L a n d a n d Wa t e r
4
Where Is Most of the
Fresh Water?
Three friends were talking about fresh water. They each had a different idea about
where most of Earth’s fresh water is found. This is what they said:
Sephali:
I think most of Earth’s fresh water is found in snow, ice caps, glaciers,
and under the ground.
Mary:
I think most of Earth’s fresh water is found in lakes, rivers, streams,
and swamps.
Pearl:
I think most of Earth’s fresh water is found in the ocean, seas, and
bays.
Who do you agree with the most? ______________________ Explain your thinking.
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
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4
L a n d a n d Wa t e r
Where Is Most of the
Fresh Water?
Teacher Notes
Purpose
The purpose of this assessment probe is to
elicit students’ ideas about the distribution
of fresh water. The probe is designed to
find out if students recognize that most of
Earth’s fresh water is found in frozen form
or groundwater.
Type of Probe
Friendly talk
Related Concepts
Fresh water, groundwater, water distribution
Explanation
The best answer is Sephali’s: “I think most of
Earth’s fresh water is found in snow, ice caps,
glaciers, and under the ground.” Most of Earth’s
water comes from the ocean and is saline. Only
about 3% of Earth’s water is fresh water. Most
fresh water is found in the form of ice, snow,
groundwater, and soil moisture. Only about
0.3% is found in liquid form on the surface
30
in lakes, swamps, rivers, and streams. A small
percentage of water on Earth is also found in
living things and the atmosphere.
Administering the Probe
This probe is best used with grades 3–12. The
probe can be extended by asking students to
draw a model showing how they think Earth’s
fresh water is distributed.
Related Core Ideas in
Benchmarks for Science
Literacy (AAAS 2009)
6–8 The Earth
The Earth is mostly rock. Three-fourths of
the Earth’s surface is covered by a relatively
thin layer of water (some of it frozen),
and the entire planet is surrounded by a
relatively thin layer of air.
Fresh water, limited in supply, is essential
for some organisms and industrial processes.
Water in rivers, lakes, and underground
N a t i o n a l S c i e n c e Te a c h e r s A s s o c i a t i o n
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L a n d a n d Wa t e r
can be depleted or polluted, making it
unavailable or unsuitable for life.
Related Core Ideas in A
Framework for K–12 Science
Education (NRC 2012)
K–2 ESS2.C: The Roles of Water in Earth’s
Surface Processes
Water is found in the ocean, rivers, lakes,
and ponds. Water exists as solid ice and
in liquid form.
3–5 ESS2.C: The Roles of Water in Earth’s
Surface Processes
Nearly all of Earth’s available water is in
the ocean. Most fresh water is in glaciers
or underground; only a tiny fraction is in
streams, lakes, wetlands, and the atmosphere.
Related Research
Although the authors found no formal research
on students’ ideas about water distribution, the
author’s interviews with children ages 10–12
revealed that many thought that fresh water
was found mostly in rivers and lakes.
Suggestions for Instruction and
Assessment
Combine this probe with “Where Would
It Fall?”—a probe that targets Earth’s total
water distribution (Keeley and Tugel 2009).
The U.S. Geological Survey’s Water Science
School website has several good representations
that show Earth’s freshwater distribution.
Use those representations to help students
visualize where fresh water comes from. This
website is available at http://water.usgs.gov/edu/
earthwherewater.html.
Have students create a physical model of
the distribution of Earth’s fresh water and
use their model to explain the critical need
for water conservation.
Use an apple as a model to demonstrate
the amount of fresh water on Earth. Cut
the apple into four quarters. Because Earth
is one-fourth land, remove one quarter to
represent the land. Three quarters remain
to represent the water that covers Earth.
Remove the skin off one of the quarters
to represent the volume of the 3% of the
water that is fresh, relative to the saltwater
quarters. Cut the skin into thirds. Two
thirds are set aside to represent the fresh
water that is frozen as glaciers and polar
ice. The last third of apple skin represents
all the fresh water on Earth to be used by
plants, animals, and humans. This illustration
can lead to a deeper discussion of water
resources and the scarcity of clean, fresh
drinking water and its global implications.
NASA has created a short lesson on the
distribution of water on Earth with a graphic
representation of the specific breakdown
of the types of water (ocean, groundwater,
glaciers, etc.). You can find this resource at
http://pmm.nasa.gov/education/lesson-plans/
freshwater-availability-classroom-activity.
References
American Association for the Advancement of
Science (AAAS). 2009. Benchmarks for science literacy online. www.project2061.org/
publications/bsl/online.
Keeley, P., and J. Tugel. 2009. Uncovering student
ideas in science, vol. 4: 25 new formative assessment
probes. Arlington, VA: NSTA Press.
National Research Council (NRC). 2012. A
framework for K–12 science education: Practices,
crosscutting concepts, and core ideas. Washington,
DC: National Academies Press.
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