Groundwater may also be polluted by chemical fertilizers and buried radioactive wastes. Take one length of clear tubing and tape to inside of cup so that the end of the tube rests on the bottom of the cup. Add a layer of gravel to the bottom of the cup. This represents the water holding material which makes up the aquifer. Place a paper filter on top of the gravel.
Many soils act as semi-permeable membranes.
Add layers of sand and soil. Spray water on top of soil - this simulates rain. This is a good way to demonstrate percolation. See food coloring in withdrawn water. Add food coloring to top of soil and ask students how much water will need to be added to the system before all the coloring is gone.