Our topic of discussion is about the longest river in the world. To answer this, it is necessary to measure the length of the river. But defining how long a river is not so easy. If many tributaries come together to form a large river, how do you define where the river actually begins? Length measurements are not always clear. A river can have more than one channel or anabranch. The length may depend on whether the center or edge of the river has been measured. Moreover the accuracy of the techniques is affected by the scale of the available maps or aerial photographs and somewhat arbitrarily. Other factors that can change the length of a river include erosion and flooding, dams, levees and cycles of channelization. That’s why there seems to be disagreement over whether the Nile or the Amazon is the longest river in the world.