Find the translation of the following terms and memorize their meaning

channel relation consumer

(in)variable storage reservoir to create

to effect conservation reservoir pond

stock tanks distribution reservoir storage

to determine computation dead storage

permeable to increase useful storage

water-surface profile to seal storage capacity

firm yield fractured rock leakage

safe yield pool level loss

pressure grouting to flow out to occur

multipurpose inflow permeable

natural conditions to flood constant

to meet the requirements run-off to conserve

Read the text to get the gist of it. Answer the following questions.

a) Do the main functions of reservoirs depend on their sizes?

b) What should the reservoir’s banks be made of?

Text A

Dams are built in the river channels to create reservoirs for storing water. Rivers in natural conditions never carry a constant amount of water. In dry summer and in winter it is very small but in spring the water in the rivers is so high that it flows out of the rivers and floods their banks, whereas water consumers require a constant amount of water invariable during the whole year. To meet these requirements the run-off of the rivers must be controlled. The control of the river run-off can be effected by creating a reservoir. There are some types of the reservoirs: storage (conservation) reservoirs and distribution reservoirs. Stock tanks or small ponds may also conserve water. Whatever the size of the reservoir, its main functions are to regulate the flow of water and to provide storage of water, their most important physical characteristic being storage capacity.

Capacity of reservoirs constructed in natural conditions must usually be determined from topographic surveys.

The storage volume between the minimum and normal pool levels is called the useful storage. Water held below minimum pool level is dead storage. In multipurpose reservoirs the useful storage may be subdivided into conservation storage and flood-control storage. Reservoir banks are usually permeable and water enters the soil when the reservoir fills and drains out as the water level is lowered. This bank storage effectively increases the capacity of the reservoir. But if the walls of the reservoir are of badly fractured rock, permeable volcanic material or limestone, serious leakage may occur. This leakage may result in a loss of water. If leakage occurs through a few channels or within a small area of fractured rock, then it is quite possible to seal this area by pressure grouting. If the area of leakage is large the cost of grouting may be too great.

The computation of the water-surface profile is an important part of reservoir design since it provides information on the water level at various points along the length of the reservoir.

Docks, houses, roads and bridges along the banks of the reservoir must be located above the water level.

Probably the most important aspect of storage-reservoir design is an analysis of the relation between yield and capacity. Yield is dependent upon inflow and it may vary from year to year. Most water-storage reservoir must have safe and firm yield, i.e. the maximum quantity of water which can be guaranteed during a critical dry period.