-1679-0572, Kalin, Robert M. ORCID logoORCID: https://orcid.org/0000-0003-3768-3848, Phoenix, Vernon ORCID logoORCID: https://orcid.org/0000-0002-8682-5200, Banda, Limbikani C. and Hinton, Rebekah G.K. ORCID logoORCID: https://orcid.org/0000-0001-5238-1405;
CORE (COnnecting REpositories)