雅思考试模拟题及答案大全 2021雅思考试:雅思模拟试题(2)

READING PASSAGE 2

You are advised to spend about 20 minutes on Questions 14-25 which are based on Reading Passage 2, "The Muang Faai Irrigation System of Northern Thailand".

Questions 14-19

Reading Passage 2 has 7 sections.

穗槐　Choose the most suitable heading for each section from the list of headings (A-L) below. Write the appropriate letter (A-L) in boxes 14-19 on your answer sheet.

N.B. There are more headings than sections, so you will not use all of them.

List of Headings

A) Rituals and beliefs

B) Topography of Northern Thailand

C) The forests of Northern Thailand

凯族肢D) Preserving the system

E) Agricultural practices

F) Village life

G) Water distribution principles

盯世　H) Maintaining natural balances

I) Structure of the irrigation system

J) User's rights

K) User's obligations

L) Community control

14. Section 1

15. Section 2

16. Section 3

17. Section 4

Answer

Example Section 5 A

18. Section 6

19. Section 7

THE MUANG FAAI IRRIGATION SYSTEM OF NORTHERN THAILAND

SECTION 1

Northern Thailand consists mainly of long mountain chains interspersed with valley bottoms where streams and rice fields dominate the landscape. Most of the remaining forests of the North are found at higher altitudes. The forests ensure regular seasonal rainfall for the whole area and at the same time moderate runoff, so that there is water throughout the year.

SECTION 2

The lowland communities have developed an agricultural system adapted to, and partially determining, the distinctive ecosystems of their areas. Practicing wet-rice agriculture in the valley-bottoms, the lowlanders also raise pigs, ducks and chickens and cultivate vegetable gardens in their villages further up the slopes. Rice, beans, corn and native vegetables are planted in hill fields above the villages, and wild vegetables and herbal medicines are gathered and wild game hunted in the forests higher up the hillsides. The forests also serve as grazing grounds for cows and buffalo, and are a source of wood for household utensils, cooking fuel, construction and farming tools. Fish are to be found in the streams and in the irrigation system and wet-rice fields, providing both food and pest control.

SECTION 3

In its essentials, a muang faai system consists of a *all reservoir which feeds an intricate, branching network of *all channels carrying water in carefully calibrated quantities through clusters of rice terraces in valley bottoms. The system taps into a stream above the highest rice field and, when there is sufficient water, discharges back into the same stream at a point below the bottom field. The water in the reservoir at the top, which is diverted into a main channel (Iam muang) and from there into the different fields, is slowed or held back not by an impervious dam, but by a series of barriers constructed of bunches of bamboo or saplings which allow silt, soil and sand to pass through.

SECTION 4

Water from the Iam muang is measured out among the farmers according to the extent of their rice fields and the amount of water available from the main channel. Also considered are the height of the fields, their distance from the main channel and their soil type. The size and depth of side-channels are then adjusted so that only the allocated amount of water flows into each farmer's field.

SECTION 5

Rituals and beliefs connected with muang faai reflect the villagers' submission to, respect for, and friendship with nature, rather than an attempt to master it . In mountains, forests, watersheds and water, villagers see things of great value and power. This power has a favourable aspect, and one that benefits humans. But at the same time, if certain boundaries are overstepped and nature is damaged, the spirits will punish humans. Therefore, when it is necessary to use nature for the necessities of life, villagers take care to inform the spirits what they intend to do, simultaneously begging pardon for their actions.

SECTION 6

Keeping a muang faai system going demands cooperation and collective management, sometimes within a single village, sometimes across three or four different subdistricts including many villages. The rules or common agreements arrived at during the yearly meeting amount to a social contract. They govern how water is to be distributed, how flow is to be controlled according to seasonal schedules, how barriers are to be maintained and channels dredged, how conflicts over water use are to be settled, and how the forest around the reservoir is to be preserved as a guarantee of a steady water supply and a source of materials to repair the system.

SECTION 7

The fundamental principle of water rights under muang faai is that everyone in the system must get enough to survive; while many patterns of distribution are possible, none can violate this basic tenet. On the whole, the systems also rest on the assumption that local water is common property. No one can take control of it by force, and it must be used in accord with the communal agreements. Although there are inequalities in land holding, no one has the right to an excessive amount of fertile land. The way in which many muang faai systems expand tends to reinforce further the claims of community security over those of individual entrepreneurship. In the gradual process of opening up new land and digging connecting channels, each local household often ends up with scattered holdings over the whole irrigation areas. Unlike modern irrigation systems, under which the most powerful people generally end up closest to the sources of water, this arrangement encourages everyone to take care that no part of the system is unduly favoured or neglected.

Questions 20-23

The chart below illustrates the agricultural system of the lowland communities.

Select words from Reading Passage 2 to fill the spaces in the chart. Use UP TO THREE WORDS for each space. Write your answers in boxes 20-23 on your answer sheet.

Area Activity

Example

Forests

grazing cows, buffalo

Forests

Hill fields

Villages

Valley bottom gathering …… (20) ……, hunting wild animals

cultivating …… (21) ……

raising …… (22) …… cultivating vegetables

growing …… (23) ……

Question 24

From the list below, select the three main structures which constitute the muang faai irrigation system. Write the THREE appropriate letters, in any order, in box 24 on your answer sheet.

A) channels

B) saplings

C) dam

D) barriers

E) reservoir

F) water

Question 25

From the list below, select two criteria for allocating water to farmers. Write TWO appropriate letters, in any order, in box 25 on your answer sheet.

A) field characteristics

B) social status

C) location of field

D) height of barriers

E) fees paid

F) water available

洛阳大华雅思提醒您，
假如遇到“笑眯眯”的帅哥考官，那估计7分没跑了，如果遇到不苟言笑的大叔，只能说运气衰暴了，如果碰到一脸傲娇的老太太，还是回去默默再报一场，祈祷下次考口语时能够遇到一位友善仁慈的考官。
以上的“考官论“神雹槐并没有一定的科学依据，雅思口语有公开的评分标准，相对来说还是比较客观的。那么，所谓的高分口语表达和低分表达的差距在哪里呢?
8分口语和6分口语间最大的区别在于以下三点：
1、The high level answers are a more natural style.
这点指，高分答案往往用一种更口语化，更像Native Speaker的表达。
2、The high level answers use more linking phrases.
虽说口语没有答偏题这一说，但是语句中的逻辑性还是需要的。太过混乱的逻辑会让考官听不明白你到底在说什么。因而，连接词的使用很重要。
3、The high level answers are more detailed when describing or explaining something, (using reasons / examples / comparisons).
高分的答案更具体，更详细，不抽象。小伙伴们完全可以用举栗子或者用对比这种简单的手法，来给自己的口语表达添色。
Question 1: Do you like your university?
6分表达: Yes. My teachers are very good and I have lots of friends there.
点评：这是个典型的6分答案，无功无过。虽然把问题讲清楚了，但用词和语句都太过简单，回答不够有力，很难拿高分。
8分表达: Yes I do. I think my university`s great, because I mean, firstly, the teachers there are all really good, you know, I`ve learnt a huge amount from them. And another thing I really like about my university is the friends I`ve made there.
点评：类似于I mean, you know 这类是比较native的口头表达，并不难学。但是烤鸭们要切记，一定不能用过量。简简单单的去剖析细节，分数就比笼统的一肆袭句话来的漂亮。
Question 2: How often do you watch TV?
6分表达: Not often, because I prefer using the Internet.
点评：后面加来一句I prefer，并没有单单说一个Not often。不足的是，对于Part 1而言，这类问题的回答仍是太过简短。建议3-4句话为佳。
8分表达: Not that often actually. I mean, I probably only watch it about two or three times a week, basically because I prefer watching stuff on the Internet.
点评：actually，这一个词的使用是较为地道的表达。相信大家日常跟local聊天的时候，可以发现，他们时时刻刻都喜欢把xxxx actually挂在嘴边，我们也可以学起来。另外，two or three times a week是一个细游友节，补充说明之前的not often究竟是一周几次。Prefer watching stuff on the Internet又是一个细节，说明自己不常看电视的原因。
Question 3：Do you prefer eating at home or eating in a restaurant?
6分表达: I prefer eating at home because it`s healthier than eating out.
点评：很好，给出了原因。但是小编建议，可以再往深处挖一点点，再加一点口语化的词汇，例如Simply Because这类词组，才能给考官一个给你高分的理由。
8分表达: I`d say I generally prefer eating at home, simply because the food I eat at home is a lot healthier than the food you get in most restaurants.
点评：是不是觉得很native~ I’d say，simply because大家可以学着用起来，the food I eat at home is a lot healthier，解释了前文所说的为什么喜欢在家里吃饭的原因，比较级的运用可以算是小小地show off一下哟。
Question 4：When was the last time you received a gift?
6分表达: About five weeks ago.
点评：这个回答太过简短了吧?口语是一个communication的过程，就算咱是有啥答啥的实在人，也千万不要用这种answer来敷衍考官。
8分表达: Let me have a little think, um…… I suppose it must have been about five or six weeks ago, and it was some chocolate that a friend of mine gave me when he came over to my home for dinner (coz my friends all know that I`m a bit of a chocoholic!)
点评：假如遇到不会答的问题怎么办?切记切记，雅思口语考试其实也是一个交流的过程，考官不一定期望你知道所有问题的答案，但一定expect你有response。Let me have a little think……I suppose……这就是非常好的开头。
Question 5: Would you like to move to another city in the future?
6分表达:No, because I love my hometown.
点评：如此的答案，令人有一种无法深入交流的错觉。如此简短的句子如何能展示你的口语能力，让考官心服口服给你个高分?
8分表达: No I wouldn`t, the main reason being that I love my hometown, so if I moved somewhere else, I`m sure I wouldn`t be as happy as I am living here.
点评：同样是歌颂家乡好，话锋一转，在这个表达中就柔和了许多。虚拟语气的运用显示出了较好的语言功底。小编再次重申，理由(reasons)和例子(examples)在口语中是非常非常重要的得分点!!!
Question 6: Can you describe your home a little?
6分表达: My home is big, for example we have a big living room. And um……We also have a good view because our flat is very high.
点评：其实这个答案并不会得很低分。一般想要6分的同学完全可以这样说。对于想要7分甚至于是更高的烤鸭们而言，切记切记，一定要explain more!
8分表达: Yeah, sure. Well first of all, it`s pretty big. For example, the living room is about three or four times the size of this room. And, um…what else… oh yeah, and another thing to mention is the view, because we live quite high up, on the twentieth floor, so we`ve got a really nice view of the city centre.
点评：在考试的高压下假如能说出这样的答案，那么7分妥妥的。对于家的描述可以说是雅思的经典题型，其变体的出现频率非常高，但烤鸭们要回答得好还是有点难度的，因为可讲的东西有很多，稍不留神就会显得messy。这个回答中，告诉了考官房间的大小(three or four times the size of this room)，楼层的高低。全篇都是细节，非常符合高分的三大准则。

如：剑五Test 2的Section 4中的题目：Average daily requirement for an * in Antarctica is approximately _______ kilocalories.解题时就会注意到这里有地点限定词in Antarctica(南极洲)，可以联想到录音材料中的陷阱就是告诉考生不同地区的人的日均卡路里摄入量，而此题的答案需要的仅仅是生活在南极洲一个成年改核人的日均需求量。

此题原文为... an * in the UK will probably need about 1700 kilocalories a day on average; someone in Antarctica will need about 3500 ...正如先前预料的陷阱一样，材料中先提到了英国一个成人的热量日均需求量为1700，但我们只要明确了地点限定词Antarctica为定位词，在后半句中抓出正确答案3500也就易如反掌了。

又如：However，women are more prepared to _____ about them. (剑五 Test1 Section 4) 这道题的定位词即为more prepared，不过不得不提醒一下，prepared作为一个形容词会有很多的同义词或者是近义词比如：ready，willing或者done in advance等。在雅思听力中，形容词本身是非常容易被其他词同义替换掉的，即同义替换原则，故此处不是以prepared这个词为定位标准，准确的说而是以more这个比较雀歼谈级的程度为定位点，即听题时注意是否有比较级出现。此题录音原文中说women are far more willing to learn，可见prepared没有出现，但是more这个比较级的程度限定词却出现了。

4) 特殊标点，如引号、括号、破折号等附近的内容。

一般引号中的内容表示是在录音原文中引用的话，一定会原词重顷碰现，故也是绝佳定位词，如剑4 Test 3 Section 3 Question 22是一道选择题，提干部分为The “Study for Success” seminar last for…，审题时很容易确定用特殊标点引号中的内容作为定位词，这部分答案对应的听力原文为 there’s our intensive “Study for Success” seminar on the first and second of February，引号中的定位词在听力原文中原词重现了，需要抓住的时间类答案也就不会错过了。

5) 复杂定位情况，即空格出现在句子当中，一般使用主语和谓语定位。

在考题中如果能发现到以上四种最典型的定位词固然最好，如果没有，也是常有的事，这个时候我们就要把重点放到名词和动词上。尤其是主+系+表结构中的主语，如：剑五 Test 5 Test 1 Section 1中的题目 The customer’s candidate number is_____.这道题目中定位词即为主语customer’s candidate number。因为主语基本由名词或者名词词组构成，而名词的变化可能性最小，所以当空上所填为表语的时候，一定要将主语标出。

谓语主要指动宾结构中的动词，如：剑4 Test 1 Section 4中的句子填空题ways of planning our _________better。这道题的定位词可以确定为plan，因为题目中需要填写的是plan的宾语，故用plan这个动词定位是最直接的做法。新东方网雅思频道在此需要指出的是，谓语动词一般会有很多种同义词以及主被动的转述，因此考生在标出谓语动词的同时亦应考虑其同义转述及主被动转述的出现，比如听力材料中plan可能被替换成design。此题的原文为...and how we can better plan our cities using trees..., 先前确定的定位词plan原词重现，答案也就是显而易见的cities了。

本文来自雅思作文网liuxue86.com《雅思模拟试题学术类写作一例》。

△Writing Task 1

You should spend about 20 minutes on this task.

The chart below shows the number of men and women in further education in Britain in three periods and whether they were studying full-time or part-time.

Write a report for a university lecturer describing the information shown below.

You should write at least 150 words.

The most prominent trend shown in the graph is an enormous rise in the number of people traveling to and from work by car in the 40 years from 1950 to 1990. In the same period, there was a steep drop in the numbers of people riding bicycles or walking. In addition, the trend was accompanied by a slight decline in the number of bus users.

In 1950, only about 5% of all commuters used cars. This shot up to over 25% in 1970, and to about 30% in 1990. The number of foot travelers halved in both 20-year periods successively, and bike riders followed suit. The use of buses rose sharply until 1970, and then declined to somewhat lower than its former level over the next 20 years.

The graph suggests that people are becoming less active. In 1950, most people traveled to and from work in th is city either on foot or, to a slightly lesser extent, by bike. But by 1990, cars were by far the most popular mode of transport, and almost as many people were still traveling by bus in 1990 as in 1950, with very few using bikes or walking.

△Writing Task 2

You should spend about 40 minutes on this task.

Present a written argument or case to an educated non-specialist audience on the following topic.

The first car appeared on British roads in 1888. By the year 2000 there may be as many as 29 million vehicles on British roads.

Should alternative forms of transport be encouraged and international laws introduced to control car ownership and use?

You should write at least 250 words.

You should use your own ideas, knowledge and experience and support your arguments with examples and relevant evidence.

There is general a greement that there are far too many automobiles crowding the roads nowadays. In fact, it is estimated that there will be as many as 29 million motor vehicles on British roads by the year 2000. Not only do these motor vehicles cause inconvenience in the form of traffic jams and accidents, they also contribute to the planet’s ever-worsening air pollution.

However, it is necessary that these efforts to improve the traffic situation be backed up by international laws to control the ownership and use of cars. This is because, first of all, pollution caused by automobiles is worldwide problem. Secondly, more people are traveling by car to other countries nowadays.

If measures are taken in a planned way to encourage alternative forms of transportation, and international laws put in place to control car ownership and use, there is no doubt that the result will be safer roads, a healthier lifestyle and a less-polluted atmosphere.

预祝您雅思作文更上一层楼,感谢您阅读《雅思模拟试题学术类写作一例》一文.

雅思阅读段落标题模拟题

雅思考试的'阅读部分，因篇幅比较长时间有限，一直是考生们难以攻克的难题。为了帮助大拿薯家能顺谨敏州利备考，下面我为大家带来雅思阅读段落标题模拟题，供大家祥蔽参考学习，预祝大家考试顺利!

试题(一)

Volcanoes-earth-shattering news

When Mount Pinatubo suddenly erupted on 9 June 1991, the power of volcanoes past and present again hit the headlines

A

Volcanoes are the ultimate earth-moving machinery. A violent eruption can blow the top few kilometres off a mountain, scatter fine ash practically all over the globe and hurl rock fragments into the stratosphere to darken the skies a continent away.

But the classic eruption—cone-shaped mountain, big bang, mushroom cloud and surges of molten lava—is only a tiny part of a global story. Vulcani*, the name given to volcanic processes, really has shaped the world. Eruptions have rifted continents, raised mountain chains, constructed islands and shaped the topography of the earth. The entire ocean floor has a basement of volcanic basalt.

Volcanoes have not only made the continents, they are also thought to have made the world's first stable atmosphere and provided all the water for the oceans, rivers and ice-caps. There are now about 600 active volcanoes. Every year they add two or three cubic kilometres of rock to the continents. Imagine a similar number of volcanoes *oking away for the last 3,500 million years. That is enough rock to explain the continental crust.

What comes out of volcanic craters is mostly gas. More than 90% of this gas is water vapour from the deep earth: enough to explain, over 3,500 million years, the water in the oceans. The rest of the gas is nitrogen, carbon dioxide, sulphur dioxide, methane, ammonia and hydrogen. The quantity of these gases, again multiplied over 3,500 million years, is enough to explain the mass of the world's atmosphere. We are alive because volcanoes provided the soil, air and water we need.

B

Geologists consider the earth as having a molten core, surrounded by a semi-molten mantle and a brittle, outer skin. It helps to think of a soft-boiled egg with a runny yolk, a firm but squishy white and a hard shell. If the shell is even slightly cracked during boiling, the white material bubbles out and sets like a tiny mountain chain over the crack—like an archipelago of volcanic islands such as the Hawaiian Islands. But the earth is so much bigger and the mantle below is so much hotter.

Even though the mantle rocks are kept solid by overlying pressure, they can still slowly 'flow' like thick treacle. The flow, thought to be in the form of convection currents, is powerful enough to fracture the 'eggshell' of the crust into plates, and keep them bumping and grinding against each other, or even overlapping, at the rate of a few centimetres a year. These fracture zones, where the collisions occur, are where earthquakes happen. And, very often, volcanoes.

C

These zones are lines of weakness, or hot spots. Every eruption is different, but put at its simplest, where there are weaknesses, rocks deep in the mantle, heated to 1,350℃, will start to expand and rise. As they do so, the pressure drops, and they expand and become liquid and rise more swiftly.

Sometimes it is slow: vast bubbles of magma—molten rock from the mantle—inch towards the surface, cooling slowly, to show through as granite extrusions (as on Skye, or the Great Whin Sill, the lava dyke squeezed out like toothpaste that carries part of Hadrian's Wall in northern England). Sometimes—as in Northern Ireland, Wales and the Karoo in South Africa—the magma rose faster, and then flowed out horizontally on to the surface in vast thick sheets. In the Deccan plateau in western India, there are more than two million cubic kilometres of lava, some of it 2,400 metres thick, formed over 500,000 years of slurping eruption.

Sometimes the magma moves very swiftly indeed. It does not have time to cool as it surges upwards. The gases trapped inside the boiling rock expand suddenly, the lava glows with heat, it begins to froth, and it explodes with tremendous force. Then the slightly cooler lava following it begins to flow over the lip of the crater. It happens on Mars, it happened on the moon, it even happens on some of the moons of Jupiter and Uranus. By studying the evidence, vulcanologists can read the force of the great blasts of the past. Is the pumice light and full of holes? The explosion was tremendous. Are the rocks heavy, with huge crystalline basalt shapes, like the Giant's Causeway in Northern Ireland? It was a slow, gentle eruption.

The biggest eruptions are deep on the mid-ocean floor, where new lava is forcing the continents apart and widening the Atlantic by perhaps five centimetres a year. Look at maps of volcanoes, earthquakes and island chains like the Philippines and Japan, and you can see the rough outlines of what are called tectonic plates—the plates which make up the earth's crust and mantle. The most dramatic of these is the Pacific 'ring of fire' where there have been the most violent explosions—Mount Pinatubo near Manila, Mount St Helen's in the Rockies and El Chichón in Mexico about a decade ago, not to mention world-shaking blasts like Krakatoa in the Sunda Straits in 1883.

D

But volcanoes are not very predictable. That is because geological time is not like human time. During quiet periods, volcanoes cap themselves with their own lava by forming a powerful cone from the molten rocks slopping over the rim of the crater; later the lava cools slowly into a huge, hard, stable plug which blocks any further eruption until the pressure below becomes irresistible. In the case of Mount Pinatubo, this took 600 years.

Then, sometimes, with only a *all warning, the mountain blows its top. It did this at Mont Pelée in Martinique at 7.49 a.m. on 8 May, 1902. Of a town of 28,000, only two people survived. In 1815, a sudden blast removed the top 1,280 metres of Mount Tambora in Indonesia. The eruption was so fierce that dust thrown into the stratosphere darkened the skies, cancelling the following summer in Europe and North America. Thousands starved as the harvests faded, after snow in June and frosts in August. Volcanoes are potentially world news, especially the quiet ones.

试题(二)

The Problem of Scarce Resources

Section A

The problem of how health-care resources should be allocated or apportioned, so that they are distributed in both the most just and most efficient way, is not a new one. Every health system in an economically developed society is faced with the need to decide (either formally or informally) what proportion of the community's total resources should be spent on health-care; how resources are to be apportioned; what diseases and disabilities and which forms of treatment are to be given priority; which members of the community are to be given special consideration in respect of their health needs; and which forms of treatment are the most cost-effective.

Section B

What is new is that, from the 1950s onwards, there have been certain general changes in outlook about the finitude of resources as a whole and of health-care resources in particular, as well as more specific changes regarding the clientele of health-care resources and the cost to the community of those resources. Thus, in the 1950s and 1960s, there emerged an awareness in Western societies that resources for the provision of fossil fuel energy were finite and exhaustible and that the capacity of nature or the environment to sustain economic development and population was also finite. In other words, we became aware of the obvious fact that there were 'limits to growth'. The new consciousness that there were also severe limits to health-care resources was part of this general revelation of the obvious. Looking back, it now seems quite incredible that in the national health systems that emerged in many countries in the years immediately after the 1939-45 World War, it was assumed without question that all the basic health needs of any community could be satisfied, at least in principle; the 'invisible hand' of economic progress would provide.

Section C

However, at exactly the same time as this new realisation of the finite character of health-care resources was sinking in, an awareness of a contrary kind was developing in Western societies: that people have a basic right to health-care as a necessary condition of a proper human life. Like education, political and legal processes and institutions, public order, communication, transport and money supply, health-care came to be seen as one of the fundamental social facilities necessary for people to exercise their other rights as autonomous human beings. People are not in a position to exercise personal liberty and to be self-determining if they are poverty-stricken, or deprived of basic education, or do not live within a context of law and order. In the same way, basic health-care is a condition of the exercise of autonomy.

Section D

Although the language of 'rights' sometimes leads to confusion, by the late 1970s it was recognised in most societies that people have a right to health-care (though there has been considerable resistance in the United States to the idea that there is a formal right to health-care). It is also accepted that this right generates an obligation or duty for the state to ensure that adequate health-care resources are provided out of the public purse. The state has no obligation to provide a health-care system itself, but to ensure that such a system is provided. Put another way, basic health-care is now recognised as a 'public good', rather than a 'private good' that one is expected to buy for oneself. As the 1976 declaration of the World Health Organisation put it: 'The enjoyment of the highest attainable standard of health is one of the fundamental rights of every human being without distinction of race, religion, political belief, economic or social condition.' As has just been remarked, in a liberal society basic health is seen as one of the indispensable conditions for the exercise of personal autonomy.

Section E

Just at the time when it became obvious that health-care resources could not possibly meet the demands being made upon them, people were demanding that their fundamental right to health-care be satisfied by the state. The second set of more specific changes that have led to the present concern about the distribution of health-care resources stems from the dramatic rise in health costs in most OECD countries, accompanied by large-scale demographic and social changes which have meant, to take one example, that elderly people are now major (and relatively very expensive) consumers of health-care resources. Thus in OECD countries as a whole, health costs increased from 3.8% of GDP in 1960 to 7% of GDP in 1980, and it has been predicted that the proportion of health costs to GDP will continue to increase. (In the US the current figure is about 12% of GDP, and in Australia about 7.8% of GDR.)

As a consequence, during the 1980s a kind of doomsday scenario (*ogous to similar doomsday extrapolations about energy needs and fossil fuels or about population increases) was projected by health administrators, economists and politicians. In this scenario, ever-rising health costs were matched against static or declining resources.

试题(三)

Disappearing Delta

A

The fertile land of the Nile delta is being eroded along Egypt’s Mediterranean coast at an astounding rate，in some parts estimated at 100 metres per year.In the past，land scoured away from the coastline by the currents of the Mediterranean Sea used to be replaced by sediment brought down to the delta by the River Nile，but this is no longer happening.

B

Up to now, people have blamed this loss of delta land on the two large dams aI Aswan in the south of Egypt，which hold back virtually all of the sediment that used to flow down the river. Before the dams were built，the Nile flowed freely carrying huge quantities of sediment north from Africa's interior to be deposited on the Nile delta.This continued for 7,000 years，eventually covering a region of over 22000 square kilometres with layers of fertile silt.Annual flooding brought in new, nutrient-rich soil to the delta region，replacing what had been washed away by the sea，and dispensing with the need for fertilizers in Egypt's richest food-growing area.But when the Aswan dams were constructed in the 20th century to provide electricity and irrigation，and to protect the huge population centre of Cairo and its surrounding areas from annual flooding and drought，most of the sediment with its naturaI fertilizer accumulated up above the dam in the southern， upstream half of Lake Nasser, instead of passing down to the delta.

C

Now, however, there turns out to be more to the story.It appears that the sediment-free water emerging from the Aswan dams picks up silt and sand as it erodes the river bed and banks on the 800-kilometre trip to Cairo.Daniel Jean Stanley of the Smithsonian Institute noticed that water samples taken in Cairo，just before the river enters the delta，indicated that the river sometimes carries more than 850 grams of sediment per cubic metre of water-almost half of what it carried before the dams were built.I'm ashamed to say that the significance of this didn't strike me until after I had read 50 or 60 studies，says Stanley in Marine Geology. There is still a lot of sediment coming into the delta，but virtually no sediment comes out into the Mediterranean to replenish the coastline. So this sediment must be trapped on the delta itself.

D

Once north of Cairo, most of the Nile water is diverted into more than 10,000 kilometres of irrigation c*s and only a *all proportion reaches the sea directly through the rivers in the delta.The water in the irrigation c*s is still or very slow-moving and thus cannot carry sediment，Stanley explains.The sediment sinks to the bottom of the c*s and then is added to fields by farmers or pumped with the water into the four large freshwater lagoons that are located near the outer edges of the delta.So very little of it actually reaches the coastline to replace what is being washed away by the Mediterranean currents.

E

The farms on the delta plains and fishing and aquaculture in the lagoons account for much of Egypt's food supply.But by the time the sediment has come to rest in the fields and lagoons it is laden with municipal，industrial and agricultural waste from the Cairo region, which is home is more than 40 million people.’Pollutants are building up faster and faster,’ says Stanley.

Based on his investigations of sediment from the delta lagoons, Frederic Siegel of George Washington University concurs. 'In Manzalah Lagoon, for example, the increase in mercury, lead, copper and zinc coincided with the building of the High Dam at Aswan, the availability of cheap electricity, and the development of major power-based industries,' he says. Since that time the concentration of mercury has increased significantly. Lead from engines that use leaded fuels and from other industrial sources has also increased dramatically. These poisons can easily enter the food chain, affecting the productivity of fishing and farming. Another problem is that agricultural wastes include fertilizers which stimulate increases in plant growth in the lagoons and upset the ecology of the area, with serious effects on the fishing industry.

F

According to Siegel, international environmental organisations are beginning to pay closer attention to the region, partly because of the problems of erosion and pollution of the Nile delta, but principally because they fear the impact this situation could have on the whole Mediterranean coastal ecosystem. But there are no easy solutions. In the immediate future, Stanley believes that one solution would be to make artificial floods to flush out the delta waterways, in the same way that natural floods did before the construction of the dams. He says, however, that in the long term an alternative process such as desalination may have to be used to increase the amount of water available. 'In my view, Egypt must devise a way to have more water running through the river and the delta,' says Stanley. Easier said than done in a desert region with a rapidly growing population.

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