Supply, Renewal and Use of Water Resources

Worldwide Supply and Renewal. The world's fixed supply of water in all forms (vapor, liquid, and solid) is enormous. If we could distribute it equally, there would be enough to provide every person on earth with 292 trillion liters (77 trillion gallons). However, only about 0.003% of the world's water supply is avail­able as fresh water for human use, and this supply is unevenly distributed.

About 97% of the earth's total supply of water is found in the oceans and is too salty for drinking, growing crops, and most industrial purposes except cooling. The remaining 3% is fresh water, but over three-fourths of it is unavailable for use by plants, human beings, and other animals, because it lies too far under the earth's surface or is locked up in glaciers, polar ice caps, atmosphere, and soil. This leaves 0.5% of the earth's water available as fresh water in rivers, lakes, and economically recoverable underground deposits (groundwater) to a depth of 1,000 meters (1.6 miles). However, when we subtract the portion of this water that is highly polluted or too difficult and expen­sive to tap, the remaining supply amounts to about 0.003% of the world's water. To put this in measure­ments that we can comprehend, if the world's water supply were only 100 liters (26 gallons), our usable supply of fresh water would be only about 0.003 liter (one-half teaspoon), as illustrated in Figure 10-1.

That tiny fraction of usable fresh water still amounts to an average of 879,000 liters (232,000 gallons) for each person on earth. The supply is continually col­lected, purified, and distributed in the natural hydro-logic (water) cycle. This natural puri­fication process works as long as we don't pollute water faster than it is replenished or add chemicals that can­not be broken down by bacterial action.

Surface-Water Runoff. The fresh water we use comes from two sources: groundwater and surface-water runoff. Precipitation that does not infil­trate into the ground or return to the atmosphere is known as surface water and becomes runoff – water that flows into nearby streams, rivers, lakes, wet­lands, and reservoirs. This flow of water is renewed fairly rapidly (12 to 20 days) in areas with average precipitation. The land area that delivers runoff, sed­iment, and water-soluble substances to a major river and its tributaries is called a watershed or drainage basin. Surface water can be withdrawn from streams, rivers, lakes, and reservoirs for human activities, but only part of the total annual runoff is available for use. Some flows in rivers to the sea too rapidly to be cap­tured, and some must be left in streams for wildlife and to supply downstream areas. In some years the amount of runoff is reduced by drought.

 

Упражнение 3.

(Парная работа) Выберите из текста Supply, Renewal and Use of Water Resources 10–15 ключевых слов. Определите, к какой части речи они относятся.

 

Упражнение 4.

(Парная работа) Передайте содержание Surface Water Runoff
в 5 предложениях.

 

Упражнение 5.

Вставьте предлоги: AT • IN • FOR • TO • OF • WITH.

1. Although they have normal motor activities, people suffering from somnambulism are not aware … their surroundings.

2. Contrary to what most people think, musicians are not particularly good … languages.

3. The virus responsible … Ebola fever comes from animal sources.

4. What he told the police is incompatible … the facts.

5. Satellite images are capable … detecting objects less than 15 cm across.

6. One of the effects of aspirin is to make patients less liable … heart attack and thrombosis.

7. They want to recruit a doctor who is qualified … tropical diseases.

8. Five research students were involved … industrial espionage.

Упражнение 6.

Прочитайте текст и найдите ответы на следующие вопросы:

1. Что происходит с частью осадков?

2. Где накапливается вода?

3. Благодаря какому процессу теряется большая часть воды?

4. Благодаря какому процессу вода просачивается вглубь земли?

5. Что такое водоносный слой?

6. Благодаря чему пополняется водоносный слой?

7. Что такое водное зеркало?

 

Groundwater

Some precipitation seeps into the ground. Some of this infiltrating water accumulates as soil moisture and partially fills pores between soil par­ticles and rocks within the upper soil and rock layers of the earth's crust. Most of this water is eventually lost to the atmosphere by evaporation from the upper layers of soil and by evapotranspiration from leaves.

Under the influence of gravity, some infiltrating water slowly percolates through porous materials deeper into the earth and completely saturates pores and fractures in spongelike or permeable layers of sand, gravel, and porous rock such as sandstone. These water-bearing layers of the earth's crust are called aquifers, and the water in them is known as ground­water. Aquifers are recharged or replenished naturally by precipitation, which percolates downward through soil and rock in what is called a recharge area. The recharge process is usually quite slow (decades to hundreds of years) compared to the rapid replenish­ment of surface water supplies. If the withdrawal rate of an aquifer exceeds its recharge rate, the aquifer is converted from a slowly renewable resource to a non­renewable resource on a human time scale.

There are two types of aquifers: confined and unconfined. An unconfined, or water-table, aquifer forms when groundwater collects above a layer of rel­atively impermeable rock or compacted clay. The top of the water-saturated portion of an unconfined aqui­fer is called the water table. Thus groundwater is that part of underground water below the water table, and soil moisture is that part of underground water above the water table. Shallow, unconfined aquifers are recharged by water percolat­ing downward from soils and materials directly above the aquifer.

To obtain water from an unconfined aquifer, a water table well must be drilled below the water table and into the unconfined aquifer. Because this water is under atmospheric pressure, a pump must be used to bring it to the surface. The elevation of the water table in a particular area rises during prolonged wet periods and falls during prolonged drought. The water table can also fall when water is pumped out by wells faster than the natural rate of recharge, creating a vacated volume known as a cone of depression.

A confined, or artesian, aquifer forms when groundwater is sandwiched between two layers of rel­atively impermeable rock, such as clay or shale. This type of aquifer is completely saturated with water under a pressure greater than that of the atmo­sphere. In some cases the pressure is so great that when a well is drilled into the confined aquifer, water is pushed to the surface without the use of a pump. Such a well is called a flowing artesian well. With other confined-aquifer wells, known as nonflowing artesian wells, pumps must be used, because pressure is insuf­ficient to force the water to the surface. Confined aqui­fers cannot be recharged from directly above them; they receive water from areas without overlying impermeable rock layers. Thus recharge areas for con­fined aquifers can be hundreds of kilometers away from wells where water is withdrawn, and the rate of natural recharge is not governed by local precipitation at the point of withdrawal as it is for unconfined aquifers.

 

Упражнение 7.

В правой колонке найдите русские эквиваленты следующих английских словосочетаний из текста Groundwater:

1. to seep 2. to accumulate 3. upper layers 4. permeable layer 5. water-bearing layer 6. groundwater 7. recharge area 8. water-table 9. unconfined aquifer 10. water supply

a. грунтовая вода b. просачиваться c. водоносный слой d. водное зеркало e. область пополнения f. верхние слои g. проницаемый слой h. неограниченный водоносный горизонт i. запас воды j накапливаться

Упражнение 8.

Составьте план пересказа текста Groundwater.

 

Упражнение 9.

(Парная работа) Перескажите содержание текста Groundwater в 10 предложениях.

 

Упражнение 10.

Переведите текст письменно. (Контрольное время – 15 минут)

 

Water is our most abundant resource, covering about 71% of the earth's surface. This precious film of water – about 97% salt water and the remainder fresh – helps maintain the earth's climate and dilutes environmental pollutants. Essential to all life, water constitutes from 50% to 97% of the weight of all plants and animals and about 70% of your body. Water is also essential to agriculture, manufactur­ing, transportation, and countless other human activities.

Because of differences in average annual pre­cipitation, some areas of the world have too little fresh water and others too much. With varying degrees of success, human beings have corrected these imbalances by capturing fresh water in res­ervoirs behind dams, transferring fresh water in rivers and streams from one area to another, tap­ping underground supplies, and attempting to reduce water use, waste, and contamination.

 

Упражнение 11.

Составьте 5 общих вопросов к тексту из упражнения 10.

 

Упражнение 12.

(Парная работа) Ответьте на вопросы, составленные в упражнении 11.

 

Lesson 3

 

Упражнение 1.

Ниже приводятся первые предложения первых 4 абзацев текста. Какие выводы Вы можете сделать о содержании текста?

A number of experts consider the availability of adequate supplies of fresh water to be the most serious long-range problem confronting the world.

In many LDCs, poor people must spend a good part of their working hours fetching water.

Although reduced average annual precipitation usually triggers a drought, rapid population growth and poor land use intensify its effects.

Other countries get enough precipitation on an annual basis but receive most of it at one time of the year.

 

Упражнение 2.

Прочитайте и переведите текст. Проверьте правильность Ваших предположений.

 

Water Resource Problems

Too Little Water. A number of experts consider the availability of adequate supplies of fresh water to be the most serious long-range problem confronting the world and the United States. At least 80 arid and semiarid countries, accounting for nearly 40% of the world's population, now experience serious periodic droughts and have considerable difficulty growing enough food to sup­port their populations. Most of these countries are in Asia and Africa. During the 1970s, major drought dis­asters affected an average of 24.4 million people and killed over 23,000 a year – a trend continuing in the 1980s. By 1985 more than 154 million people in 21 tropical and subtropical countries in Africa were on the brink of starvation because of the combined effects of rapid population growth, prolonged drought, land misuse, war, and ineffective government policies for water and soil resource management and agricultural development.

In many LDCs, poor people must spend a good part of their waking hours fetching water, often from polluted streams and rivers. To get water, many women and children in LDCs walk 16 to 25 kilometers (10 to 15 miles) a day, carrying heavy water-filled jars on their return trip.

Although reduced average annual precipitation usually triggers
a drought, rapid population growth and poor land use intensify its effects. In many LDCs, large numbers of poor people have no choice but to try to survive on drought-prone land by cutting trees, growing crops at higher, more erosion-prone eleva­tions, cultivating poor soils, and allowing their live­stock to overgraze grasslands. The resulting land deg­radation contributes to the severity of long-term drought by reducing the amount of rainfall absorbed and slowly released by vegetation and soils. In many cases, the result is desertification.

Too Much Water. Other countries get enough pre­cipitation on an annual basis but receive most of it at one time of the year. In India, for example, 90% per­cent of the annual precipitation falls between June and September – the monsoon season. This downpour runs off so rapidly that most of it cannot be captured and used. The massive runoff also leads to periodic flooding.

During the 1970s, major flood disasters affected 15.4 million people, killed an average of 4,700 people a year, and caused tens of billions of dollars in prop­erty damages – a trend that continued in the 1980s. Although floods are classified as natural disasters, human beings have contributed to the sharp rise in flood deaths and damages since the 1960s by remov­ing water-absorbing vegetation and soil through cul­tivation of marginal lands, deforestation, overgrazing, and mining. Urbanization also increases flooding, even with moderate rainfall, by replacing vegetation with highways, parking lots, shopping centers, office buildings, homes, and numerous other structures.

Death tolls and damages from flooding have also increased because many poor people in LDCs have little choice but to live on land subject to severe peri­odic flooding and because many people in LDCs believe that the benefits of living in flood-prone areas out­weigh the risks. Many urban areas and croplands in LDCs and MDCs are situated on floodplains – flat areas along rivers subject to periodic flooding – and coast-lands because these sites are level, have highly fertile topsoil deposited by rivers, are close to supplies of surface water and water transportation routes, and provide recreational opportunities.

Since 1925 the U.S. Army Corps of Engineers, the Soil Conservation Service, and the Bureau of Recla­mation have spent more than $8 billion on flood-con­trol projects such as straightening stream channels (channelization), dredging streams, and building dams, reservoirs, levees, and seawalls. Despite these efforts – and because these projects stimulate development on flood-prone land – property damage from floods in the United States has increased from about half a bil­lion dollars a year in the 1960s to an average of about $3 billion a year in the 1980s.

A number of effective methods exist for prevent­ing or reducing flood damage: replanting vegetation in disturbed areas to reduce runoff, building ponds in urban areas to retain rainwater and release it slowly to rivers, and diverting rainwater through storm sewers to holding tanks and ponds for use by industry. Floodplains should also be clearly identified, and laws or zoning regulations should be used to discourage their use for certain types of development. Sellers of property in these areas should be required to provide prospective buyers with information about average flood frequency.

 

Упражнение 3.

Определите подлежащее и сказуемое в каждом предложении первого абзаца текста Water Resource Problems.

 

Упражнение 4.

Найдите в тексте примеры этих частей речи.

v.	n.	adj.	adv.	prep.

 

Упражнение 5.

Вставьте в предложения: DESPITE THE FACT • NAMELY •

OBVIOUSLY • ACTUALLY • YET • HENCE • THEREBY.

1. Symptoms such as pain, fever, and vomiting are not diseases. … they are defense mechanisms.

2. "Psychotic" means that a patient has lost touch with reality, …"neurotic" refers to a less serious state.

3. People have always recognized the waste, brutality, and inhumanity of war, … it goes on.

4. The mesosphere is important … that it contains only about 0.1 per cent of the total mass of the atmosphere.

5. As a rule, aquatic reptiles use the same means of propulsion as fish and whales, … they use powerful beats of the tail.

6. The heat increases, … the entropy increases.

7. Cells and antibodies may co-operate, … destroying invading bacteria.

8. For a person who weighs less, the concentration of alcohol will … be proportionally higher.

 

Упражнение 6.

Прочитайте следующие слова и определите их соответствия
в русском языке:

Periodic, experts, population, tropical, combined, agricultural, vegetation, massive, percent, season, cultivation, center, transportation, recreational.

 

Упражнение 7.

Прочитайте текст. (Контрольное время – 5 минут)

 

The U.S. Situation

Overall, the United States has plenty of fresh water, but much of its annual runoff is not in the desired place, occurs at the wrong time, or is contaminated from agricultural and industrial activ­ities. Most of the eastern half of the country usually has ample average annual precipitation, while much of the western half has too little. Many major urban centers in the United States are located in areas that already have inadequate water or are projected to have water shortages by 2000.

In the eastern half of the United States, where there is usually no shortage of water, the major prob­lems are flooding, inability to supply enough water to some large urban areas, and increasing pollution of rivers, lakes, and groundwater. For example, 3 million residents of Long Island, New York, must draw all their water from an underground aquifer that is becoming severely contaminated by industrial wastes, leaking septic tanks and landfills, and salt water from the ocean, which is drawn into the aquifer when fresh water is withdrawn.

The major water problem in arid and semiarid areas in the western half of the country is a shortage of runoff due to low average precipitation, high rates of evaporation, prolonged periodic drought, and rapidly declining water tables as farmers and cities deplete groundwater aquifers faster than they are recharged. Present water shortages and conflicts over water sup­plies will get much worse if more industries and peo­ple migrate west as projected and compete with farm­ers for scarce water.

 

Упражнение 8.

Выберите из текста в упражнении 7 10–15 основных, с точки зрения смысловой нагрузки, слов (ключевые слова). Определите,
к каким частям речи они относятся.

 

Упражнение 9.

Составьте 5 альтернативных вопросов к тексту из упражнения 7.

 

Упражнение 10.

(Парная работа) Ответьте на вопросы, составленные в упражнении 8

 

Упражнение 11.

Переведите текст письменно. (Контрольное время – 30 минут)

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