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[ AZ Extension Water Quality  ] [ Youth Activities ] [ Glossary ]
Activity G-2: Contamination of an Aquifer
This youth activity is one in a series of two activities that can be used to introduce groundwater concepts.  It is a good introductory activity and can be adapted for all grades.
Purpose:
To illustrate how water flows through an aquifer, how groundwater can become contaminated, and how difficult it is to clean up contamination.
Background:
Many communities obtain their drinking water from underground sources called aquifers.  Water suppliers drill wells through soil and rock into aquifers for the groundwater contained in the aquifer.  Unfortunately, the groundwater can become contaminated by harmful chemicals that percolate down through soil and rock into the aquifer - and eventually into the well.  Groundwater contamination by chemicals is caused by industrial, agricultural, and urban runoff and/or the improper management of chemicals, including improper disposal of household chemicals, such as lawn care products and cleaners.  Such contamination can pose a significant threat to human health.  The measures that must be taken by utilities to either protect or clean up contaminated aquifers are quite costly.
Materials:
for each group of students:
* 1- 6" x 8" plastic box or disposable aluminum cake pan
* 2 lbs non-water soluble plasticine modeling clay or floral clay
* 3-4 lbs white aquarium gravel
* pea gravel
* small drinking straw
* glue or caulking
* food coloring
* 8 to 10 - 6 oz paper cups (no larger)
* water
* white paper
Procedure:
  1. Set up a model aquifer as shown in the diagram on the back.  Make a small hole in one end and insert a section of a drinking straw to serve as the drain spout.  Seal the hole around the straw with glue, clay, or caulking.  In addition, seal the clay layers of the model against the side of the container.


  2. Place 10 drops of food coloring on the surface of the model near the highest end.  This dye represents chemicals or other pollutants that have been spilled on the ground.


  3. Slowly pour one 6-ounce cup of tap water on the aquarium gravel areas as shown in the diagram.  Collect the water as it runs out of the straw and place the cup with water on the white paper.  Repeat this process starting with 6 ounces of tap water and continue the flushing process until all the food coloring is washed out and the discharge water is clear.  (Collecting the water in white cups or in test tubes held up against a white background will also enable students to detect faint coloration.)


  4. Record the number of flushings required until a cup contains water with no visible color.  [Note: 6 ounces of water in this model equals about 1 inch of rain.]
schematic diagram of model
Discussion:
Before the Activity
  1. Where does the water go that falls on the surface of the ground?  How about any chemicals or other pollutants that fall on the ground?  (Some chemicals/pollutants are washed away by rain, some become attached to rocks and soil, and some end up in the groundwater.)


  2. What influences the time needed to flush an aquifer clean?  (Depth and volume of the water table, type of underlying rock and soil, nature and concentration of the pollutant.)
After the Activity
  1. After flushing, is the water in the model aquifer completely free of food coloring?  (Probably not; trace amounts may remain.)


  2. What keeps the chemical contamination in the demonstration from reaching the lower levels of the model aquifer?  (The clay layer.)


  3. What are some of the problems that might result from a major chemical spill near a watershed area?


  4. What steps could be taken to avoid damage to an aquifer?
Extensions:
  1. Discuss the need for proper disposal of hazardous industrial wastes and harmful household chemicals, including used motor oil.


  2. Simulate nitrate pollution due to fertilizer runoff.  Pollute the aquifer with a small amount of soluble nitrate and perform a standard nitrate test after each successive flushing.


  3. Knowing the annual rainfall in your area and that in this model 6 ounces equals 1 inch of rain, how long would it take for the aquifer to flush itself clean if 100% of the rain went to infiltration, 50% infiltration, 10% infiltration, 1% infiltration?  [Note: The local Extension office may know about how much of the rain goes to infiltration.]
This activity was adapted by Dr. Kitt Farrell-Poe from Science Demonstration Projects in Drinking Water (Grades K-12) by the US Environmental Protection Agency, Office of Water, EPA 570/9-90-007, April 1990.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture, The University of Arizona. The University of Arizona College of Agriculture is an Equal Opportunity employer, authorized to provide research, educational information, and other services only to individuals and institutions that function without regard to sex, race, religion, color, national origin, age, Viet Nam Era Veteran's status, or disability.

For problems or questions regarding this web contact Dr. Kitt Farrell-Poe.
This document was last modified: 31-Aug-2005 .