Background: All rivers flow differently. A large river, like the Mississippi River, might not have the same flow pattern as a small river like the Narraguagus River in Cherryfield, Maine. Scientists and government agencies record and keep track of water levels for a lot of different reasons. Some are interested in fish habitat, some need to know how much power a hydroelectric dam could produce, and still others are monitoring for potential flooding. This graph shows daily water level records for the Allagash River in northern Maine and the South Yadkin River in North Carolina.

Source: USGS