supplying power for 25 per cent of the population. 2006 floods Heavy rains in 2006 caused the Omo to flood its lower course, drowning at least 456 people and stranding over 20,000 people over the space of five days ending 16 August. While seasonal heavy rains are normal for this part of the country, overgrazing and deforestation are blamed for this tragedy. "The rivers in Ethiopia have less capacity to hold as much water as they did years before, because they are being filled up with silt," World Food Programme spokeswoman Paulette Jones said. "It takes less intensity of rainfall ... to make a river in any particular part of the country overflow." The seasonal flooding of the Omo River is vital to the indigenous groups that live along it. The flood brings fertile silt and inundates the banks with water, making river bank cultivation possible. The diverse peoples along the lower Omo—which include the Turkana, Dassanach, Hamer, Nyangatom, Karo, Kwegu, Mursi, Bodi, and Me'en—derive a great portion of their food supply from flood retreat cultivation. The large and destructive flood of 2006 is the only one that has occurred within the past fifty years. The recent drop in the level of Lake Turkana, which is generally recognized to receive about ninety percent of its waters from the Omo River's inflow, has already caused a rise in salinity level. The increased size of the delta, now about in extent, has provided lands for recessional cultivation and pasture for cattle and other domestic livestock of the pastoralists and agro-pastoralists indigenous to the lower Omo basin. See also Gibe River List of Ethiopian rivers List of fossil sites (with link directory) Omo Kibish Formation Omo Remains List of World Heritage Sites in Ethiopia Notes References Butzer, Karl W. (1971). Recent history of an Ethiopian delta: the Omo River and the level of Lake Rudolph, Research paper 136, Department of Geography, University of Chicago, 184 p., LCCN 70-184080 Camerapix (2000). Spectrum Guide to Ethiopia, First American Ed., Brooklyn: Interlink, Crandall, Ben (2007). The Omo River Valley, eMuseum @ Minnesota State University, Mankato; website accessed 31 October 2007 Hurd, W. (2006). "Rangers by Birth", Cultural Survival Quarterly, 30.2, website accessed 31 October 2007 UNESCO World Heritage Centre (2007). Lower Valley of the Omo, World Heritage List, website accessed 31 October 2007 Vannutelli, L. and Citerni, C. (1899). Seconda spedizione Bòttego: L'Omo, viaggio d'esplorazione nell'Africa