(1) A natural or artificial waterway of perceptible extent which either periodically or continuously contains moving water, or which forms a connecting link between two bodies of water. (2) The part of a body of water deep enough to be used for navigation through an area otherwise too shallow for navigation. (3) The deepest portion of a stream, bay, or strait through which the main volume of current of water flows. (4) An open conduit for water either naturally or artificially created, but does not include artificially created irrigation, return flow or stockwatering channels.