SUMMARY
To satisfy its water needs increasingly growing,Moroccohas an important infrastructure of dams. However, demographic and economic expansion ofMoroccocould lead to a deterioration of the water quality of these artificial lakes. The Moulouya watershed is among the most important watersheds inMorocco, it contains to the present five major dams, among them the Hassan II dam, which became operational in 2005. This dam is one of the largest Moroccan reservoirs with a maximum storage capacity of 400 million cubic meters. However, increased human activities upstream of the dam associated with the phenomenon of erosion could lead to pollution of this water mass. The aim of our study was to assess the water quality of the reservoir through the search of bacterial indicators of fecal contamination, via a monthly followed, during the study period from September 2011 until August 2012.Detection of fecal coliforms (CF) and fecal streptococci (SF) in the waters of the dam was a presumption of its contamination by the feces. With the exception of bottom waters that were loaded with spores of sulphite-reducing anaerobes (ASR), the waters of the other stations in the water column did not contain these spores. However, water levels in total coliforms (CT), CF and SF were qualified water quality of the dam as good to excellent, this according to the Moroccan standards of quality of surface waters.