。 Saving Water
The wor。ld is not only hungry,but al。s。o thirsty for wate。r. This may seem strange to you, since nearly 75 % of the earth。's surface is covered with water. But about 97% of thi。s huge amount is sea water, or sa。lt water. Man can only drink and use the other 3% -- the fre。sh water that comes from rivers, lakes,underground, and other so。urces. And we cannot even use al。l of th。at, because some of it is in the form of icebergs and glaciers. Even worse, som。e of it has been pollu。ted.
However, as things stand today, this sma。ll amount of fresh water, which is constantly being replaced by rainfall, is still enough for us. But our ne。ed for water is increasing rapidly-- almost day by day. Only if we take steps to deal。 with this problem now can。 we avoid a severe worldwide water shortage later on. A limited water supply would have a bad effect on agriculture and industry. Let me give you。 just one small exampie of how necessary water is to industry. Did you know that to produce a single ton of steel, it takes about 91, 000 liters of water?
We all have to learn how to stop wasting our precious water. One of the fir。st steps we should take is to develop ways of reusing it. Experiments have already been done in。 this field, but only on a small s。cale. For us, the systems are as important as the spacecraft.
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