The Blue Nile and White Nile have completely different journeys before they meet. The Blue Nile starts at Lake Tana high in the Ethiopian mountains, where heavy rains rush down steep valleys and pick up rich dark soil along the way. The White Nile starts much further south, flowing gently from Lake Victoria through flat wetlands called the Sudd in South Sudan.
When the two rivers meet at Khartoum, the water from each one does not mix straight away. For a short stretch, you can look down from a bridge and see a clear line where darker blue-grey water sits next to lighter tan-coloured water - like two halves of a smoothie that haven't been stirred yet. Gradually the currents blend the two together into the single Nile that then flows north through Sudan and Egypt all the way to the Mediterranean Sea.
The Nile at Khartoum is incredibly important for the people and wildlife of Sudan. Farmers grow crops in the thin strip of green land along its banks. Birds like the African fish eagle and the sacred ibis live near the water. Hippos, Nile monitor lizards and soft-shelled turtles also call the river home. The Nile has kept this part of Africa alive and green for thousands of years.