Inchampalli-Nagarjunasagar Link

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Godavari (Inchampalli) - Krishna (Nagarjunasagar) Link forms a part of the scheme of transfer of surplus waters of Mahanadi and Godavari rivers to the deficit basins of Krishna, Pennar, Cauvery and Vaigai. The link scheme is an important part of various proposals under the Peninsular Rivers Development Component of National Perspective Plan.
This link canal proposes to irrigate the command areas proposed under Kakatiya canal Stage – II of Sri Ram Sagar Project, and Srisailam left bank canal. A major portion of the surplus quantity diverted is to be discharged into Nagarjunasagar reservoir for further diversion to water short Pennar and Cauvery basins etc. after meeting the entire deficit of Krishna basin as envisaged in the Peninsular Rivers Development Component of the NPP.

Godavari (Inchampalli) – Krishna (Nagarjunasagar) link canal project comprises of the following components.

  • A storage reservoir on river Godavari at Inchampalli with F.R.L. 112.77 m, gross storage capacity of 10374 Mm3 , live storage capacity of 4285 Mm3 and minimum draw down level of 106.98 m and two other intermediate reservoirs viz. Peddavagu & Tummalagutta.
  • A link canal of length 299.256 km (including a tunnel of 9.150 km length) off-taking from the foreshore of the Inchampalli reservoir and out-falling into the existing Nagarjunasagar reservoir via Musi reservoir.

The link canal further off-takes from the Musi reservoir with FSL of 187.300 m. The head available at Musi reservoir is about 9.70 m which is adequate for generation of power in the form of mini hydel scheme (canal power house). Hence, a canal powerhouse has been proposed at the canal off-take from Musi reservoir for generation of power by utilising the head of about 9.700 m, available between the reservoir FRL(Full Reservoir Level) and the canal FSL. The water to be drawn from the Musi reservoir for onward transmission to the link canal will be guided through this powerhouse to generate power. It is proposed to install 15 units of 5 MW bulb turbines with one standby unit. The effective installed capacity of the powerhouse will be 70 MW. An approach channel of 3 km long from the reservoir to the powerhouse is proposed to suit the topography at the Musi head works. The water after power generation will be released to the main canal through a tailrace channel.

The link canal runs in moderate lifts and by gravity in its initial stages upto RD 60.500 km. The total lift involved is about 107 m in four stages: at RDs 0.000, 18.000, 26.500 and 60.500 kms are 35, 38, 23 and 11 m respectively. The link canal is designed as a lined canal of trapezoidal section with bottom rounded corners. The maximum carrying capacity of the canal is 1090 cumecs with corresponding cross section of 109.60 m bed width and 6.75 m full supply depth. The canal passes mostly through agricultural fields except in the initial reaches of about 35 kms where it is running through dense reserved forests.

A quantum of 16426 Mm3 of water is planned for diversion through this canal. Out of this, 1664 Mm3 (1427 + 104 + 133) is to be used for irrigation, domestic and industrial uses in the command area enroute and 562 Mm3 will be lost in transmission and the balance 14200 Mm3 will reach river Krishna at the existing Nagarjunasagar reservoir.

The water received at the tail end of the link canal will be stored in the existing Nagarjunasagar reservoir on the Krishna river. The gross and live storage capacities of the reservoir at F.R.L. 179.83 m are 11560 Mm3 and 5733 Mm3 respectively. The dead storage level is 149.050 m. Part of water so diverted to Nagarjunasagar reservoir will be used in meeting the entire deficit in Krishna basin by meeting the requirement of Nagarjunasagar Project (NSRBC & NSLBC). Balance water is proposed to be further diverted to Pennar, Cauvery and Vaigai river basins through a network of link canals.

This link will provide irrigation to the command areas under Kakatiya canal Stage – II of Sri Ram Sagar Project and Srisailam left bank canal under Nagarjunasagar project in the districts of Khammam, Warangal and Nalgonda. A lead canal is proposed to transfer water from Inchampalli – Nagarjunasagar link canal to Kakatiya canal Stage–II. The lead canal takes-off from the link canal at RD 97.500 km after traversing a distance of 21.85 km it outfalls into the Kakatiya canal (Stage–I) at RD 260.700 km.

The command area of 178055 ha proposed under Kakatiya Canal Stage – II of Sri Ram Sagar Project by the Govt. of Andhra Pradesh will be taken over by the link canal from the water short existing Sri Ram Sagar Project and a quantity of 684 Mm3 will be utilised from the link canal. Also an area of 109250 ha of ongoing Srisailam Left Bank Canal taking off from Nagarjunasagar foreshore will be commanded utilising 743 Mm3 of water through the link canal, thereby reducing the pumping costs (at Alimineti Madhav Reddy Lift Irrigation Scheme) as planned by the Govt. of Andhra Pradesh.

Apart from irrigation, it is also proposed to provide water for future domestic and industrial requirements in the command area as well as all the townships along the link canal on either side within a distance of 20 kms. The quantity to meet the above domestic and industrial requirements projected to 2050 AD is estimated to be around 104 Mm3 and 133 Mm3 respectively.

Power House with an installed capacity of 975 MW at the toe of the dam, planned under the Inchampalli Joint Project is proposed to be modified as a pumped storage scheme with reversible turbines for generation of peaking power. Since the water cannot be diverted to Nagarjunasagar reservoir by gravity owing to the topography, a series of pumping stations in four stages have been proposed along the canal in its head reaches for lifting the water to a static head of about 107 m in order to transfer the water to endemically needy areas.

Direct benefits from the link project due to irrigation, domestic and industrial water supplies enroute the canal are estimated to be Rs. 1217 crore per annum. The capital cost of this project is Rs. 26289 crore at 2003-04 price level. Based on the quantum of water consumed en route the canal, apportioned cost is worked out to be Rs.2754 crore and the annual cost to be Rs. 541 crore. The Benefit Cost Ratio works out to 2.25 and the Internal Rate of Return with and without distributional and employment effect are assessed as 17.86% and 14.81% respectively. The B.C. ratio may undergo a change if the cost of transferring surplus waters from the upstream link canal is also considered.

Source:National Water Development Agency (NWDA)

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