The discharge of a stream is the product of its velocity (V - length of travel per unit of time such as feet/second) times depth of the water (D - unit of length) times width (W of the water- units of length). (Make sure all all three lengths are expressed in the same unit.)
Discharge = V x D x WIf length is measured in feet and time in seconds, Discharge has units of feet3/sec or cubic feet per second (cfs).Depth times Width gives the cross-sectional area. The shape of the channel is important because of the reduction in velocity due to friction along the channel margins. In a natural situation, an increase in discharge (cubic feet/second) will result in an increase in all three parameters - the river becomes wider, deeper and flows at a higher velocity.
