Polavaram Project is a multi-purpose irrigation project which has been accorded national project status by the central government. This dam across the Godavari River is under construction located in West Godavari District and East Godavari District in Andhra Pradesh state and its reservoir spreads in parts of Chhattisgarh and Odisha States also.
Polavaram called as "Life Line Of Andhra Pradesh". National River-Linking Project, which works under the aegis of the Indian Ministry of Water Resources, was designed to overcome the deficit in water in the country. As a part of this plan, surplus water from the Himalayan rivers is to be transferred to the peninsular rivers of India. This exercise, with a combined network of 30 river-links and a total length of 14,900 kilometres (9,300 mi) at an estimated cost of US$120 billion (in 1999), would be the largest ever infrastructure project in the world. In this project's case, the Godavari river basin is considered as a surplus one, while the Krishna River basin is considered to be a deficit one. As of 2008, 644 tmcft of underutilised water from Godavari River flowed into the Bay of Bengal.Based on the estimated water requirements in 2025, the Study recommended that sizeable surplus water was to be transferred from the Godavari River basin to the Krishna River basin.
In July 1941, the first conceptual proposal for the project came from the erstwhile Madras Presidency. Later Diwan Bahadur L. Venkata Krishna Iyer, then chief engineer in the Presidency's irrigation department, made the first survey of the project site and made a definitive proposal for a reservoir at Polavaram. Sri Iyer not only visioned cultivation of 350,000 acres (140,000 ha) over two crop seasons through this project, but also planned for a 40 megawatt hydroelectric plant within the project. The entire project was estimated to cost about 65 million (US$960,000). The old final designs of Polavaram dam was planned at full reservoir level (FRL) 208 ft MSL with 836 tmcft gross storage capacity and 150 MW hydroelectric plant. By 1946–47, the estimated cost rose to 1.29 billion. It was named the "Ramapada Sagar Project" since the backwaters of the reservoir would touch the Lord Rama temple at Bhadrachalam. In the old finalised project design by Dr. K.L. Rao, the right bank canal of Polavaram project was extended to south of Krishna River to serve irrigation needs in old Guntur district by envisaging aqueduct across the Krishna River.
The project presently under construction is scaled down to FRL 150 ft MSL. The project cost estimate in 2004 stood at 86.21 billion.
In 1980, then Chief Minister of Andhra Pradesh T. Anjaiah laid the foundation stone for the project. However the project stayed idle until 2004 when the Y. S. Rajasekhara Reddy-led government came to power. In 2004, the Government of Andhra Pradesh sanctioned 13.2 billion (US$190 million) for the project. Soon after, tenders were issued for the commensurate worth of services for the right canal of the project. For the left canal, another 13.53 billion were sanctioned by the state government.
The dam could not be taken up for construction during the last century on techno economical grounds. The proposed dam site at Polavaram is located where the river emerges from the last range of the Eastern Ghats into plains covered with deep alluvial sandy strata. At Polavaram, the river width is about 1500 m. In view of large depth of excavation which is more than 30 m deep, to reach hard rock at this dam site, the dam project was not found economical to take up. However a lucrative alternate site is feasible located in upstream of Polavaram site where the river passes through deep gorges of Papi hill range. The width of river is about 300 m only in the rocky gorge stretch. Thirty years back, this alternative was found technologically challenging task to connect the reservoir with the irrigation canals via tunnels across the ghat area. Also costly underground hydro electric station is mandated compared to river bed based hydro electric station. When the project was actually taken up in the year 2004, the old finalised designs at Polavaram site are adopted without re-examining the latest cost of upstream alternate site in view of state of the art construction technology of tunnels and underground hydro electric station. The progress up to the year 2012 in construction of dam structures and the hydro electric station is almost nil. The alternate site located in the gorge stretch is still worth of re-examination to reduce the ever increasing cost of Polavaran dam.
The spillway and non-overflow dam are founded on Khondalite bed rock in Polavaram Project.Khondalites, which are feldspar-rich, often contain soft graphite, hard garnet, etc. in addition to other minerals. Khondalites are highly weathered and hence unsuitable at dam site.
The dam construction involves building of a 1.5 m thick concrete diaphragm wall up to depths from 40 to 120 m below the river bed under the earth dam which is first of its kind in India. The purpose of diaphragm wall is to secure the river bed stability for withstanding the water pressure across the dam.
The project reservoir has live storage 75.2 tmcft at canal's full supply level of 41.15 m MSL and gross storage 194 tmcft thereby enabling irrigation of 23,20,000 acre (including stabilisation of existing irrigated lands) in Krishna, West Godavari, East Godavari, Visakhapatnam, Vizianagaram and Srikakulam districts of Andhra Pradesh. The silt free dead storage water of nearly 100 tmcft up to spillway crest level 24.5 m MSL, can also be used in downstream lift irrigation projects (Pattiseema lift, Tadipudi lift, Thorrigedda lift, Pushkara lift, Venkatanagaram lift, Chagalnadu lift, etc.) and Dowleswaram Barrage during the summer months. All the irrigated lands under these lift schemes can be supplied from Polavaram right and left canals by gravity flow when Polavaram reservoir level is above the canal's full supply level of 41.15 m MSL. However these lift stations are to be operated every year during the dry season to draw water from the substantial dead storage available behind the flood gates of the Polavaram dam. So these lift schemes are not for few years operation till the Polavaram dam is constructed but for permanent operation regularly for at least four months in every year.
The project would constitute an earth-cum-rock fill dam of 2,310 metres (7,580 ft) length, spillway of 907 metres (2,976 ft) with 44 vents to enable discharge of 3,600,000 cu ft/s (100,000 m3/s) of water. To its left, 12 water turbines, each having 80 megawatt capacity, were to be installed. The right canal connecting to Krishna River in the upstream of Prakasam Barrage (173 kilometres (107 mi) long) discharges 17,500 cu ft/s (500 m3/s) at head works and left canal (182 kilometres (113 mi) long) discharges 17,500 cu ft/s (500 m3/s) of water.
Indira Dummugudem lift irrigation scheme starting at 17°33′49″N 81°14′49″E is under construction to supply irrigation water for 200,000 acres in Khammam, Krishna and West Godavari districts drawing Godavari River water from the back waters of Polavaram reservoir. This is a joint project between Andhra Pradesh and Telangana states.
Interstate water sharing
As per the inter state agreements dated 4 August 1978 (page 89) and 29 January 1979 (page 101) with Andhra Pradesh, the states of Karnataka and Maharashtra are entitled to use 21 tmcft and 14 tmcft respectively out of the unallocated waters of Krishna river when Godavari water transferred in a year by Polavaram right bank canal from Polavaram reservoir to Prakasam barrage across Krishna river is not exceeding 80 tmcft at 75% dependability. When additional Godavari water exceeding 80 tmcft is transferred from Polavaram reservoir, Karnataka and Maharashtra are entitled with additional water from the unallocated Krishna river waters in the same proportion provided all the following conditions are satisfied.
The additional Godavari water from Polavaram project should be transferred to the Krishna river in the upstream of Prakasam barrage. Such additional Godavari water quantity to be shared is decided based on 75% dependability.
The transferred water shall also displace the water discharges from Nagarjuna Sagar Dam for the Krishna delta requirements. Krishna delta is the area located down stream of Prakasam barrage which is part of Krishna basin. It does not include adjacent coastal river basins which are being irrigated by the Krishna waters from the Prakasam barrage.
Thus Andhra Pradesh is entitled to transfer Godavari water in excess of 80 tmcft in three out of four years (below 75% dependability) reducing the water releases from Nagarjunasagar dam for Krishna delta requirements and need not share water with other states beyond 80 tmcft.
The above interstate water sharing agreement does not cover the Godavari water transferred to Krishna river which is not displacing the water releases from the Nagarjunasagar dam for the requirements of Krishna delta. Thus Andhra Pradesh need not share with other states the water transferred via Krishna river or any reservoir located on Krishna river for the water needs of any of its area (including Krishna basin) other than Krishna delta.
A barrage would be constructed on Krishna river located near 16°34′41″N 80°24′43″E in the upstream of Prakasam barrage with FRL at 24m MSL to receive Godavari water diverted from Polavaram dam. This barrage would also enable a new road / bridge link diverting south bound road traffic from Hyderabad side on NH9 to Guntur district without touching Vijayawada city
A low level lift canal from the Krishna river located near 16°42′50″N 80°08′24″E at 20 m MSL in the downstream of Pulichintala dam will be executed to feed Godavari water diverted from Polavaram Dam to some of the existing command area (situated below 60 m MSL) under Nagarjuna Sagar right bank canal to facilitate extension of Nagarjuna Sagar right bank canal connecting to Kandaleru feeder canal / Somasila reservoir for serving irrigation needs in Prakasam, Potti Sriramulu Nellore and Chittur districts including Chennai drinking water supply. A branch from this lift canal is also extended up to Pulichinthala dam (FRL 53.34 m MSL) to store Godavari water in Pulichintala reservoir during drought years and to irrigate low lands along Krishna river up to Pulichintala dam.
Another high level lift canal from above Krishna river location 16°42′50″N 80°08′24″E up to 90 m MSL would be constructed to join Nagarjuna Sagar tail pond (FRL 75 m MSL) irrigating lands en route along Krishna river in Guntur district. During drought years, the water transferred by this canal to Nagarjuna Sagar tail pond is further lifted to Nagarjuna Sagar and Srisailam reservoirs with the existing pumped storage hydro units for use in all the projects receiving water from these reservoirs. This high level lift canal is an alternative to Dummugudem to Sagar lift canal planned in Telangana region which would transfer Godavari river water from Dummugudem to Nagarjuna Sagar tail pond.
Another lift canal drawing water from the Polavaram right bank canal near 16°38′20″N 80°37′53″E at 30 m MSL would be constructed by pumping water to 70 m MSL to irrigate mid lands in Krishna district up to Pulichintala dam. All these pumping stations can be envisaged with high level ponds to incorporate peaking electricity generation capability to achieve multi purpose benefits. Ultimately the Polavaram right bank flood flow canal would be constructed to augment water transfer for meeting shortages in the Krishna river basin and the needed environmental flows downstream of Prakasam barrage. Refer to Google Earth data for more geographical information.
A 25 MW hydropower station can be established utilising Polavaram right bank canal water near Vijayawada city by transferring water via Budameru river and Eluru canal to Prakasam barrage pond. Refer Talk Page
A lift canal starting at 175m MSL receiving water from Polavaram reservoir, would irrigate most of the high lands in West Godavari and Krishna districts. This canal originating from a new balancing reservoir located near 17°14′43″N 81°27′57″E in Eastern Ghats area, will be connected to the Polavaram reservoir with a fore shore pump house to lift the water by 150 meters to feed in to a Fifteen (15) km long tunnel across the Eastern Ghats. The balancing reservoir would also serve as the upper pond for using the pumping station as peaking hydro power station.
Off shore fresh water reservoir
An off shore fresh water storage reservoir of capacity 700 Tmcft could be constructed along the sea coast of Chirala to store the Krishna & Godavari river flood waters for creating additional irrigated area in Prakasam, Potti Sriramulu Nellore, Cudapah, Chittoor districts and further transfer of Godavari water to Kavery river in Tamil Nadu under interstate rivers linking project. This project is similar to Kalpasar Project to store Narmada River water in Gulf of Khambhat sea.
Fresh water reservoirs can be established in the shallow sea area by constructing sea dikes / bunds/ Causeway up to the depth of 20 meters from the coast line. Water can be pumped from this artificial fresh water lagoon throughout the year for meeting agriculture, etc. needs. Also top surface of this dike can be used as coastal road & rail rout. The proposed dikes would be similar to the land reclamation of North Sea area called Delta Works in Netherlands or Saemangeum Seawall in South Korea. This project with 20 meters average depth is lesser challenging technically when compared to Saemangeum Seawall project which is having 36 meters average water depth.
The sea area up to 20 meters depth adjacent to coast line between the locations (near 15°46′31″N 80°48′45″E) where southern branch of the Krishna river is joining the sea and the mouth of the Gundlakamma River (near 15°33′23″N 80°13′37″E), is highly suitable for creating the off shore fresh water reservoir. The width of the sea up to 20 m depth is nearly 30 km wide and the required length of the sea dikes is nearly 70 km. The area of the off shore reservoir would be nearly 2000 km2. A barrage would be constructed across the Krishna river (near 16°04′41″N 80°52′49″E) near Mopidevi town. A flood canal (25 km long) from this barrage would feed Krishna river water to the off shore water reservoir. A flood canal from Dowleswaram Barrage would also connect by gravity to this proposed barrage to feed Godavari water to the off shore fresh water reservoir. The off shore dike extending up to 8 m msl high, would also reduce drastically the cyclone damage and flooding in Chirala, Bapatla and Nizampatnam coastal areas. It would also greatly improve the irrigated coastal lands drainage in Guntur and Prakasam districts. The sea dike can also serve as an access way to a major deep sea port which can be located on the deep sea side of the 70 km long dike.Locks arrangement (similar to Panama canal) would be provided for the movement of ships from the open sea in to the fresh water reservoir. This reservoir area can also be used for shipping, ship breaking, ship building, etc. purposes. Part of the fresh water reservoir area can also be used for locating floating solar power plants to generate the needed water pumping power. Nearly 1100 tmcft water of Godavari and Krishna flood waters can be utilised for irrigation, etc requirements with this off shore fresh water reservoir.
Vast lands in the districts of Prakasam, Nellore, Cudapah and Chittoor are drought prone and do not have adequate water sources for irrigating the dry lands. Water from this off shore fresh water reservoir would be pumped uplands to Ramathirtham water tank (near 15°37′37″N 79°48′47″E) which is at 85 m msl. From this water tank, dry lands in Prakasam and Nellore districts up to Tamil Nadu boarder can be brought under irrigation by gravity canals. From this canal, water would be further pumped to the uplands of Chittoor and Cudapah districts up to 600 m msl across the Seshachalam mountains. This canal would also be extended with lifts to transfer 350 tmcft water up to the Kavery river in Tamil Nadu state during South-west monsoon period. The total cost to Andhra Pradesh state would be less than Rs 300 billions which is nearly Rs 1,00,000 per acre of irrigated land.