Explore the Surface

Here's a simple experiment students can try to explore the differences between permeable and impervious surfaces, and see why surface matters when it comes to stormwater.

Vocabulary to know before you start

Impervious surfaces: Hard surfaces that do not allow water or other liquids to soak in or pass through. Impervious surfaces are sealed off and impenetrable. Examples include roofs, roads, parking lots, and sidewalks.

Permeable surfaces: Surfaces that allow water and other liquids to soak in or pass through, like water trickling through a sponge or sieve. Examples include fields, gardens, and forest floors. Some human-made surfaces can be permeable, too.

Kitchen sponge (JPG)


  • Large cup or glass
  • Standard kitchen sponge
  • Water
  • Plastic wrap
  • Clay
  • Cloth
  • Small stones
  • Tray or tub

What to do

  1. Do this activity on a tray or in a tub or sink.
  2. Wet the sponge and then wring out most of the water. Place the sponge vertically inside the cup. The sponge should fit snugly near the top of the cup.
  3. Pour water slowly over the sponge. What happens to the water? Where does it go? Is the sponge permeable or impervious?
  4. Drain the water out of the sponge. Wring out the sponge again and put it back inside the cup.
  5. Plan a design to make the surface impervious using the other materials available. Test your design.
  6. What worked well to keep the water from soaking into the sponge? What didn't work well?

Copyright 2017 Water Education Group, LLC