Contribution of a geostatistical model of electrical conductivity in the assessment of the water pollution index of the Quaternary aquifer of the Lake Chad basin (Kousseri-Cameroon)

Abstract

The shallow Quaternary aquifer of the Lake Chad Basin is an important source for the supply of drinking water and irrigation in the town of Kousseri (Cameroon). However, the lack of knowledge on the quality of groundwater, constantly subject to various forms of pollution, poses a serious threat to human health and social progress. This study, based on the assessment of the Pollution Index (PI) of these waters using a geostatistical model of electrical conductivity, is a contribution to the management of water resources of this border area between Cameroon and Chad. The results show a spatial heterogeneity of electrical conductivity. This heterogeneity is linked to local peculiarities thus making it possible to distinguish six groups of electrical conductivity. The analysis of the groundwater pollution index reveals the theory of optimal electrical conductivity (OEC). This globally leads to a spatial compartmentalisation of PI in two groups: (i) a PI compartment between 0 and 1.63 characterized by a very small extent of contamination by nitrates and (ii) a PI compartment > 1.63 corresponding to areas where the extent of nitrate contamination is high, to varying degrees. This spatial compartmentalisation of PI is similar to the geostatistical model of electrical conductivity. This model indicates a double mineralisation characteristic of shallow aquifers from periurban to urban environments: “natural” mineralisation linked to geochemical processes and “localized” mineralisation linked to elements of anthropic origin. The approach applied in this study can be used for similar groundwater around the world or by researchers with insufficient budgets.