Use of Multicriteria Analysis (MCA) to Map the Specific Vulnerability of Groundwater in the City of Daloa (Central-Western Ivory Coast)

In Daloa, the waters from wells and springs from shallow aquifers are used for drinking, given the low water coverage and organoleptic quality of water from the public network. However, the lack of an adequate sewage system and human activities could lead to a risk of chemical contamination of this water table. Yet, the vulnerability and contamination of groundwater in urban areas are a major concern that requires greater attention. It therefore seems necessary to map the specific vulnerability linked to chromium in order to identify the areas requiring special attention. To do this, we opted for Multi-Criteria Analysis, which takes many parameters into account and is suitable for porous media. This method is based on a numerical rating system, which takes into account hydrogeological, human and pollutant characteristics. Field data, laboratory data and maps were used. Using ArcGis software, the data was interpolated, reclassified and rated. The combination of maps indicates three classes of vulnerability: average (0.79%), high (97.53%) and very high (1.68%), with satisfactory validation criteria (coincidence rate: 78.26% and margin of error 0.68%). Consequently, there is a potential risk of contamination of alterite aquifers throughout the city. The MCA has produced satisfactory results, but these can be supplemented by a numerical mass transport model to validate the degree of vulnerability.