The catchment area of the Nile-the longest river in the world at 6695 km-links 10 African countries: Egypt, Sudan, Ethiopia, Eritrea, Uganda, the Democratic Republic of Congo, Kenya, Rwanda, Burundi, and Tanzania (Figure 1). A treaty regulating water use was signed in 1929 (revised in 1959) between Egypt and Sudan, which greatly favors Egypt. But more and more water is being claimed by countries upstream. Altogether, some 300 million people share the water of the Nile. The question of use represents an enormous potential for conflict, and water issues are now being addressed by the Nile Basin Initiative.