At 6,650km long, the Nile is the longest river on the planet ... they reached the confluence of the White and Blue Niles and chose to continue up the White. Here's where things get historically ...

In Sudan’s capital, Khartoum, the Blue Nile merges with the White Nile, a snaking river that has passed through the swamps of South Sudan, where much of it evaporates. Blue and White together ...