英语听力：自然百科 神奇水世界 Water-3

 Out there is a river valley that's been carved into the rock. It's been carved by running water, just flew down here smoothly¹ off this rock bed and then cascaded² down to the valley north there. Six thousand years ago, that was a big river.

 

Satellite images reveal that the river bed I'm standing³ in is just one of a network of past river valleys that crisscrossed the Sahara desert. Ten thousand years ago, this dry, empty place was entirely⁴ different. Little is known about the early Saharans who lived here then, but we do know that they depended entirely on water. Water formed the lakes in which they swam. Water nourished the plants which fed the animals they hunted. Water filled the clay pots from which they drank, but then the climate changed. 

 

About five and a half thousand years ago, the Sahara began to dry. The rains failed, the river shrank and the lakes dried out. For the early Saharan people, there was only one option - to follow the rains and abandon the desert.

 

The fortunes of the early Saharan people revealed a universal timeless truth: our fate is inextricably linked to water. The problem is the water never stands still. It's always on the move across the planet. We think of this as a blue planet, but while water is abundant, most of it is no use. More than ninety-seven percent of the earth’s water is salty ocean which we can't drink or use to grow crops. Less than three percent is fresh water on which all human life hangs. What's more, that tiny fraction is often hard to depend on, because fresh water has a life cycle all of its own. 

 

The water seems so familiar, doesn't it? But to see its remarkable⁵ qualities, you have to go to some extreme length.

 

1 smoothly   

adv.平滑地，顺利地，流利地，流畅地

参考例句：

• The workmen are very cooperative,so the work goes on smoothly.工人们十分合作，所以工作进展顺利。
• Just change one or two words and the sentence will read smoothly.这句话只要动一两个字就顺了。

2 cascaded   

级联的

参考例句：

• His money cascaded away in a couple of years. 他的钱在三两年内便滚滚流失了。
• The water cascaded off the roof in the thunderstorm. 雷雨中水象瀑布一样从屋顶泻下。

3 standing   

n.持续，地位；adj.永久的，不动的，直立的，不流动的

参考例句：

• After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
• They're standing out against any change in the law.他们坚决反对对法律做任何修改。

4 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

5 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。