RESUMEN
The monitoring of the organic pollution level and the ecological and health risks of the waters from the Déganobo lake system were the subject of this study. In its implementation, the water samples were collected monthly in this aquatic ecosystem over a year (from August 2021 to July 2022). The organic pollution level of these waters was assessed using their Chemical Oxygen Demand, determined in accordance with NF T 90-101 standard. The ecological and health risks were assessed based on the SEQ-Eau V2 water quality guidelines. Their COD seasonal mean values were between 220,000±51,872 and 361,333±48,273 mg/L O2. So, their organic pollution was relatively very significant, with the corollary of the zero of its seasonal transparencies and of its seasonal dissolved oxygen contents. The seasonal dynamics of organic matter in these waters was essentially linked to the hydroclimate (rainfall and ambient temperature) on the watershed of this lake system. The low meteorite waters inputs in dry seasons favoured the increase of their COD by the important punctual wastes inputs of various origins (domestic, agricultural, industrial, hospital, etc.); in opposite of the important meteorite waters inputs in rainy seasons causing their renewal. The consequences of their important COD values are severe ecological and health risks, as highlighted by SEQ-Eau V2 water quality guidelines. So, this lake system is under the strong anthropogenic pressures. This study could serve as complementary information on its pollution level and contribute to decision-making for its rehabilitation, its protection within the framework of its sustainable development.