4. The koyana Dam is one of the largest dams in
Maharashtra, India. It is a rubble- concrete dam
constructed on koyana River which rises in
Mahabaleshwar, a hillstation in Sahyadri ranges. It is
located in koyana Nagar, Satara district, nestled in the
Western Ghats on the state highway between Chiplun
and Karad.
The main purpose of dam is hydroelectricity with
some irrigation. Koyana Hydroelectric Project is the
largest completed hydroelectric power plant in India
having a total installed capacity of 1,920 MW. Due to
its electricity generating potential koyana river is
considered as the ‘life line of Maharashtra.
5. In the early 20th century, there was a survey of the koyana River as
hydro-electric source by the Tata Group.
The 1928 financial crisis caused the project
to be shelved. After the independence of India, it was taken
over by the Government of Maharashtra. In 1951 koyana Dam
Division started to look into the project. The project was approved in
1953 and work commenced in early 1954 and completed in 1962.
6. Features
Type of dam-Rubble-concrete dam
Impounds-Koyna River Height-103.2 m
(339 ft)
Length-807.2 m (2,648 ft)
Reservoir Creates –Shivajisagar Lake
Total capacity -2,797,400,000 m³
(2,267,900 acre. Ft)
Surface area-891.78 km² (344 sq mi)
8. >The koyana Hydroelectric Project is the largest completed hydroelectric power plant in India.
> It is a complex project with four dams including the largest dam on the koyana River known as the koyana
Dam hence the name koyana Hydroelectric Project.
>The project site is in Satara district near Patan. The village Helwak near the dam was later known as
koyananagar.
> The total capacity of the project is 1,960 MW.
> The project consists of four stages of powergeneration.
>All the generators are located in underground powerhouses excavated deep inside the mountains of the
Western Ghats.
>A dam foot powerhouse also contributes to the electricity generation.
> The project takes advantage of the height of Western Ghats. Thus a very large hydraulic head is
available over a very short distance.
9. Stage l and ll
1st and 2nd stages share same powerhouse with total eight
Pelton turbine units.
- Capacity- four turbines having of 65 MW each for 1st stage
and 75 MW each for 2nd stage.
The water from The shivajisagar reservoir is taken through an
intake structure known as Navja tower near village of Navja
into the head race tunnel.
> Then it travels towards the surge tank. It is further divided
into four pressure shafts which run vertically downward
delivering water to the turbines.
Then the water is discharged into the tail race tunnel.
10. > A dam foot powerhouse was also
constructed which is used to generate
electricity by the water which is
discharged from the koyana Dam for
irrigation purpose.
>It has two Francis turbine units of 20
MW each. This powerhouse is run
according to the irrigation requirements
of the downstream areas. 17-18/41
> The combined installed capacity of the
two
>stages and the dam foot powerhouse is
600 MW.
11. Stage lll and Vl
>It was observed that the water still had a hydraulic head of about 120
m which could be used.
>To use this head, the Kolkewadi Dam was constructed at this location.
>It forms a balancing reservoir and maintains head.
>This dam impounds the tail race water from Stage I and II. This water
is drawn through penstocks and
electricity is generated by four Francis turbine units
with a capacity of 80 MW each.
>The tail race water from these stages then flows through a channel
and joins the Arabian Sea near Chiplun.
The installed generating capacity of this stage is 320 MW
12. >Later in the 1980s, the electricity demand of the
Maharashtra increased tremendously resulting in
inadequate power supply.
>The Planning Commission accorded approval to Stage IV
with installation capacity of 4 x 250 MW. Thus, one more
stage called Stage IV was introduced, thus converting the
koyana Power Station into a peaking power station
complex with load factor of about 18.7%.
>This scheme also draws water from the existing
shivajisagar reservoir same as Stages I and II.
13. Future Plans
To utilize more water
from the shivajisagar
reservoir, another dam
foot powerhouse is
being constructed on
the left bank of the dam.
This powerhouse will
employ a pumped
storage scheme. Also
lake tapping is
proposed for the intake
system.
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