What's a Hydrograph
A hydrograph shows the amount of water flowing in a stream over a period of time. One cubic foot per second (cfs) is equal to one cubic foot of water flowing by every second, a rate equivalent to about 7.48 gallons per second. The data for a hydrograph comes from a stream gauge. To read a hydrographic, pick a date and move up to where it intersects the graph. Then read horizontally to the left to the discharge of the stream for that date (click on the graph at right for an example of how to read a hydrograph.