Hyderabad:A gate of the Tungabhadra dam in Hospet district of Karnataka was washed away after its chain link snapped around midnight of Saturday (August 10). The incident resulted in a heavy discharge of flood into Sunkesula barrage in Kurnool district of Andhra Pradesh.
It occurred when the gates of the dam on Tungabhadra river, a tributary of river Krishna, were being closed as the inflows had receded with rains in the upper reaches subsiding. The dam had a storage of about 100 tmcft (thousand million cubic feet) when it happened.
Now, all the 33 gates of the dam are lifted to let out about 60 tmcft of water downstream into the Krishna river to take up repairs on the affected gate since it can only be done when the water storage is below 40 tmcft, a senior irrigation official explained.
As a result, about one lakh cusecs (cubic feet per second) of flood is flowing in Krishna. The Andhra Pradesh State Disaster Management Authority issued a press release asking people residing in Kurnool town and adjoining mandals of Kosigi, Mantralayam, Nandavaram and Mantralayam to be vigilant.
The statement said “the floodwaters are being discharged at a significant rate. People in the affected areas should be alert and take necessary precautions to ensure their safety”.
The Engineer-in-Chief of irrigation of the State Venkateswara Rao told The Wire that the water release from Tungabhadra dam was only 35,000 cusecs prior to the incident. Since the discharge was stepped up to one lakh cusecs all of a sudden, an advisory was necessitated to warn public against taking the risk of walking on the river bed or straying anywhere nearby.
Major disaster was averted in Nalgonda district
A few days back, a major disaster was averted at an intake well and pumphouse complex constructed by Hyderabad Metropolitan Water Supply and Sewerage Board (HMWSSB) at the foreshore of Nagarjunasagar dam in Nalgonda district in Telangana.
A flood of 3.5 lakh cusecs flowing into the dam resulted in water gushing into a tunnel taking off from the reservoir and linked to the complex. A huge retaining wall of the intake well collapsed as the newly constructed gate of the tunnel was blown up due to water pressure.
The Rs 2,215 crore project is under construction since July 2021 as part of a larger scheme to take drinking water from Krishna to meet the needs of the burgeoning population of Hyderabad till 2050.
The project aimed to draw water from the dead storage level of the reservoir in peak summer. It was supposed to be an alternative to an existing water supply scheme from the reservoir at higher water level.
There was fortunately no loss of life because it happened at 7 AM on August 2 during the shift changing time of workers. About one hundred workers from Odisha were employed by the contracting agency to work in three shifts.
The water that entered through the tunnel flooded the surge pool at a depth of 83 meters as the tunnel slided at the other end. The soil of the bund in the reservoir was recently removed which resulted in the water entering the tunnel. A strong gate was fitted at the end of the tunnel.
A senior official of HMWSSB who did not want to be quoted said investigation was underway to know why the soil was removed at this point of time when it was known that the dam will get heavy flood. He said the engineers went by previous experience that the flood will not reach up to the point of the tunnel till August end.
The project envisaged construction of three tunnels at different depths of water in the dam. The first tunnel was constructed at the lowest level i.e. 455 ft, second at 504 ft and third at 547 ft.
The instant work was going on at the second tunnel and was scheduled to be completed by next March. Since the intake well is fully flooded, the completion will be delayed by two months, the official explained.
He added that the reconstruction of the side wall was not an issue as it could be done by a mere Rs 15 to 20 crore. The challenge was to dewater the surge pool and the tunnel. A team of technical experts visited the site on Sunday (August 11) to study the situation and submit report to the government.
The incident led to a political war between the ruling Congress and the opposition Bharat Rashtra Samiti (BRS).
BRS, Congress trade allegations
The BRS accused the government of hiding the incident till a picture of the side wall crashing was posted on the social media by a worker on August 9.
The BRS working president K.T. Rama Rao asked the Chief Minister A. Revanth Reddy to take the responsibility for not making a statement on the floor of the Assembly because the House was in session on that day. Reddy left for US within 24 hours.
Irrigation Minister N. Uttam Kumar Reddy, who visited the project along with his Cabinet colleague Ponguleti Srinivas Reddy said the Congress had nothing to do with the execution of work as it was grounded by the BRS government with its own choice of executing agency.
The Congress recalled similar incidents of flooding of pumphouses at Kannepalli and Annaram on Kaleswaram lift irrigation project two years ago due to poor quality of works. Nearly 30 high cost motors were damaged then. A couple of piers of Medigadda barrage of the project also sank during BRS rule.
