The water power
Water power is a valuable source of energy. When such fuels as coal, oil, and even nuclear fuels are burned up as a source of energy, they cannot be reused.
Water is the most common substance on earth. It covers more than 70 percent of the earth’s surface. It fills the oceans, rivers, and lakes. And in the ground and in the air we breathe. Water is everywhere.
Without water, there can be no life. Every living thing-plants animals and people – must have water to live. In fact, every living thing consists mostly of water. Your body is about two-thirds water. A chicken is about three-fourths water, and the pineapple is about four-fifths water. Most scientists believe that life itself began in water, in the salty water of the sea.
Ever since the world began, water has been shaping the earth. Rain hammers at the land and washes the soil into rivers. The oceans pound against the shores, chiseling cliffs and carrying away land. Rivers knife through rock, and build up land where they empty into the sea. Glaciers plough valleys and cut down mountains.
Water helps keep the earth’s climate from getting too hot or too cold. Land absorbs and releases heat from the sun quickly. But the oceans absorb and release the sun’s heat slowly. So breezes from the oceans bring warmth to the land in winter and coolness in summer.
Throughout history, water has been people’s slave, and their master. Great civilizations have risen where water supplies were plentiful. They have fallen when these supplies failed. People have killed one another for a muddy water hole. They have worshipped rain gods and prayed for rain. Often, when rains have failed to come, crops have withered and starvation has spread across the land. Sometimes the rains have fallen too heavily and too suddenly. As a result, rivers have overflowed their banks, drowning everything and everyone in their paths.
Today, more than ever, water is both slave and master to people. We use water in our homes for cleaning, cooking, baking, and carrying away wastes. We use water to irrigate dry farmlands so we can grow more food. Our factories use more water than any other material. We use the water in rushing rivers and thundering waterfalls to produce electricity.
Our demand for water is continually increasing. Every year, there are more people in the world. Factories turn out more and more products, and need more and more water. We live in a world of water. But almost all of it, about 97 percent is in the oceans. This water is too salty to be used for drinking, farming, and manufacturing. Only about 3 percent of the world’s water is fresh (unsalty). Most of this water is not easily available to people because it is locked in glaciers and icecaps.
There is as much water on earth today as there ever was, or ever will be. Almost every drop of water we use finds way to the oceans. There, it is evaporated by the sun. It then falls back to the earth as a rain. Water is used an reused over and over again. It is never used up.
Although the world as a whole has plenty of fresh water, some regions have water shortage. Rain does not fall evenly over the earth. Some regions are always too dry, and others too wet. A region that usually gets enough rain may suddenly have a serious dry spell, and another region may flooded with too much rain.
Some regions have water shortage because the people have managed their supply poorly. People settle where water is plentiful, near lakes and rivers. Cities grow, and factories spring up. The cities and factories dump their wastes into the lakes and rivers, polluting them. Then the people look for new sources of water. Shortage also occur because some cities do not make full use of their supply. They have plenty of water, but they do not have enough storage tanks and distribution pipes to meet the people’s needs.
As our demand for water grows and grows, we will have to make better and better use of our supply. The more we learn about water, the better we will be able to meet this challenge.
Interesting facts about water
How much water is on the earth?
There are about 1.4 thousand million cubic kilometer of water. There are over 0.9 million million liters of water per cubic kilometer.
How much of the earth’s water is fresh?
Only about 3 percent of the earth’s eater is fresh. About three-fourths of the fresh water is frozen in glaciers and icecaps. Glaciers, and icecaps contain as much water as flows in all the earth’s rivers in about 1000 years.
How much water do living things contain?
All living things consist mostly of water. For example, the body of a human being is about 65 percent water. An elephant is about 70 percent water. A potato is about 80 percent water. A tomato is about 95 percent water.
How much water does a person take in over a lifetime?
On the average, a person takes about 60600 liters of water during his or her life.
What are the different forms of water?
Water is the only substance on earth that is naturally present in three different forms. It can be present as a liquid, a solid(ice), and a gas (water vapour).
How much water does a person use every day?
On average, each person in developed country uses about 260 liters of water a day in the home.
What is the largest single use of water?
The largest single use of water is by industry. It takes about 570 liters of water to make the paper for one Sunday newspaper, and about 1340 liters of water per kilogram of aluminium.
Can water ever be used up?
Water is used and reused over and over again, it is never used up. Every glass of water you drink contains molecules of water that have been used countless times before.