The Blue Nile River has its sources in Lake Tana. The Nile has 400m wide above the waterfall; in the gorge below, it follows a much narrower course estimated to be 40m deep. The Nile is made up of several rivers. In South Sudan, the Sobat merges into the White Nile. In the Sudanese capital of Khartoum, the White Nile and the Blue Nile converge, and further north, they are joined by the Atabara, which also has its source in Ethiopia. The Nile received most of its water from the Blue Nile (59 percent) and the rest from the White Nile (14 percent), the Sobat (14 percent) and the Atabara (13 percent). It is the longest River in the World, passing through nine countries with a drainage basin of over three million square kilometers, and is a life source for over 200 million people and numerous animals and plants.