Investigations on the state of potability of the city of Mao water consumption in the Kanem province in Chad were carried out in 2000. Three pieces of information (i) the physico-chemical analysis (ii) the bacteriological analysis and (iii) the piezometric measurements of the water points were crossed. The results show that 25% of the sampled water points have abnormal concentrations of nitrates of iron and ammonium total respectively 55mg / ml, 1.85mg / ml and 0.65mg / ml values that are beyond the limit of the national standard. These abnormal concentrations of chemical elements could have origins linked to human activities. Bacteriological analysis detects fecal coliforms, Escherichia coli, fecal enterococci and total aerobic flora in 35% of the structures sampled and analyzed. Finally, the piezometric measurements show an overall low piezometric level in the city and highlight two piezometric domes in the center of the city which orient the direction of groundwater flow in all directions, converging towards the outskirts of the city.