Tungabhadra Dam

In 1860, Sir Arthur Cotton of Madras Presidency originally conceived the Tungabhadra project. His proposals were further modified and developed subsequently, evolving it into a joint scheme with the Kingdom of Hyderabad. N. Paramseswaran Pillai accordingly revised the scheme in 1933. In 1940, Madras ordered a detailed investigation of the scheme. Based on the agreements made, an examination of a number of alternatives was conducted by L. Venkata Krishna Iyer, the then Superintending Engineer, Bellary, and F. M. Dowley, Chief Engineer, both from the kingdom. In 1942, further detailed investigations of the project were done by M. S. Thirumale Iyengar from the presidency. The report he thus submitted was accepted by the Government of Madras with certain modifications fixing the sill level at RL 1550 ft. The June 1944 agreement between Madras and Hyderabad enabled the two governments to finally begin the construction of the Tungabhadra project.

The Tungabhadra Project was formally inaugurated by laying foundation stones on 28 February 1945 by Nawab Azam Jah, the Prince of Berar, on the left side of the dam and by the Baron Sir Arthur Hope, Governor of Madras, on the right. However, owing to India's freedom in 1947, the explosive political unrest in Hyderabad in 1948, and due to differences of opinion in certain technical matters, much headway could not be made until January 1949. Madras and Hyderabad engineers were sharply divided on:

1. The nature of mortar to be used in the construction of the dam,
2. The design of spillway,
3. The design of overflow and non-overflow sections of the dam, and
4. The contraction joints

These differences were referred to a board of engineers chaired by Sir M. Visveswaraya, the former prime minister of the Kingdom of Mysore and the chief architect of the Krishnaraja Sagar Dam in Mysore.

Excavation of the riverbed started in 1947 and masonry construction on 15 April 1949. With the help of a cofferdam constructed earlier, the foundation excavation was continued even during the floods season. The riverbed portion was tackled during the summer of 1950 (1949–50). Masonry in the riverbed blocks started in the 1951, followed by vigorous progress.

By 1952, the canals reached an advance and decisive stage of the construction. On 30 January 1952, the Government of Madras ordered (GO 382) an investigation of the high-level canal. On 15 November 1952, detailed estimates were prepared up to Mile 79/2 covering the reach just before Chinna-Hagari.

A major portion of the construction of the dam was over by the middle of 1953. The low-level canal excavation up to Mile 173 was completed by 1953. The water was led down into the canal on 1 July 1953 to derive partial benefits. Acquisition of lands and villages and rehabilitation of the displaced population from the water spread area of up to 1630 ft contour were completed by September 1953. About 90 villages and 54,452 people were affected. By October 1953, the structures were completed, substantially enabling the storage of water in the reservoir up to +1613.00 ft.

In 1954, an investigation of the remaining portion of canal from Mile 79/2 to Mile116/0 was completed and a project report was submitted to the Government of India for approval. The proposals were further reviewed and a final project report was submitted to the Planning Commission for clearance, estimating the costs at Rs. 21.90 crores.

Power canal works started in June 1954 and were completed by May 1957. The reservoir circle was entrusted with the construction of canal works in 1956. The balance portion of the low-level canal from Mile 173 to 203 that had to be excavated by the Government of Andhra Pradesh was completed by the end of March 1957. The balance of the works, namely the spillway, bridge road on the top of the dam, construction of utility tower, manufacture of crest grates for storing water up to 1633 level were completed in all respects by the end of June 1958. In 1958, water was let out up to and inclusive of Distributory 42 to serve an area of about 1.80 lakh acres. The cost of dam and appurtenant works was Rs. 16.96 crores.

The dam forms the biggest reservoir across the Tungabhadra River with 101 tmcft of gross storage capacity at full reservoir level (FRL) 498 m MSL, and a water spread area of 378 square kilometres.[2] The dam is 49.39 meters high above its deepest foundation.[3] The left canals emanating from the reservoir supply water for irrigation to the entirety of Karnataka. The two right bank canals—one at low level and the other at high level—serve irrigation for Karnataka and the Rayalaseema region of Andhra Pradesh. Hydropower units are installed on canal drops. The reservoir water is used to supply water to downstream the barrages Rajolibanda and Sunkesula located on the Tungabhadra River. The identified water use from the project is 220 tmcft by the Krishna Water Disputes Tribunal. Karnataka and Andhra Pradesh got 151 tmcft and 79 tmcft water use entitlement respectively.[4]

In 1954, the Central Water Commission advised the participating states to execute the water harness project in two stages. The first stage included an unlined canal with a head discharge of 2300 cusecs and the second stage a lined canal with 4000 cusecs head discharge.

The first stage scheme was inaugurated by Sir Chandulal Madhavlal Trivedi, Governor of Andhra Pradesh, on 2 October 1956 under the presidency of K. Manjappa, Chief Minister of Mysore. The first stage was almost completed by June 1966 at a cost of Rs. 920 lakhs: the canal was commissioned by releasing water for irrigation on 27 July 1966.

The second stage was approved in June 1967 for Rs. 385 lakhs. The works were completed by June 1970 at an estimated cost of Rs. 487 lakhs.

The Tungabhadra Hydroelectric Scheme was undertaken in the composite Madras State in the post-war period under the first five-year plan in the year 1950. The work on the project was taken up in 1951 but no appreciable progress was achieved till the end of 1953. The powerplant commission was then divided into two stages.

During 1957, two units of 9 MW each at the dam's powerhouse were installed and, in 1958, two units of 9MW each were installed at the powerhouse in Hampi. With this, the first stage of the scheme was completed in 1958. Power generation of this stage was commissioned during 1960–61.[5]

The second stage under this scheme was taken up in 1959. The plant erection started in the dam's powerhouse in November 1962 and in the powerhouse in Hampi in February 1963. Units 3 and 4 of both powerhouses started functioning by June 1964. The left side the powerhouses are designed to accommodate 4 units of 9MW each.