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The usable percentage of existing freshwater is reduced
by pollution and contamination. The amount of water that is usable
by humans is very small. |
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Materials: |
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display of world or globe |
5- or 10-gallon aquarium (or other transparent container) |
measuring cup |
plastic quart containers (enough for one for every group of three students) |
eye dropper |
5 gallons of water |
tablespoons (enough for one for every group of three students) |
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Procedure: |
- Show students the five gallons of water in the aquarium. Explain
that the five gallons represent all the water on the earth and five
gallons equals 1,280 tablespoons of water. Now obtain the values
of water by calculating the percentages. For example: 97.2%
= oceans, so take 0.972 X 1280 = 1244.16 tablespoons.
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- Once the values have been determined, ask the students to calculate
the volume of water other than the amount contained in oceans (this
total amount is about 34 tablespoons).
- Divide students into teams and place 34 tablespoons of water into
each group's plastic quart jar. Then ask the students to remove
the water represented by freshwater lakes and rivers (this amount is
about 0.111 tablespoons or 1/10 tablespoon of water).
- Next ask the students to remove the amount of water represented by
rivers using the eye dropper (this amount is one-thousandth of a tablespoon
or less than one drop of water).
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Extensions: |
- Have the students consider how fragile the freshwater supply is
that's available to us through rivers and lakes.
- Discuss with the students how dependent we are on our survival for
this small percentage of water on the earth's surface (i.e., most
humans can not exist for more than three days without water).
Ask students to estimate the volume of freshwater they use on a daily
and weekly basis.
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This activity was adapted by Dr. Kitt Farrell-Poe from Water Quality
Indicators Guide: Surface Waters - A Teacher's Handbook. United
States Department of Agriculture and National Council for Agricultural
Education. |
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
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