Tributary
From Simple English Wikipedia, the free encyclopedia
A tributary of a river is another river that flows into it. If one river flows into a second river, then the first river is a tributary of the second river.
For example, in the United States the Missouri River flows into the Mississippi River. That means the Missouri River is a tributary of the Mississippi River.
A river and all its tributaries form the catchment of that river.
A watershed separates the catchments of separate rivers.