Finish the following sentences according to the text.

1) Reservoirs are built for …

2) … must be controlled to provide water consumers with …

3) There are some types of the reservoirs: …

4) The main functions of the reservoirs are …

5) The most important physical characteristic is …

6) Capacity of the reservoirs must be determined from …

7) Useful storage may be subdivided into … and …

8) Leakage may occur if …

9) The relation between yield and capacity is …

10) Yield depends on …

11) Most water-storage reservoirs must have safe and …

Fill in the table according to the text.

Answer the following questions.

1) Why are dams built in the river channel?

2) Do rivers carry a constant amount of water in natural conditions?

3) What do water consumers require?

4) What must be controlled?

5) What can effect the control of the river run-off?

6) What types of the reservoir do you know?

7) What are the major functions of the reservoir?

8) What must be determined from topographic surveys?

9) What are the useful and dead storages?

10) What may the useful storage be subdivided into?

11) When may leakage occur?

12) When is the cost of grouting great?

13) Must constructions along the banks of the reservoir be located above the water level?

14) What is the most important aspect of storage-reservoir design?

15) What is yield dependent upon?

Read the text again, make its plan and title it.

Make a short summary of the text.

Do you know the meaning of the following terms? Fill in the correct word from the list below.

1) _______ can retain excess water from periods of high flow for use during periods of drought.

2) Many cities provide for the construction of _______because of the varying rate of water consumption during the day.

3) _______ is the maximum elevation to which the reservoir surface will rise during ordinary operating conditions.

4) _______ is the lowest elevation to which the water surface in the pool is to be lowered under normal conditions.

5) _______ is the amount of water which can be supplied from the reservoir in a specified interval of time.

6) _______ is the process of deposition of a solid material from a state of suspension or solution in a fluid (usually air or water).

7) _______ is lack or insufficiency of rain for an extended period that severely disturbs the hydrologic cycle in an area.

8) ________ is a high-water stage in which water overflows its natural or artificial banks onto normally dry land, such as a river inundating its floodplain.

Find the synonyms of the following words in text A.

Find the antonyms of the following words in text A.

Make sure you know the nouns formed from the following verbs.

Make sure you know the verbs formed from the following nouns.

Fill in the correct prepositions then choose any five items and make sentences.

1) to be effected ___ sth.; 2) the size ___ the reservoir; 3) to be constructed ___ natural conditions; 4) to be determined ___ surveys; 5) to be subdivided ___ sth.; 6) to enter ___ sth.; 7) to be located ___ sth.; 8) to be dependent ___ sth.; 9) to vary ___ sth. ___ sth.; 10) to result ___sth.

Find the translation of the following terms and memorize their meaning.

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.

Decide whether the following statements are true or false according to the text.

1) Bed loads are carried by water flow along the river bed.

2) The velocity and turbulence of water in the reservoir isn’t reduced.

3) Some suspended particles may pass the dam with water discharged through sluiceways.

4) The useful life of a reservoir depends on sediment inflow.

5) Reservoir sedimentation can be prevented.

6) The useful life of a small reservoir is longer than that of a large reservoir.

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?

What is not mentioned in Text B?

1) Reservoir sedimentation.

2) Functions of a reservoir.

3) Sediment transport by stream.

4) Physical characteristics of a reservoir.

5) Influence of bed load on the useful life of a reservoir.

6) Downstream deposition of suspended particles.

7) Site selecting for a reservoir.