Students will learn about the ways in which water can become polluted and why it is important to conserve water by developing a model and watching a demonstration of the pollution of a lake. This activity is a great companion to any lesson on water, conserving natural resources, pollution, etc. Students will learn about the ways in which water can become polluted and why it is important to conserve water by developing a model and watching a demonstration of the pollution of a lake.

20 minutes

• A clear plastic washtub big enough to hold several gallons of water (a clear plastic storage container would work well)
• Enough clean water to fill the plastic washtub 3/4 full; one gallon separate
• A bottle cap
• Slotted spoon
• Spoon
• Tongs
• Other tools useful for moving small items
• Laundry soap
• Salt
• Vegetable oil 
• Small pieces of paper
• Small pieces of trash and food
• Food coloring
• Rocks and soil
• Towels

1. Fill a clear washtub with water and place in the center of the classroom. Have students circle around the washtub, and tell them a story, starting with the tub representing a crystal clear, clean lake. The fish that live in the lake are happy, humans can swim in it, and mammals can drink from it. However, people keep coming to the lake and polluting it! You and I are very dependent on the water from this lake. What might we need it for? Farmers who farm close to the lake rely on it as well. Why might they need it?
2. Set out the salt, food coloring, paper, trash pieces, vegetable oil, soil and rocks, and laundry soap out. Have students choose an item, add it to the washtub, and tell the story that matches it:
   • Vegetable oil: (Student’s name who chose item) works as a mechanic in car repair shop. He spends a lot of time changing the oil in cars, so he has a lot of used engine oil. It costs a lot of money to properly dispose of the oil, so he dumps it in the lake instead. Is this good for the lake?
   • Salt: Let’s pretend this salt represents fertilizers that are used on golf courses, lawns, and farm fields. They are important for helping grasses grow, but sometimes can travel down through the soil and end up in water, like our lake.
   • Food coloring: Chemicals are used a lot in America. We use them to do many things, but often need them to keep insects and weeds off of our lawns, golf courses and farm fields. Just like fertilizers, these chemicals can travel through the soil and get into our water, like the lake.
   • Laundry soap: (Student’s name who chose item) owns a laundromat next to the lake. Sometimes, soaps and suds leftover from her washing machines drain into the lake.
   • Trash: a family comes to the lakeshore to have a nice picnic, but it’s a blustery day. The trash from their picnic flies away in the wind and ends up in the water.
   • Paper: while driving by the lake, (student’s name who chose the item) had his/her windows down. A gust of wind blew several receipts from stores and a letter into the lake.
   • Soil and rocks: The biggest pollutant of our water is soil! (Student’s name who picked the item) lives close to the lake. He/she recently removed the trees and shrubs bordering the lake, so now when it rains, the exposed soil runs into the lake! This can clog fish gills, stop underwater plants from photosynthesizing, and smother smaller water dwelling creatures.
3. Have students examine the washtub in its polluted state. Ask students if they think the water can still be used for drinking, swimming and living in. Why might the water not be healthy anymore? How would this impact the community and the farmers around the lake?
4. Have students take turns with a utensil such as a slotted spoon or tongs trying to remove pollution from the lake. Students will notice that larger items are easily cleared away, but some can’t be removed from the water. That’s why it is important to take care of the water before it becomes polluted!

Joyce Isaacson

This activity was adapted from Joyce Isaacson at East Pottawattamie Agriculture in the Classroom in Iowa.