Summary: Students observe a simple wetland model that demonstrates wetland functions. The first part of the procedure demonstrates how wetlands prevent flooding and soil erosion. The second part of the procedure demonstrates how wetlands improve water quality by filtering sediments and pollutants.
- 90 minutes (two 45-minute class periods)
- Modeling clay
- Rolling paint pan (or small aluminum pan)
- Carpet or florist oasis foam
- Watering can or similar device
- Cup of soil
- Jar of muddy water
Part 1 – Build a Model Wetland
The first part of the procedure demonstrates how wetlands prevent flooding and soil erosion.
- Explain that wetlands, like all habitats, are complicated natural systems. They perform some very important functions such as filtering pollutants, reducing flood damage, and preventing soil erosion. Some wetlands, at times, recharge groundwater supplies.
- Explain that you will make a wetland model to demonstrate some of these functions in a very simplified way.
- Put the clay along one side of the pan. Fit the piece of carpeting or sponge into the wetland area along the edge of the clay. Slowly sprinkle some rain on land (the clay) and let the students observe and describe what is happening. Ask: If I make it rain on the model, what do you think will happen to the rainwater? (Rain will flow downhill.) The wetland (carpeting) will slow the rate of flow, and the excess rain will slowly enter the body of water. Point out that the wetland absorbed some of the water—pick up the wetland and squeeze some water out to prove it.
- Ask students: What do you think will happen if the wetland is removed?
- Answer: The water will not be absorbed; it will flow more quickly into the body of water.
- Remove the carpeting and water.
- Pour the same amount of water on the model at the same spot and rate as before.
- Have the students note any differences. The water should fill the body of water much more quickly and may eventually overflow and flood the land. That’s because it is no longer retained by the wetland.
Discuss the Results
- Explain that most wetlands are shallow basins that collect water and slow its rate of flow and also retain water for a time. This slowing process helps reduce flooding and also helps prevent soil erosion.
- Ask students: If a wetland is destroyed, and houses are built in its place, what might happen to the houses during a severe rainstorm? Why?
- Answer: They might be flooded because the wetland will not be there to absorb and slow the rush of water from higher ground.
- In many areas, wetlands are drained and filled, and houses and marinas are built right along the water. Without a wetland buffer, these developed areas, particularly along the coast, are often subjected to severe flooding and erosion, especially during violent storms.
Part 2 – Modify the Wetland Model
The second part of the procedure demonstrates how wetlands improve water quality by filtering sediments and pollutants.
- Pour the water from the last demonstration out of the model, squeeze out the “wetland” and replace the piece of carpeting.
- Spread a layer of soil over the clay.
- Explain that this demonstration will be just like the first, except that topsoil will cover the clay.
- Ask students: What do you think will happen to the bare soil when it rains?
- Answer: The rain should pick up and carry some sediment over the land and into the body of water.
- Explain that this water represents polluted runoff such as silt from farmlands and construction sites or salt from snow-covered streets.
- Ask the students to compare the water that ends up in the body of water with the muddy water in the jar.
- Explain that the carpeting trapped the soil particles, making the water in the body of water much clearer. The uphill side of the wetland should be coated with trapped sediment.
- Remove the carpeting, pour out the water, and try the experiment again.
- What happens without the wetland in place? Ask the students why all the soil particles end up in the body of water this time.
- The thick mat of plant roots in a wetland helps trap silt and some types of pollutants, much as the carpet or foam did in the model. Without a wetland, excessive amounts of silt and pollutants can end up in lakes, rivers and other bodies of water.
Discuss the Results
- How might muddy water affect fish?
- Makes it harder for them to see and breathe with clogged gills, and could lead to death.
- How might the muddy water affect other animals and plants?
- Settling sediment smothers clams, plants do not get sunlight needed for growth, birds and other animals that eat fish or plants have less to eat if food sources die or cannot be seen in muddy water, etc.
- How might the muddy water affect boats and ships?
- The mud settles out and eventually fills channels important for navigation.
- How might all of this affect you?
- Decrease in natural resources and food sources; decline in quality of drinking water; impacts on recreation such as swimming and fishing; change in aesthetics; change in community economy, such as shipping problems that affect jobs and industry, etc.
- How can we prevent these undesirable effects?
- By protecting wetlands and helping to make their benefits known!
- Ask students to describe how wetlands function to reduce flooding and retain sediments.
- Ask students to analyze what would happen to water, sediments, homes and wildlife if wetlands were destroyed.
Students, individually or as small groups, can make their own detailed wetland models using small aluminum foil pans, clay, and florist’s foam, carpet or sponges.
- Provide reference books with pictures of different types of wetlands.
- Students can use an assortment of collected material to decorate their models.
- Have students present their models by explaining their particular characteristics.
- Use long pine needles for reeds and toothpicks to attach plants.
- Shape wetland creatures from clay, or glue paper cutouts to toothpicks.
- Dried flower heads make nice trees, and small pine cones painted green form evergreens.
- For cattails, use cotton swabs. Paint sticks green and cotton parts brown, or paint toothpicks green, and attach bits of brown clay to the tops.
Adapted with permission from “A Wetland in a Pan: from WOW! The Wonder of Wetlands, for the Great Lakes Education Program. Modified by Julie Champion, Metro Beach Nature Center, Michigan; Bette Nebel, Macomb County Community College, Michigan; and Michael Schichtel, Mohawk Elementary School, Michigan.