National Ground Water Association

By Kimberly Mullen, CPG

Objective

Students will create a simulated wetland to understand how wetlands actually filter and clean the water as it travels through the wetland.

• Cotton batting (comes in a roll, used in quilting, found with sewing supplies)
• Clay (can use natural clay or modeling clay)
• Topsoil or potting soil
• Pea-gravel or any small stones
• Vegetable oil
• 2-liter pitcher
• Large pan or box (plastic or metal).

General suggestions
(for the instructor)

1. Depending on materials available, this lab can be run as a demonstration (with students assisting) or in teams of students (each creating their own wetland filter).
2. If working in student teams, give students the opportunity to create their own filter system (what they think will work best) using the batting, soil, and gravel. Have the student teams showcase (present) their wetland filter and explain why they built it the way that they did. Then have the team pour the contaminated water as the whole class observes to see if the filter works. Have students record their observations for each team effort. Which filter worked? Why/why not?
3. If doing the lab as a demonstration, get student input as to how to build the wetland filter (ask the students what each kind of material represents in a wetland, what order would it be in, why?). Have students take turns and build the filter. Pour the contaminated water and have students record their observations. What did they see? Did it work? Why/why not?
4. Explain the entire lab to the students. All instructions should be read before dividing into teams and handing out the materials.
5. If cotton batting cannot be found, aquarium filter material can be substituted. Can also substitute aquarium gravel for pea-gravel.
6. The recommended order would be:
   • Gravel/stones (representing bedrock)
   • Clay (representing hydric soil)
   • Cotton batting (representing the wetland plant root system)
   • Topsoil (representing the A Horizon))
   • Additional gravel (representing alluvial material).
   Allow students to think about the order on their own, but try to guide them and as what each material represents and to the order that is actually found in a wetland

Lab Activity #1: Building a wetland filter 
(for the students)

1. Working in your student team, decide who will record the observations and decisions. These must be written on the team lab sheet.
2. Collect the following materials:
   • Pan/container (to build the wetland filter in)
   • 12-inch x 12-inch square of cotton batting
   • One section of clay
   • 2 cups of topsoil
   • 4 cups of gravel.
3. The wetland filter must only take up one-half of the provided container. It should be in the middle of the container, with one-fourth on each end of it (this will be for the water filtering through).
4. As a team, you must now decide how to build the wetland filter. The filter should represent what occurs in a real wetland. Each team must determine what each material represents in nature (e.g., what does the clay represent? the cotton batting?). This must be recorded on the team lab sheet.
5. After deciding on the order and why, begin building the wetland. Remember to only use one-half of the container for the wetland. The container must have one-fourth on each end for the water filtering.
6. Notify your teacher when you have reached this step. Once all teams are at this point, each team will present their filter to the class and explain the order that was used.
7. Now it is time to test each filter (one at a time, as the class observes). A designated team member will fill a 2-liter pitcher with 1 liter of tap water. Add a small amount of top soil and 2 capfuls of vegetable oil. Stir well.
   
   As the mixture is being prepared, each team must place a small block under one end of their container to create a slight slope (allowing water to flow).
   
   As the class watches, slowly pour the contaminated water at the high end of the container. Each team will test their filter systems. All observations should be records for each team.
8. What happened to the contaminated water?
9. Which filter system worked best? Why? Which filter systems did not work well? Why?
10. Using this filter model, why are wetlands important in today’s world? Why should we preserve wetland areas?