A novel method of sensitivity analysis testing by applying drastic method and fuzzy optimization method to assess Groundwater vulnerability to pollution, case of Senegal River basin in Mali
Abstract. Vulnerability to groundwater pollution from Senegal basin was studied by two different but complementary methods: the DRASTIC method (which evaluates the intrinsic vulnerability) and the fuzzy method (which assesses the specific vulnerability taking into account continuity of the parameters). The validation of this application has been tested by comparing the membership in groundwater and distribution of different classes of vulnerabilities established as well as the nitrate distribution in the study area. Three vulnerability classes (low, medium and high) have been identified by both the DRASTIC method and by fuzzy method (passing by normalized model). An integrated analysis reveals that high class with 14.64 % (for the DRASTIC method), 21.68 % (for normalized DRASTIC method) and the very high grade 18.92 % (for that of fuzzy) are not the most dominant. In addition, a new method for sensitivity analysis was used to identify (and confirm) the main parameters which impact de vulnerability to pollution with fuzzy membership. And the results showed that vadose is the main parameter which impacts groundwater vulnerability to pollution while net recharge has the least contribution to pollution in the study area. It was found also that Fuzzy method better assesses the vulnerability to pollution with a coincidence rate of 81.13 % against 77.35 % for the DRASTIC method. These results are a guide for policy makers on protection areas sensitive to pollution and identification of the sites before later hosting the socio-economic infrastructures.