The Orissa government has said that the severe flood in Mahanadi river system leading to heavy damage of life and property was due to cloud burst and instant rise in water level of rivers downstream of Hirakud dam and not because of mismanagement in release of water from the reservoir as being accused in some quarters.
It said, the contribution of Hirakud dam water to the flood was only 18 percent.
“Out of the maximum discharge of 15.81lakh cusecs of water at Munduli on 20th September, only 2.76 lakh cusec water came from Hirakud dam”, Arabinda Behera, commissioner-secretary, water resources department, Orissa government said.
The contribution of the downstream rivers to the flood was significant with Tel contributing about 11.92 lakh cusecs of water. Besides, the rise in water level in the rivers was instant as the rain was forecast on 15th September and it started pouring the very next day, leaving little time to react, Behera added.
He said, this is not the first time that such a thing has happened. Similar situation prevailed in 1982 when all gates of the dam were closed on 29th August with the water level at 620 feet in the morning. But by the afternoon the situation became alarming with 9.5 lakh cusecs of water flowing into the reservoir, forcing the authorities to release 5.5 lakh cusecs.
On that fateful day, within only 9 hours, the reservoir water level increased sharply from 620 feet at 6 am in the morning to 629.45 feet by 3 pm. The very next day the water flow at Khairamal was 14.3 lakh cusecs and at Baramula 15.7 lakh cusec.
Refuting the allegation that high release of water from the dam, causing the current devastating flood, was necessitated because the reservoir operators had consistently kept the water level way above the recommended level right from August 1, this year, he said, the water level was maintained somewhere between the upper and the lower limit. It may be noted Hirakud, being a multi-purpose project, has no specific flood cushion like Rengali dam project.
So certain rule curves have been adopted since 1952 with subsequent revisions. The rule curves as revised in 1988 is being followed at present in the management of the Hirakud dam, said Hirakud dam official.
“The rule curve is not a sacrosanct yard stick as there are pressing demands of the farmers of Hirakud command area for irrigation and simultaneous requirements of water for power generation. So the level of water in the reservoir was maintained higher than the recommended level of 590 feet”, he pointed out.
Interestingly, some experts support the government’s contention that at 590 feet level of the reservoir, it will not be possible to supply the required water to the farmers and meet the demand for hydro power generation.
Though the real level of water in Hirakud dam in August this year was higher than the upper limit of the rule curve, it has been lower than the upper limit throughout the month of September.
Behera argued that even if the 2.78 lakh cusec water released from Hirakud would have been stopped, there would not have been any substantial difference in the intensity or gravity of the flood. “It would have at best delayed it by few hours”, he added.
But contrary to the beliefs in many quarters, there is no exclusive flood cushion and the decision on the quantum of water released from the dam is taken by the authorities looking at the tradeoff between the requirement of water for irrigation, power and flood control.
The operational decision on the management of the reservoir on day to day basis is taken by the technical personnel in charge of the Hirakud dam management. The amount of storage and release of water is decided before 24 hours keeping the dam safety at the forefront.
