16. Read the text to get the gist of it. Answer the following questions.
a) Do all suspended particles deposit in the reservoir?
b) What does the useful life of a reservoir depend on?
Text B ________
In every stream some suspended particles are carried by water flow along the river bed. They are called the bed load. Since the specific gravity of soil materials is about 2.65, the suspended particles tend to settle to the channel bottom but upward currents counteract the gravitational settling. When water reaches reservoir, the velocity and turbulence are greatly reduced. The larger suspended particles and most of the bed load are deposited at the head of the reservoir. Smaller particles remain in suspension longer and deposit farther down the reservoir, although the very smallest particles may remain in suspension for a long time and some may pass the dam with water discharged through sluiceways, turbines or spillways.
All reservoirs are filled with sediment. If the sediment inflow is large compared with the reservoir capacity, the useful life of the reservoir may be very short. Small water-supply reservoirs can be filled with sediment during the first year after their completion. Reservoir planning must take into account data on the probable rate of sedimentation in order to determine whether the useful life of the proposed reservoir will be sufficient to warrant its construction.
Actually reservoir sedimentation cannot be prevented but it may be retarded. One way of doing it is to select a site where the sediment inflow is low. After a site has been selected it is necessary to construct such a reservoir the capacity of which would be large enough to ensure a prolonged useful life of the reservoir. Although trap efficiency of large reservoirs is high it does not increase linearly and the useful life of a large reservoir is longer than that of a small reservoir if all other factors remain constant.
17. Decide whether the following statements are true or false according to the text.
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Bed loads are carried by water flow along the river bed.
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The velocity and turbulence of water in the reservoir isn’t reduced.
-
Some suspended particles may pass the dam with water discharged through sluiceways.
-
The useful life of a reservoir depends on sediment inflow.
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Reservoir sedimentation can be prevented.
-
The useful life of a small reservoir is longer than that of a large reservoir.
18. Answer the following questions.
1) What is carried by water flow along the river bed?
2) Why do the suspended particles tend to settle to the channel bottom?
3) What happens when water reaches reservoir?
4) What happens to the larger suspended particles?
5) What happens to the smaller suspended particles?
6) What happens to the very smallest suspended particles?
7) All reservoirs are filled with sediment, aren’t they?
8) When may the useful life of the reservoir be very short?
9) What must be taken into account planning a reservoir?
10) What is the way of reservoir sedimentation retarding?
19. What is not mentioned in Text B?
-
Reservoir sedimentation.
-
Functions of a reservoir.
-
Sediment transport by stream.
-
Physical characteristics of a reservoir.
-
Influence of bed load on the useful life of a reservoir.
-
Downstream deposition of suspended particles.
-
Site selecting for a reservoir.
20. Make a short summary of Text B.
21. Choose the right meaning of the words in bold in Text B.
-
gravity
a) серьезность
b) самотеком
c) сила тяжести
-
head
a) напор
b) голова
c) верховье
-
data
a) база
b) параметры
c) сведения
-
rate
a) норма
b) коэффициент
c) рассматривать
-
site
|
a) место |
b) помещать |
c) установка |
22. Match the following terms with their definitions.
|
a) spillway |
c) sluiceway |
e) velocity |
|
b) capacity |
d) sluice |
f) sediment |
1. The matter that settles to the bottom of a liquid; material deposited by water, wind, or glaciers.
2. Quickness of motion, rapidity of movement.
3. An artificial channel into which water is let by a sluice.
4. An artificial passage for water fitted with a valve or gate for stopping or regulating flow.
5. The potential or suitability for holding, storing, or accommodating; the maximum amount or number that can be contained or accommodated.
6. A passage for surplus water to run over or around an obstruction (as a dam).
23. Find the synonyms in the text.
|
1) to warrant - … |
5) a place - … |
|
2) to settle - … |
6) long - … |
|
3) to achieve - … |
7) competent - … |
|
4) speed - … |
8) to choose - … |
24. Find the opposites in the text.
|
1) small - … |
4) beginning - … |
|
2) to increase - … |
5) to force - … |
|
3) high - … |
6) to interact - … |
25. Fill in the correct preposition, then choose any two items and make sentences.
1) to remain ___ suspension; 2) to be filled ___ sth.; 3) to compare ___ sth.; 4) to take ___ account; 5) ___ order ___ do sth.
26. Translate the following words into English using the vocabulary of the text.
Взвешенные частицы; вдоль дна реки; оседать на дно канала; противодействовать гравитационному оседанию; сниженная скорость; оставаться в взвешенном состоянии; проходить через плотину; приток наносов; принимать в расчет полученные данные; вместимость водохранилища; определять срок службы водохранилища; вода, пропускаемая через турбины; после завершения строительства; проектирование водохранилища; естественные и искусственные водохранилища.
