Nagarjuna Sagar Dam
|Nagarjuna Sagar Dam|
Nagarjuna Sagar Dam
|Official name||నాగార్జునసాగర్ ఆనకట్ట
Nagarjuna Sagar Dam
|Location||Guntur district, Andhra Pradesh & Nalgonda district, Telangana|
|Construction began||10 December 1955|
|Construction cost||1300 crore rupees|
|Dam and spillways|
|Height||124 metres (407 ft) from river level|
|Length||1,550 metres (5,085 ft)|
|Creates||Nagarjuna Sagar Reservoir|
|Total capacity||11,560,000,000 m3 (9,371,845 acre·ft)|
|Active capacity||5,440,000,000 m3 (4,410,280 acre·ft)|
|Catchment area||215,000 square kilometres (83,000 sq mi)|
|Surface area||285 km2 (110 sq mi)|
|Turbines||1 x 110 MW (150,000 hp) Francis turbines, 7 x 100.8 MW (135,200 hp) reversible Francis turbines|
|Installed capacity||816 MW (1,094,000 hp)|
Nagarjuna Sagar Dam is the world's largest masonry dam. It was built on the Krishna River at Nagarjuna Sagar in between Guntur district of Andhra Pradesh state and Nalgonda district of Telangana state, India. The construction duration of the dam was between the years of 1955 and 1967. The dam created a water reservoir whose capacity is 11,472,000,000 cubic metres (4.051×1011 cu ft). The dam is 490 feet (150 m) tall and 0.99 miles (1.6 km) long with 26 gates which are 42 feet (13 m) wide and 45 feet (14 m) tall. Nagarjuna Sagar was the earliest in the series of large infrastructure projects initiated for the Green Revolution in India; it also is one of the earliest multi-purpose irrigation and hydro-electric projects in India. The dam provides irrigation water to the Prakasam, Guntur, Krishna, Khammam and Nalgonda districts along with electric power to the national grid. It holds second largest reservoir in India after Indira Sagar in Madhya Pradesh followed by Bhakra dam. It is the largest dam in India in terms of Length,1,550 metres.
The proposal to construct a dam to use the excess waters of the Krishna river was planned by the Nizam of Hyderabad and engaged British Engineers in 1903 to irrigate Telangana. Since then, various competing sites in Siddeswaram, Hyderabad and Pulichintala were identified as the most suitable locations for the reservoirs. The perseverance of the Raja Vasireddy Ramagopala Krishna Maheswar Prasad (Raja of Muktyala) who donated 55000 acres of his land and fifty five million British Pounds in wealth paved way for the site identification, design and construction of the dam. Nagarjunasagar was the earliest in the series of "modern temples" taken up to usher in the Green Revolution in India. The dam was built with local know how under the able engineering leadership of K.L. Rao.
Project construction was officially inaugurated by Prime Minister Jawaharlal Nehru on 10 December 1955 and proceeded for the next twelve years. The reservoir water was released into the left and right bank canals by Prime Minister Indira Gandhi in 1967. Construction of the hydropower plant followed, with generation increasing between 1978 and 1985, as additional units came into service.
The construction of the dam submerged an ancient Buddhist settlement, Nagarjunakonda, which was the capital of the Ikshvaku dynasty in the 1st and 2nd centuries, the successors of the Satavahanas in the Eastern Deccan. Excavations here had yielded 30 Buddhist monasteries, as well as art works and inscriptions of great historical importance. In advance of the reservoir's flooding, monuments were dug up and relocated. Some were moved to Nagarjuna's Hill, now an island in the middle of the reservoir. Others were moved to the mainland.
- Catchment Area : 215,000 km2 (83,000 sq mi)
- Location of dam : Nalgonda District and Guntur District
- -+Water spread area at FRL of dam : 285 km2
- Masonry dam
- Spillway of dam : 471 m
- Non-over flow dam : 979 m
- Length of Masonry dam : 1450 m
- Maximum height : 125 m
- Capacity in TMC's : 157.61
- Earth dam
- Total Length of Earth dam : 3414 m
- Maximum height : 128 m
- Power Generation
- Power Units : 1 No. conventional (110 MW capacity), 7 nos Reversible (100 MW capacity)
- Canal power house
- Right side : 3 units 30 MW (each)
- Left side : 2 units 30 MW (each)
Effect of the project
The project benefited farmers in the districts of Nalgonda, Guntur, Krishna, Prakasam and Khammam. The right canal (Jawahar canal) is 203 km (126 mi) long and irrigates 1.113 million acres (4,500 km2) of land. The left canal (Lalbahadur Shastri canal) is 295 km (183 mi) long and irrigates 0.32 million acres (1,300 km2) of land in Nalgonda and Khammam districts of Telangana region. The project transformed the economy of above districts. 52 villages were submersed in water and 24000 people were affected. The relocation of the people was completed by 2007.
The hydroelectric plant has a power generation capacity of 815.6 MW with 8 units (1x110 MW+7x100.8 MW). First unit was commissioned on 7 March 1978 and 8th unit on 24 December 1985. The right canal plant has a power generation capacity of 90 megawatts (120,000 hp)with 3 units of30 megawatts (40,000 hp) each. The left canal plant has a power generation capacity of 60 megawatts (80,000 hp) with 2 units of 30 MW each. The tail pond is under advanced stage of construction to put to use the pumped storage features of 7x100.8 MW units.
Many times, it happens that power generation from the 150 MW canal based units is not optimised when the Nagarjunasagar reservoir is overflowing on its spillway and very less water is required for irrigation from the canals during the monsoon floods. Power generation from canal based hydro units can be optimised by running these units during the flooding period by releasing the water fully in to the canals. The unwanted canal water can be released in to the natural stream when it is crossing the major stream. Thus run off power can be generated from the water going down unutilised in to the river by the canal based power units also.
Also, the water level in the Nagarjunasagar reservoir shall be maintained above the minimum level required for these units in most of the time by releasing water from the upstream Srisailam reservoir to optimise the power generation from the canal based units during dry season.
Tapping dead storage potential
The left and right bank canals sill level is fixed at 490 feet (150 m) MSL to supply irrigation water to two million acres. The unutilized storage capacity is nearly 180 TMC below the canals sill/bed level. Nagarjuna Sagar reservoir also meets the Krishna delta water requirements to the extent of 100 TMC by letting water down stream into the river. Nearly 1.3 million acres (5,300 km2) is irrigated under Krishna Delta Canals. There is a possibility to utilize most of this idle dead storage capacity to store the river flood water further and use as carry over storage. Nearly 150 TMC idle storage up to 380 ft MSL, can be used leaving 30 TMC for silt settlement. This is possible by installing Water Powered Pump (WPP) units at the base of the dam.
WPP units are to be located at the toe of the Nagarjuna Sagar dam with tail water level of 240 ft MSL on either side of the river. The WPP units can be connected below 380 ft MSL level to the reservoir with the technique called under water reservoir / lake tapping. Under water lake tapping method was implemented successfully in Koyna Hydroelectric Project to install additional hydroelectric units without emptying the Koyna reservoir. The cost would be Rs 15 billion for utilizing 150 TMC storage additionally. If the same storage is created under a new reservoir, it would cost not less than Rs 50 billion. Water can be supplied to high level canals at sill 580 ft MSL on both right and left banks without consuming electricity with WPP units to irrigate dry lands further in Nalgonda, Warangal, Khammam, and Guntur districts
- "India: National Register of Large Dams 2009". Central Water Commission. Retrieved 7 August 2011.
- "Nagarjunasagar". Archived from the original on 2007-01-24. Retrieved 2007-01-25.
- "Rao, K.L., Cusecs Candidate: Memoirs of an Engineers hi, 1978, Metropolitan, p. 31"
- The Hindu : Magazine / Focus : Taming the Krishna
- Welcome to APGENCO
- "Taming the Krishna". The Hindu (Chennai, India). 2005-12-18. Retrieved 2007-01-24.
- "Nagarjunakonda". Retrieved 2007-01-25.
- Brief Profile of Nagarjuna Sagar Dam
- Andhra Pradesh Hydel Power plants
- Nagarjuna Sagar Water Powered pump (WPP) Units
- Lake tap
Media related to Nagarjuna Sagar Dam at Wikimedia Commons
- Nagarjuna Sagar - Community Website & Photo Gallery
- Article on the dam in The Hindu
- Tale of Nagarjuna Sagar