Safety Concern

In 1979, safety concerns were raised by Kerala Government after an earthquake, that resulted in leaks and cracks in the dam. A state agency, Centre for Earth Science Studies (CESS), Thiruvananthapuram, had reported that the structure would not withstand an earthquake above magnitude 6 on the Richter scale. The then Tamil Nadu government lowered the storage level to the current 136 feet (from 142.2 feet) at the request of the Kerala Government to carry out safety repairs.
Current safety concerns hinge mainly around the issues listed below:
Risk Factors

1. Age of the dam: The dam is 116 years old as of 2011. It has outlived its expected life span of 50 years. Strengthening the existing dam has its limitations and may not prove to be effective in the event of a disaster (reference: Morvi Dam)
2. Construction Material: The dam was constructed using lime and mortar. Seepage and leaks from the dam have caused concern.
3. Earthquakes: The dam is situated in a seismically active zone . CESS has reported that the dam cannot withstand earthquakes above 6 point on the Richter scale. Several earthquake tremors have occurred in the area in recent times. An earthquake measuring 4.5 on the Richter scale occurred on June 7, 1988 with maximum damage in Nedumkandam and Kallar (within 20 kms of the dam).
4. Changing weather patterns leading to incessant rains, flooding and overflow of the dam^.
5. Insufficient or improper safety maintenance and safety monitoring of the dam

Potential adverse impact in the event of a disaster

1. Impact on lives and property downstream in the event of a disaster: The estimated population of the five districts of Kerala downstream is 3.5 million. Villages such as Vallakadavu, Vandiperiyar, Upputhara, Ayyappankoil, Kumili and parts of Kattappana and other parts of Idukki and Ernakulam Districts would be immediately affected, with loss of lives and property.
2. Impact on flora and fauna including endangered species such as tiger and elephants in the Periyar Wildlife Sanctuary.
3. Impact on tourism: Thekkady Reservoir and Periyar Wild Life Sanctuary are important and popular tourist spots in Kerala^{[citation needed]}.
4. Impact on Idukki Dam and the disastrous consequences of an Idukki Dam disaster.
5. Impact on agriculture, drinking water supply and power generation in southern Tamilnadu.
6. Impact of a disaster on the general economy of Kerala and Tamilnadu.