Tributary

A confluence, where two or more bodies of water meet, usually refers to the joining of tributaries.

These terms are defined from the perspective of looking downstream, that is, facing the direction the water current of the main stem is going.

This information may be used to avoid turbulent water by moving towards the opposite bank before approaching the confluence.

In the United States, where tributaries sometimes have the same name as the river into which they feed, they are called forks.

For example, the American River in California receives flow from its North, Middle, and South forks.