See the relative volume of water available that is clean, safe, and available to drink.
Please find a printable PDF of this activity here.
- 4 one-liter plastic bottles with labels removed
- Eye dropper
- Small cup
- Food coloring
- Milliliter measuring instrument (pipette, graduated cylinder, eyedropper, or cough syrup dispenser)
- Copy of the water cycle poster (available in English and Spanish)
- Optional: Inflatable globe showing ocean and land surfaces.
- Optional: 1 additional one-liter bottle; use if you have more time, are working with older children, or are doing math calculations as part of the activity.
Prepare the bottles
- Bottle 1: Fill one entire bottle with water. This represents all water in all forms (solid, liquid, gas) on the planet.
- Bottle 2: Fill a second entire bottle with water. Remove 30mL of water from the bottle and place it in a third bottle. Add a few drops of blue food coloring to Bottle 2. Bottle 2 represents the 97% of water on Earth that is found in the ocean.
- Bottle 3: Add a few drops of red food coloring to the bottle with 30mL of water. Bottle 3 represents the 3% of freshwater in the planet in all forms.
- Optional bottle: Add 6 mL of water and a drop of yellow food coloring to the fifth bottle. This represents liquid freshwater, but 75% of this water is trapped underground or is otherwise inaccessible.
- Bottle 4: Add 1.5mL of water and pour into the fourth bottle. Add a drop of green food coloring. This represents the amount of surface water available.
- Place caps on all the bottles.
Discuss freshwater resources
- Review the water cycle using the water cycle poster.
- Next, show how much freshwater is available for people to use, compared to the total amount found on the planet.
- Imagine that Bottle 1 represents this total amount of water on Earth. How many forms does water take on the planet? What are those forms? (liquid, solid, gas)
- Where is most water found on the planet? Bottle 2 (blue water) represents the 97% in the ocean. Can we drink this water? (No, it is salty.) With adults and older kids, discuss the energy and money it takes to desalinate sea water. A future engineer could develop a better process than we know of now!
- How much freshwater is there on Earth? Bottle 3 (red water) represents the 3% of water on earth that is fresh. But where is the most of the freshwater found? 80% of this water is frozen at the poles, in ice caps and mountain glaciers.
- Optional bottle. How much liquid freshwater is there on Earth? This bottle (yellow water) represents the 0.6% of water that is liquid, but 75% of this water is trapped underground or is otherwise inaccessible.
- How much freshwater is on Earth's surface and easily accessible? Bottle 4 (green water) represents the amount of freshwater that is on the earth’s surface that is easy to get to. Compare to Bottle 1.
- How much of this water is actually safe to drink? Would you take a drink out of a puddle in a parking lot or a lake with a harmful algal bloom? Take an eyedropper and fill it with water from Bottle 1. Very slowly squeeze a single drop of water from the eyedropper into each student's hand. That’s it, just a drop in your hand! This is 0.00003% of Bottle 1, the total water available for people to use.
- What do we need to do about water? (Don’t waste water. Keep it clean. For older students: encourage your communities to support clean water laws.) Think about actions you and your communities can take to help preserve freshwater resources.
Adapted from Project WET “A Drop in the Bucket” (The Watercourse and Council for Environmental Education.)