The flood plains support extensive fisheries. These profound hydrological changes result in far reaching limnological changes as well. Flood regimes of the rivers differ from north to south within the region. In the north, the run-off tends to be concentrated into a few floods in August and September, while in the south it is more likely to be spread throughout the year. Many of the streams are temporary, running for only a few months out of the year.
Several issues are central to water and ecosystem management in the sub-region.
Threats The increasing stress on Africa's freshwater resources is the result of natural and human causes. Rapid population growth, pollution from pesticides and fertilizers, and industrial effluent all contribute to Africa's water stress. Another cause of stress is environmental degradation. Forests, which serve as important water catchment areas, are being cleared for fuel wood, lumber, and agriculture. Existing agricultural land is being degraded by soil erosion and devegetation.