MAINSTREAM English Communication Ⅲ Second Edition 教科書原典文字データ
Chapter4
Water is the only substance that occurs at ordinary temperatures as a solid, a liquid, and a gas.

As a solid, itoccurs as ice and it is usually found in glaciers and ice caps. As a liquid, water makes up three-quarters of thesurface of the earth in the form of oceans, rivers, and lakes. As a gas, water vapor occurs as fog, steam, andclouds.
Water is very important to life. From 50 to 90 percent of the weight of living creatures is water. Water is an
important part of all living cells. For example, the blood of animals consists mostly of water. Water is also
important in breaking down foods for the body to use.
With so much water on the earth, how could there possibly be a water problem? The answer is simple. Of all
the world’s water, only 2.5 percent is not salty and can be used by human beings. Of that tiny percentage,
two-thirds is frozen in ice caps and glaciers and so cannot be easily used. Of the remaining third, 20 percent islocated in remote places. The rest of the unsalted water comes as rain, but this rainwater is often unusable or

本文の元となった原典の英文をwasted. The problem, then, is that humans can use less than収録しております。
0.08 percent of the wateron the planet.
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At the same time, people today are using more and more water. Water use is expected to grow by
40 percent over the next twenty years. By then, 3 billion people will face a shortage of water. The
shortage will have several causes. First, the human population is growing rapidly, so there will be
more people who need water. But more important is the fact that people are becoming richer. Aspeople get more money their lifestyles change, and they use more and more natural resources,including water. For example, the world population increased 300 percent in the last century, butwater use increased 600 percent.
People use most water for agriculture. 70 percent of the water used today is for growing crops.
However, up to 50 percent of that water is actually wasted. Moreover, modern ways of farming use
more water. Another problem is pollution. Development not only increases the demand for water but
also makes some water supplies unusable. Water from modern industries is often polluted. Thismeans it cannot be reused, thus reducing the amount available for people.
Water shortages will likely be a disaster in the future, but they are already a major problem. 20
percent of the world’s population does not have safe drinking water, and 50 percent has poor
sanitation. As a result nearly 500,000 young children die every year. This could get much worse inthe future. Because of serious water shortages, large numbers of people will have to leave arid areas
and move to wetter regions. Another possibility is that there may be wars as governments try tocontrol water resources.
One possible solution to the water shortage problem is technology. For example, salt could be
removed from seawater in desalination plants. However, desalination is expensive, and it is poor
people who need water most. A better solution is learning how to use water more efficiently andeffectively. Better water use will also require international cooperation. This means developednations will have to learn to use less water.

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