Modeling Earth’s Water — Fresh vs. Salty

Activity Source: 

Source: U.S. Geological Survey.
Adapted with permission.

We drink water every day — we can’t live without it! About 70 percent of Earth’s surface is covered by water, but how much of Earth’s water is actually drinkable? In other words, how much is liquid freshwater — not salty or frozen?

• Globe or world map
• Water cycle diagram
• 100 gummy bears
• Plastic knife or scissors
• Computer with internet access
• Camera


  1. Imagine that all the water on Earth is represented by 100 gummy bears, and each bear represents 1 percent of Earth’s total water.
  2. On your own or in a group, do your best to split the bears into two piles — one to represent all of Earth’s water you think that is salty and the other to represent all its freshwater, including ice.
  3. Next, divide your freshwater pile of bears into two smaller piles — one that you think represents all the freshwater that’s frozen and one that shows all that’s liquid. If you want to go even further, you can try to split your liquid freshwater pile to show how much is under the Earth’s surface (groundwater) vs. on the surface (rivers, lakes, streams). Use a plastic knife or scissors to split bears into smaller piles if necessary.
  4. Your piles are a model of Earth’s water cycle reservoirs. Take a photo of your model. Visit to see an example of the completed “salty vs. freshwater” model. Use the data to adjust your model if necessary.
You also can find details about the water cycle (diagram available in 60+ languages) and learn about the reservoirs and pathways of water on Earth. Show us your model by tagging us on  social media @USGS_YES and #saltyvsfreshwater #earthscienceweek2021.
      5. Discuss what you learned and how the amount of freshwater on Earth is important to you and to life on the planet!


• Do you know where the water in your home comes from?
• Earth is unique in our solar system in that water can exist in all three phases of matter (solid, liquid, and gas). Research other planets and moons in our solar system to discover which have the right temperature and/or atmospheric pressure ranges to allow water to be stable in solid, liquid, or gaseous states.