Vol.:(0123456789) 1 3 Modeling Earth Systems and Environment https://doi.org/10.1007/s40808-020-00912-9 ORIGINAL ARTICLE Vulnerability assessment of an aquifer in the basement complex terrain of Nigeria using ‘LAHBUD’ model Olayiwola G. Olaseeni 1  · Michael I. Oladapo 2  · Gbenga M. Olayanju 2 Received: 7 June 2020 / Accepted: 27 July 2020 © Springer Nature Switzerland AG 2020 Abstract We integrated hydrogeological and hydrogeophysical parameters to evaluate aquifer vulnerability to contamination in a base- ment complex terrain in Nigeria. Aeromagnetic and Shuttle Radar Topography Mission (SRTM) data were used to generate the composite lineament density map. Lithology information was obtained from the existing geological map, while land-use and land-use changes were derived from the Landsat 8 imagery. We also acquired 216 vertical electrical soundings (VES) to estimate the geoelectric parameters including depth to aquifer, hydraulic conductivity, and bedrock relief maps. The informa- tion obtained from geoelectric parameters, lithology, lineament density, and land use were used as the parameters in assessing the aquifer vulnerability using multi-criteria decision analysis (MCDA) in the context of the analytical hierarchy process (AHP). The assigned weights for the various aquifer vulnerability indices are 0.4569, 0.2482, 0.1469, 0.0775, 0.0402 and 0.0303 respectively for lithology (L), depth to aquifer (A), hydraulic conductivity (H), bedrock relief (B), land-use (U) and lineament density (D). These values were normalized and used in establishing a consistency ratio of 6.94%, which is lower than 10% (recommended limit). The MCDA was used to develop the aquifer vulnerability (‘LAHBUD’) model which was used to classify the study area into very low, low, moderate, high, and very high aquifer vulnerability zones. Geochemical parameters obtained from water samples were used to validate the ‘LAHBUD’ model, and gave 81% agreement in predict- ing the risk level of possible contaminant infuence with the conceptual model, and thus confrm the reliability of the model adopted for this study. Keywords Depth to aquifer · Hydraulic conductivity · Lithology · Bedrock relief · Lineament density Introduction Groundwater is an essential natural resource to man and its quality is important for the sustainable use of groundwater for man’s consumption (Oguama et al. 2019). Groundwater is very useful in human day-to-day activities such as agri- cultural, recreational, domestic and industrial uses (Akinlalu et al. 2017; Akinwumiju and Olorunfemi 2018; Oyeyemi et al. 2018a, b, 2019; Oguama et al. 2019; Omolaiye et al. 2020). Groundwater refers to water that exists within pore spaces and cracks of rocks beneath the earth’s surface (Oseji and Ofomola 2010; Oguama et al. 2019). The quality of water available for human consumption is liable to the con- siderable threat of contamination due to the susceptibility of a built-up terrain to pollution and anthropogenic sources in urban areas (Olowe et al. 2016; Fatoba et al. 2017; Burri et al. 2019; Omotola et al. 2020). Contamination of ground- water is not limited to urban civilisation, but could also be a major problem to human existence in rural areas. Environ- mental protection has become the obligation of diferent lev- els of government when considering a planning application especially in the area of groundwater development. An aquifer is a geologic formation, which is composed of geologic units that are porous and sufciently permeable enough to yield water in usable quantities either to a bore- hole, well or spring. Moreover, vulnerability is the ability of human or environmental resources to sustain deformation due to stress (Mogaji et al. 2014; Agyare et al. 2017; Ahada and Suthar 2018). Therefore, aquifer vulnerability can be described as the degree of degradation of natural ground- water quality, especially by human activities. Processes * Olayiwola G. Olaseeni olayiwola.olaseeni@fuoye.edu.ng 1 Department of Geophysics, Federal University Oye-Ekiti, Oye-Ekiti, Ekiti, Nigeria 2 Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria