Litho-stratigraphic and hydrogeological evaluation of groundwater system in parts of Benin Metropolis, Benin City Nigeria: The key to groundwater sustainability

Abstract

Previous studies revealed that soil properties play a significant role in aquifer contamination. Consequently, it is necessary to understand the nature and  properties of soil in carrying out groundwater evaluation. This study evaluates the subsurface geology and groundwater flow direction in Okpagha, Iguomo, Ikhueniro and Okhuahe suburbs in Benin City, Nigeria. Six boreholes were drilled by means of manual (rotary) method in different parts of the study area and each borehole was logged in order to  understand the lithology, depth to water table, static water level as well as flow direction. The results obtained show that aquifer within the study areas were confined, semi confined to unconfined and was dominated by sands with minor clay and lignite  interbed. It was observed that aquifer becomes shallower towards eastern portion of the study areas with increase in sand and decrease in clay  materials. It was also observed that groundwater flow map revealed a flow direction of North-West to South-East from North West to South East. The decrease in the depth of aquifer and increase in sand material could be explained by the  closeness to sea level. This phenomenon can enhance the infiltration of contaminants into aquifer thereby contaminating the groundwater bodies. It is therefore necessary to constantly monitor the groundwater quality in this suburbs in order to be aware of the quality of water resources being consumed because poor water quality can impact public health negatively. Furthermore, the authors advise that boreholes should be drilled in the direction of groundwater flow for maximum yield

Keywords: Groundwater, lithology, borehole, aquifer, water quality and contaminants