Our transcription: The velocity of a river also tends to increase if the amount of water in the river channel increases. The quantity of water moving through a river is called its "discharge." The discharge of a river is how much water it's actually carrying. We usually measure this as a volume per unit time. In the United States we commonly say "cubic feet per second." Most of the rest of the world would talk about the number of "cubic meters per second" that are moving down the channel. Discharge increases from the head of the stream to the mouth of the stream as the drainage basin increases in size. There's simply a larger area to contribute discharge, contribute flow to the streams.