The world is not only hungry for food,but it is also thirsty

The world is not only hungry for food,but it is also thirsty for water.This may seem strange to you,since nearly 70 percent of the earth's surface is covered with water.However about 97 percent of this huge amount is sea water,or salt water.Human can only drink and use the other 3 percent-the fresh water from rivers,lakes,underground streams,and other sources.And we cannot even use all of that,because some of it is in the form of icebergs and glaciers (冰川).Even worse,some of it has been polluted.
However,as things stand today,this small amount of fresh water 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.We all have to learn how to stop wasting our valuable water.One of the first steps is to develop ways of reusing it.Today in most large cities,water is used only once and then sent out into a sewer system (下水道).But it is possible to pipe used water to a purifying (净化) plant.There it can be treated with chemicals so that it can be used again,just as if it were fresh from a spring.However,even if every large city purified and reused its water,we still would not have enough.What we'd have to do is make use of the vast reserves (储备) of seawater in the world by removing the salt.If we take these steps we'll be in no danger of drying up.
1.Why can't humans fully use all the fresh water in the world?2.In what way can we still have enough fresh water for our future use?3.What's one of the effective measures to stop the water crisis?4.What's the next step we should take in dealing with the problem?5.Is the author's tone in the passage alarmed (惊慌的),concerned,dismissive,or pessimistic?

世界不仅饥饿的食物,但它也是渴水.你可能会觉得奇怪,因为近百分之70的地球表面被水覆盖着.但是大约百分之97的数量庞大的海水,或盐水.人只能喝,用其他百分之3从江河,湖泊,地下河流,和其他来源.我们甚至不能使用,因为它的一部分是在冰山和冰川的形成（冰川）.更糟糕的是,其中一些已经被污染了.
然而,今天的情况,这种少量的淡水对我们来说还是足够.可是我们对水的需求日益快速的增加.如果我们采取措施来处理这个问题,现在我们可以避免严重缺水的世界.我们必须学会如何停止浪费我们宝贵的水.第一步就是要发展水再利用的方法.今天大多数大城市,水是仅使用一次,然后被送到了下水道（下水道）.但它是可以用于水净化管（净化）植物.它可以用化学物质可用于重新处理,就好像是刚从一个春天.然而,就算每个大城市的纯化和使用再生水,我们仍然没有足够的.我们所要做的就是利用庞大的储备（储备）世界海洋的除盐.如果我们采取了这些措施,我们会在没有枯竭的危险.
1.为什么人类不能在世界上充分利用所有的新鲜水?2.怎样才能有足够的新鲜的水对我们的未来?3.一个停止水危机的有效措施是什么?4.下一步我们要处理的问题是什么?5.是作者的语气在通道报警（惊慌的）,关注,不屑一顾,还是悲观?