APPLICATION OF MULTI CRITERIA DECISION ANALYSIS TO DEVELOP GROUNDWATER POTENTIAL CONCEPTUAL MODEL IN A BASEMENT COMPLEX ENVIRONMENT

Abstract

This study applied the multi criteria decision analysis in the context of the analytical hierarchy process to subsurface resistivity data acquired from Ijebu-jesa town, Osun state to achieve an unbiased integration of several parameters in the order of their hydrogeologic importance to consequently produce a groundwater conceptual model of the area. The coefficient of anisotropy, aquifer resistivity, aquifer thickness, overburden thickness and overburden resistivity were the parameters derived from the results of the interpretation of resistivity sounding data obtained in forty six locations within the study area. These parameters were the main subsurface factors controlling the flow and accumulation of groundwater resources in the area. Each parameter was assigned appropriate weight based on Saaty’s nine-point scale and the weights were normalized through the Analytic Hierarchy Process (AHP). The consistency of judgments was also checked by obtaining the consistency ratio. The consistency ratio was obtained to be 0.08 indicating that the judgments made were consistent and unbiased. The groundwater conceptual model of the area was produced from the rating of these parameters and from the Groundwater Potential Index (GWPI) model equation developed. The conceptual model classified the groundwater potential of the study area into very low, very low - low, low - moderate, moderate - high and high - very high regions. The results obtained from this study established that the groundwater conceptual model produced from the GWPI obtained from the application of multi criteria decision analysis to subsurface factors is accurate and reliable. It has also proven the ability of the methodology adopted as a good decision making tool in the presence of two or more conflicting criteria. This ability makes it a useful tool that can be adopted in the groundwater prediction domain.