Title: Hydrologic Cycle 226

Key Words: Hydrologic cycle, water cycle, ancient water

National Standard: 8 (Characteristics and spatial distribution of ecosystems on Earth)

State Standard: 12 (Characteristics and distribution of ecosystems)

Teaching Level: Middle School

Introduction: Physical processes create, maintain, and modify Earth. One process essential to life on our planet is the hydrologic cycle. Diagrams are a common visual learning tool used to understand this important cycle. Diagrams vary in their effectiveness. In this lesson, students are asked to evaluate the effectiveness of several different hydrologic cycle diagrams.

Objective: Students will interpret and analyze diagrams of the hydrologic cycle and use them to generate geographic questions about Earth's water supply.

Materials: Several different diagrams of the hydrologic cycle taken from encyclopedias, textbooks, and/or posters.
Jug of water and enough small paper cups for each student.
Handout: Evaluate Diagrams of the Hydrologic Cycle.
Optional: Overhead transparencies of several diagrams of the hydrologic cycle.

Procedure: Ask for a few student volunteers to pass out small paper cups and pour a small amount of water into each. Invite students to drink it. Ask the question, "How old is the water you just drank?" Students might say a week or two, a month, or refer to the shelf life if you used bottled water. The correct answer is "Ancient - as old as the Earth's systems have been working!"
Explore an enjoy this fact. Give a few provocative examples to continue the flow of thought about the ancient nature of our water supply. Examples are:
This water could have been drunk by Cleopatra!
It could have helped make a stalagmite or stalactite!
It could have been absorbed by the roots of a giant sequoia!
It could have run down a sewer in New York City!
It could have been snow in Canada or rain on Mount Olympus!

Invite students to give more examples, the more creative the better. Thinking geographically can be fun!

Ask students what could be responsible for this phenomenon. The answer of course is the hydrologic cycle.

Distribute several diagrams of the hydrologic cycle. Ask students to explain why the water we have today is the same water that was here in ancient times (Answer: The original water has been going through the hydrologic cycle ever since then).
Ask students to vocalize the information contained in the diagrams. Depending on the level of students, the technical terminology could be used. The simple diagrams leave out such terms as transpiration. The more comprehensive ones include a plethora of terminology.

If students do not begin generating geographic questions on their own, use these samples to start: "What makes the cycle work?" (The sun is the engine that runs it.)
"How does the water stay in the cycle?" (Gravity.)
"How does the water underground move?" (Follows the path of least resistance and gravity.) "Why is there fresh water and salt water in the diagram?" (The ocean is salty because it collects. The salt and other minerals in all our water accumulate and stay in suspension making the ocean saltier than the flowing water.)
"If there's always the same amount of water in the cycle, why do we have water shortages?" (Earth's water is unevenly distributed; sometimes we use up groundwater faster than nature can recharge it, and there can be periods of drought.)
"Where in the ground is the water stored?" (Aquifers.)
"Where on the surface of the earth is water stored?" (Lakes, rivers, wetlands, man-made reservoirs.)
"Why don't the rivers dry up?" (Some do temporarily; some don't because of their volume and the groundwater that recharges them.)

Use the handout "Evaluate Diagrams of the Hydrologic Cycle" to help students rate the various diagrams that are being used. Then ask a few volunteers to tell why they rated certain ones better than others.

Draw conclusions. Some examples are: Without the hydrologic cycle, life on Earth would cease.
The diagrams help us visualize and understand the hydrologic cycle.
Some diagrams are more helpful than others.
The water we have today is the same water that was around "way back when Earth was young."

Evaluation/Assessment: Students will draw their own diagrams. Grades will be based on neatness, completeness, and accuracy. Completeness can reflect the level of detail originally used, labels, arrows, spot illustrations, the inclusion of the sun, groundwater, directions, title, etc.

Make a picture book in the shape of a water drop. Each page reflects an event in the history of that drop. Captions should add detail and creativity. The title should be appropriate and catchy. A diagram of the hydrologic cycle should be shown somewhere in the book. The rubric for scoring should be developed by the students before undertaking the project. This process of developing the rubric should be guided by the teacher.

Extension/Enrichment: Find out what kind of aquifers are under the surface where you live, where the town water supply is located, where the waste water treatment plant's discharge spot is located.
Locate aerial photographs and satellite images to get a different view of where the water is located. The satellite images can reveal underground water as well as surface water sources.

Write a poem, rap, or a song to celebrate the hydrologic cycle.

Watch and critique the music video "Pass it on Down" by the group Alabama.

Reflection: How successful was this lesson? Did all students benefit? Were there any surprises? What might you do differently another time? Please note any changes that will make this lesson more effective and useful inn the future and pass them along to the NHGA. We appreciate your comments.
Thank you,
The authors

Handout: Evaluate Diagrams of the Hydrologic Cycle

Fill in each blank with "yes" or "no."
Diagram 1 Diagram 2 Diagram 3 Optional
1. Does it have a title?

2. Does it show the sun?

3. Does it show enough arrows underground
to explain the cycle underground?

4. Does it have labels?

5. Is it crowded with too many words?

6. Is it easy to read and see details?

7. Does it show landforms and water bodies?

8. Does it show every step in the cycle?

9. Does it show vegetation?

10.Does it show the presence of
human/environment interaction, e.g. wells?

11.Does it use terms you do not know?

If so, list them here.

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