The volume of water that passes through a given cross-section per unit time; commonly measured in cubic feet per second (cfs) or cubic meters per second (m

3

/s). Also referred to as flow.

In its simplest concept discharge means outflow; therefore, the use of this term is not restricted as to course or location, and it can be applied to describe the flow of water from a pipe or from a drainage basin. If the discharge occurs in some course or channel, it is correct to speak of the discharge of a canal or of a river. It is also correct to speak of the discharge of a canal or stream into a lake, a stream, or an ocean. (See also streamflow and runoff.)

Discharge data in USGS reports on surface water represent the total fluids measured. Thus, the terms discharge, streamflow, and runoff represent water with sediment and dissolved solids. Of these terms, discharge is the most comprehensive. The discharge of drainage basins is distinguished as follows:

Yield: Total water runout; includes runoff plus underflow.

Runoff: That part of water yield that appears in streams.

Streamflow: The actual flow in streams, whether or not subject to regulation, or underflow.

Each of these terms can be reported in total volumes or time rates. The differentiation between runoff as a volume and streamflow as a rate is not accepted.