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Water and Life

Water is essential for most life processes, including photosynthesis, cellular respiration, and other chemical reactions that occur in organisms.

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How Much Water Is There?

How Much Water is There?

Credit: bdamon
Source: http://www.flickr.com/photos/57325827@N00/9395109573
License: CC BY-NC 3.0

Sometimes it feels like there’s nothing but water. When it’s pouring, the ground is soaked and you have to walk through puddles to get where you need to go. But, really, there’s not that much water on Earth. Not compared to the amount of other Earth materials.

Why It Matters

  • The oceans hold 96.5% of all of Earth’s water. The remaining 3.5% is in glaciers, the soil, the atmosphere, groundwater, streams, lakes and living things.
  • Earth has around 326 million trillion gallons of water.
  • Credit: U.S. Department of the Interior | U.S. Geological Survey
    Source: http://ga.water.usgs.gov/edu/watercyclesummarytext.html
    License: CC BY-NC 3.0

    Distribution of Earth's Water [Figure2]


  • Several billion gallons of this water are sitting on store shelves in water bottles, sodas, and other liquids.

Show What You Know

With the links below, learn more about the distribution of water. Then answer the following questions.

  1. Why is most of Earth’s water not useful for humans and other terrestrial organisms?
  2. Why is groundwater so important?
  3. Why should groundwater be used wisely?
  4. What does it mean to say that by 2025, the United Nations predicts that 1.9 billion people will be living with water scarcity and 2/3 of the population will have some kind of water stress?

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    Image Attributions

    1. [1]^ Credit: bdamon; Source: http://www.flickr.com/photos/57325827@N00/9395109573; License: CC BY-NC 3.0
    2. [2]^ Credit: U.S. Department of the Interior | U.S. Geological Survey; Source: http://ga.water.usgs.gov/edu/watercyclesummarytext.html; License: CC BY-NC 3.0

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