A watershed is the geographic boundary of a creek, river or stream – it’s the area of land from which water drains to a particular water body. Watersheds come in all shapes and sizes, and there are watersheds for every body of water, whether it is the creek flowing through your neighborhood or the Mississippi River. No matter where you are, you are in a watershed. A river basin consists of all the watersheds that flow to that river.
Think of a funnel. Everything that falls into it, flows together, concentrates and flows from a single point into a receiving body or stream. Just as gas flows through a funnel to your lawnmower, water flows from the land within the watershed, to the creek, down the creek and into the receiving stream.