Did dams exacerbate Kerala's once-in-century floods?
Taken by surprise
"There was absolutely no warning from the government side," said Pathrose, describing the devastating flooding that hit his village of Okkal, in Kerala state, on Aug. 15. Pathrose says local authorities had advised his fields were safe, despite the incessant rains that battered Kerala at the peak of the monsoon.
In pic: Farmer, Joby Pathrose watches television with his son Alan inside their house in Okkal village in Ernakulam.
Floods be damned
As the rain intensified in mid-August state authorities were forced to release water from 35 dams to manage rising waters in reservoirs, many of which are used to generate hydroelectricity.
Big factor in the devastation
More than half a dozen experts who Reuters consulted were divided on the extent to which dam water spills contributed to the flooding, but almost all, including India's Central Water Commission (CWC), said reservoirs levels were too high ahead of the disaster.
"Because of this carelessness the disaster proportions were multiplied," said Himanshu Thakkar, co-ordinator of the South Asia Network of Dams, Rivers and People (SANDRP), a non-governmental body that advocates for better water management practices.
Focus on reservoir operations
State government officials say the severity of the flooding was due to a once-in-a-century storm that could not reasonably have been prepared for, and that the spilling of dam water had little impact.
No emergency plans
These protocols, while recommended by the CWC, are not yet mandated by law. CWC says it is merely an advisory body and it hopes a new dam safety bill, under federal consideration, will make dam operators more accountable.
Dams were full
Dam management experts who spoke to Reuters said such levels were dangerously high for the middle of India's monsoon season.
"One of the key advantages of a dam is it can help moderate floods," said SANDRP's Thakkar, an engineering graduate from the elite Indian Institute of Technology (IIT) Mumbai. "That didn't happen as Kerala's dams were already full by end-July. Dams aren't supposed to be full before the end of the monsoons."
The data also shows that if the water levels in Idukki and Idamalayar had been slowly lowered to closer to their historical averages in the two weeks before the worst flooding began they would have been able to absorb all the rain that fell during the mid-August storm.
"The release could have started earlier so that by Aug. 9 there would have been left-over capacities in the reservoirs to store the water," said Biswajit Mukhopadhyay, director of water resources at U.S-based engineering firm IEA, who analysed some of the publicly available data at the request of Reuters.
N.S. Pillai, chairman of the Kerala State Electricity Board (KSEB), a state-run body that manages most of Kerala's big dams, said that was a "highly hypothetical and imaginary conclusion". Heavy rain had not been forecast and blaming the dams for the flooding was "not justifiable", he said.
That was when more intense rainfall forced KSEB to rapidly ramp-up releases of water from Idukki and Idamalayar reservoirs, which feed into the Periyar.
When the state was alerted
James Wilson, who works for the Kerala government as special officer on a inter-state water advisory committee, said blaming KSEB was unfair, as Kerala's dams only have the capacity to store less than a tenth of the state's annual rainfall, and even less in years of extreme rainfall.
"However you prepare you have a problem with these type of events," said Wilson, adding Kerala's steep hills and relatively short river lengths give officials little time to react to freak rainfall.
There will be flood
"The release from reservoirs had only a minor role in flood augmentation," said CWC in a report.
The report noted however, that most of the dams were already "at or very close to" full reservoir levels just before the most intense rain, and it called for a review of water storage norms at all major reservoirs in Kerala. It also shows nearly half the outflows into the Periyar between the peak flood days of Aug. 15 to Aug. 17 were from within the catchment areas of big dams.
In court filings, Tamil Nadu said the water released from the Mullaperiyar dam only constituted a small part of the spill from the much bigger Idukki reservoir.
The IMD has also responded, saying it "issued all necessary severe weather warnings".
KSEB's Pillai said forecasts failed to predict the intensity of the rain.
"If reliable forecasting is done in respect of very heavy and extremely heavy rainfall, we can manage dam operations very efficiently," said Pillai, warning that more conservative water storage would lower KSEB's power generation ability.
"If somebody strongly believes these dams should be used for flood control, I can only differ with them," he said.
Nayan Sharma, an expert on river engineering and a former professor at IIT Roorkee, says hydroelectric dams incentivise operators to stockpile water as turbines are most efficient at full reservoir levels.
This came after a 2017 report from India's Comptroller and Auditor General, the government spending watchdog, criticised the lack of dam operating manuals and emergency action plans (EAPs) for reservoirs in many states.
Kerala's revenue secretary and head of disaster management, P.H. Kurien, said he has twice written to KSEB requesting EAPs and has yet to receive them.
Manuals were still being prepared
Authorities in towns, meanwhile, say that evacuation warnings were given.
"We made repeated microphone announcements about the opening of dam gates and asked people to move to safe places," said N.R. Jayaraj, deputy superintendent of police in Aluva, a town on the Periyar's banks that was badly hit by the floods.
All the warning they got
"We were told the dam gates would be opened and we'd have to be alert, but no one was warned to expect this much water," said K.C. Anupama, who works at a school in Neriamangalam, adding the school is 20 feet above the river and was still flooded.
"No one in their wildest dream thought this would happen. No one thought waters would get here."