Polavaram Project
The Polavaram Project is an under-construction multi-purpose irrigation project on the Godavari River in the Eluru District and East Godavari District in Andhra Pradesh, India. The project has been accorded National Project status by the Central Government of India. Its reservoir back water spreads up to the Dummugudem Anicut, i.e. approx back from Polavaram dam on main river side and approx on the Sabari River side. Thus, back water spreads into parts of Chhattisgarh and Odisha States. Polavaram Hydroelectric Project and National Waterway 4 are under construction on left side of the river. It is located upstream of Sir Arthur Cotton Barrage in Rajamahendravaram City and from Rajahmundry Airport.
History
In July 1941, the first conceptual proposal for the project was mooted by the Madras Presidency. Diwan Bahadur L. Venkatakrishna 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 envisaged cultivation of over two crop seasons through this project, but also planned for a 40 MW hydroelectric plant within the project. The project, when it was conceived in 1946–47, was estimated to cost Rs 129 crore.In 1980, Chief Minister of Andhra Pradesh Tanguturi Anjaiah laid the foundation stone for the Polavaram irrigation project. In the year 2004, Y. S. Rajasekhara Reddy performed bhoomi pooja with the estimation cost of 8,261 cr, and the administrative sanction was accorded for construction of right and left canals at a cost of Rs 1,320 crore and Rs 1,353 crore.
Y. S. Rajasekhara Reddy Congress government completed 33% of project before 2014. The Polavaram Project Authority was constituted by the Union Cabinet in May 2014 and the construction of project head works were taken up. The Naidu government acquired the necessary lands for the right canal by solving court petition issues of farmers who lost their agricultural lands from both districts of West Godavari and Krishna; the Pattiseema Lift Irrigation Project has been launched in order to pump the Godavari river water and sent it to the Krishna river. In June, the state was bifurcated under the Andhra Pradesh Reorganisation Act. In December 2017, it was reported that the project contractor, Transstroy, was seeking a deadline extension and a budget escalation. Transstroy was reported to have its ₹4,300 crore loan turn NPA in July 2015. In January 2018, the state government signed a new contract for the project spillway, spill channel, and stilling basin concrete work with Navayuga Engineering. By June 2018, of the required had been acquired. On June 11, 2018, the Polavaram diaphragm wall was completed, marking a significant milestone in the project construction. On January 7, 2019, the Polavaram project entered the Guinness Book of World Records by pouring 32,100 cubic meters of concrete in 24 hours by Navayuga Engineering. The project beat the existing record of 21,580 cubic meters, which was achieved by Abdul Wahid Bin Shabib, RALS Contracting LLC and Alfa Eng. Consultant, in Dubai between May 18 and 20 in 2017. The Chief minister of Andhra Pradesh N. Chandrababu Naidu unveiled the first crest gate on 24 December 2018.
File:Nitin Gadkari addressing the media during his visit to Polavaram project site, at Polovaram, West Godavari District of Andhra Pradesh.JPG|thumb|left|250px|Union Minister of Water Resources Nitin Gadkari, along with Andhra Pradesh Chief Minister N. Chandrababu Naidu, Irrigation Minister Devineni Uma Maheswara Rao, and other officials, addressing the media at the Polavaram project site in 2018.
Progress
Purpose
The 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 at an estimated cost of US$120 billion, would be the largest 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 underused water from Godavari River flowed into the Bay of Bengal. But as of 2017, over 3000 tmcft are drained unused into the Bay of Bengal. Based on the estimated water requirements in 2025, the Study recommended that sizable surplus water was to be transferred from the Godavari River basin to the Krishna River basin.The live storage available above 140 ft msl moderates substantially the flood wave of probable maximum flood to reduce the effect of PMF downstream of Polavaram dam. The capacity of the right and left canals are 17,500 cusecs each. During the monsoon months, nearly 360 tmcft of Godavari flood flows at the rate of 3 tmcft per day can be diverted into the canals. At least another 190 tmcft water from the water stored in the Polavaram reservoir along with lean season inflows, excluding the downstream Godavari Delta water requirements, can be diverted into these canals. Thus the total annual water use capacity of the Polavaram project is 550 tmcft. The water storage available in Sileru river basin is used as usual for the full water requirements of the Godavari Delta when natural inflows in the river falls short of its requirements and minimum environmental flows.
The hydropower plant will generate 2.29 billion kWh of renewable electricity annually. Polavaram Reservoir will also create the potential to install nearly 158,000 MW of pumped-storage hydroelectric plants in the future.
Alternate site
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. Due to the depth of the bedrock at this dam site, the dam project was not found economical to take up. However, a lucrative alternate site is located upstream of the Polavaram site where the river passes through deep gorges of Papi hill range. The width of river is about in the rocky gorge stretch. Thirty years back, this alternative was found to be technologically challenging due to the need to connect the reservoir with the irrigation canals via tunnels across the ghat area. Also, it would need a costly underground hydroelectric station, compared to the riverbed-based hydroelectric station. When the project was actually taken up in the year 2004, the old finalised designs at Polavaram site were adopted without re-examining the latest cost of the upstream alternate site in view of state-of-the-art construction technology of tunnels and underground hydroelectric stations. The progress up to the year 2012 in construction of dam structures and the hydroelectric station is almost nil. The alternate site located in the gorge stretch still merits re-examination to reduce the ever-increasing cost of Polavaram dam.The spillway and non-overflow dam are founded on Khondalite bedrock in the 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 sites.
Technical details
The project reservoir has a live storage of 75.2 tmcft above the canal's full supply level of MSL and a gross storage of 194 tmcft, thereby enabling irrigation of in Krishna, West Godavari, Eluru district, East Godavari, Visakhapatnam, Vizianagaram, and Srikakulam districts of Andhra Pradesh. The silt-free dead storage water of nearly 100 tmcft above the spillway crest level, MSL, can also be used in downstream lift irrigation projects and Dowleswaram Barrage during the summer months. Chintalapudi lift / Jalleru project will supply water to irrigate most of the highlands in Eluru district and NTR districts, including the existing command area under Nagarjunasagar left canal in AP, facilitating 40 tmcft of saved Krishna river water for diversion to Rayalaseema from Srisailam reservoir. GoAP announced the decision to construct the Purushothapatnam Lift Irrigation Scheme to transfer water at the rate of 3,500 cusecs to the Polavaram left bank canal and further pumping at the rate of 1,400 cusecs to Yeleru reservoir for feeding Yeleru canal, which is supplying water to Vizag city. Uttarandhra Sujala Sravanthi lift irrigation scheme will also use the Godavari water and a sanction of ₹2,114 crores was made in 2017 for its first phase. 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 floodgates of the Polavaram dam. So these lift schemes are not only for operation for a few years until the Polavaram dam is constructed but also operate every year for at least four months during the dry season after construction of Polavaram dam. Nearly 80 tmcft of live storage capacity available to Andhra Pradesh in Sileru river basin can also augment the water availability to the Polavaram project during the dry season.The dam construction involves the 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 the first of its kind in India. The purpose of diaphragm wall is to stabilize the riverbed to withstanding the water pressure across the dam. The project would constitute an earth-and-rock-fill dam long, a spillway long with 48 vents to enable discharge of of water. The spillway is located on the right bank of the river, for which an approach and spill channels nearly 5.5 km long and 1.0 km wide is envisaged involving nearly 70 million cubic meters of excavation which, is nearly 2/3 of the project's total earthwork. The maximum flood level at Polavaram is MSL and lowest water level is MSL. Two cofferdams are planned, one up to MSL, to facilitate a faster pace of work on the dam to complete the first phase of the project by June 2018. With the cofferdams' inclusion and the bed level of the approach and discharge canals of the spillway increased to MSL, the spillway-related rock excavation is reduced by 70%, leading to substantial cost reduction in the project's headworks cost. Ultimately, the material of cofferdams would be excavated and reused for the peripheral portions of the main earth-and-rock-fill dam. On the left side of the river, 12 water turbines, each having an 80 Megawatt capacity, were to be installed. Without removing the upper and lower coffer dams after the construction of the ECRF dam, the 960 MW hydropower plant cannot be commissioned, as they are blocking the water passages of the powerhouse. The right canal connecting to Krishna River upstream of Prakasam Barrage discharges at the headworks, and the left canal discharges of water.
Indira Dummugudem lift irrigation scheme starting at is under construction to supply irrigation water for 200,000 acres in Khammam, Krishna, Eluru, and West Godavari districts, drawing Godavari River water from the backwaters of Polavaram reservoir. This is a joint project between Andhra Pradesh and Telangana states. This project was shelved and merged with another project by the Telangana state.