Evaluation of the Vulnerability to Groundwater Pollution of the Makiso Municipality in Kisangani (DR Congo) Using the DRASTIC Parametric Method and GIS

Abstract

The Makiso municipality is located in an urban area influenced by a very high rate of land occupation by houses. This land use has an impact on the quality of the groundwater exploited by wells and springs. This groundwater helps to make up for the deficit caused by the lack of a water distribution network. It is also threatened by pollution from human activities. In order to protect the groundwater in Makiso municipality from pollution, the study of the intrinsic vulnerability assessment in the aquifers was carried out by applying the DRASTIC method and the Geographic Information System (GIS). The results obtained using this method were grouped into two degrees of vulnerability (medium and high), with variations in DRASTIC indices of [141 - 145] for the medium degree and [146 - 175] for the high degree. The high vulnerability class is the most dominant, with a percentage of 96.5% of the study area. The medium vulnerability class, which represents 3.5% of the area of the Makiso municipality, is mainly located in the western (medical plateau district), central (Lualaba district) and southern (commercial district) sectors in the form of isolated pockets. A comparison of the nitrate distribution map with the final vulnerability map shows that the areas defined as highly vulnerable by the DRASTIC method and the areas with high nitrate concentrations (above 0.11 mg/l) are in agreement. On the other hand, there are other areas with low nitrate concentrations (below 0.05 mg/l) which correspond to the high vulnerability indices.