What happens when it rains?
All the water we are talking about comes from rain or snow or runoff, so what happens when it rains?
This is a hydrograph. It is what hydrologist and other natural scientists use to measure water in a stream.
They measure the amount of water in the stream or flow rate, over a period of time.
As is rains, more water enters the stream and the flow goes up. When the rain stops, and the water has a chance to move through the watershed, the flow goes back to normal.
In a forested watershed, the water soaks into the ground and takes it time getting to the stream.
In a developed watershed, rain doesn't have a chance to soak into the ground, water rushes to the stream as stormwater runoff, raising the flow quickly and dramatically. We get more runoff, arriving faster.
The more development we have, the more opportunity for impervious surfaces, the more runoff we end up with.
