Watershed in a Box

Grades: 3 to 6

Time: 45 minutes to 1 hour 

LESSON PURPOSE: 
Students will build a desk-top model of a watershed to observe the path of surface water.

OBJECTIVES: 
Students will define a watershed as a drainage basin that collects surface water from surrounding land.  Students will describe the boundaries of a watershed as a line formed by the highest elevations surrounding the drainage basin.  Students will identify non-point sources of pollution in their watershed model.  Students will propose best management practices to control watershed pollution.

MATERIALS NEEDED:

• Foil roasting pans or plastic boxes Aluminum foil squares (approx. 1’x2’, or double the size of the boxes)
• Spray bottles containing water colored with blue food coloring waterproof marker (sharpie)
• "pollutant": yellow jello to represent phosphorous

PROCEDURE:

1. Intro: Students can gently crumple the foil to show mountains and valleys formed by plate movements:
   Flat squares of foil can represent earth’s topology before tectonic action.

   Place the foil on the desk, and place hands flat on top of each side of the foil- (left hand on the left side, right hand on the right side.)

   Slowly slide hands together, causing the foil to crumple between.

2. Activity: Students should fit their gently crumpled foil into the roasting pan. Using the waterproof marker, they can draw a line connecting the high points surrounding large drainage basins in the model. They might name the drainage basins to delineate different watersheds.

   Use the spray bottle to "rain" on the model. Students can observe how water travels through their watersheds, collecting as bodies of water.

   Sprinkle yellow jello onto various points of the model to represent sources of pollution. Explain the sources, such as:

   1. a golf course is built- it uses fertilizers to maintain lush grass
   2. a new housing development is created on the shore of the lake
   3. roads are built to the new developments
   4. septic systems are installed
   5. a logging operation harvests trees from a wooded area

   Rain" again on the model. Students will observe that surface run-off carries the "pollutant" into bodies of water in the watershed. Polluted bodies of water will turn green when the yellow jello mixes with the blue water.

3. Discussion: Students will observe that pollutants can travel even from sources at a distance from their drainage basins. This is called "non-point source" pollution. While none of the activities were illegal, they all had an impact on the cleanliness of the water.

CLOSURE: 
Best Management Practices (BMP’s) can be instituted to reduce non-point source pollution. Vegetated buffers, replanting of cleared forest, silt fencing of disturbed areas, septic tank maintenance, and phosphate-free fertilizers are examples of pollution reduction measures

EXTENSIONS:
Students might create new models to observe the effects of BMP’s on their model.