The many small streams that come together at the source of a river are called what?

tributary

A tributary are collection of small streams that come together into a mainstream river or a lake. It does not flow directly into the ocean for water from the small stream will flow into the drainage basin and groundwater before leading out into an ocean.

delegated (sometimes called enumerated or expressed) powers are specifically granted to the federal government in article i, section 8 of the constitution. this includes the power to coin money, to regulate commerce, to declare war, to raise and maintain armed forces, and to establish a post office.