Many communities obtain their drinking water from underground sources called aquifers. Water suppliers or utility officials often drill wells through soil and rock into aquifers for the ground water contained therein to supply the public with drinking water. Home owners who cannot obtain their drinking water from a public water supply, will have their own private wells drilled on their property. Unfortunately, ground water can become contaminated by harmful chemicals, such as lawn care products and household cleaners that were used or disposed of improperly, and any number of other pollutants, that can enter the soil and rock, polluting the aquifer and eventually the well. Such contamination can pose a significant threat to human health. The measures that must be taken by well owners and water plant operators to either protect or clean up contaminated aquifers are quite often costly.
The purpose of this experiment is to illustrate how water is stored in an aquifer, how ground water can become contaminated, and how this contamination ends up in a drinking water well. You will see how careless use and disposal of harmful contaminants above the ground can potentially end up in the drinking water below the ground.
Materials needed
- 1 clear plastic cup that is 2 3/4" deep x 3 1/4" wide
- 1 piece of modeling clay or floral clay that will allow a 2" flat pancake
- White play sand that will measure 1/4" in bottom of the cup
- Aquarium gravel (natural color if possible) or small pebbles (approximately 1/2 cup) (HINT: As many small rocks may have a powdery residue on them, you may wish to rinse and dry them on a clean towel prior to use. It is best if they do not add cloudiness to water.)
- Red food coloring
- 1 bucket of clean water and small cup to dip water from bucket
Procedure
- Pour 1/4" of white sand in the bottom of each cup completely covering the bottom of the container. Pour water into the sand, wetting it completely (there should be no standing water on top of sand). You will see how the water is absorbed in the sand, but remains around the sand particles as it is stored in the ground and ultimately forming part of the aquifer.
- Flatten the modeling clay (like a pancake) and cover 1/2 of the sand with the clay (press the clay to one side of the container to seal off that side). The clay represents a "confining layer" that keeps water from passing through it. Pour a small amount of water onto the clay. Now, you will see how the water remains on top of the clay, only flowing into the sand below in areas not covered by the clay.
- Use the aquarium rocks to form the next layer of earth. Place the rocks over the sand and clay, covering the entire container. To one side of the cup, slope the rocks, forming a high hill and a valley. These layers represent some of the many layers contained in the earth's surface. Now pour water into your aquifer until the water in the valley is even with your hill. You will see the water stored around the rocks. These rocks are porous, allowing storage of water within the pours and openings between them. Pay attention to how "surface" supply of water (a small lake) has formed. You will be able to see how “surface” supply of water (a small lake) has formed, and how both ground and surface water supplies is used for drinking water purpose.
Use the food coloring and put a few drops on top of the rock hill as close to the inside wall of the cup as possible. This practice can show up in the ground water and their drinking water. You will see that the color spreads not only through the rocks, but also to the surface water and into the white sand at the bottom of the cup. This is one way pollution can spread throughout the aquifer over time.
Source: Environmental Protection Agency