The world i not only hungry, hut alo thirty for water. Thi may eem trange to you. ince nearly 75 % of the earth' urface i covered with water. But about 97% of thi huge amount i ea water, or alt water. Man can only drink -and ue the other the freh water that come from river, lake.underground- and other ource. And we cannot even ue all of that, becaue ome of it i in ihe form of iceberg and glacier. Even wore, ome of it ha been polluted.
However, a. thing tand today, thi mall amount of freh water, which i contantly being replaced by rainfall, i till enough for u. Hut our need for water i increaing rapidly almot day by day. Only if wc take tep to deal with thi problem now can wc avoid a evere worldwide water hortage later on. A limited water upply would have a bad effect on agriculture and indutry. Let rne give you jut one mall example of how neceary water i to indutry. Did you know that to produce a ingle ton of teel, il take about 91*000 liter of water?
We all have to learn how to top wating our preciou water. One of Ihe firt tep wc hould take i to develop way of reuing it. Experiment have already been done in thi field, but only on a mall cale. For u. the ytem are a important a the pacecraft.