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2.2: Concept- Water Distribution

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    6772
  • 201412291419915540114619_62392a1f12f4392e23f98540dfb7a40d-201412291419916847816267.jpg

    What do you have to do to get water?

    In the developed world, we just open a tap. Clean water is available all the time. In many developing regions, women have to walk long distances to get clean water. Sometimes there isn't a source of clean water, and they just get what they can find. We take water for granted in the developed world.

    Water Problems: Not Enough Water

    Most Americans have plenty of fresh, clean water, but many people around the world do not. In fact, water scarcity is the world’s most serious resource problem. How can that be? Water is almost everywhere. However, much of it is unusable, and what is usable is not always located where it is needed.

    Video: The Water Challenge 2030

    Where is all the water?

    One problem is that only a tiny fraction of Earth’s water is fresh, liquid water that people can use. More than 97 percent of Earth’s water is salt water in the oceans. Just 3% is freshwater. Most of the freshwater is frozen in ice sheets, icebergs, and glaciers (Figure below).

    201412291419915540130433_93a87ed1a59821d0aee5ea5e9be9110a-201412291419916847965942.jpgThis glacier in Alaska stores a lot of frozen freshwater.

    Rainfall and Water Supply

    Rainfall varies around the globe. About 40% of the land gets very little rain. Almost the same percentage of the world’s people don’t have enough water. You can compare global rainfall with the worldwide freshwater supply at the two URLs below. Drier climates generally have less water for people to use. In some places, people may have less water available to them for in an entire year than many Americans use in a single day! How much water is there where you live?

    Wealth and the Water Supply

    Richer nations can drill deep wells, build large dams, or supply people with water in other ways. In these countries, just about everyone has access to clean running water in their homes, and water is cheap and easy to get. It’s no surprise that people in these countries use the most water. In poorer nations, there is little money to develop water supplies. Therefore, people get their water where they can.

    Water Shortages

    Water shortages are common in much of the world. A drought is a period of unusually low rainfall. People are most likely to run short of water during droughts. Human actions have increased how often droughts occur. One way people can help to bring on a drought is by cutting down trees. Trees add water vapor to the air. With fewer trees, the air is drier and droughts are more common.

    We already use six times as much water today as we did a hundred years ago. As the number of people rises, our need for water will grow. By the year 2025, only half the world’s people will have enough clean water. Water is such a vital resource that serious water shortages may cause other problems.

    • Crops and livestock may die, so people will have less food available.
    • Other uses of water, such as industry, may have to stop. This reduces the jobs people can get and the products they can buy.
    • People and nations may fight over water resources.
    • In extreme cases, people may die from lack of water.

    Figure below shows the global water situation in the 2030s with water stress and water scarcity on the map.

    201412291419915540160752_eb8722d91fb602405386611df8a98484-201412291419916848098928.pngBlues indicate no predicted water stress; pinks and lavenders predict water stress, and salmon to brown indicates water scarcity (variations of those colors indicate the amount of irrigation that will be done to produce crops).

    75% of Southern California's water supply comes from the snowpack in the Sierra Nevada Mountain Range. This video by Science Friday explains how NASA uses specialized instrumentation in the Airborne Snow Observatory to carefully measure the water content.

    Video: Forecasting the Meltdown

    Summary

    • Freshwater is not evenly distributed across the planet.
    • Many of the world's people live without access to enough clean water. That percentage is likely to increase as populations grow.
    • During a drought, life may become very hard for many people.

    Review

    1. How is Earth's water distributed?
    2. How do wealthier nations deal with water problems? How do poorer nations deal with water problems?
    3. What is a drought? What can happen during a drought?

    Learning Extension

    3553678-1556673995-6904917-42-pencil-clipart-classroom-14.jpgView the video and then complete the questions, following your teacher's instructions.

    Use the video resource below to answer the questions that follow.

    Video: Water Scarcity

    Learning Extension Questions

    1. What is water scarcity?
    2. Why do people take water for granted?
    3. How much freshwater is there on Earth?
    4. How many people do not have access to clean water?
    5. What will occur by 2025?
    6. What is physical water scarcity? Where does this occur?
    7. What is economic water scarcity? Where does this occur?
    8. What are two things you can do to reduce your water consumption?
    Image Reference Attributions
    201412291419915540114619_62392a1f12f4392e23f98540dfb7a40d-201412291419916847816267.jpg [Figure 1] License: CC BY-NC
    201412291419915540130433_93a87ed1a59821d0aee5ea5e9be9110a-201412291419916847965942.jpg [Figure 2] Credit: Frank Kovalchek (Flickr:Alaskan Dude)
    Source: http://www.flickr.com/photos/72213316@N00/7588197286/
    License: CC BY 2.0
    201412291419915540160752_eb8722d91fb602405386611df8a98484-201412291419916848098928.png [Figure 3] Credit: J Liu, C Folberth, et al.;Hana Zavadska
    Source: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0057750 ; CK-12 Foundation
    License: CC BY 2.5