After 26 long years, the Idukki dam in Kerala, one of the highest arch dams in the continent, is expected to be opened soon due to rising water levels. The water will be released by opening the sluice gates of the Cheruthoni dam, built on the Cheruthoni river, a tributary of the Periyar.
The emergency decision was taken to regulate the rising water levels in the Periyar, a result of the record high rains Kerala has received this monsoon.
On Friday, the water levels in the dam rose to 2393.16 feet from the earlier recorded high of 2392 feet. The full capacity of the dam is 2403 feet.
A high-level meeting was conducted with the Chief Minister where it was decided that the dam would be opened when the water levels reach 2400 feet.
"We decided that we would open the shutters in a trial run even before this. If the water reaches 2400 feet, we would be forced to open the shutters to reduce the levels. So instead of risking this, we will open the shutters in a controlled manner before the level reaches 2400 so that the pressure is less on us," Idukki Collector Jeevan Babu told TNM.
It was Power minister MM Mani who cautioned the KSEB officials (Kerala State Electricity Board) against taking such a risk by waiting until the water levels reached 2400 feet. Thus, it was decided to advance the opening of the dam.
"During the high-level meeting held with the CM, none of the authorities or officials had ground-level expertise in dealing with the situation. The dam was last opened 26 years ago. Therefore, it was decided that a survey would be conducted and steps would be taken during the findings from the survey," the Collector added.
The meeting, attended by CM Pinarayi, Revenue Minister E Chandrasekharan, Water Resources Minister Matthew T Thomas and Revenue Additional Secretary PH Kurian, discussed the precautions to be taken before opening the shutters.
The historic re-opening of the dam will have some consequences for those living close to the reservoir. However, the Collector and other officials state that the opening of the shutters will be carried out in an extremely controlled manner.
"The trial run may be conducted once the water levels reach 2397 feet (the water level on Friday was 2393 feet). It will be decided depending on how much more rainfall the district will receive.”
Idukki received 192.3 cm of rainfall this year, which is 49% more than what the hilly district received the previous year.
"Once the shutters are opened, it will be opened only for specific and short periods of time. And even in this trial run, we have decided to evacuate those staying close to the dam for the time being," the Collector added.
According to the Kerala Disaster Management authorities, the gushing waters of the Periyar could drown close to 4,500 buildings along 100 metres of the Periyar. This information is based on inputs from previous years.
"A survey conducted by the authorities mentioned that buildings along 50 metres of the dam will be affected. The exact damage can be estimated once a proper ground study is done. As for the damage, not all parts of the river bank will be flooded. Except for the valley, most parts of the river are narrow and in certain flat regions, water may fill up. However, if we see that the water levels are rising more than desired, we can close the shutters. The exercise will be thoroughly monitored," the Collector said.
The survey, conducted by the revenue department, the KSEB and the Kerala Water Authority, will be based on satellite imagery of the dam and surrounding areas. It will estimate the number of people to be evacuated when the sluice gates are opened.
The high range reservoir has three dams - Idukki, Cheruthoni and Kulamavu. While the Idukki dam holds Periyar's waters, the other two dams direct the water to the 780 MW hydro-electric power project, begun by the Kerala State Electricity Board.
The 45 year-old dam has been untouched since October 12, 1992 when it was last opened. The 550 foot high, double curvature dam is built on a spot in the course of the Periyar between two granite hills - named the Kuravan and Kurinchi.
Since this dam was built with no shutters, the sluice gates on the adjacent Cheruthoni dam will be opened, releasing the water into Cheruthoni river ( a tributary of the Periyar). The water will then merge with the main Periyar - the longest river in the state with a 244 km course.
The state disaster management authorities have prepared a list of buildings around 100 metres of the dam and details of the residents too will be collected soon, according to reports.