watercourse

A natural stream arising in a given drainage basin but not wholly dependent for its flow on surface drainage in its immediate area, flowing in a channel with a well-defined bed between visible banks or through a definite depression in the land, having a definite and permanent or periodic supply of water, and usually, but not necessarily, having a perceptible current in a particular direction and discharging at a fixed point into another body of water. (Source: BJGEO)