The White Nile is the longer of the river's two main arms. It starts its journey in the heart of the continent from within a mosaic of mountains, lakes and rivers. It then passes through an arid rocky zone and an immense swamp before joining forces with the Blue Nile at Khartoum.

The Sudd is one of the largest swamps in the world covering 32,000km² (1,2355 square miles) at the height of its flood. Silt and marsh sediments are thought to be an astonishing 10km (6 miles) deep. A labyrinth of floating papyrus islands, it supports enormous numbers of fish. The marshes and flood plains are home to over 400 species of bird and more than 90 species of mammal, including some of the greatest concentrations of large mammals on earth. As many as a million white-eared kob have been known to live here, 1,000 per km². As the rains set in, their massive migration rivals that of East Africa's wildebeest.

Just below Lake Albert, the White Nile contracts from a width of 50m (16ft) to just 7m (23ft) as it cascades over the falls, creating an immensely powerful water surge. At the base of the waterfall, surprisingly large crocodiles gather. Unable to travel further upstream, they concentrate here and line the banks as they bask in the sun.

The Ruwenzori or 'Mountains of the Moon', sit between the humid forests of the Congo Basin and the monsoon lands of East Africa. Ruwenzori - the local name - means rainmaker. With an average annual rainfall of about 2,000mm (78 inches), they are the wettest mountains in Africa. The Ruwenzori's glaciers, frozen at some 5,000m (16,500ft) above sea level drip feed bogs which in turn feed mountain streams, rivers and the great African lakes of Victoria, Albert, Edward and George.

Lake Victoria has an insect population unrivalled anywhere on Earth. During the rainy season, an extraordinary event is triggered by the new moon. Fly larvae ascend from the bottom of the lake and those that make it past the fish emerge at the surface, struggle free of their larval shells and rise up into the air. There they join others in breeding swarms that merge to form vast clouds of billions of flies. Drawn by the flies, terns migrate here from Europe and gather in huge colonies.