What's the world's longest river? That depends on how your measure them.
Measuring a river is not as simple as it seems because many rivers join together in river systems, so it is sometimes difficult to pinpoint where one individual river begins. The generally accepted method among scientists is to measure the length of the longest continuous river channel in a given river system.
Although the accepted way of measuring a river's size is by its length, the magnitude of a river can also be measured by its volume, and therefore crowning the largest river in the world can be a thorny issue.
The Nile
Flowing northward through the tropical climate of eastern Africa and into the Mediterranean Sea, the Nile river is the longest river in the world at 4,135 miles (6,650 kilometers), according to the U.S. National Park Service.
The Nile runs through Egypt, as well as nine other African nations Sudan, Eritrea, Ethiopia, Uganda, Kenya, Tanzania, Rwanda, Burundi and the Democratic Republic of Congo. More than 300 million people depend on the Nile for their water supply and the irrigation of seasonal crops, according to the Council of Ministers of Water Affairs of the Nile Basin.