Wetland – nature’s purification (filtering)
- Explain to students that wetlands are complex systems and that many processes are still not understood in full detail. Tell them that they will build a model of a wetland and demonstrate three of the many essential functions wetlands perform. Some of them are important for self-purification.
- Make a model of a wetland:
- Divide the students into teams and provide each team with materials to create its own wetlands model.
- Spread a sloping layer of plasticine modelling clay in half of the box to represent land. Leave the other half of the pan empty to represent a lake or other body of water. Shape the clay so that it gradually slopes down to the body of water. Smooth the clay along the sides of the pan to seal the edges.
- Combine a couple of pieces of kitchen sponge together that will completely fill the width of the pan along the edge of the clay. This will represent the wetland. Do not place the sponge into the model yet.
- Demonstrate the filtering function of wetlands using the wetland model:
- Pour out the clear water. Leaving the sponge in place, pour some muddy water onto the clay. Compare the water that flows through the wetland and into the body of water with the water left in the jar.
- What happened? (Students should conclude that part of the soil in the muddy water was trapped by the wetland and that wetlands can act as a filter for sediment and some pollutants. You should also point out that the sponge holds water, which is also an important function.)
- Remove the sponge and pour out the clear water again.
- Why do all the soil particles end up in the body of water? (The students should infer that without the wetland to act as a filter, most of the soil and perhaps pollutants flow directly into the body of water).
- Explain to students that wetlands help prevent the deposition of eroded soil (sediment) and other pollutants in bodies of water.
- Pour out the clear water. Leaving the sponge in place, pour some muddy water onto the clay. Compare the water that flows through the wetland and into the body of water with the water left in the jar.
Additional resources:
https://www.zhaw.ch/de/lsfm/dienstleistung/nachwuchsfoerderung-angebote-fuer-schulen/play-with-water/secrets-of-rivers/vegetation-as-filter/
https://www.zhaw.ch/de/lsfm/dienstleistung/nachwuchsfoerderung-angebote-fuer-schulen/play-with-water/cleaning-water-with-plants/
