Explained: How Karnataka's Tungabhadra Dam Gate Washed Away

One of the gates of the Tungabhadra dam in Karnataka was washed away this week due to the snapping of chain link.

A flood alert was sounded in downstream Koppal as authorities immediately opened all except five dam gates to take off the pressure on just one.

Anticipating a potential threat from the Tungabhadra reservoir in Karnataka's Vijayanagara district, the Andhra Pradesh government has issued a flood alert in low-lying areas of the Kurnool district.

What happened?

On August 10, the chain link of crest gate no 19 at the Tungabhadra Dam snapped. This gate, a major part of the dam's infrastructure for over 70 years, gave way under the pressure of the water. The snapping of the chain caused an uncontrolled outflow of approximately 35,000 cubic feet per second (cusecs) of water. 

The dam was holding a substantial amount of water due to the monsoon rains. The pressure exerted by the stored water, combined with the decades-old weakened chain link, likely led to the failure.

This unexpected breach raised alarms in both Karnataka and Andhra Pradesh.

Why is this serious?

The broken gate needs to be repaired, but 60-65% of the water in the reservoir must be drained first, which may impact irrigation in upstream fields. The sudden release of water may cause flooding in downstream areas, affecting districts in Karnataka and Andhra Pradesh. 

Heavy rains, predicted for the next week, may worsen the situation.

Why are farmers fearful?

The sudden release of water poses a significant risk of flooding in low-lying areas and may damage or destroy crops. Excess water could lead to crop loss, affecting the livelihood and income of farmers.

The damage to the gate may disrupt irrigation channels, impacting farmers' ability to water their crops.

The situation is unpredictable. Flooding and waterlogging may affect the preparation and planting of upcoming crops, leading to long-term consequences for farmers.

Government response

Both Karnataka and Andhra Pradesh governments have responded swiftly to the crisis.  In Karnataka, Deputy Chief Minister DK Shivakumar visited the dam and announced the formation of an expert committee to assess the condition of all dams in the state, reported PTI. The committee will focus on preventing such incidents in the future and ensuring the safety of the dam infrastructure.

Karnataka Chief Minister Siddaramaiah is also visiting the site to discuss the issue with engineers and board members.

Andhra Pradesh Chief Minister Chandrababu Naidu has been actively monitoring the situation. He directed the deployment of engineering teams to the dam and issued flood alerts to the districts.

To manage the situation and reduce the pressure on the damaged gate, the authorities were forced to open all 33 crest gates, significantly increasing the water discharge to around 1,00,000 cusecs.

Efforts are underway to restore the crest gate, with a temporary gate being considered.

What next?

The repair of the damaged gate is expected to take time, and in the meantime, water management will be a critical concern. The Karnataka and Andhra Pradesh governments are working together to mitigate the impact. The expert committee's findings will be crucial in determining the long-term safety of the dam and preventing future incidents.

Unlike other dams that have double chain links for added security, the Tungabhadra Dam has a single chain link for each gate. This design flaw meant that if the chain failed, there was no backup to hold the gate in place.

For now, the focus remains on ensuring the safety of residents in the affected areas and providing support to farmers at risk of losing their crops. The situation is being closely monitored and further developments will determine the next steps in managing this crisis.