A River basin is the portion of land drained by a river and its tributaries. It encompasses all of the land surface dissected and drained by many streams and creeks that flow downhill into one another, and eventually into one river. The final destination is an estuary or an ocean. As a bathtub catches all the water that falls within its sides, a river basin sends all the water falling on the surrounding land into a central river and out to the sea.
Everyone lives in a river basin. Even if we don’t live near the water, we live on land that drains to a river or estuary or lake, and our actions on that land affect water quality and quantity far downstream. There are 17 river basins in North Carolina, draining 52,337 square miles of surface and underground waters. The topography of each basin determines the area that it drains, and whether that water – from creeks, rivers, springs, and aquifers – flows into the Atlantic Ocean or Gulf of Mexico.
When rain falls on your street, roof or yard, what creek or river will it flow through on its way downhill towards the sea? When you drain your bathtub or sink, where does the water go? When you turn on your tap to get a drink of water, where does the water come from?
As an artery connects the parts of a body to one another, so a river threads together the creeks and streams, valleys and hills, lakes and underground springs that share a common assembly of water. Whatever happens to surface or groundwater in one part of the river basin will find its way to other parts. If water is diverted out of its downward course in one section, other parts will come to “know” of its absence. A river basin comes closer than any other defined area of land, with the exception of an isolated island, to meeting the definition of an ecosystem in which all things, living and non-living, are connected and interdependent.