Watershed in a Cup
Did you know that we get our drinking water from an ecosystem that holds about 21% of the planet’s surface fresh water? That’s right – the Great Lakes hold one fifth
of the fresh water freely available to all the plants and animals in the world. The tricky part is that we also live
in the watershed that provides our water. Think of a watershed as a big bowl; anything on the sides of the bowl gets washed down into the bottom. The “bottom” of our bowl is Lake Erie. Anything on our roads, parking lots, driveways or any paved surfaces washes into the storm drains and right into the lake.
The good news is we can protect our waters by maintaining green spaces like forests, wetlands, and parks. Green spaces act like sponges when it rains, letting water soak in and move slowly to the lake. They filter and trap fertilizers and pesticides, engine oil, trash, and animal droppings. To learn how it works, try this activity!
Build a watershed
- two plastic water bottles (or clear plastic cups)
- ¼ c unpopped popcorn or gravel
- ¼ c cornmeal or sand
- ¼ c topsoil or potting soil
- two cups
- purple powdered drink mix (or red & blue food coloring)
- raisins, pepper flakes, sprinkles (or other things to be “trash”)
- cooking oil
Make your runoff
- Cut off and recycle the tops of two water bottles. Poke holes in the bottom of one of the remaining bottoms. Add (in this order) ¼ cup unpopped popcorn or gravel, ¼ cup cornmeal or sand, ¼ cup topsoil or potting soil. Place the bottle with your layers into the empty bottle, so they nest together, but there’s space inside the bottom bottle. (Tip: if your bottles won’t fit together, cut a vertical slit in the top of the empty bottle for some more wiggle room.) This is your watershed!
Make it rain
- Get two cups of water, set one aside to be your clean water. To the second cup add the drink mix or food coloring, a raisin or two (dog poop), some pepper flakes (plastic bags), and some sprinkles or ripped up paper – whatever you think looks trashy. Add a little cooking oil to represent automotive oil. This is your dirty water. How does it look or smell? Would you want to drink this? (Science safety tip: Never drink your experiment.)
- Gently pour about ¼ cup of clean water in the top and watch carefully. What happens to the water? How quickly does it start coming out the bottom? Does it look or smell different when it comes out the bottom?
- Now, carefully pour out the clean water. Put the bottles back together and pour in about ¼ cup of the dirty water. Make sure some of that nice trash makes it in! Again, watch carefully. What does the water look like when it comes out? What’s different?
In this experiment each layer represents a different layer of soil in the ground. These layers are called “soil horizons” and each one has different size particles and ingredients. Do you think the process works the same without one of the layers? Try the activity again with only two layers – what’s different?
Look in the top of the bottle – have any of your ingredients collected on top? Imagine that's your yard or park. What can you do to make it better? The next time it rains, think about where all that water goes, and how you can help keep it clean. The lake thanks you!