LESSON 1 Activity 2

Where Is All of the Water on Earth?

Grades:

4th - 12th

Objective:

Students learn just how little water is available to everyone and every living thing on this planet to share. Students will realize that because so little water is readily available, it is imperative to keep water bodies clean and free of pollution not only for our use, but for future generations.

Method:

A visual representation using water containers will convey the point of this exercise more clearly than a list of numbers.

Materials:

A chart with percentages (below), 1 gallon jug of water, a small container, a cotton ball, an ice cube tray, a cup with sand or soil, an empty cup, an eye-dropper, a tablespoon, and some salt.

PERCENTAGES OF WATER ON EARTH

OCEANS

97.5%

FRESH WATER

2.5%

   Glaciers / Polar Ice Caps

79%

   Groundwater 20%
   Lakes, Streams, etc.

1%

ATMOSPHERE .001%


Time:

Preparation Time: 20 minutes
Class time: 25 minutes

Procedure:

  1. Explain to students that the full gallon of water represents all of the water on Earth. Ask them to guess how much of the surface of the Earth is covered with water. The surface of the Earth is 78% water and 22% land. (A picture of the Earth from space or a globe might be useful when explaining this.)

  2. Use the eye-dropper to take one drop of water out of the gallon. Put the drop into the cotton-ball, which represents the atmosphere (clouds). This is 1/1000 of 1% of the total.

  3. Show how much water is readily available by taking 7 Tbs (3.2 oz.) out of the gallon of water and placing it in the small container. The 7 Tbs represent all the 2.5% of fresh water on Earth, while the remaining water in the gallon (125 oz.) represents the 97.5% in the oceans. Add the salt to the gallon jug.

  4. Out of all the fresh water, 79% (5 Tbs) is frozen in polar ice caps and glaciers. Disperse the 5 Tbs into the ice cube tray to represent the frozen water.

  5. The remaining 2 Tbs represent the groundwater and surface water on the planet. Use the eye-dropper to get two drops of water to represent the water in lakes, streams and other water bodies (1% of the fresh water). The remaining water (20% of the fresh water) can be placed in the cup with sand to represent groundwater.

  6. Show the students the two drops of water (the surface fresh water). This is all of the fresh water that is readily available to us. Discuss why clean water is imperative to everyone.

Optional: A simpler way to achieve the objective of this exercise uses a meter stick. Tell the students that the 100cm length of the ruler represents 100% of the Earth's water. Color two spaces (2cm) green, representing the 2% in glaciers, and color another space (1cm) blue to represent fresh water -- groundwater and surface water collectively. Color the rest (97cm) yellow to illustrate the 97% that is salt water.

Assessment:

  1. Many people believe that the water on this planet is an "unlimited" resource, and that we do not have to worry about how much we waste. Do you feel the same way?

  2. In this activity, we have talked about water naturally occurring in many places: oceans, lakes, streams, the atmosphere, and glaciers. Where else might water be found naturally? (plants and animals - biomass)

NYS Learning Standards:

Math, Science, and Technology
Standard 3 - Mathematics: Mathematical Reasoning; Number and Numeration
Standard 4 - Science: Physical Setting 2
Standard 7 - Interdisciplinary Problem Solving: Connections


Source: This activity was adapted from Southern Rhode Island Conservation District's Active Watershed Education Curriculum Guide.