Question

    Rivers are earthly arteries(要道) for the nutrients, deposits and freshwater that sustain healthy, diverse ecosystems. Their influence extends in multiple dimensions—not only along their length but below­ground to aquifers(蓄水层) and periodically into nearby floodplains.

They also provide vital services for people by fertilizing agricultural land and feeding key fisheries and by acting as transportation corridors. But in efforts to ease ship passage, protect communities from flooding, and draw off water for drinking and irrigation, humans have increasingly constrained and broken these crucial water ways. “We try to control rivers as much as possible,” says Gunther Grill, a hydrologist at McGill University.

In new research published in May in Nature, Grill and his colleagues analyzed the barriers to 12 million total kilometers of rivers around the world. The team developed an index(指数) that evaluates six aspects of connectivity—from physical fragmentation (by dams, for example) to flow regulation (by dams or levees) to water consumption—along a river’s various dimension. Rivers whose indexes meet a certain threshold(临界值) for being largely able to follow their natural patterns were considered free­flowing.

The researchers found that among rivers longer than 1,000 kilometers (which tend to be some of those most important to human activities), only 37 percent are not blocked along their entire lengths. Most of them are in areas with a minimal human presence, including the Amazon and Congo basins and the Arctic. On the contrary, most rivers shorter than 100 kilometers appeared to flow freely—but the data on them are less comprehensive, and some barriers might have been missed. Only 23 percent of the subset of the longest rivers that connect to the ocean are uninterrupted. For the rest, human infrastructure is starving estuaries(河口) and deltas (such as the Mississippi Delta) of key nutrients. The world's estimated 2.8 million dams are the main cause, controlling water flow and trapping deposits.

The new research could be used to better understand how proposed dams, levees and other such projects might impact river connectivity, as well as where to remove these fixtures to best restore natural flow. It could also help inform our approach to rivers as the climate changes, says Anne Jefferson, a hydrologist at Kent State University, who was not involved in the work. Existing infrastructure, she says, “has essentially been built to a past climate that we are not in anymore and are increasingly moving away from.”

1.According to the passage, which of the following is NOT a function of rivers?

A.Easing ship passage. B.Fertilizing agricultural land.

C.Transporting people or goods. D.Sustaining healthy ecosystems.

2.What does the underlined word “constrained” in Paragraph 2 most probably mean?

A.Exhausted. B.Restricted.

C.Consumed. D.Expanded.

3.The underlined word “them” in Paragraph 4 refers to “________”．

A.earthly arteries B.human activities

C.entire lengths D.unblocked rivers

4.What does Anne Jefferson mean by the underlined sentence in the last paragraph?

A.Existing infrastructure has been perfectly built.

B.Existing infrastructure doesn't depend on the past climate.

C.Existing infrastructure determines the future climate.

D.Existing infrastructure doesn’t fit the changing climate.

Answer

1.A

2.B

3.D

4.D

【解析】

这是一篇说明文。文章讲述了河流在维护健康生态系统、促进农业发展及运输方面发挥的作用，但是人类活动对于河流功能的发挥产生了很大的不利影响，要结合气候条件调整水利设施的建设。

1.

细节理解题。根据前两段中的“Rivers are earthly arteries(要道) for the nutrients, deposits and freshwater that sustain healthy, diverse ecosystems. They also provide vital services for people by fertilizing agricultural land and feeding key fisheries and by acting as transportation corridors. But in efforts to ease ship passage…humans have increasingly constrained and broken these crucial water ways. ”可知，河流是维持健康多样生态系统所需要的养分，沉积物和淡水的运输通道。它们还通过给农业土地施肥和为主要渔业提供食物以及充当运输走廊，为人们提供重要的服务。但是，在努力减轻船舶通行压力和保护社区免受洪水侵袭方面，人类越来越多地限制和破坏了这些关键的河流。”由此可知A项（努力减轻船舶通行压力。）不是河流发挥的功能。故选A。

2.

词义猜测题。根据第二段中的“broken these crucial water ways. We try to control rivers as much as possible.”可知，人类越来越多地破坏了这些关键的河流，因为人们试图尽可能地控制河流。and之前的动词与and之后的内容在意义是相近的，即人类“控制”河流的活动对河流应该发挥的作用产生了消极的影响，结合选项可知，restricted（限制）能够符合语意的需要。故选B。

3.

词义猜测题。根据第四段中的“The researchers found that among rivers longer than 1，000 kilometers, only 37 percent are not blocked along their entire lengths. Most of them are in areas with a minimal human presence, including the Amazon and Congo basins and the Arctic. ”可知，研究人员发现，在长度超过1000公里的河流中，只有37％的河流在整个长度上都没有被阻塞。它们中的大多数位于很少有人居住的地区，包括亚马逊河和刚果盆地以及北极地区。因此them指代的是“只有37％在整个长度上都没有被阻塞的河流”，即D项（畅通的河流）。故选D。

4.

词义猜测题。根据最后一段可知，这项新研究可以用来更好地理解拟建的水坝，堤坝和其他类似项目如何影响河流的连通性，以及在何处拆除这些固定装置以最好地恢复自然流量。肯特州立大学水文学家安妮·杰斐逊（Anne Jefferson）说，这也可以帮助我们了解随着气候变化而对河流的处理方式。她说，现有的基础设施是在过去的气候条件下建设的，我们现在的气候条件已经不是过去那样了，并且正在逐渐地发生变化。”即Anne Jefferson所说的话意味着：现有的基础设施无法适应不断变化的气候。故选D。