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Water and Carbon Cycles

Global water stores and residence times

  • 3 things to know
  • A2 Unit 3

Overview

Largest single store of fresh water on Earth, approximate residence time of water in the atmosphere and fossil water.

What you need to know

Answer each one before you reveal it.

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Key term

How is the world's fresh water divided between its main stores?

Key term

Why is most of the world's fresh water unavailable to people?

Key term

Name the largest single store of fresh water on Earth.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What proportion of the Earth's water is held in the oceans?

    Model answer

    About 97%, which leaves only around 3% as fresh water.

  2. 2

    How is the world's fresh water divided between its main stores?

    Model answer

    Roughly 69% is locked in ice caps, glaciers and permanent snow, about 30% is groundwater, and only around 1% is in lakes, rivers, soil and the atmosphere combined.

  3. 3

    Why is most of the world's fresh water unavailable to people?

    Model answer

    The great majority is frozen into ice sheets and glaciers or held deep underground, so it cannot readily be abstracted.

  4. 4

    Name the largest single store of fresh water on Earth.

    Model answer

    The Antarctic ice sheet, which holds most of the world's ice and therefore most of its fresh water.

  5. 5

    State the approximate residence time of water in the atmosphere.

    Model answer

    About nine or ten days.

  6. 6

    Why is the atmospheric store of water so small and yet so important?

    Model answer

    It holds only about a thousandth of one percent of global water, but every drop of precipitation passes through it and it is what carries moisture from ocean to land.

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