Materials 

• Watering can
• Measuring cup
• Clay (non-hardening)
• Clear plastic trays (tops to seedling trays)
• Wax paper
• Tape
• Vegetable oil
• A variety of spices
• Carpet or sponges cut up into small piece

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Procedure

1. How is the land around rivers developed by people? Ask the students to list some different ways that people use rivers and the land around rivers. Use a local example if your town or city is located on or near a large river.
   
2. Divide the students up into groups of four to six students each and introduce the activity to the students. Each group represents a new community along a river. They will plan and build a model of their community, which will be reviewed and tested in a certain way (revealing the rainwater test too early might reduce the impact of the lesson).
   
3. Have each group create a drawing for their new community. Guidelines for the plan:
   1. streams should be included in the landscape. There should be several streams flowing from the land portions of the model into the river.
   2. the community can have homes, shopping areas, factories, mines, lumber companies, hotels, recreational facilities, natural areas, public parks, whatever the students think the community would need to be a place where people would want to live.
      
4. Each group should create a model of their community with clay on a clear plastic tray with raised sides.
   1. a piece of wax paper should be placed on the bottom of the tray
   2. clay represents the land and should be placed in the model accordingly. A thin layer of clay can be placed in sections in the model to represent the land between the streams and river. Clay should not be placed where the river and streams will flow.
   3. the river and land should end two inches from the end of the tray- this is the ocean or lake that the river flows into.
   4. if time allows, students can create small models of the buildings or plant life of their community with clay or other waterproof materials.
      
5. Once all of the groups have finished their models, discuss the terms point source water pollution, non-point source water pollution, and runoff with the students. Refer to the lesson’s background section. Explain to the students that they will be testing to see how much pollution the community they designed might be producing.
   
6. One group at a time, prepare and test the student’s models. 
   1. the teacher will place small amounts of “pollution” on developed areas of the models according to a key. An example key would use spices (pepper, paprika, etc.) to represent point source pollution, and vegetable oil to represent non-point source pollution. The amount of “pollution” should be correlated to the size of the source of pollution. Example: a small factory would get 1/8 teaspoon of pepper and a large factory would get 1/2  teaspoon of pepper sprinkled over it; a lawn would get a half drop of vegetable oil and a golf course or farm field would get two drops.
   2. the teacher can place pieces of carpet or sponge in areas that represent natural places (parks, fields, forests, marshes, etc.) or in a water treatment plant if the students included one (if possible do not introduce the idea of a water treatment plant until a second run through of the activity)
   3. create a slight slope to the model by placing a book or other object under one end. The flow of the river in the model should be towards the “lake” or “ocean” portion of the model where there is a two inch open space.
   4. make it rain on the model with water from a small watering can: use the same amount of water for each group’s model, such as 250 ml.- the runoff from the rain should flow into the streams and river and collect in the “lake” or “ocean“
   5. the students should determine what pollution entered the runoff?; how much runoff and pollution the carpet (natural areas) held onto; how they could improve their model to help with the pollution
   6. follow the same procedure with each group
      
7. If time permits, conduct a second trial of the experiment. This time with improvements to the models
   a. have the groups modify their models in ways that will lesson the amount and impact of their pollution
   b. they can include water treatment plants, buffer zones of vegetation, collection pools, etc.
   c. a chart can be created that shows the differences between the results of trial 1 and trial 2.

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Follow-up questions

1. What can we do to help? Have the students list things that they can do to lessen the amount of pollution they create in their daily activities.

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