A rivulette :)
Small creeks, streams and rivers that flow into larger rivers are called tributaries
tributaries
Tributaries
Tributaries are the smaller rivers and where they join is called a confluence
Don't know if I am answering your question correctly. But to my understanding we call them "sub-rivers" or "tributaries" which will merge into the main rivers.
a lake ? It is a tributary
Rivers
estuaries :)
They flow into 'The Tigris' and 'Ufratis' rivers!
Tributarys.
a tributarie
Small streams flow into rivers and the rivers flow to bigger rivers.