Shallow aquifer characteristics, borehole yield and groundwater resource sustainability assessment in the Osun drainage basin, southwestern Nigeria

Abstract

This study assessed the hydrogeological characteristics of 59 boreholes from the Osun Drainage Basin, Southwestern Nigeria with a view to examining the sustainability of its groundwater resource. Data on borehole parameters (depth of hole, static water level and yield) were acquired from Osun State Rural Water and Sanitation Agency and Bayowa (2013). Likewise, hydrogeological parameters (longitudinal unit conductance, hydraulic conductivity and transmissivity) were extracted from Akinwumiju (2015). The techniques of descriptive and inferential statistics were adopted to analyze these data while the relationship between yield and other hydrogeological parameters was also modeled. Results revealed that aquifers are generally shallow, thin and less porous across the study area; indicating relatively low groundwater yield potentials. Correlation and regression analyses revealed that hydraulic conductivity, transmissivity and longitudinal unit conductance were factors influencing borehole yield in the study area. However, all the four parameters examined in this study were observed to have their individual influence on borehole yield at varying degrees. It was concluded that the basin's groundwater resource might not be able to sustain her population in the process of time as indicated by the low mean yield (0.98 l/s) computed for the study area but for the continuous recharge from seasonal precipitation.

Keywords: Groundwater Yield, Borehole Parameters, Basement Complex, Osun Drainage Basin, Groundwater Sustainability