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Abstract

The population in Senegal is currently growing at a rate of 2.75%, adding approximately 447.000 every year. The population, which sits above 17 million, is estimated to surpass 50 million by 2077 (World Population Review, 2021). This unregulated swelling of the population affects mainly Dakar (the capital and largest city in the country), and it is expected to represent more than 54% of the population by 2030. In Dakar, in which approximately 80% of water resources come from groundwater reservoirs, this unsustainable urban growth has increased the vulnerability of the aquifers to contamination from point and non-point sources including wastewater disposal through wastewater infiltration beds and onsite sanitation systems (a significant source of contamination).In an attempt to monitor and map the movement of leachate plumes from toilets from the vadose to the saturated zone, we installed, in the vicinity of a public school toilet actively used by pupils in Thiaroye - an outskirt in Dakar, from the morning until the evening, an electrical resistivity tomography (ERT) system. Point sensors measuring at a daily basis the variation of nitrate and electrical conductivities were already installed in the site at 0.75 m, 2 m, and 5 m. Through our studies, we were able to define the spatiotemporal extension of the leachate from the vadose to the saturated zone. We still have to combine the regional ERT with local geochemical measurements to discriminate and quantify the contribution of each pollutant. The results will allow policymakers to better plan remediation mechanisms.