The Nile is the world's longest river at 4,135 miles. It has two sources, one at Lake Victoria, in Uganda (the White Nile) and one at Lake Tana, in Ethiopia (the Blue Nile).The entire Nile River Delta is estimated to drain an area of 1,293,000 square miles. This area is so vast that is has a number of different climate areas. North, in Egypt and Sudan, rainfall is sparse. More to the south, in and around Ethiopia, rainfall is heavy, contributing to the floodwaters that rush downstream and eventually create the wonderfully fertile soil that supports so much of life in Egypt and Sudan. Dams, the most notable being the Aswan High Dam, have been built along the route to prevent massive flooding of populated areas.The Nile River Delta is home to many species of animals, including crocodiles, turtles, baboons, wildebeest, and more than 300 species of birds, including fishing eagles, ibis, and the Nile Valley Sunbird.