Pollution des eaux de surface par les éléments nutritifs et lien avec l'urbanisation à l'échelle des bassins versants de l'Okpara à Parakou (Bénin)

In developing countries, cities urbanization usually lack planning processes and quantitative consideration of impacts on aquatic receptors. This work evaluates by defining a nutrient quality index, the link of urban increasing with surface water resources quality. Four basins of different levels of urbanization in the Parakou city in West Africa served as a framework for the study. For headwater basins, which are essentially urban extension area (Ganré in the North and Dama in the South), the results indicate that the surface waters are of a very close and fairly good quality with a minimal index of 0.95 in the rainy season and 0.88 in the dry season. The basins of the old urban core, Kokouro and the wonka are at 0.84 in the rainy season and 0.89 in the dry season at the minimum. The quality index deviations obtained are not more than ± 0.08. Good consistency is obtained between our quality index with the organic pollution index of Leclercque and 72.49% variance of the dependency link between urbanization and surface water pollution can be explained by the quality indices and subdivision indices. These results indicate the need for better management of urban sprawl for the preservation of the quality of surface water resources.