The objective of this work is to characterize the quality of drinking water in the city of Mao and its surroundings. This study is based on 20 water samples collected in the city of Mao and its surroundings between 2018 and 2020. The parameters considered are the physicochemical parameters (pH, T°, Electrical conductivity), major chemistry and bacteriological. The chemical analysis made it possible to highlight three types of chemical water facies: chlorinated and sulphated calcium and magnesium facies; a calcium and magnesian bicarbonate facies and finally a sodium and potassium chloride or sodium sulphate facies. The results of the physico-chemical analyze are for the most part below the drinking water standard defined by the WHO / Chad except the boreholes of “Fezan, the Eglise Cath, and Djougou N” which have concentrations of nitrates above. above the standard set by WHO/Chad. Indicators of bacteriological pollution were identified in seven boreholes (“Bozonga1, Hydraulique, Lycée A. Zezerty, Hopital, Governorat, Ecole N Inst, STE (Société Tchadienne des Eaux)”).

Keywords: Assessment, Chad, Mao, Quaternaire aquifer, physico-chemical and bacteriology,