Evaluation de la vulnérabilité de la nappe libre de la zone des Niayes (Sénégal) par les méthodes DRASTIC, SINTACS et Index de Susceptibilité (SI)

The Niayes area is home to the Quaternary sands of the northern Senegalese coastline. It offers economic potentialities such as it attracts industry and farmer. Thus, the pressures of anthropogenic origins combined with pejorative climatic conditions, expose it to environmental and social risks, to the extent that the vulnerability of groundwater to pollution calls on researchers and decision-makers. The study presented in this article aims to assess the level of groundwater vulnerability to pollution, using three methods: DRASTIC, SINTACS and SI. The Arc Gis software was used. The parameters used as input data include hydraulic conductivity, static groundwater level, soil type, topographic slope and recharge. Several degrees of vulnerability are identified from south to north ranging from "low" to "high". It is noteworthy that the further away from the coast, the lower the vulnerability and the overall vulnerability of the area, with high-vulnerability areas. To validate our results, we have superimposed a map of nitrate concentration with those of the vulnerabilities to see the most suitable method with this type of pollutant. Comparison of the different results makes it possible to deduce that the SI method is the most appropriate for the assessment of the vulnerability to nitrate pollution, with a 70% coincidence rate between the nitrate concentrations and the different classes of vulnerability.