AMARENDRA NATH ROY at 14:28, 13 November 2025

2025-11-13T14:28:48Z

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{{Short description|Power plant in India}}
{{Infobox power station
| name = Koyna Hydroelectric Project
| image = Koynaa dam.jpg
| image_size =
| image_caption = Koyna Dam
| location = Satara district, Maharashtra, India
| coordinates = {{Coord|17|24|06|N|73|45|05|E|type:landmark_region:IN|display=inline,title}}
| status = Operational
| construction_began = 1954
| owner = Maharashtra State Water Resources Dept, Chief Engineer Electrical, Govt of Maharashtra
| operator = Maharashtra State Power Generation Company ltd
| website =
}}
[[File:Shivasagar.jpg|thumb|Shivasagar lake]]

The '''Koyna Hydroelectric Project''' is the [[List of power stations in India|largest]] [[hydroelectricity|hydroelectric]] power plant in [[India]].<ref name="Largest_hydroelectric_power_plant_in_India">{{cite web|url=http://www.india-reports.com/articles/ElectricityInIndia/electricity_india_hydroelectric_largest_powerplant.aspx|title=Largest Hydroelectric Power Plants in India|access-date=20 August 2011|website=India Reports|archive-url=https://web.archive.org/web/20120105001630/http://www.india-reports.com/articles/ElectricityInIndia/electricity_india_hydroelectric_largest_powerplant.aspx|archive-date=5 January 2012|url-status=usurped}}</ref> It is a complex project with four [[dam]]s including the largest dam on the [[Koyna River]], [[Maharashtra]], hence the name Koyna Hydroelectric Project. The project site is in [[Satara district]].

The Koyana Dam is situated near Koyananagar village. On river Koyana.

The total capacity of the project is {{nowrap|1,960 [[Megawatt|MW]]}}. The project consists of four stages of power generation. All the [[Electric generator|generator]]s are located in [[underground powerhouse]]s excavated deep inside the mountains of the [[Western Ghats]]. A dam foot [[power station|powerhouse]] also contributes to the [[electricity generation]]. Due to the project's electricity generating potential the Koyna River is considered as the life line of Maharashtra. The Sharavathi Pumped Storage Hydropower Project would be a larger project of 2000MWe in southern India and outside the Koyna plant.

The project takes advantage of the height of Western Ghats. Thus a very large [[hydraulic head]] is available over a very short distance.

==History==
In the early 20th century, there was a survey of the Koyna River as a potential hydro-electric source. After the [[World War I|First World War]], a hydro-electric project on the Koyna river was investigated by the [[Tata Group]]. The 1928 financial crisis caused the project to be shelved. In 1951 Koyna Dam division started to look into the project. The project was approved in 1953 and work commenced in early 1954. The second stage of the project was made using a [[World Bank]] loan (Project loan number 24-IN).<ref name="wb1970">{{cite book |title=report and recommendation to the Directors on a proposed credit to India for the Andhra Pradesh agricultural credit project |date=1 December 1970 |publisher=World Bank / International Development Association |location=Washington |page=2 |url=http://documents.worldbank.org/curated/en/716001468034216122/pdf/multi0page.pdf |access-date=29 October 2018}}</ref>

==Description==
[[File:Head Race T.jpg|thumb|Head race tunnel]]
[[File:Head Race Tu.jpg|thumb|Head race tunnel]]
[[File:Koyna Switchyard.jpg|thumb|Outdoor switchyard]]

The project is composed of four dams with the major contributors being the [[Koyna Dam]] and [[Kolkewadi Dam]]. The water from [[Shivasagar]] reservoir was formed by the Koyna Dam and is used in the 1st, 2nd and 4th stages. This water is drawn from head race tunnels situated below the reservoir. Then it travels through vertical pressure shafts to the [[underground powerhouse]]s. The discharged water from these stages is collected and stored in [[Kolkewadi Dam]] situated near village of [[Alore]]. The water is drawn from the [[penstocks]] of Kolkewadi Dam to an underground power station in the 3rd stage and then discharged to the Arabian Sea.

The electricity generated in all the stages is delivered to the main [[electrical grid]]. The project is run by the [[Maharashtra State Electricity Board]].

{| class="sortable wikitable"
! Stage !! Unit number !! Installed capacity ([[Watt#Megawatt|MW]]) !! Date of commissioning !! Status
|-
| Stage I || 1 || 70 || 1962 May || Running <ref>{{cite web|url=http://www.infraline.com/Details/updated-april-2011pophali-hydro-power-stationpromoter-113247.htm|title=Updated: April 2011 Pophali Hydro Power Station Promoter|author=Infraline Energy Research|work=Infraline Energy|access-date=20 April 2015}}</ref>
|-
| Stage I || 2 || 70 || 1962 August || Running
|-
| Stage I || 3 || 70 || 1963 January || Running
|-
| Stage I || 4 || 70 || 1963 February || Running
|-
| Stage II || 5 || 80 || 1967 June || Running
|-
| Stage II || 6 || 80 || 1966 November || Running
|-
| Stage II || 7 || 80 || 1966 June || Running
|-
| Stage II || 8 || 80 || 1966 March || Running
|-
| Stage III || 9 || 80 || 1975 July || Running
|-
| Stage III || 10 || 80 || 1976 January || Running
|-
| Stage III || 11 || 80 || 1977 May|| Running
|-
| Stage III || 12 || 80 || 1977 || Running
|-
| Stage IV || 13 || 250 || 1981 || Running
|-
| Stage IV || 14 || 250 || 1981 || Running
|-
| Stage IV || 15 || 250 || 1981 || Running
|-
| Stage IV || 16 || 250 || 1981 || Running <ref>{{cite web|url=https://globalenergyobservatory.org/geoid/3904|title=Koyna I-IV (Pophali) Hydro Power Plant India - GEO|access-date=20 April 2015}}</ref>
|-
|}

Besides this dam foot powerhouse part of power plant also produces 40 MW through two generating units of 20 MW each, totalling 1960 MW. Details of each stage are given below.

===Stage I and II===
The first stage of the project was approved in late 1953 and construction began in early 1954. Initially a two-stage construction was conceived. But the total generation capacity of the two stages was too large for load forecasts of that time. So a time lag of more than 10 years was proposed between the two stages. Within two years thereafter, it came to be noticed that the 10 years time tag between these two stages will not be affordable and to cope up with the power requirements, the two stages should be merged and both the stages should be constructed simultaneously. Hence, it was accepted that the two stages have to be executed as one.

The 1st and 2nd stages share same powerhouse with total eight [[Pelton turbine]] units. Each of the two stages has four turbines having capacity of 65 MW each for 1st stage and 75 MW each for 2nd stage. The water from Shivasagar 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.

A dam foot powerhouse was also constructed which is used to generate electricity by the water which is discharged from the Koyna 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.

The combined installed capacity of the two stages and the dam foot powerhouse is 600 MW.

===Stage III===
Initially a [[weir]] was proposed to divert the water coming out of tail race tunnel of Stage I and II. But it was later 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 the 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.

===Stage IV===
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 × 250 [[Megawatt|MW]]. Thus, one more stage called Stage IV was added to power system of Stages I and II, thus converting the Koyna Power Station into a peaking power station complex with [[load factor (electrical)|load factor]] of about 18.7%. This scheme also draws water from the existing [[Shivasagar]] reservoir same as Stages I and II.

A nonconventional intake system was created by piercing the lake from the bottom by [[Rock blasting|blasting]] the rock plug using [[dynamite]].<ref>{{cite web|url=http://www.indiaenvironmentportal.org.in/files/Koyna.pdf|title=Under water lake tapping at Koyna project |access-date=29 December 2012}}</ref> This double lake tapping process was the first of its kind in [[Asia]].<ref name="Lake_tapping">{{cite web|url=http://archive.indianexpress.com/Storyold/85410|title=Rane triggers lake tapping at Koyna|date=14 March 1999|access-date=20 April 2015}}</ref>

The water in head race tunnel is directly drawn from the reservoir and delivered to the head [[surge tank]]. Then four pressure shafts take the water downward vertically. The four huge [[Francis turbine]] units of 250 MW each generate electricity and tail race water is taken into the [[Kolkewadi Dam]] reservoir through tail race tunnel. A revolutionary gas insulated [[switchgear]] system is used in the [[underground powerhouse]] of this stage.

The installed capacity of this stage alone is 1000 MW. This stage is mostly used to cater for the peak hour demands of the [[electric grid]].

==Features==

{|class="wikitable sortable"
! class="unsortable"| !! class="unsortable"| Stage I & II !! class="unsortable" | Stage III !! class="unsortable" | Stage IV
|-
| colspan="4" style="background:azure;" |'''Dam'''
|-
| Catchment area || {{Convert|891.78|km2|mi2|0|abbr=on}} || {{Convert|25.04|km2|mi2|0|abbr=on}} || rowspan="4" | Capacity of stage I & II is utilised
|-
| Capacity || 2797 [[million cubic metre|MCM]] || 36 MCM
|-
| Max. height above foundation || 103.02 m || 63.30 m
|-
| Length || 807.72 m || 497.00 m
|-
| colspan="4" style="background:azure;" |'''Intake works'''
|-
| Head race tunnel length || 3748 m || 4551 m || 4230 m
|-
| Intake tunnel diameter || 6.4 m circular || 7.4 m D shape || {{nowrap|7 m × 9.50 m}} horseshoe shape
|-
| Discharge capacity || 164 m3/s || 170 m3/s || 260 m3/s
|-
| colspan="4" style="background:azure;" |'''Pressure shafts'''
|-
| Number || 4 || 4 || 4
|-
| Length(each) || 616 m || 192 m || 590 m
|-
| colspan="4" style="background:azure;" |'''Power house'''
|-
| Approach tunnel length || 864 m || 780 m || 988 m
|-
| Tail race tunnel length || 2215 m || 4543 m || 2314 m
|-
| Number of turbines || 4 (stage I) + 4 (stage II) + 2 (dam foot powerhouse) = 10 || 4 || 4
|-
| Type of turbine || Pelton (stage I & II) Francis (dam foot powerhouse) || Francis || Francis
|-
| Installed generation capacity || 600 MW || 320 MW || 1000 MW
|-
| style="background:azure;" | '''Switch yard''' || 4572 m || 340 m || {{nowrap|134 m × 18 m}} underground
|-
| style="background:azure;" | '''Load factor''' || 60% || 24% || 18% (1 + 2 & 4)
|}

*This is the largest completed [[hydroelectric]] project in [[India]].<ref name="Largest_hydroelectric_power_plant_in_India"/>
*The water used for generation of electricity joins the [[Arabian Sea]] near [[Chiplun]] while the water which discharges through the [[spillway]]s of the dam in [[monsoon season]] joins the [[Bay of Bengal]] through the [[Krishna River]].
*The process of double lake tapping was the first of its kind in [[Asia]].<ref name="Lake_tapping"/>
*All the components of the project such as [[power station|powerhouse]]s, head race and tail race tunnels, pressure shafts are constructed underground.
*The modern gas insulated [[switchgear]] system is used in 4th stage of the project.

==Future plans==
To utilise more water from the [[Shivsagar Lake|Shivasagar]] reservoir, another dam foot powerhouse is being constructed on the [[river|left bank]] of the dam. This [[power station|powerhouse]] will employ a [[pumped storage]] scheme. Also lake tapping is proposed for the intake system.

==Tourism==
The impounded water of the [[Koyna Dam]] though has submerged a significant amount of [[rain forest]] of the [[Western Ghats]], it has helped a lot to the surrounding forest by supplying water all round the year. Hence a wide [[biodiversity]] of plants and animals is observed in the evergreen forest surrounding the reservoir area.

===Koyna Wildlife Sanctuary===
[[File:Surge Well.jpg|thumb|A part of the evergreen forest in surrounding area of the project]]
{{Main|Koyna Wildlife Sanctuary}}

Koyna Wildlife Sanctuary has dense forests with three major sections, Vasota, Maharkhor and Indavli Met, and the sanctuary is endowed with natural protective boundaries – [[Shivasagar Lake]] on one side, and the slopes of the Western Ghats on both the sides. This protective cover has enabled the emergence of a diverse variety of flora and fauna in the sanctuary. Some of the endangered species of trees found in the sanctuary are ''Dhup'' (''[[Boswellia serrata]]''), ''[[Euphorbia longan]]'', and ''[[Elaeocarpus]]'' spp., apart from many other species of trees. The sanctuary has a diverse variety of fauna including tigers and panthers; gaurs and sambars; barking and mouse deer; pythons and cobras; common [[langur]]s and [[Indian giant squirrel]]s. Many species of birds are found in the sanctuary including brown capped woodpecker; [[Asian fairy bluebird]]; and [[crested goshawk]].

Another attraction of the sanctuary is [[Vasota Fort]] which lies deep in the forest and is located at a height of {{convert|1120|m|ft|0|abbr=on}} above sea level. The legend states that the fort was constructed by [[Malwa]] king [[Bhoja|Raja Bhoja]] in 1170.

=== Nehru Memorial park ===
When the project work was nearing completion, on 10 April 1960, the then [[Prime Minister of India]] Pt. [[Jawaharlal Nehru]] visited the Koyna Project. To commemorate this event a tableau was unveiled at his gracious hands on the right flank hillock of Koyna Dam.
This project came up with an idea of immortalizing this place and this event by constructing a beautiful park and naming it as "Nehru Memorial Park". This park is a major attraction for tourists. An upstream side view of dam is visible from this garden. There is an [[auditorium]] named 'Yashogatha' (meaning: story of success) which relives a small element of the tremendous efforts taken by the engineers and workers associated with project.

=== Ozarde falls ===
[[File:Ozarde Waterfall.jpg|thumb|Ozarda fall]]
Due to the large rainfall in the hilly region surrounding the reservoir, some beautiful falls are generated in the [[monsoon season]]. The largest of them is the Ozarda falls near Navaja village 10 km from Koyna. This is also a major attraction for tourists visiting in monsoon season.

== See also ==
{{stack|{{Portal|India|Water|Renewable energy}}}}
* [[Koyna Dam]]
* [[Koyna Wildlife Sanctuary]]
* [[List of power stations in India]]
* [[List of conventional hydroelectric power stations]]

== References ==
{{Reflist|}}

== External links ==
{{commons category}}
* {{Official website|https://www.koynaproject.org/}}

[[Category:Hydroelectric power stations in Maharashtra]]
[[Category:Underground power stations]]
[[Category:Pumped-storage hydroelectric power stations in India]]
[[Category:1962 establishments in Maharashtra]]
[[Category:Energy infrastructure completed in 1962]]

Koyna Hydroelectric Project - Revision history

AMARENDRA NATH ROY at 14:28, 13 November 2025