The Dayet Er Roumi lake located in the biogeographic zone of the central meseta belonging to the province of Khemisset, constitutes the only permanent natural lake of low altitude in Morocco. The lake's water body is the essence of the existence of this natural and environmental space. The objective of the present study was on the one hand to evaluate the current state of the bacteriological quality of the waters lake Dayet Er Roumi, and on the other hand to define the risks of the pollution

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... ers lake, and its origin. In order to carry out this work well, the evolution of the bacteriological parameters of the waters lake during the period from October 2020 until September 2021 was studied at the level of four stations of sampling. The obtained results showed that the waters of Dayet Er Roumi are confronted with a strong pressure generated by the discharges of domestic waters of the neighbouring agglomerations and also by activities of natural, agricultural and tourist origin. Indeed, the bacterial load is expressed by a high load of bacteria indicative of fecal contamination which varies between 50 and 346•10 3 CFU/1 ml for total aerobic mesophilic flora (TAMF) at 22 °C, 6 and 72•10 3 CFU/1 ml for TAMF at 37 °C, 15 and 62•10 3 CFU/100 ml for total coliforms (TC), 0 and 4350 CFU/100 ml for faecal coliforms, 0 and 16 350 CFU/100 ml for faecal streptococci, 1 and 13•10 3 CFU/20 ml for sulphite-reducing anaerobes, 38 and 22 680 CFU/100 ml for Staphylococcus aureus and between 160 and 33 600 CFU/100 ml for Pseudomonas aeruginosa. These results largely exceed the Moroccan standards for the water intended for irrigation. They could be the cause of possible contamination of irrigated crops as well as groundwater in the region, and consequently have repercussions on human health.