a creek
A tributary.
resorvoir
It is called a tributary
a small stream that runs into a main stem river or lake
The smaller stream is a tributary of a larger stream, river or lake.
When other rivers or lakes join to the main river . It is called the tributary .
exactly what you said the main stream and tributaries
A tributary is a stream or river that flows into a larger main river. It contributes water, sediment, and nutrients to the main river system. Tributaries play a crucial role in the overall watershed ecosystem.
Creek
It is a tributary.
A small freshwater river or stream flowing into a larger river is called a tributary or feeder river. A tributary is a stream or river that flows into a mainstem (or parent) river or a lake. For example, a tributary can be a creek that flows into a river. Or it can be a small river that flows into a larger river. A tributary does not flow directly into a sea or ocean. Some large rivers can have up to 100 tributaries. The spot where the smaller and larger river meet is called a "confluence". In contrast, a body of water that branches off and flows away from the main river is called a distributary.
A main channel is any shallow body of a river or a stream