The floodgates of Tungabhadra dam in Karnataka have opened the floodgates for the political blame game in the state, even as the Andhra Pradesh State Disaster Management Authority warned people living along the Krishna river to remain vigilant. The incident occurred in Hospet on Saturday night when Gate 19 of the dam was washed away due to heavy floods following a chain break.
“The flood flow is nearly 35,000 cusecs per second and a total of 48,000 cusecs per second will be discharged downstream. People of Kosiri, Mantralayam, Nandavaram and Kouthalam in Kurnool district should exercise caution,” R Kurmanadh, general manager of the agency, said in a release. He also advised residents living along the Krishna River to avoid crossing canals and streams.
Karnataka Deputy Chief Minister DK Shivakumar said that two companies have been contacted to repair the dam gates. Fearing structural damage to the dam, all gates were opened, from where 38,000 cusecs of water was released to the neighboring states of Andhra Pradesh and Telangana, Shivakumar said, adding that the inflow was 28,000 cusecs.
As authorities try to resolve the issue, News18 looks at the dam, the functionality of the crest gates and the political war of words surrounding the accident:
What is a top door and how does it function?
Top gates, also called spillway gates, control overflow or reservoir water levels. According to the Beijing Water Conservancy and Hydropower Company, the top gate uses a bottom hinge flap to control the water level. Gates are usually hydraulically operated and rotate on hinges to facilitate opening and closing movements. These gates have proven to be the best option for allowing a variety of materials, including ice, to pass downstream, making them adaptable to a variety of conditions.
An engineering portal says another advantage of top gates is that they provide good control of upstream water levels because they act like top-adjustable weirs. Therefore, they are more commonly used in dams where upstream water levels need to be maintained within a narrow range.
About Tungabhadra Dam
The more than 70-year-old scheme was conceived in 1860 by British engineer Sir Arthur Cotton at the Madras Presidency to provide irrigation facilities, generate electricity and control floods in the area .
However, construction of the scheme did not begin until 1949 as a joint venture between the Kingdom of Hyderabad and the Madras Presidency. The project was completed in 1953.
Also known as Pampa Sagar, the dam spans the Tungabhadra River near the towns of Hosapet and Koppal. Tungabhadra Reservoir and Mullaperiyar Dam in Kerala have the unique feature of being the only two reservoirs in the country built using a combination of mud and limestone.
What went wrong on Saturday?
On Saturday night, 40,000 cusecs of water were released into the Tungabhadra river through 10 crest gates. At around 12:50 p.m., a link on the 19th gate broke, causing the gate to shift and cause water to pour into the river. To reduce the pressure, all 33 mountaintop gates were opened. By Sunday morning, the flow increased to one hundred thousand cubic seconds. This is the first time in the 70-year history of Tungabhadra dam that it has suffered such damage.
“Water flows out of the summit gate with great force. The water level in the dam must be lowered by 20 feet. Only then can the condition of the summit gate be assessed.
Downstream areas including Koppal, Vijayanagara, Ballari and Raichur have been alerted, but authorities said the dam suffered structural damage The possibility is very low.
What's the solution?
The first step is to empty about 60% of the reservoir so restoration can begin. According to dam officials, water releases from other gates need to be increased to relieve pressure on the damaged gates.
To replace the damaged gates, at least 60 tons cubic feet of the 100 tons cubic feet of water currently stored in the dam will need to be released. This process, along with construction of the new summit gate, is expected to take four days or more.
Bharatiya Janata Party complains
The BJP has accused the Karnataka government of negligence and wastage of water, causing misery to farmers who depend on water for their livelihood.
Opposition leader Ashoka accused Shivakumar, who is also the water resources minister, of working for the party high command and not his department. “For him, the welfare of the party is more important than the people. If he had held a meeting with the technical team, this would not have happened.
BY Vijayendra, chairman of the Bharatiya Janata Party, said that more than 30 villages downstream of the reservoir are facing the threat of flooding and asked the government to evacuate villagers in the area as soon as possible.
