Comparative study of groundwater vulnerability to contamination assessment methods applied to the southern coastal sedimentary basin of Benin

Study region: Southern coastal sedimentary basin of Benin, south of Benin, West Africatudy focus: Groundwater vulnerability and contamination in Benin is a major concern that need proper attention as groundwater resource is the main source for irrigation and drinking water supply in most of districts of Benin. To protect this precious resource, it is important to know the degree of vulnerability in each location of the basin. In this study, DRASTIC, additive model of DRASTIC (DRASTIC(LcLu)), classic DRASTIC weights modified using Shannon's entropy (Entropy weight DRASTIC), Entropy weight DRASTIC(LcLu) and AVI were applied to the southern coastal sedimentary basin of Benin to assess the groundwater vulnerability across the basin. The applied approaches were validated using nitrate (NO3-) concentration. The results showed that the addition of landcover/land use parameter to the classic DRASTIC helps to improve the method for better definition of the vulnerable areas in the basin and also, the weight modification using entropy improved better the method as Entropy weight DRASTIC(LcLu) showed the highest correlation with nitrate concentration across the southern coastal sedimentary basin of Benin.