The inauguration of the newly-installed crest gates at the Tungabhadra reservoir on June 25 marks the formal end of a prolonged phase of anxiety, emergency repairs, and large-scale rehabilitation triggered by the washing away of one of the dam’s spillway gates in August 2024.

What began as a sudden structural failure in one bay of the historic reservoir soon grew into a much wider concern over the health of the entire gate system at one of south India’s most important inter-State irrigation projects. The crisis eventually led to a decision to replace all 33 crest gates of the dam, an exercise now completed at a cost of about ₹51 crore.

Back in 1940s and 1950s

The Tungabhadra project, built near Mallapur village in Hosapete taluk of Vijayanagara district in north Karnataka, is an inter-State irrigation project serving Karnataka, Andhra Pradesh and Telangana. Work on the project began in 1945, and water was first released into the canals in 1953. The spillway gates were installed in 1955, and had remained in operation for nearly 69 years.

The crisis came on the night of August 10, 2024, when Spillway Gate No. 19 was washed away from its groove around 10.50 p.m. when the reservoir was close to its capacity. The incident caused a sudden release of water through the damaged bay, and immediately raised fears over the safety of the ageing spillway system. With the command area looking at a promising agricultural season after a difficult drought year, the possibility of losing a large volume of stored water triggered anxiety among farmers dependent on the reservoir for irrigation.

The immediate challenge before the authorities was not only to manage the emergency at the damaged bay, but also to save as much water as possible for irrigation. Technical teams initially faced the prospect bringing down the water level in the reservoir to the minimum possible to carry out repairs. Instead, engineers led by hydro-mechanical expert N. Kannaiah Naidu moved towards the more difficult alternative of installing a temporary stop-log arrangement at the damaged gate bay, so that a substantial amount of water could be retained without excessive drawdown.

Temporary stop gate

Following visits to the reservoir by the State leadership in the days after the incident, directions were issued to take up the stop-log work immediately in consultation with gate-design experts and fabrication firms. The temporary stop-log gate for Gate No. 19 was installed within seven days, on August 17, 2024. On that day, the reservoir was holding 71.35 tmcft of water. This helped retain water, and ensured irrigation water supply for both the 2024 kharif and rabi crops.

The stop-log operation took care of the immediate crisis, and bought time for the authorities to examine the structural condition of the remaining gates. Subsequent technical inspections and a comprehensive health check-up of all the spillway gates shifted the focus from a single damaged gate to the long-term safety of the entire crest gate system. Based on the recommendations of technical committees, the Tungabhadra Board decided to replace all the spillway crest gates of the dam rather than merely restore the one that was washed away.

As part of the process, the Board entrusted the work of replacing Gate No. 19 to Ahmedabad-based Hardware Tools & Machinery Projects Private Limited on April 23, 2025, before the larger replacement exercise was taken up across the spillway system. The eventual overhaul turned into a major hydro-mechanical operation involving the dismantling of old gates, and installation of an entirely new set within a narrow working window. The work also covered the replacement of lifting chains, and bevel gear units associated with the gate operating system, along with trial runs and quality checks.

With all 33 new crest gates now in place, the rehabilitation exercise is expected to significantly strengthen the structural safety and operational reliability of the Tungabhadra reservoir. Engineers associated with the work have indicated that the overhaul is likely to extend the functional life of the project by another 50 years.

Water sharing between States

Under the first Krishna Water Disputes Tribunal award, the project has a water allocation of 230 tmcft, including 18 tmcft earmarked towards reservoir evaporation. Of this, Karnataka’s share is 151.49 tmcft, while Andhra Pradesh and Telangana together account for 78.51 tmcft. The project facilitates irrigation for about 17.33 lakh acres — 9.26 lakh acres in Karnataka, 7.20 lakh acres in Andhra Pradesh, and 0.87 lakh acres in Telangana.