Groundwater Models

After testing different types of substances for their permeability, sixth graders made groundwater models to show how the permeability affects the movement of water underground.   The models were constructed using layers of clay soil, sand, and gravel.  A layer of carbon was added to topsoil to complete the model.   The carbon represented the decayed remains of plants and animals, known as humus.

            Once the models were complete, students tested how well the ground removes pollutants from water by pouring a solution of cocoa, pepper, and food coloring over the topsoil.   This solution represented pollution made up of different particle sizes.

            As the water soaked into the ground, students noticed how quickly each material absorbed the water and where the water flowed once it reached a saturation point.  Students also watched for the pollutants to see if they appeared in the water that was pumped from the bottom of the aquifer. 

            Students then injected food coloring below the topsoil between two impermeable layers of clay.  They found that the food coloring would travel downhill toward the water well through the more permeable layer of sand.

            In conclusion, students decided that the earth did a great job of filtering the water.  They also decided that pollutants injected into the interior of the earth could travel a long way from the injection site because of the differences in permeability of the earth’s substances.

A real life application of the experiment is seen in the outdoor classroom wetland area.  Run off is allowed to filter through the ground which is the earth’s way of keeping the water clean for future uses.