Nagarjuna Sagar Dam is a masonry dam across the Krishna River at Nagarjuna Sagar, which straddles the border between Nalgonda district in Telangana, and Palnadu district in Andhra Pradesh. The dam provides irrigation water to the districts of Nalgonda, Suryapet, Khammam, Bhadradri Kothagudem districts of Telangana and also Krishna, Guntur, Palnadu,, Prakasam, and parts of West Godavari districts of Andhra Pradesh. It is also a source of electricity generation for the national grid.
Constructed between 1955 and 1967, the dam created a water reservoir with gross storage capacity of , its effective capacity is 6.92 cubic km or 244.41 Tmcft. The dam is tall from its deepest foundation and long with 26 flood gates which are wide and tall. It is jointly operated by Andhra Pradesh and Telangana.
Nagarjuna Sagar Dam was the first in a series of major infrastructure projects termed as "modern temples" initiated for achieving the Green Revolution in India. It is also one of the earliest multi-purpose irrigation and hydroelectric projects in India.
History The Nizam made the British engineers begin the survey work for this dam across the Krishna River in the year 1903.
The project's construction was officially inaugurated by Prime Minister Jawaharlal Nehru on 10 December 1955 and proceeded for the next twelve years. Raja Vasireddy Ramagopala Krishna Maheswara Prasad, popularly known as the late Muktyala Raja, was instrumental in the construction of the Nagarjuna Sagar Dam through active political lobbying and the donation of one hundred and ten million GBP in 1952 and of land. It was the tallest masonry dam in the world at that time, built entirely with local know-how under the engineering leadership of Kanuri Lakshmana Rao.
The reservoir water was released into the left and right bank canals by Prime Minister Indira Gandhi on 4 August 1967. Construction of the hydroelectric power plant followed, with power generation increasing between 1978 and 1985 as additional units came into service. In 2015, the diamond jubilee celebrations of the project's inauguration were held, alluding to the prosperity the dam has ushered into the region.
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 and the successors of the Satavahanas in the Eastern Deccan. Excavations yielded 30 Buddhist monasteries as well as artwork and inscriptions of historical importance. Prior to the reservoir's flooding, monuments were dug up and relocated. Some were moved to Nagarjunakonda, now an island in the middle of the reservoir. Others were moved to the nearby mainland village of Anupu.
The site of the dam was selected in 2022 to be developed as part of the UDAN scheme. The selection calls for the development of a water aerodrome at the site.
Data
Catchment Area : Full Reservoir Level (FRL): msl Water spread area at FRL: 285 km2 Gross storage capacity at FRL: 312 TMC MDDL of river sluices: msl Masonry dam Spillway of dam : 471 m Non-over flow dam : 979 m Length of Masonry dam : 1450 m Maximum height : 125 m 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)
Utilisation Irrigation The right canal (Jawahar canal) is long with a maximum 311.5 cumecs capacity and irrigates of land in Guntur and Prakasam districts. The left canal (Lalbahadur Shastri canal) is long with maximum 311.5 cumecs capacity and irrigates of land in Nalgonda, Suryapet, Krishna, West Godavari and Khammam districts. The project transformed the economy of above districts. 54 villages (48 in Nalgonda and 6 in Guntur) were submersed in water and 24,000 people were affected. The relocation of the people was completed by 2007.
Alimineti Madhava Reddy lift irrigation canal draws water from the Nagarjuna Sagar reservoir to irrigate of land in Nalgonda district. This lift scheme with pump house located near Puttamgandi village on the left bank of Krishna river also supplies nearly 20 TMC water for the drinking water needs of Hyderabad city. Nearly 80% of the Nagarjuna Sagar water used in Hyderabad city is available for irrigation use in Nalgonda district in the form of regenerated water/treated sewage water. In addition, the high level flood flow canal drawing water from the left side shore of the reservoir also supplies irrigation water in Nalgonda district.
Power generation The hydroelectric plant has a power generation capacity of 815.6 MW with 8 units (1x110 MW+7x100.8 MW). The first unit was commissioned on 7 March 1978 and the 8th unit on 24 December 1985. The right canal plant has a power generation capacity of 90 MW with 3 units of 30 MW each. The left canal plant has a power generation capacity of 60 MW with 2 units of 30 MW each.Andhra Pradesh Hydel Power plants The tail pond is under advanced stage of construction to put to use the pumped storage features of 7 x 100.8 MW units. And it will be used for irrigation.
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 less water is required for irrigation from the canals during the monsoon floods. Power generation from the canal based hydro units can be optimised by running these units during the flooding period by releasing the water fully into the canals. The unwanted canal water can be released into the natural stream when it is crossing the major stream. Thus run off power can be generated from the water going down unutilised into the river by the canal based power units 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.
Tourism Nagarjunasagar Dam is one of the popular weekend getaways. It is 65 km away from Nalgonda, 97 km away from Suryapet, 146 km away from Guntur, 184 km away from Vijayawada and 152 km away from Hyderabad. Thousands of tourists visit the dam when gates are open in monsoon season (around September / October).
Some of the nearby tourist places of interest include:
Buddhavanam, Telangana Nagarjunakonda in Andhra Pradesh – Has to be reached by a boat from boating point operated by Andhra Pradesh Tourism Development Corporation or TSTDC. Anupu in Andhra Pradesh Ethipothala Falls near Macherla in Andhra Pradesh – The water released from the Nagarjuna Sagar right bank canal, the Chandravanka and Suryavanka streams keeps the water fall live or flowing during the rainy season.
Environmental aspects The artificial lift irrigation based diversion of the river from its natural delta area into Nalgonda district caused erosion of the fluorine-rich volcanic rocks in Nalgonda and contaminated its groundwater supply. It also caused uncertain flows of water into the Krishna River delta area and a shrinkage of the natural wonder "The Kolleru Lake". The use of erosion resistant canals interfered with the natural silting process of a river to the deltas and created long-term ecological issues to the health of the delta lands. Reduced flows into the sea resulted in land salination and sea encroachment of coastal lands in Diviseema. The diversion of Krishna water for 200 km to Hyderabad resulted in massive evaporation losses especially in summer and reduced the size of Krishna River. Many forest preserves along the natural Krishna flow are now categorized as "completely degraded" forest areas. The Krishna River was once home to an ecological wonderland of freshwater fish and aquatic population that is now completely depopulated. The river stopped being navigable since the year of Nagarjuna sagar construction.
Impact on Hyderabad water security Water planning for Hyderabad city started in 1920 with the tapping of Musi River for 15 Mgd. It progressed to tapping Esi (Himayat Sagar 1927 – 11mgd) and Manjira (1965–1993 – Majira and Singur dams) for another additional 130 Mgd. It took a huge leap during 1995–2004 with the commissioning of Krishna river water project (Phases I – III) at a total cost of over ten thousand crores to supply an additional 190Mgd to Hyderabad from Nagarjuna sagar. The project incurs an additional evaporation and leakage loss of 64 Mgd. About 30% of the water naturally flowing to Krishna Delta before 1995 is now diverted to Hyderabad.
Future potential Methods to harness huge dead storage The left and right bank canals sill level is fixed at 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 80 TMC by letting water downstream into the river. Nearly 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 to use as carry over storage. Nearly 150 TMC idle storage up to 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.
It is technically feasible to generate power from the existing hydro turbines from the lower head (75 to 50 meters) by running the turbines below the rated speed. However, major modifications of generators are to be done for running below the rated speed and improve the power generation efficiency.
The sill level of the right bank canal powerhouse (3 x 30 MW) is at MSL. It is possible to draw water from the dead storage by tapping water from the penstocks to feed water to a pump house (3 x 15 MW) located on the left side of the powerhouse. The pump house will have three pump sets each of 5000 cusecs flow capacity to feed into the NS main right bank canal. Power generation from the 90 MW powerhouse is no way affected since its units can only operate when the reservoir level is above 540 ft MSL and the pumping units need to operate below the 508 ft MSL to draw water from the dead storage. Thus nearly 50 TMC water can be utilized during the drought years. The power generation units are normally in operation for five months in a year when the water level is above its minimum draw down level at MSL. During the drought years, the additional water availability is more valuable than the pumping power consumption. The consumed pumping power is compensated fully by the enhanced generation from the 44 MW capacity mini hydel plants located on the downstream canals.
The sill level of river sluices of the dam is at MSL. Nearly 90 TMC of water from the dead storage can be released from the river sluices to the downstream river tail pond during drought periods and further pumped to the adjacent right bank canal by constructing a pumped storage hydroelectric power (PSHP) station. The PSHP station can also be used to transfer Godavari water to the Nagarjuna Sagar reservoir by converting the existing right bank canal powerhouse (3 x 30 MW) into PSHP units to transfer 15,000 cusecs into the Nagarjuna Sagar reservoir. Both PSHPs together can also be used for energy storage purposes on daily basis by consuming surplus power and generating electricity during the peak load hours.
The reservoir dead storage water below the 125 m MSL can be fully released into the downstream river/tail pond through the existing diversion tunnel which was in use to divert the river flow during the dam construction.
Pumped storage hydro power potential Nagarjuna Sagar reservoir, serving as low level reservoir, has potential to install nearly 2,18,000 MW high head pumped storage hydroelectric plants on its right side.