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Understanding the hydrochemical and hydrogeological physiognomies of subsurface water in a semi-arid region is important for the effective management of water resources. This paper presents a thorough review of the hydrogeology and hydrochemistry of the Hadejia-Yobe basin. The hydrochemical and hydrogeological configurations as reviewed indicated that the Chad Formation is the prolific aquifer in the basin.  Boreholes piercing the Gundumi formation have a depth ranging from 20-85 meters.  The hydrochemical composition of groundwater revealed water of excellent quality, as all the studied parameters were found to have concentrations within WHO and  Nigeria’s standard for drinking water quality.  However,  further studies are required for further evaluation of water quality index, heavy metal pollution index, and irrigation water quality. Also, geochemical, and stable isotope analysis is required for understanding the provenance of salinity and hydrogeochemical controls on groundwater in the basin.

This study assessed shallow groundwater in rural Kebbi State using Pearson’s Correlation (r), Factor Analysis (FA), and Hierarchical Cluster Analysis (HCA). One hundred (100) shallow groundwater samples were drawn randomly from hand-dug shallow wells in 10 Local Government Areas (LGAs). Physical parameters (pH, temperature, TDS, EC, salinity) were analysed in situ using hand-held metres. Separate water samples were taken to analyse ions (Fe, Zn, K, Mg, Mg, HCO3, Ca). Results revealed that shallow groundwater is lightly acidic, except in Zuru and Fakai LGAs, where an alkaline condition occurred. Correlation analysis revealed that the dissolved solids in shallow aquifers result from natural geological and anthropogenic influences. However, FA had shown that most of the variability in shallow groundwater is influenced by natural geological factors with little evidence from anthropogenic inputs. The HCA categorised shallow groundwater into three groups: those shallow wells having higher concentrations of Zn and Cl with more elevated salinity and temperature; those shallow wells having very low salinity in central Kebbi State, and those shallow aquifers having alkaline waters. Except for higher Fe and Zn concentrations, the shallow aquifers contained water of excellent quality for drinking. Correlation analysis, FA, and HCA present simple statistical tools for assessing the hydrochemistry of groundwater.

This review presented a detailed re-assessment of the hydrogeology and hydrochemistry of the Tropical Anambra Basin. It identified and discussed the major geological formations and their groundwater potentials. The geological examination showed that the  Ajali Formation is confined in places forming an artesian condition; the potentials of this aquifer decline in the western basin due to a decrease in thickness. The sandstone associates of the Nsukka Formation are aquiferous and have produced high-pressure artesian boreholes along the Oji River. The Imo Shale is characterized by permeability stability all over much of the intermediate unit. The Bende-Ameki aquifer has a lesser amount of groundwater when equated to other formations; the geologic characteristics do not produce favorable hydrogeological conditions for groundwater occurrence. The stratigraphical and structural framework suggested the presence of an efficient throughflow in the basin. Based on physical and chemical parameters of water quality, the basin holds water of acceptable quality. While there are considerable investigations on the hydrogeology and hydrochemistry, studies are short of analysis of the hydrogeochemical evolution of groundwater, water quality index, heavy metals pollution index as well as total hazard quotient.  Suitability of groundwater based on agricultural water quality indices (e.g. SAR) is also salient. Therefore, future studies should address these owing to increasing dependence on groundwater.

This review attempted a detailed description of geological and hydrogeological configurations of Cross River and Imo-Akwa Ibo basins. It presented a synthesis of hydrochemistry and a description of the hydrogeological configurations of the two basins. Hydrogeologically, most areas under Cross River and  Imo-Kwa-Ibo are poor in terms of groundwater potentials. Based on the hydrochemistry, the basins hold water of excellent quality.  Groundwater sources fall in soft to moderately hard classes. The entire sources groundwater has a TDS concentration of less than 500 mg/l. Groundwater classification based on electrical conductivity (EC) showed EC levels were less than 500  µS/cm. Most of the examined cations and anions are within WHO reference guidelines for drinking water quality. However, no broad analysis of water quality based on water quality indices. Also, studies modeling pollution or the impact of land use changes on groundwater quality are wanting. Thus, further analysis of the hydrochemistry of groundwater aquifers is recommended.