Dusk on the Omo River.The Omo River rises in the Ethiopian Highlands and flows for over 600 miles before discharging its waters into the northern end of Lake Turkana. Once a year following rains in the highlands, the river rises and bursts its banks, flooding the low-lying plains. After the water has subsided, people living near the river plant crops in the fertile soil. Without flooding, there would be no agriculture because the annual rainfall of the region is too low.