Four river basins in the Sahel cross national boundaries. It is important to note that these rivers in general have their sources in the more abundant rainfall areas to the South and carry significant quantities of water north to drier areas and, in the case of the Niger River, over 2,000 km across two countries. The effective use of the water resources in these basins will be a major factor in the long-term development of their riparian Sahelian countries.