A policy brief recently released by the AfriWatSan team at the Université Cheikh Anta Diop of Dakar provides new information on the hydrological impacts of extreme rainfalls. Indeed, new observations recorded in the AfriWatSan urban monitoring facility in the Thiaroye and Keur Massar suburb of Dakar show how extreme rainfalls flush faecal pollutants from septic tanks into shallow groundwater. High-frequency observations of groundwater levels and daily rainfall over the last 4 years highlight the importance of heavy rainfalls in generating groundwater recharge indicated by sharp rises in water tables to heavy rainfall events. New evidence from the AfriWatSan urban observatory…