The drainage basin: key features

On land, water accumulates on the surface through lakes and rivers. Each river is confined to its drainage basin, the region of land where the river drains from its origin, where it starts, to its mouth, where it concludes by flowing into a sea, ocean, or lake, along with its smaller contributing streams.

The main features of a drainage basin

The edge of a drainage basin is marked by an elevated ridge called the watershed. When a tributary converges with the main river, it is called a confluence. In certain instances, confluences are distinctly visible if the two converging rivers have differing water characteristics, such as the confluence in Brazil, where the River Negro and the River Solimoes merge.