Concern about Pazhassi dam’s safety gives way to relief as it survives overflow caused by heavy flooding

A sigh of relief given as the Pazhassi irrigation dam across the Valapattanam river at Kuyiloor near Mattannur withstood both the overflow that lasted for nearly 20 hours. An atmosphere of panic and concern about the safety of the dam arose when the flood water rose above the road level over the barrage on August 7.

The dam site on Tuesday was the destination of large number of people who defied heavy downpour to witness the flood water overflowing the barrage for the first time since the project’s partial commissioning by then Prime Minister Morarji Desai in 1979. The failure of the irrigation engineers to lift some of its shutters triggered concern about the capacity of the irrigation dam to survive the floods. The 245-metre long barrage, however, is still standing as the water level in the reservoir came down to the level of 18.2 metres on Wednesday from 29.2 metres that caused fears of an imminent collapse of the dam.

The barrage raises the water level in the river by about 15 metres and diverts its waters to the left bank main canal. The Pazhassi irrigation project with its canal systems has been originally envisaged to feed 16,200 hectares under cultivation in the district.

As the area under cultivation has drastically shrunk over the decades, the reservoir today is used as the major source of drinking water in the district. The water-level in the reservoir exceeded 28.35 metres, which is the road level over the barrage for the first time in the last 33 years. Normally, the water in the reservoir is maintained at the full reservoir level (FRL) of 26.52 metres if the shutters could be closed in early November. But the flash floods and landslips caused by heavy downpour in the eastern hill areas bordering Karnataka took the project officials unawares.

“The flood water that inundated parts of the Iritty town was over one metre above the FRL of the reservoir since Monday night,” project Executive Engineer P.D. Rajan told The Hindu. When water overflows above the dam, then its safety as well as capacity to endure water pressure was a major issue, he said adding that the dam’s survival of the overflow now points to its engineering strength.

According to the irrigation officials the water that reached the catchment area exceeded the reservoir’s maximum flood discharge capacity of 3510 cubic metre per second. Parts of Iritty, especially those near the bus stand there, that were flooded on Tuesday have been declared as catchment areas of the project, they said adding that many of the shops affected by the flood water are located in the areas declared as catchment of the reservoir. Illegal constructions in these areas were evicted in the past, they said adding that both the authorities and owners of the shops turn a blind eye to the danger as water level in the area normally causes problem only for one or two months during monsoon. Some of the low-lying roads near the catchment normally experience flooding whenever the water level in the reservoir goes beyond the free board level of 27.02 metres, they said.

Even though the water level in the reservoir came down on Wednesday, the National Disaster Response Force personnel who reached the site were pressed into service for lifting the seven of the total 16 radial steel shutters that could not be opened. Mr. Rajan said that Water Resource Minister P.J. Joseph, who had visited the site on Tuesday, announced the sanctioning of Rs. 7 crore for the repairing of the shutters.

Special Correspondent from Thiruvananthapuram adds:

The government has suspended K. M. Gopalan, Assistant Engineer of Pazhassi Irrigation Project (Velliyambra Section) for dereliction of duty.

An official release said, quoting the Minister for Water Resources P. J. Joseph that the engineer had failed to take necessary steps when the overtopping of Pazhassi dam caused floods and loss of life and crops.

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