Watercourse
"An open conduit either naturally or arti cially created that periodically or con- tinuously contains moving water, or which forms a con- necting link between two bodies of water. River, creek, stream, run, reach, branch, and tributary are some of the terms used to describe natural channels." (Virginia Polytechnic Institute and State University, n.y.)
Sources
Virginia Polytechnic Institute and State University. "A Glossary of Water-Related Terms", by Brian Benham. Publication 442-758