Discharge

The amount of water flowing in a stream is called its DISCHARGE, which is the volume of water moving in a stream during a given time interval. Time is usually expressed as seconds, but volume can be in cubic feet (ft³) or cubic meters (m³). So, discharge can be either cubic feet per second (ft³/s, also termed cfs) or cubic meters per second (m³/s). We'll be using the metric system for our determinations, but at the end of this activity you have the opportunity to convert from m³/s to cfs.

Click "Start" to observe the block of water move downstream at a rate of 1.0 meters per second. (It takes 10 seconds for the cubic meter block to move 10 meters.) The example stream above is confined to a 1 meter square channel. Discharge here then, is 1.0 cubic meters/s. Later in this exercise you will determine the cross-sectional area of a stream and the stream's velocity through that area. By multiplying the area times the stream's velocity, you will be able to estimate the stream discharge.