Sub-Concept: The Water Cycle
Agricultural Context: Agriculturalists must make wise use of a scarce water supply
Exercise: Global Water Distribution Demonstration
Applied Principle: Water is essential to all living things. Of all the water on earth, only a very
tiny proportion is available for use by humans; therefore, we must learn to use it wisely.
Goals:
Materials:
References: Klumpp, M. and Ruby, S. (undated). "A drop in the bucket." Oklahoma Aqua
Times Teacher's Guide. Stillwater, OK: Cooperative Extension Service, Division of Agricultural
Sciences and Natural Resources, Oklahoma State University.
Mississippi Soil and Water Conservation Commission. (undated). "Going, going, gone!" Oh, Give Me A Home! Creative Learning Activities - Water Quality/Nonpoint Source Pollution. Jackson, MS: Mississippi Soil and Water Conservation Commission.
2. Tell the students that the water in the plastic container represents the earth's total water supply.
(See Figure 1.)
3. Pour one ounce (1/8 cup) of the water from the gallon container into the measuring cup. The
water in the measuring cup represents all the earth's land water.
Engage the class in a discussion of what this water consists of (lakes, rivers, streams, underground
water, etc.).
Land water, for this activity, is defined as the water found on and under the earth's land surface
that is potentially available for man's use, about 0.65% of the total amount of water on earth.
This water may or may not be potable (drinkable); for example, part of the land water is found in
saline lakes. These lakes contain such high concentrations of salts that the water is not potable.
The water remaining in the jug represents all the water which is not available for human use.
Engage the class in a discussion of where this water is and why we can't use it. (It is stored in the
oceans, seas, and polar icecaps, and consists of 99.35% of the total amount of water on earth.)
4. Using the dropper, remove a dropper full of water from the land water. The water in the
dropper represents all good quality water found in the world's freshwater lakes, rivers and ground
water.
5. Put a drop of red food coloring into the measuring cup to show that the remaining land water is
not drinkable without treatment.
Class discussion: Why is this water not drinkable/usable? What impact has man had on the
condition of this water? Was there a greater percentage of drinkable water some time in the past?
What kind of treatment do they think the water has to undergo?
6. Now, release one drop of water from the water dropper into a small metal bucket. Make sure
your students are very quiet, so that they can hear the sound of the drop hitting the bottom of the
bucket. Refer to this "Drop in the Bucket" as your state's share of the world's water.
7. Class discussion: What are the implications of having such a minuscule amount of water
available to meet all of our needs? What conclusions can we draw about how we should use
water? What are some ways they have seen water wasted/misused? How much water do they
think they/their families use in one day? What about animals?
8. Explain that this unit will include activities and discussions about where our water comes from
and how we use it.
TEACHER BACKGROUND SHEET
The U.S. Department of the Interior/Geological Survey has compiled global water distribution
information as follows:
Location % of Total Water
Surface Water Freshwater lakes 0.009
Saline lakes/inland seas 0.008
Average in stream channels 0.001
Subsurface Water Vadose water (just below surface and in the soil) 0.005
Groundwater within depth 0.31
of half a mile
Groundwater - deep lying 0.31
Other Water Icecaps and glaciers 2.15
Atmosphere (at sea level) 0.001
World oceans 97.2
TOTAL (rounded) 100%
Of the water which is available, only a small portion is potable (drinkable) without treatment.
This is due in large part to the impact of man on water sources/resources. It is important for
students to understand that water, indeed all natural resources, should not be taken for granted.
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