The Pavement Effect

 
Have you ever noticed water flowing down the street when it rains? Have you ever
wondered where the water flows to? Have you thought about what's in the water?
When it rains onto a forest or a field, some of that rain is absorbed by the ground,
replenishing groundwater that is used by many for drinking water. Some of the rain is
taken up by plants, and some of it simply evaporates. But very little of the rain flows
over the ground.

In a more developed setting, such as our cities and towns, rain falls onto pavement,
or other surfaces such as roofs, sidewalks, parking lots, and driveways that don't
allow the water to be absorbed by the ground. The water that you see flowing down
the street is called storm water runoff.

It's Not Just Rain

When storm water hits the pavement, it picks up and mixes with what's there. That
might include:

• oil, grease, and automotive fluids;
• fertilizer and pesticides from gardens and homes;
• bacteria from pet waste and improperly maintained septic systems;
• soil from poor construction site management;
• sand from wintertime snow removal;
• soap from car washing;
• debris and litter

So the water flowing down the street is not just rain; it's polluted water, and it heads
directly to our local water bodies.

Why is it a Problem?

Many people assume that storm water flows down stormdrains and then to a
treatment facility. Unfortunately, that is almost never the case. Storm water either
flows directly into local waters or down stormdrains, which channel it into local water
bodies. The polluted runoff closes swimming beaches and fishing grounds, threatens
water resources, harms natural areas, and contributes to flooding.