Geoelectrical, Hydrogeological and Hydrochemical Investigations of the University of Calabar Campus (SE Nigeria): Implications for sustainable groundwater development

Abstract

The rapid increase in population and infrastructural development has triggered unplanned groundwater development leading to severe stress on groundwater couple with several unsuccessful boreholes or failure of existing in the University of Calabar, Calabar (Nigeria). Hence, an integrated hydrogeological study was undertaken in the university using vertical electrical sounding (VES), to delineate and characterise aquifers and assess the groundwater quality for drinking and irrigation uses, in addition to evolution and human health risk assessment. The results reveal two water bearing units. The first is composed of medium-coarse-gravelly sand with thickness and resistivity in the range 3.6–118.8 m and 540–3500 Ω m, while the second underlying the first aquifer is composed of clayey, fine-medium sand with resistivity and thickness values in the range 44–2200 Ω m and 50 - α. Aquifer parameters from VES and pumping tests showed average hydraulic conductivity (K) and transmissivity (T) of 180 m/day and 25,740 m²/day for the first aquifer and 180 m/day and 21,384 m²/day for the second aquifer. Regionally, the groundwater flow in the university occurs toward the south. Hydrochemical data show that all the physical parameters, major and minor ions, trace and rare earth elements are within the maximum acceptable limits for drinking and agricultural uses. The dominant hydrochemical facies are Na⁺-Ca²⁺-Cl^--SO₄^2-, Mg²⁺-Ca²⁺-HCO₃^--Cl^- and Ca²⁺-Mg²⁺-HCO₃^--Cl^- with silicate weathering, ion exchange and reverse ion exchange as the major processess controlling the groundwater chemistry. Health risk of water through oral (drinking) and dermal (bathing) pathways showed that values of hazard quotients (HQs) and hazard index (HI) of all the trace elements (Al, As, Cd, Co, cr, Cu, Fe, Mn, Ni, Pb, Zn) were less than one. This suggests that these elements does not pose any adverse risks to the local people through drinking and bathing, but children are more sensitive than adults. This study will serve as a guide for future sustainable development and management of groundwater resource in the university and its environs.