A river of northeast Africa. It is the chief headstream of the Nile and flows about 1,609 km (1,000 mi) from northwest Ethiopia to Sudan. At Khartoum it merges with the White Nile to form the Nile River proper. the Blue Nile one of the two rivers that form the River Nile. It starts in Ethiopia in East Africa, and flows north to Khartoum in Sudan, where it joins the White Nile