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Colourless, odorless, tasteless and calorie free: water is vital to all life on earth. No human, animal or plant can live without it. From elephant to microbe, water is essential and there is no substitute for it. Each of the 6 billion people on Earth needs to consume, in liquids and food, about two and a half liters of water every day to look healthy. Without water it is impossible to grow crops or to raise livestock. No water, no food, no life!
Fortunately there is plenty of water when photographed from outer space; our beautiful planet looks as if it should be called water not Earth. Indeed, if the world's water should evenly cover the face of the planet, it would form a global ocean 2.5km deep. The Earth’s entire land surface will fit into the Pacific Ocean with room to spare.
Of course most of the earth's water is in the seas, and seawater is salty. If a person drinks only seawater, he or she would soon perish of thirst or dehydration while the body tries to flush out the excess salt. Seawater is also not a good choice for agriculture or industry because it kills most crops and rusts most machinery.
A mere 3 percent of the world's water is fresh, not salty. Of all of the fresh water, about 99 percent of it is locked up in glaciers and ice caps or is deep underground. One percent does not sound much. Are we likely to run short of fresh water? Probably not, because according to resources, if this one percent is evenly distributed around the world and rationally used, it would be enough to sustain twice or three times the world's population. Basically the total amount of water on earth neither increases nor decreases.
May, who lives in the United States, begins her day with a shower, brushes her teeth with water running, flushes the toilet and then washes her hands. She may use enough water to fill the average bathtub. By the end of the day, May, like many others who live in the States has used over 350 liters of water - enough to fill a bathtub about two and half times. For her water is always available so she can take it for granted.
For Chioma who lives in West Africa, it is a different story. She gets up long before it is dawn, dresses, balances a large empty basin on her head and walks 3 kilometers to the nearest river. There she bathes, fills the basin with water and then returns home. This daily routine takes an average of 3 hours. For the next hour she filters the water to remove objects and then divides the water into three containers - one for drinking another for cooking and the last for her evening bath. Washing of clothes must be done by the riverside.
So while there is plenty of fresh water worldwide, it is not evenly distributed. That is the first major problem scientists must reckon with. For example, while Asia has 36 percent of the water filling the world's lakes and rivers, that continent is home to about 60 percent of the world's population. In contrast, the Amazon River contains 15 percent of the world's river water but only about 0.4 percent of the world's population lives close enough to make use of it. A number of experts believe that humans may cause some changes in climate involving rainfall. Deforestation, Over-cultivation, Over-grazing all strip the soil bare.
Barren land may also cause a decrease in rainfall, for a great deal of the rain that falls in forest is water that just evaporated from the vegetation itself. In other words, vegetation acts like a huge sponge that absorbs and holds water that falls as rain. Remove these trees and undergrowth and less water is available to form rain clouds.
Just how dramatically human actions affect rainfall is still a matter of debate. More research still needs to be done. It is certain that water shortage is widespread. Already shortages threaten the economies and health of 80 countries according to the World Bank and 40 percent of the earth’s inhabitants – more than 2 billion people – have no access to clean water.
When faced with water shortages, rich countries usually manage to buy their way out of the situation. They build dams; employ expensive technology to recycle their water. Poor nations do not usually have such options. They must choose between to ration clean water, which might curb progress and reduce food production or to use untreated water, which results in the spread of diseases.
The uneven distribution of water is complicated by a second problem. As populations grow so does the demand for water. Rainfall worldwide remains roughly constant, but population soars. Water consumption has doubled at least twice this century and some estimate that it can double again within the next 20 years. Of course growing numbers of people require not just more drinking water but more food. Food production in turn requires even greater amounts of water. Agriculture must compete with the demands of industries and people.
Added to the problems of water shortage and demands is pollution. According to one estimate, the amount of water wasted – domestic and industrial – that pours into the world’s rivers every year amounts to 450 cubic kilometers. Many rivers and streams are polluted from their beginning to their end.
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