'millions at risk' as deltas sink 河流三角洲下陷,数百万人“-凯发k8官网

'millions at risk' as deltas sink 河流三角洲下陷,数百万人“
文章来源:未知 文章作者:meng 发布时间:2009-09-22 02:52 字体: [ ] 
(单词翻译:双击或拖选)

most of the world's major river 2 are sinking, increasing the flood risk faced by hundreds of millions of people, scientists report.

科学家报导,世界上主要河流的三角洲正在沉没,加剧了数百万人面临的洪水危险。

3 that would 4 land" width="226" border="0" src="/upimg/090922/4_030219_1.jpg" />
damming rivers has slowed the flow of sediment that would replenish land

damming and diverting rivers means that much less sediment(沉淀物) now reaches many 1(三角洲) areas, while extraction of gas and groundwater also lowers the land.

rivers 5 include the colorado, nile, pearl, rhone and yangtze.

about half a billion people live in these regions, the researchers note in the journal nature geoscience.

they calculate that 85% of major deltas have seen severe flooding in recent years, and that the area of land vulnerable to(易受……攻击) flooding will increase by about 50% in the next 40 years as land sinks and climate change causes sea levels to rise.

"we argue that the world's low-lying deltas are increasingly vulnerable to flooding, either from their feeding rivers or from ocean storms," said albert kettner from the university of colorado in 6, us.

"this study shows there are a host of human-induced factors that already cause deltas to sink much more rapidly than could be explained by sea level alone."

most of the at-risk river basins are in the developing countries of asia, but there are several in developed nations as well, including the rhone in france and the po in italy.

the po delta sank by 3.7m during the 20th century, mainly from 7(甲烷) extraction, the researchers say.

sinking feeling

the researchers drew on data from various space missions including the shuttle 8 topography mission, an 11-day project run from the shuttle endeavour in 2000, and the moderate resolution imaging spectroradiometers (modis) carried on two nasa satellites.

combined with historical records and measurements of sea level rise, this allowed the team to view how fast land was sinking in some deltas, and to look at the various factors that might be responsible.

of the 33 major deltas studied, 24 were found to be sinking.

possibly the worst affected is the chao phraya, the river that flows through bangkok. in some years, parts of the delta have sunk relative to sea level by 15cm (six inches).

this is significantly more than the global rate of sea level rise as a consequence of climate change (1.8-3.0mm per year).

the flow of sediment down to the chao phraya delta has been almost 9 blocked, the researchers report - by taking water out for irrigation, damming the river, and directing the main flow through just a few channels.

normally, this sediment would add to the height of the land, a process known as aggradation(加积,淤高).

taking water from 10(含水层) for drinking, industry and agriculture is also compacting the ground, making it sink.

as the ground falls and sea level rises, people become more vulnerable to 11(淹水,洪水) during storms.

"every year, about 10 million people are being affected by storm surges," said irina overeem, another of the study team from the university of colorado.

"hurricane katrina may be the best example in the us, but flooding in the asian deltas of the irrawaddy in burma and the ganges-brahmaputra in india and bangladesh have recently claimed thousands of lives as well."

the team identifies the mekong and the pearl river delta near hong kong as places where similar disasters are likely in future.



点击收听单词发音收听单词发音  

1 gxvxz     
n.(流的)角洲
参考例句:
  • he has been to the delta of the nile.他曾去过尼罗河三角洲。
  • the nile divides at its mouth and forms a delta.尼罗河在河口分岔,形成了一个三角洲。
2 43c57dfa20ce8f0825105bdcb3548822     
希腊字母表中第四个字母( delta的名词复数 ); (河口的)三角洲
参考例句:
  • tidal channels, deltas, and washover fans are characteristically associated with offshore bars. 潮汐水道、三角洲和冲刷扇典型地与滨外砂洲伴生在一起。
  • i know many of the early civilizations prospered on deltas. 我知道很多古老的文明都是在三角洲上蓬勃发展起来的。
3 isbyk     
n.沉淀,沉渣,沉积(物)
参考例句:
  • the sediment settled and the water was clear.杂质沉淀后,水变清了。
  • sediment begins to choke the channel's opening.沉积物开始淤塞河道口。
4 kcayv     
vt.补充;(把…)装满;(再)填满
参考例句:
  • i always replenish my food supply before it is depleted.我总是在我的食物吃完之前加以补充。
  • we have to import an extra 4 million tons of wheat to replenish our reserves.我们不得不额外进口四百万吨小麦以补充我们的储备。
5 tzuzg0     
adj.不自然的,假装的
参考例句:
  • she showed an affected interest in our subject.她假装对我们的课题感到兴趣。
  • his manners are affected.他的态度不自然。
6 bnbzs     
n.巨砾;卵石,圆石
参考例句:
  • we all heaved together and removed the boulder.大家一齐用劲,把大石头搬开了。
  • he stepped clear of the boulder.他从大石头后面走了出来。
7 t1eyx     
n.甲烷,沼气
参考例句:
  • the blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
  • methane may have extraterrestrial significance.甲烷具有星际意义。
8 ktuxx     
n.雷达,无线电探测器
参考例句:
  • they are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
  • enemy ships were detected on the radar.敌舰的影像已显现在雷达上。
9 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。
10 25c4600513b703affac796567751e105     
n.地下蓄水层,砂石含水层( aquifer的名词复数 )
参考例句:
  • and in africa, the aquifers barely recharge at all. 非洲的地下水开采以后几乎得不到补充。 来自时文部分
  • aquifers have water contents over 30%. 含水层的水含过30%。 来自辞典例句
11 y4fxi     
n.the act or fact of overflowing
参考例句:
  • otherwise, inundation would ensue to our dismay. 若不疏导,只能眼巴巴看着它泛滥。
  • therefore this psychology preceded the inundation of caudillo politics after independence. 在独立后,这一心态助长了考迪罗主义的泛滥。
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