Characteristics of River Systems
The basic function of the rivers is to convey surplus rain water from land to sea. Annually the rivers carry fresh water, equivalent to 25 cm of rain, evenly distributed ' over the whole land surface.
The point of origin of the river is the 'source'; the path it takes, is the 'course'; the streams which pin it along the course are the 'tributaries'; and the channel within which it flows is the 'bed'. Its point of entry into the sea or lake or estuary is called its mouth.