话题七:生态环保类(一)Theneedtofeedagrowingpopulationisputtingmuchpressureontheworld'ssupplyofwater
With97%oftheworld'swatertoosaltytobedrunkorusedinagriculture,theworldwidesupplyofwaterneedscarefulmanagement,especiallyinagriculture
Althoughtheideaofawatershortage(短缺)seemsstrangetosomeonefortunateenoughtoliveinahighrainfallcountry,manyoftheworld'sagriculturalindustriesexperienceconstantwatershortages
Althoughdamscanbebuilttostorewaterforagriculturaluseindryareasanddryseasons,thecostsofwaterredistribution(重新分配)areveryhigh
Notonlyistherethecostoftheengineeringitself,butthereisalsoanenvironmentalcosttobeconsidered
Wherevalleys(山谷)arefloodedtocreatedams,housesarelostandwildlifehomesdestroyed
Besides,watermayfloweasilythroughpipestofields,butitcannotbetransportedfromonesideoftheworldtotheo