The world is not only hungry,but also thirsty for water. This may seem strange to you, since nearly 75 % of the earth's surface is covered with water. But about 97% of this huge amount is sea water, or salt water. Man can only drink and use the other 3% -- the fresh water that comes from rivers, lakes,underground, and other sources. And we cannot even use all of that, because some of it is in the form of icebergs and glaciers. Even worse, some of it has been polluted.

　　However, as things stand today, this small amount of fresh water, which is constantly being replaced by rainfall, is still enough for us. But our need 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 first steps we should take is to develop ways of reusing it. Experiments have already been done in this field, but only on a small scale. For us, the systems are as important as the spacecraft.

　　節(jié)約用水

　　我們的世界不僅饑餓，而且因?yàn)槿彼�而干渴。�?duì)你來(lái)說(shuō)這可能似乎奇怪：因?yàn)槲覀兊牡厍虮砻?5％由水覆蓋著。但是，這巨大的數(shù)量中97％是海水、或咸水。只有剩下3％

　　的來(lái)自河流、湖泊、地下，和其他來(lái)源的淡水供人們飲用、使用。即使如此，這3％的水源我們也不能夠完全使用，因?yàn)橛行┑�水是以冰山或冰河的形式存在。更糟糕的是，一些水源已遭受了污染�?br />
　　然而，盡管按現(xiàn)狀看來(lái)，這些少量的淡水即使時(shí)常轉(zhuǎn)化成雨水的形式，對(duì)我們來(lái)說(shuō)，也仍然夠用�？墒俏覀儗�(duì)水的需求卻日益迅速增長(zhǎng)。我們只有現(xiàn)在采取措施解決這一問(wèn)

　　題才能避免未來(lái)世界范圍內(nèi)的嚴(yán)重水資源缺乏。限量供水會(huì)對(duì)農(nóng)業(yè)和工業(yè)產(chǎn)生不良的影響。我們舉個(gè)小小的事例就能證明水對(duì)工業(yè)的必要性。每生產(chǎn)一噸鋼材就要消耗91，000升水，你知道嗎?

　　我們必須杜絕對(duì)寶貴水資源的浪費(fèi)。我們應(yīng)該采取的第一步就是要發(fā)展水再利用的方法。該領(lǐng)域的實(shí)驗(yàn)已在進(jìn)行，但是僅是小規(guī)模地進(jìn)行。水資源再利用系統(tǒng)的重要性

　　對(duì)我們而言，與空間站不相上下。

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