The White Nile is the longer but lesser of the Nile's two main branches, the Blue Nile carrying far more water. Defining its true start is a famously contested matter. In the broadest sense the river drains from Lake Victoria, but the most distant headwaters lie further south still, in the highlands of Burundi and Rwanda. The Kagera River, fed by streams rising in Nyungwe Forest and the hills of Bururi, is the longest feeder into Lake Victoria, and somewhere among its tributaries sits the ultimate source of the Nile, a point geographers have argued over for more than a century and a half. The river changes names as it travels, a different title for nearly every stretch, as though no single word could hold the whole of it.

In Uganda the river is called the Victoria Nile, and it begins at Jinja, where Lake Victoria pours out at the lake's northern shore. From the start it has been harnessed for power: the Nalubaale and Kiira stations sit at the outlet, and the once-famous Bujagali Falls downstream were submerged by a dam in 2011. The river then runs northwest to Lake Kyoga and on toward Lake Albert. Its most dramatic moment comes at Murchison Falls, where it is compressed into that seven-metre gorge and hurled into the western arm of the East African Rift. Beyond the falls it spills into Lake Albert, facing the Blue Mountains of the Congo across the water, having crossed Uganda from one great lake to another.

Draining out of Lake Albert, the river becomes the Albert Nile and flows north toward the border, dividing Uganda's West Nile region from the rest of the country. Crossing into South Sudan it takes the name Mountain Nile, or Bahr al-Jabal, "river of the mountain." There it meets one of the most extraordinary obstacles on its course: the Sudd, an immense wetland where the river loses itself in a maze of channels, reeds, and floating vegetation so vast it stalled would-be navigators for generations. The Sudd swallows enormous quantities of water to evaporation, so that the river emerging from it is much diminished. At Lake No the Mountain Nile merges with the Bahr el Ghazal, and only here, in the strictest definition, does the "White Nile" truly begin.

From Lake No the White Nile runs slow and swamp-free into Sudan, gathering the sediment-rich floodwaters of the Sobat that deepen its pale colour. It passes Malakal and, downstream, Kodok, the site of the 1898 Fashoda Incident, when a French and a British expedition met on its banks in a tense standoff that came to symbolise the end of the European Scramble for Africa. Finally, at Khartoum, the White Nile meets the Blue Nile flooding down from the Ethiopian highlands, and the two become simply the Nile. The river that began in a Ugandan lake and squeezed through a seven-metre gorge now sets out across the Sahara, bound for Egypt and the sea, carrying the histories of half a dozen nations in its current.