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31 States in the Gulf of Mexico Watershed
More than 70 percent of the Earth's surface is covered
by water. But of all that water, about 97 percent
is salty ocean water - - great for squids, but hard
to process for use by landlubbers like us. Of the
remaining three percent of Earth's water, more than
two-thirds is frozen in glaciers and polar ice sheets.
That leaves less than one percent of the water on
Earth for our use - - and most of that water is groundwater,
which is water stored underground in porous rock and
loose sand and gravel. The activity that follows will
give you an idea of how limited good, clean fresh
water is - - and how much we rely on it.
Activity:
(for students in Grades 4-8)
Objective:
To demonstrate how limited freshwater
is
Materials:
5 one-gallon jugs; 2 glass jars; measuring
cup
Activity:
Fill five one-gallon jugs
with water. Place them at the front of
the room. Imagine that this water represents
all the water on Earth. How much of the
five gallons do you think represents fresh
water (use a cup for a measure)? (Discuss
the percentages of salt water and fresh
water described above.)
Now pour 2 ½ cups from one of the gallon jugs into jar number one. This amount represents all the fresh water in the world. From this jar, measure 3/4 of a cup into jar number two. What's left in jar one represents all the fresh water that is inaccessible because it is frozen in polar ice caps. The 3/4 cup in jar number two represents all of the fresh water available to us for drinking and other uses. (Remind the class that much of even this little bit of water lies deep in the earth and is not easy for us to reach in economical ways.)
For
Discussion:
Where do you find fresh water? Does it
look clean and drinkable?
(Extracted from the National Geographic Society Teacher's Handbook - Geography: Reflections on Water)
