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CWC amends rule curve of hydel dams in Kerala to avoid flooding

Thiruvananthapuram: Foreseeing the possibility of repetition of 2018 flooding scenario during the upcoming monsoon, the Central Water Commission (CWC) has amended the rule curve of hydel dams in the state. The shutter gates of the Idukki reservoir will be opened when the water level reaches 2,373 feet on June 10.

Earlier the threshold water level for opening the shutters was 2,398 feet.

A rule curve is a pre-defined level of water to be maintained on a specified date in the reservoir to fill it in stages during the monsoon season, considering conservation and flood control aspects.

“A blue alert will be issued four feet below the rule level (2,369 feet) and an orange alert will be issued two feet below the rule level (2,371 feet) and a red alert will be issued one foot below the rule level”, said a senior official in the Kerala State Electricity Board (KSEB).

The power consumption in the state has reduced substantially during the lockdown period which has resulted in less water being drawn by hydroelectric dams in Kerala. As a result, the storage capacity of the reservoirs is higher than it was the previous year. This, experts warn, could potentially cause another flood in the state if the water is not released from the reservoirs before the monsoon. 

Incidentally, the weather agencies have already predicted above normal rainfall for this year in the country. If the state receives more rainfall, the hydroelectric dams under Kerala State Electricity Board (KSEB), including in Idukki, will be opened this year due to excess storage.

As per the data from Kerala State Load Despatch Centre on May 10, the water storage level in hydroelectric dams in the state is at 36 per cent. The figure was 25.9 per cent during the corresponding period in 2019, which is a difference of 10 percentage points.

The storage in the hydroelectric dams normally reduces to below 20% in the last week of May. This year, however, due to reduced power consumption, the storage is expected to be over 30 per cent in the last week of May.

“Having very high storage in the Idukki dam, before the onset of monsoon, especially with the forecast for normal to above normal rainfall, will be a big risk for the Periyar river basin as well as the lower reaches of the Chalakudy river. Immediate measures may be taken to reduce the live storage capacity at Idukki and to bring it down to around 15%,” quoted, a letter written by a team of scientists and environmental experts to the state government.

As per the team of experts, if a special flood protocol is not devised by the government before the onset of the monsoon season, it could probably lead to a repeat of floods that the states witnessed in 2018. 

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