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(Note: This story is in script form. the script is in normal print, questions are printed in italics, and what you should do to make the model is in bold.) Imagine you are outside, you've removed some grass and are digging a deep hole.
What would you expect to find? ______________________________
If you were digging this hole in southwest Michigan you would most likely find sand and gravel. These
soil types and others were left here thousands of years ago by the ice and snow masses we call glaciers. If you kept digging
the hole deeper, eventually you'd be forced to stop. Solid rock, or a layer of clay acting like rock,
would block your way.
(Remove the green grass (carpet) from the cup. Look at and feel the gravel. Pretend the cup
contains gravel that the glaciers "left behind". The bottom of the cup is solid rock.) The word "groundwater" tells us what it is ... water found in the ground.
Do you know the source of this water? _____________________________
From your understanding of the water cycle you know that when it rains, snows or sleets,
some of the water falling to earth will evaporate right away, some will be used by plants, some
ends up in the oceans, lakes or other places. You also know somw water soaks into the ground,
working itself down deeper and deeper. This water is on its to becoming groundwater.
(Pour water over the gravel until the cup is half full. The water has been dyed blue
to help us see it.)
Watch as the water moves down through the gravel, traveling through the spaces between each particle of
gravel. Notice how the bottom of the cup acts just like solid rock or clay and stops the water from going down
any farther. Look at the gravel in the upper part of the cup. the spaces are not filed with water, but the
gravel is wet. (Touch the gravel to prove to yourself that water is there even though it may be
hard to see.) There is water clinging to the gravel particles but the spaces are filled with air.
Now look at the bottom half of the cup and observe how the water fills every space between the
gravel particles. The air that used to occupy those spaces has been pushed out by water.
This is groundwater. The gravel (sand, or other soil combination) that holds or stores the
groundwater is called an aquifer.
The water table marks the top of the groundwater. (Find the water table "line" on your
model.) In a few minutes we will change where the water table is located.
Can you predict what we are about to find? ___________________________
To really be an aquifer, it is necessary for the soil particles to store water and allow the
water to move back up to the surface of the earth so it can be used. To get water out of the ground
we often dig a hole, called a well, and use a pump to draw the water out of the aquifer.
(Using your finger "drill a well", by making a hole into the gravel. Place a soap pump into the
hole. Be sure the tube reaches down into the cup's groundwater.)
(Begin pumping groundwater out of your aquifer. Pump it into another cup.)
What happens to the water table as you pump? ________________________ You probably saw the water table drop as you pumped and know if you kept pumping, your
aquifer would eventually run out of groundwater. People used to say the "well ran dry".
This still happens, as folks that live in California will tell you. To keep the system
going, more water needs to be added. (Add a little more water to the aquifer by "raining" on
it with your sprinkling can.)
So far we have used our model to help us understand the concepts of: groundwater, aquifer,
water table and well. You will now see how groundwater is sometimes made unfit to use
when it is contaminated.
Squirt several drops of yellow food coloring onto the
gravel. "Rain" on it to make it seep down into the groundwater.)
The dye represents a chemical that can be dissolved in water and carried down to aquifer with rain or snow. Some of
the contaminants that have been found in groundwater include:
(Begin pumping again.)
Pretend the water is from your home well or the city well that supplies
drinking water to your house.
What is happening to the yellow contamination as you pump? _____________ The water being pumped out will turn green as the "contaminant" comes through. in "real life" it isn't
so easy to spot a contamination problem. contaminated water might not look, smell or taste bad. In addition,
it may be hard to find the source of the contamination. Groundwater moves much slower than it did
in our model. (Sometimes only inches a year.) It may be years before the contamination becomes known.
By then it may be too late to make the responsible people clean it up.
APPLICATION TO REAL LIFE Groundwater clean-up is expensive (sometimes millions of dollars). It can also take
many, many years. What e must do is to prevent contamination from occuring.
What can we do to protect our groundwater? ___________________
Note: **Document prepared by | ||||||||||||||||||
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Institute of Water Research - MSU |
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