Nagarjuna Sagar Dam built across the Krishna River at Nagarjuna Sagar in Nalgonda district of south Indian state of Telangana is the tallest and largest masonry dam in the world. The dam was constructed as a major part of Indian Green Revolution started in India during early 1960s under the Prime Ministerial leadership of Late Sri Lal Bahadur Shastri.
The construction of the dam was done in between 1955 to 1967 and the complete project cost to the Government of India was INR 132.32 crore. The reservoir of the Nagarjuna Sagar Dam with a total capacity of 408.24 Tmcft (1 Tmcft = 1 Billion cubic ft) is the second largest in India superseded by only the Indirasagar Dam (430 Tmcft) in the state of Madhya Pradesh.
The dam standing 409 ft (124.663 mtr) tall from its deepest foundation and approx 4.86 km (approx 3 miles) long (including the masonry and earthen dam); was and still is the greatest masonry dam in the world.
Today the dam provides the irrigation water along with electricity to at least seven major districts of Telangana and Andhra Pradesh- Prakasham, Krishna, West Godavari and Guntur in Andhra Pradesh; Nalgonda, Khammam and Suryapet in Telangana.
Location of Nagarjuna Sagar Dam
The dam is built across the Krishna River in the town of Nagarjunasagar in Nalgonda district of Telangana state. The town is surrounded with lush greenery and picturesque nature in one of its purest forms. Ironically, the town of Nagarjunasagar derived its name not from the dam; but from the name of a Buddhist scholar and guru named- Acharya Nagarjuna.
Nagarjunasagar is well connected to the major cities of Hyderabad, Mahboobnagar and Nalgonda through a network of roads. The town is only 155 km from the state’s capital Hyderabad. The nearest railway station is at Macherla; at a distance of around 24 km. A good number of state transport buses ply to the Nagarjunasagar every day.
Construction History of Nagarjuna Sagar Dam
The Nagarjuna Sagar Dam was an archeological disaster as it was built sinking almost all the town of Nagarjunakonda; an ancient Buddhist settlement which was also the capital of Ikshvaku dynasty. Lord Rama and Prince Siddhartha are believed to be belonging to Ikshvaku Dynasty founded by king Ikshvaku. The site was once a major education destination of Buddhism with students as far as China and Sri Lanka visiting there.
The archeological disaster struck the place when a major Hydroelectric Dam i.e. Nagarjuna Sagar Dam, was inaugurated on 10th December 1955 by the then Prime Minister of India- Jawaharlal Nehru.
The whole town was sunk by the reservoir leaving only an island at the centre; which is now known as ‘Nagarjunakonda’. Fortunately many of the relics and artifacts were successfully discovered, shifted and restored by dedicated archeologists.
Though the construction of the dam was formally inaugurated in 1955, the idea of a dam’s construction to tap the potential of Krishna River was sown decades back in pre-independence era of India. Nizams of Hyderabad along with British Engineers were the first to envision a dam across Krishna River for tapping its irrigational potential. Subsequently they worked on several locations before finalizing the dam’s location.
As per the survey conducted under the guidance of the Nizam of Hyderabad, only one left canal to the dam was proposed by the Nizam to irrigate the areas under his rule.
However, the government didn’t find the idea feasible without another canal, and sensing the government’s noble intentions, an engineer and former Union Minister for irrigation K.L. Rao a.k.a Kanuru Lakshmana Rao (1902-1986) did an extensive survey of the region, looking for a possible site across Krishna which would make an ideal location for the construction of both the left and right bank canal.
K.L. Rao proposed the present site to the Khosla committee; which was constituted to look into the proposals of a dam across Krishna. The committee visited the location and approved the construction of the dam with both side canals.
Then Prime Minister of India Jawaharlal Nehru immediately sanctioned the project and ordered the Buddhist relics to be shifted to a nearby hill.
Finally the water in both of the left and right canals was released on 4th August 1967 by then Prime Minister Smt. Indira Gandhi. The Nagarjuna Sagar Power House was constructed and augmented between 1978 and 1985; reaching a total installed capacity of 815.6 MW (958.6 MW Including Nagarjuna Sagar Power House and Nagarjuna Sagar Right/Left Bank Canal Power Houses).
From its beginning to its completion spanning for almost 15 years the dam employed nearly 50000 labors, mainly from the town of Hospet in Karnataka who had worked for the successful completion of Tungabhadra Dam.
The dam stands to testify the pain which our labors, engineers and civil servants went through to make the dam a success and a symbol of progressive India. K.L Rao and Mir Jaffer Ali; who were the Chief Engineers for eight years are only a few notable names associated with the project.
The dam also celebrated its Diamond Jubilee in 2015; remembering the prosperity it leads to and the contribution by the engineers, Nizams and the politicians as well.
Construction Details – Civil
When the dam was being built during the initial stage it resembled a giant ant hill with labors carrying construction materials through a complex network of stages. Such mesmerizing was the huge construction of the dam that it is known to inspire the construction of Three Gorges Dam, China.
The dam is a masonry dam relying only on its weight to counter the hydraulic pressure upstream. The masonry dam has a length of 1449.528 mtrs (4756 ft). The length of the spillway and non overflow area of the dam are 470.916 mtrs (1545 ft) and 978.612 mtrs (3211 ft) respectively.
The dam reaches to a height of 124.663 mtrs (409 ft) from its deepest foundation. The maximum base width and top width of the dam are 97.536 mtrs (320 ft) and 8.534 mtrs (28 ft) respectively. The dam also has a 9.373 mtrs broad roadway on top. The top of the dam is 184 mtrs high from the foundation.
The spillway of the dam houses 26 crest gates (45 inches X 44 inches) and two chute sluice vents of size 10 inches X 25 inches; and has a height of 124 mtrs (407 ft ) from the river level. The total spillway discharge capacity of the dam is 17000 cusecs at full gate opening.
The diversion tunnel of the dam also has a discharge capacity of 20000 cusecs at full gate opening. There are two canals located on left and the right side of the dam with water supplied to them by the left and right head sluices respectively.
Masonry Dam is flanked by the earth dam on both sides. The length of the left and right earth dams are 2560.32 mtrs (8400 ft) and 853.44 mtrs (2800 ft) respectively. Maximum height and top width of the earth dam are 25.908 mtrs (85 ft) and 9.296 mtrs respectively. The earthen dam has a top level of above 185.928 mtrs (610 ft).
The Reservoir
The Nagarjuna Sagar Dam reservoir with a total capacity of 408.24 Tmcft (9000000 acre-feet) and the active capacity of 44,10,280 acre-feet is the second largest in India after the Indirasagar Dam, Madhya Pradesh with a total capacity of 430 Tmcft.
It has a total catchment area of 2,14,185 square km and a surface area of 285 square km. The FRL (Full Reservoir Level) and the Minimum Draw Down Level (MDDL) of the reservoir are 590 ft and 510 ft respectively.
Details – Power Houses
There are three separate power houses working as associated entities with the Nagarjuna Sagar Dam.
- The Nagarjuna Sagar Power House
This Power House is located at the toe of the dam and has 8 Turbines- one 100 MW Francis Turbine and 7 X 100.8 MW reversible Francis Turbines; making the Power House’s total installed capacity of 815.6 MW. The turbines in the Power House were subsequently installed between March 1978 and December 1985. The power house uses pumped storage method to generate electricity.
The Turbines were made by BHEL and Melco-Japan. (BHEL is an abbreviation for Bharat Heavy Electricals Limited).
- The Nagarjuna Sagar Left Canal Power House
The left canal power house is located in the hydroelectric basin of east flowing Krishna River and was completed in 1992. The Power House has 2 Kaplan Turbines with individual capacity of 30.6 MW; making the total capacity of the power house 61.2 MW.
- The Nagarjuna Sagar Right Canal Power House
The right canal power house is located on the Right Canal at the toe of Nagarjuna Sagar Dam and was completed in 1990. It has three Kaplan turbines with a capacity of 30.6 MW each; making the plant’s total installed capacity 3 X 30.6 MW= 91.8 MW.
All the three entities combine to make the total capacity of Nagarjuna Sagar Hydroelectric Project to 968.6 MW.
Irrigational Utilization of the Dam
The construction of the dam and canals brought a phenomenal change in the lives of the farmers of the region by supporting rice cultivation in at least seven districts spanning over an area of 40 lakh acres with its Right and Left Bank Canals.
The Right Bank Canal which is also known as Jawahar Canal has a length of 203 km with a capacity of 305 cumecs (cubic meter per second). It irrigates nearly 4520 square kilometers of the land in Prakasham and Guntur districts.
The Left Canal also known as the Lal Bahadur Shastri Canal has a length of 179 km with a capacity of 311.5 cumecs and irrigates an area of around 4080 square kilometers in the districts of Krishna, Khamman, West Godavari, Suryapet and Nalgonda.
The Canals transformed the agriculture economy of the region and the rice produced today is exported to Burma and Sri Lanka. The canals project submerged 48 villages in Nalgonda and 6 in Guntur districts; relocating around 20000 people till 2007.
Nagarjuna Sagar Tail Pond
Nagarjuna Sagar Tail Pond is a multipurpose reservoir located across the Krishna River 21 km downstream of the Nagarjuna Sagar Dam. The Tail Pond has a total capacity of 6 Tmcft. The tail pond was completed in 2014 and plays a significant role in storing the excess water from Nagarjuna Sagar 815.6 MW Power House while in pumping mode and generating full power.
The water stored in the Nagarjuna Sagar tail pond is also used for agriculture and electricity generation of up to 50 MW.
Other Projects on Dam and Their Environmental Impacts
Due to the extensive use of its water for irrigation and dams, the Krishna River is not joining the sea most of the years. The extensive use of the Nagarjuna Sagar Reservoir’s water by the Srisailam Left Bank Lift Irrigation Project in Nalgonda which irrigates nearly 1500 square kilometers of land in Nalgonda has contributed hugely to the loss of water in Krishna; resulting in its termination before the confluence with sea.
The Project also supplies 20 TMC drinking water to the city of Hyderabad. The water level of the Nagarjuna Sagar is also at times maintained by supplying water from the upstream Srisailam Reservoir.
The enormous amount of water diversion of the Krishna River has resulted in the River drying out before reaching the sea and has also caused large scale destruction of forests and natural habitats.
FAQs about Nagarjuna Sagar Dam
Q1) Where is Nagarjuna Sagar Dam located?
Ans- At Nagarjunasagar in Nalgonda district of the state of Telangana.
Q2) Across which river is the dam built?
Ans- The dam is built across the Krishna River.
Q3) What is the distinct feature of the dam?
Ans- It is world’s largest masonry dam.
Q4) When did the foundation of the dam laid?
Ans- The foundation stone of the dam was laid on 10th December 1955.
Q5) When was the construction completed?
Ans- The construction of the dam was completed in 1967.
Q6) What was the total cost of the project?
Ans- Total cost of the project at completion was INR 132.32 crores.
Q7) Which dam surpasses the Nagarjuna Sagar Dam in terms of reservoir capacity?
Ans- Indirasagar Dam in Khandwa district of Madhya Pradesh with a capacity of 430 Tmcft.
Q8) Where from did the town of Nagarjunasagar derive its name?
Ans- The town got its name from a Buddhist scholar and guru – Acharya Nagarjuna.
Q9) What is the distance between Nagarjunasagar and Hyderabad?
Ans- Distance between Nagarjunasagar and Hyderabad is around 155 km.
Q10) What is the nearest railway station to Nagarjunasagar?
Ans- Macherla Railway Station at 24 km.
Q11) Which ancient Buddhist town was submerged by the reservoir?
Ans- The ancient Buddhist town named- Nagarjunakonda.
Q12) Who inaugurated the start of construction work and when?
Ans- Prime Minister Jawaharlal Nehru on 10th December 1955.
Q13) Which Indian Nizam played a crucial role in dam’s preliminary stages?
Ans- Nizam of Hyderabad.
Q14) What is the name of island located in the centre of the reservoir?
Ans- The Island created in the centre of the reservoir is called Nagarjunakonda.
Q15) When was the dam completed?
Ans- The dam was completed in 1967.
Q16) Who inaugurated the canals of the dam?
Ans- The canals were inaugurated by then Prime Minister of India Smt. Indira Gandhi on 4th August 1967.
Q17) How many labors were employed for the dam’s construction?
Ans- Nearly 50000 labors were employed for the dam’s construction over a span of 15 years.
Q18) When were the first and last turbines of the Nagarjuna Sagar Power House installed?
Ans- The first turbine was installed in 1978 and the last in 1985.
Q19) What is the total length of the masonry dam?
Ans- Total length of the masonry dam is 1449.528 mtrs (4756 ft).
Q20) What is the total length of the spillway of the dam?
Ans- The spillway of the dam has a total length of 470.916 mtrs (1545 ft).
Q21) What is the maximum height of the Dam?
Ans- The dam reaches to a height of 124.663 mtrs (409 ft) from its deepest foundation.
Q22) What is the width of the dam on top and base?
Ans- The maximum top width and base width of the dam are 8.534 mtrs (28 ft) and 97.536 mtrs (320 ft) respectively.
Q23) How many gates the spillway has?
Ans- The spillway has 26 Crest Gates and two Sluice Chute vents.
Q24) How much is the overall spillway discharge capacity of the dam?
Ans- The spillway has a total discharge capacity of 17000 cusecs at full gate opening.
Q25) How much is the discharge capacity of the Diversion Tunnel of the dam?
Ans- The diversion tunnel of the dam has a discharge capacity of 20000 cusecs at full gate opening.
Q26) What is the length of Left and Right Earthen Dams?
Ans- The lengths of the Left and Right Earthen Dams are 2560.32 mtrs (8400 ft) and 853.44 mtrs (2800 ft) respectively.
Q27) How much is the total reservoir capacity of the dam?
Ans- The total reservoir capacity is 408.24 Tmcft.
Q28) What is the catchment area of the reservoir?
Ans- The reservoir has a total catchment area of 2,14,185 square kilometers.
Q29) How much is the total surface area of the reservoir?
Ans- The surface area of the reservoir at FRL (Full Reservoir Level) is 285 square kilometers.
Q30) What is the total installed capacity of Nagarjuna Sagar Power House?
Ans- Nagarjuna Sagar Power house has a total installed capacity of 815.6 MW.
Q31) What is the total installed capacity of Left and Right Canal Power Houses?
Ans- Total installed capacity of the Left and Right canal Power House is 61.2 MW and 91.8 MW respectively.
Q32) What is the other name and length of the Right Bank Canal?
Ans- The Right Bank Canal is also known as Jawahar Canal and is 203 km long.
Q33) What is the other name and length of the Left Bank Canal?
Ans- The left Bank Canal is also known as Lal Bahadur Shastri Canal and is 179 Km long.
Q34) Name the districts benefitted by the Right Bank Canal?
Ans- The Right Bank Canal irrigates nearly 4520 square kilometers of the land in Prakasham and Guntur districts.
Q35) Name the districts benefitted by the Left Bank Canal?
Ans- The left Bank Canal irrigates around 4080 square kilometers in the districts of Krishna, Khamman, West Godavari, Suryapet and Nalgonda.
Q36) How many villages were submerged for the Canal Project?
Ans- Total 54 villages – 48 in Nalgonda and 6 in Guntur.
Q37) Where is the Tail Pond of Nagarjuna Sagar Dam located?
Ans- The Tail Pond of the dam is located 21 km downstream of the dam.
Q38) Which projects contributed towards drying out of the Krishna River before it reaches the sea?
Ans- Nagarjuna Sagar, Almaty, Srisailam and Ujjani Dams have stopped the flow of Krishna River before it reaches the delta.