Water–Facts and Figures

Lesson 1

WATER RESOURCES

Блок 4

The Southern Oscillation

The locations of the furnaces, the convective zones of rising air and low surface pressures, are determined by temperature patterns at Earth's surface. The air ascends where surface temperatures have maxima. The seasonal north-south migrations of the convective zones therefore tend to keep those zones in the summer hemisphere. Over Africa and South America the zones of heavy rainfall are difficult to dislodge from the continents because surface temperatures can attain higher values on land than over the oceans. The maritime continent of southeastern Asia is an entirely different matter because its eastern boundary coincides with that of the pool of warm water that covers the western tropical Pacific. Should this pool expand eastward, so would the region of rising air and heavy rainfall, which is exactly what happens interannually during El Nino. On such occasions, the eastern tropical Pacific experiences an increase in sea surface tem­peratures and in rainfall, a decrease in surface pressure, and a relax­ation of the trade winds. Because of this eastward shift, the tropical regions west of the date line, including India and southeastern Africa, experience decreases in rainfall.

In the same way that the seasonal cycle is an oscillation between winter and summer, so the Southern Oscillation is a fluctuation between El Nino and a complementary state, which has been given the apposite name La Nina. Whereas the seasonal cycle is forced by regular variations in the intensity of sunlight, the Southern Oscillation corresponds to a natural mode of oscillation of the coupled ocean and atmosphere and is literally the music of our spheres (the atmosphere and hydro­sphere).

Упражнение 1.

Прочитайте и переведите следующий текст.

Hydrology is a science dealing with the waters of the earth, their occurrence, distribution and circulation, their chemical and physical properties and their interaction with the environment. In this context, water is viewed in the same way as soil, vegetation, climate or rock, as an element of the landscape to be investigated and ultimately understood by means of rigorous scientific quantification and analysis. Water, the subject of hydrology, is both commonplace and unique. It is found everywhere in the earth's ecosystem and taken for granted in much of the developed world. It is, however, the only naturally occurring inorganic liquid and is the only chemical compound that occurs in normal conditions as a solid, a liquid and a gas. Its distribution over the globe is amazingly uneven.

Water plays a fundamental part in the distribution of chemicals through its central role in many chemical reactions, the transport of dissolved chemicals and the erosion and deposition of sediments. Its gaseous form, water vapour, is the principal greenhouse gas in the earth's atmosphere, an order of magnitude greater than CO2, which is the second most important greenhouse gas.

About 97% occurs as saline water in the seas and oceans. Only the remaining 3% is fresh water and of this, considerably more than one half is locked up in ice sheets and glaciers and another substantial volume occurs as virtually immobile deep groundwater. The really mobile fresh water, which contributes frequently and actively to rainfall, evaporation and streamflow, thus represents only about 0.3% of the global total. These estimated values of global water storage must be treated with caution because of the difficulties of monitoring and exact quantification at the macroscale. For example, the volumes of the ocean basins and of the major ice sheets depend upon sea bed and sub-ice topography which have only recently been mapped with reasonable accuracy. Reserves of deep groundwater are difficult to assess and estimates are periodically revised, usually upwards, like those of fossil fuels. Shallow groundwater storage is more accessible and mostly easier to estimate, although the proportion of usable non-saline water is still far from certain. Atmospheric water vapour content is normally monitored either by radio-sonde balloons released daily from just 1500 global locations or from ultra-red spectrometers in weather satellites. Unfortunately, due to the presence of clouds, IR spectrometry is more difficult to interpret for the air layers closest to the earth's surface, where water vapour values are the highest.

In the past, hydrologists focused their attention on the relatively small amount of fresh water occurring either as rivers, lakes, soil water and shallow groundwater, or in the vegetation cover and the atmosphere. Increasingly, however, it is recognized that the oceans play a dominant role in the global water and energy budgets and that large-scale perturbations of the hydrological system may result from changes in sea surface temperature, such as those associated with El Nino, or from modifications of the thermo-haline ocean circulation which may result from the increasingly rapid break-up of major ice sheets in both the northern and southern hemispheres. It is also important to recognize that the small volume of mobile fresh water is itself distributed unevenly in both space and time. Wetland and prairie, forest and scrub, snowfield and desert, each exhibits different regimes of precipitation, evaporation and streamflow, each offers different challenges of understanding for the hydrologist and of water management for the planner and engineer, and each poses different benefits and threats to human life and livelihood as between the developed and the developing world.

Упражнение 2.

Ответьте на вопросы:

1. What does hydrology deal with?

2. Where is water found on the planet?

3. What is unique about water as a chemical compound?

4. What is the principal greenhouse gas on the earth?

5. How much saline and fresh water is there on our planet?

6. Why should global water storage values be treated carefully?

7. What has been mapped only recently?

8. Which water reserves are easier to be estimated? Which are more difficult?

9. How is water vapour content monitored?

10. What water did hydrologists study in the past?

11. What plays the main role in the global water and energy budgets?

12. How unevenly is water distributed?

Упражнение 3.

Соедините слова в колонках A и В.

A.	В.
sea	fuel
ice	gas
water	flow
stream	water
greenhouse	management
ocean	bed
water	sheet
earth's	storage
fossil	surface
soil	basin

Упражнение 4.

Переведите следующие выражения на английский язык:

Посредством (при помощи), оставшийся, неравномерный, относительно, принимать как должное, быстрый, зависеть от, или…или.., как... так и..., из-за (2), однако, хотя, все еще, между, следовательно (2), близко, в основном, к сожалению, значительно, тот же самый, свойство, встречаться, представлять, оценка (2).

Упражнение 5.

Образуйте причастия 1 и 2 рода из следующих глаголов. Найдите примеры таких причастий в тексте из упражнения 1.

Estimate, develop, investigate, depend, remain, grant, understand, show, focus, recognize, associate, use, occur, find.

Упражнение 6.

Образуйте наречия из следующих слов:

Increase, consider, main, substantial, day, period, frequent, globe, ultimate, nature, science, amaze, virtual, large.

Упражнение 7.

Образуйте соответствующие части речи из приведенных
в скобках слов:

Glaciers store water over (relate) long timescales compared to rivers and lakes -hundreds to a few thousands of years. Ice sheets store water for even (long) - ten thousands of years. But the shorter glacier timescales are (compare) to human timescales, so people notice how glaciers change, and these changes have obvious impacts on the human environment. Many river systems depend on glacier melt, which (maintain) the water supply through the summer. As glaciers shrink, so does the (freeze) water supply they store. This is one of the reasons why it is important to measure how and understand why glaciers change over time.

Glacier meltwater (event) makes its way to the ocean, where it can affect global sea level. As terrestrial ice masses grow, sea level (fall); and as masses shrink, sea level (rise). At the last glacial maximum, about 18,000 years ago, the growth of ice sheets and glaciers (cause) sea level to lower by about 120 meters. Most of that change (be) due to the formation of large ice sheets in northern North America and Europe, but mountain glaciers, too, had their role.

Упражнение 8.

Поставьте глаголы в скобках в форму страдательного залога:

Approximately 97% of the fresh water available in the world is underground. Wells provide groundwater for individual domestic needs, communities, cities, industry, crop irrigation and agriculture. Some wells tap hot water, or geothermal resources. In other cases, groundwater (use) solely for its cooling capabilities. Some wells (dig) just to study water quality or quantity: these (call) monitoring or observation wells.

Regardless of its purpose, a well (define) as an artificial hole in a land surface created to access a liquid. It normally has a small diameter, typically less than 3 meters and usually (measure) in centimeters. Wells may (construct) to seek water, oil or natural gas.

Упражнение 9.

Составьте вопросы к тексту из упражнения 8.

1. Where/ fresh water/ available?

2. What/ groundwater/ provided/ for?

3. Wells/ tap/ solely/ cold water?

4. What kind of wells/ dug/study/water quality or quantity?

5. How/ a well/ defined?

6. How big/ its diameter?

7. Why/ wells/ constructed?

Упражнение 10.

В приведенном ниже тексте используйте следующие слова: can, providing, however, satellites,due to, cooling, atmospheric, causes, boarded, observers.

Snow and ice account for just over 75% of the Earth's freshwater, although most of this is held as ice in Antarctica and Greenland, with
a residence time of the order of 10, 000 years. Snow has a great hydrological importance. It has a … effect on climate by increasing the albedo and modifying the surface radiation balance and the near-surface air temperature, and it … a great amount of energy to be expended on melting. Seasonal snow cover changes are known to affect global … circulation, and may have an important role influencing climatic change. In arid and semi-arid areas … by high mountains, including the semi-arid western United States, northern India and Iran, snowmelt is an important seasonal source of water. The presence of snow on the ground is important … disruption of travel and commerce, and seasonal flood risk may be increased by snowmelt. In addition to … a store of water, snow cover can serve as protective insulation for soil and crops through the winter. Information on the spatial distribution of snow was traditionally based on reports from … at meteorological stations. But it is difficult to gain a broad picture of the areal extent of snow cover from such local observations. Due to its high albedo, snow cover can be readily distinguished from snow-free ground using visible radiation reflectance. Remote sensing, from aircraft or … enables the rapid mapping of the extent of snow cover over large areas. It is,…, often difficult to distinguish snow from cloud cover using visible reflectance alone, without repeated photography over time to filter out the variable cloud pattern. This … be overcome by the use of "passive" microwave radiation emitted naturally by the Earth's surface. This can penetrate cloud cover and allow the mapping of snow extent unobstructed by weather effects. However, passive microwave data have a low spatial resolution of several tens of kilometers.

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