Where on Earth Is the Water?
SCIENTIFIC
Introduction
Use this simple demonstration to shock students about the distribution of fresh water.
BIO FAX!
Concepts
•Life
•Ecology
•Water cycle
Background
Fresh water is essential to every non-marine organism on Earth. The availability of fresh
water is frequently the environmental pressure that influences the structure of ecosystems
and therefore shapes the evolution of organisms.
The fresh water on Earth is distributed as follows:
Ice in the poles and in glaciers
68.7%
Ground water
30.1%
Soil moisture, atmospheric
0.9%
moisture, and permafrost and ground ice
Surface water (including our reservoirs) 0.3%
————
100%
The amount of fresh water available to most terrestrial life on Earth is only a tiny fraction (0.3%) of the Earth’s total.
Civilization requires a large supply of fresh water. By damming rivers and tapping wells, humans have increased the amount
of fresh water available. New ecosystems arise wherever fresh water pools.
Materials
Drinking glass
Pipet, disposable
Graduated cylinder, 100-mL
Water
Safety Precautions
This demonstration is not considered hazardous, but always follow appropriate laboratory safety guidelines.
Procedure
1. Fill a drinking glass with 100 mL of water.
2. Hold up the glass of water and tell the class that it represents all of the fresh water on Earth. Ask them to estimate how
much of it is available for organisms to use.
3. Pour 69 mL of the water into the graduated cylinder, then remove 0.3 mL with a pipet. Save the pipet for step 5. Hold
up the graduated cylinder and tell the students that this water represents the water that is frozen in polar ice caps and
glaciers so is not available to most organisms. Empty the graduated cylinder.
4. Pour 31 mL of the water (all of what is left) into the cylinder. Tell the class that this represents the proportion of the
water that is underground, in soil and in the atmosphere.
5. Hold up the pipet from step 3. Explain to the students that this represents all of the surface water that is available for
most non-marine organisms. Squeeze it into the glass and emphasize how small a quantity it is.
NGSS Alignment
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Publication No. 10782
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Where on Earth Is the Water? continued
This laboratory activity relates to the following Next Generation Science Standards (2013):
Disciplinary Core Ideas: Middle School
MS-LS2 Ecosystems: Interaction, Energy and
Dynamics
LS2.A: Interdependent Relationships in
Ecosystems
MS-ESS2 Earth’s Systems
ESS2.C: The Roles of Water in Earth’s
Surface
Processes
Disciplinary Core Ideas: High School
HS-ESS2 Earth’s Systems
ESS2.C: The Roles of Water in Earth’s
Surface
Processes
Science and Engineering
Practices
Constructing explanations and
designing solutions
Crosscutting Concepts
Scale proportion and
quantity
Systems and system models
Reference
This activity was adapted from A Demo A Day—A Year of Biological Demonstrations, Bilash, Borislaw, Shields, Martin ; Flinn
Scientific: Batavia, IL (2001).
The USGS Water Science School. The World's Water. http://water.usgs.gov/edu/earthwherewater.html (accessed July 2015).
Material for Where on Earth is the Water? is available from Flinn Scientific, Inc.
Catalog No.
GP2056
AP5153
Description
Graduated Cylinder, 100 mL
Hydrographic Relief Globe
Consult your Flinn Scientific Catalog/Reference Manual for current prices.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.