Measuring Earth’s Water

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Source: NASA.
Adapted with permission.

Even though our home planet has a lot of water, over 73 percent of that is salt water. We need freshwater to meet most of our needs, and precipitation supplies much of this valuable natural resource. Did you know that NASA, in a partnership with the Japanese, has a satellite that measures precipitation as it falls from the clouds to the ground?

NASA’s Global Precipitation Measurement (GPM) mission includes an international constellation of satellites that fly above Earth and use remote sensing to collect these measurements. You
can learn more about Earth’s freshwater resources and how GPM helps us monitor them in the “Water Cycle Webquest” at

Have you ever thought about how you could measure how much rain was falling in your location?


  1. Find some sort of container that can be used to hold rain. You can choose from a large number of household items, such as a can, water bottle, cup, food container, or jar.
  2. Next, find something that can be used to measure the rainfall. That could be a ruler or a tape measure, or you can develop another system that makes sense to you.
  3. Now use your measuring device to make marks on your container so you can tell how much rainfall you received. Visit this NASA website to find out why we measure rainfall in inches:
  4. Set your container outside. Don’t forget to leave the container in an open area so that nothing blocks rain from getting in. You might need to put some rocks around the base so it doesn’t get blown over.
  5. Check the container every day around the same time and record in a table how much rain has fallen. After you record the rain, empty it out.
  6. You might want to re-engineer your rain gauge after you have tried it out to make it easier to determine more accurately much rain fell.

Next Steps

• Visit the National Weather Service website ( Use the search tool to find your address. Set the timeframe to the date you measured how much rain fell. How do the results compare to your measurements? Can you explain any differences?
• Find out more about how satellites measure rainfall from space at the Global Precipitation Measurement project (