The groundwater in the alluvial aquifer of Wadi Larbaa currently a water potential for the city of Taza. The study groundwater is located in the watershed upstream of Wadi Inaouen. To highlight a potential negative impact the waters of the Oued Larbaa, mostly polluted liquids and solids from the town of Taza releases, on the waters of the alluvial aquifer, this study has considered making a bacteriological and physicochemical characterization groundwater in the aquifer. The analysis of a number of parameters indicative of water pollution (T ° C, pH, electrical conductivity, total hardness, sulphate, orthophosphate, chloride, dissolved oxygen, nitrogen compounds and bacteria germs) found that however contents of these elements are high and indicate, for the most part, the risk of major pollution of the water table by the waters of the Oued Larbaa. However, the sources and sinks close thereof show very high concentrations of these nutrients. The alluvial aquifer has a high bacteriological contamination with fecal contamination is proven by the presence of high levels of total coliforms, fecal coliforms and fecal streptococci, the use of the web could be a significant health risk to users this water for drinking and bathing.