Relating groundwater to geology in Sokoto basin, north-western Nigeria using multivariate and regression analysis: implications for groundwater availability

Abstract

Background: Geological formation's variability is responsible for spatial distribution and volume of groundwater stored in the aquifer. Groundwater availability is also determined by topography, geology, and climate, accountable for numerous natural surface indicators and groundwater availability. Objective: This paper evaluates the empirical relations between geology and sporadic groundwater levels over three geographical locations in the Sokoto basin by assessing the variability of static water level, pumping test, pumping water level and estimated yields from boreholes. Method: Hydrogeological data comprising of standing water level (Swl), pumping water level (Pwl), pumping test (Pt), and estimated yield (Ey) were derived from 612 boreholes in the Basement complex section (n=103), central Sokoto basin (n=113) and western Sokoto basin (n=396). The result shows that the Swl, Pt, and Ey were higher in the central Sokoto basin, whereas, Pwl was higher in the western Sokoto basin. Multivariate statistical analysis (Factor Analysis) was further applied to analyse the data. Results: Factor analysis indicates that most of the variability in groundwater availability in the western Sokoto basin is explained by Swl and Pwl as contained in Factor 1. Factor 2 revealed that Pt and Ey are responsible for groundwater variability in the central Sokoto basin. Factor 3, connected to the basement complex, explained 12.57%, had no high positive loadings on any hydrogeological variable. It suggests that most groundwater variability in the Sokoto basin is influenced by the Cretaceous and Tertiary sediments. The Hierarchical Cluster Analysis (HCA) revealed three types of aquifers: those aquifers with high Swl and Pwl in western Sokoto basin; those aquifers with high pumping test in the central Sokoto basin, and those aquifers having high yields comparable to the aquifers in both western and central Sokoto basin. Lastly, the general regression model shows that Swl is the significant hydrogeological parameter influencing groundwater levels. Conclusion: Even with the variability in groundwater conditions, the Sokoto basin sits on very rich aquifers to sustain different water supply programs. However, this study presents only a spatial assessment. Therefore, studies comparing groundwater conditions with geology over broader spatial and temporal scales are recommended.