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Deft dam control helps keep Tamil Nadu afloat despite heavy rains

The recent waterlogging in several parts of the State stemmed from lack of infrastructure and poor planning rather than sudden release of water from dams.

Published: 29th November 2021 06:10 AM  |   Last Updated: 29th November 2021 06:10 AM   |  A+A-

After the recent spell of rains, the Cooum flows over a Maduravoyal road in Chennai

After the recent spell of rains, the Cooum flows over a Maduravoyal road in Chennai. (Photo| Martin Louis, EPS)

Express News Service

CHENNAI: As Tamil Nadu witnessed record rains in November filling up most dams, dam managers across the State have handled the release of water from reservoirs in a phased manner without creating much havoc on the banks of rivers.

The recent waterlogging in several parts of the State stemmed from lack of infrastructure and poor planning rather than sudden release of water from dams.

Officials told The New Indian Express that better weather forecasting and emptying of dams before rains helped them handle heavy inflow of water into dams following the downpour in catchment areas. Surely, they seemed to have learnt a lesson from what the CAG termed a man-made disaster in 2015. 

This year, Chennai received three massive spells of rain on November 6-7, 17-18 and 26-27. The water was released from reservoirs in a phased manner and safely routed to the sea. "In 2015, we had no idea Chennai would receive 300 mm rainfall. Everyone was scrambling at the last minute. However, the government is now warning at least five days ahead to ensure precautionary measures are taken," said a senior official.

For instance, with heavy rains forecast for Chennai on Friday and Saturday, 2,000 cusecs of water was released from Chembarambakkam and Poondi reservoirs each on Monday itself, four days ahead of the rains. Even then on Sunday, with the water level in the Adyar rising, officials asked people living by the river to shift to shelters for safety.

The water levels at all the major reservoirs are being maintained at least 3 feet below their full capacity. 
In contrast, in 2015, 25,000 cusecs of water was released from the Chembarambakkam reservoir overnight when its maximum outflow is 32,000 cusecs. 

'Management possible as depts worked together'

"This year since water has been released ahead of rains based on forecasts, only a maximum of 3,000 cusecs was released at a time from Chembarambakkam," said P Ramachandran, retired professor of Water Resources.

Similarly, 80,000 cusecs was released from Poondi reservoir in 2015. "This year, the highest release was 37,500 cusecs for five hours. Even when the inflow went up to 45,000 cusecs, the outflow was in phases and not rushed. The reservoir has a 2,000 sq km catchment area 10 times more than Chembarambakkam," said the official.

In the delta districts, officials in charge of the Mettur Dam, which is currently releasing 22,500 cusecs, said, "From June 12 to January 28 PWD officials in the middle and lower Cauvery circle would calculate the amount of water needed per month to release. If rains increase, the outflow is reduced on the concerned days. The water flow is monitored 24 hours."

This year due to heavy rainfall in the delta region, water release from the dam reduced to 100 cusecs in October and due to heavy rains in the catchment areas in the second week of November, inflow increased causing the dam to near its full capacity.

To avoid flooding, PWD officials release a warning every four hours to Collectors of 12 districts in the delta region.

Assistant Executive Engineer of the Water Resource Department, Vaigai Dam Division, Selvam explained that while constructing a dam, a set of rules will be framed for its operation and management called 'Water Regulation Rules'.

"Based on these rules, the executive engineer incharge of the dam will decide on release and storage of water in any season. However, on the request of farmers, if water is to be released for irrigation purposes, the government has to pass an order based on inputs from the Agriculture and Statistical department to know the quantity of water to be released in the first and second phases of irrigation," he said.

Another factor for better management this year is that all departments involved, including PWD, Chennai Metro Water Supply and Sewerage Board, Greater Chennai Corporation and district administrations, are working together. "Previously, the departments operated separately and waited for the government’s nod at every step. So, there were a lot of loopholes," Selvam said.

Holiday announced...

All educational institutions will be closed on Monday in Chennai, Chengalpattu, Kancheepuram, Villupuram, Tiruvannamalai, Ranipet, Tirunelveli, Thanjavur, Thoothukudi, Kannyakumari and Tiruvallur. Only schools in Nagapattinam, Cuddalore and Tiruvarur have a holiday today. Puducherry and Karaikal declared holidays for schools, colleges on Monday and Tuesday 

Chennai to get less rain; fresh system brewing

Chennai is set to get a breather from today as showers are expected to reduce. However, Western and Southern Tamil Nadu will continue to receive intense rainfall for a couple more days.

According to IMD, thunderstorm with moderate rain is likely at most places over the rest of coastal Tamil Nadu. However, another low pressure is brewing which might cause intense spells in TN or Andhra Pradesh in five to six days

15,016 people housed in 188 relief camps in several districts, said Minister for Revenue and Disaster Management KKSSR Ramachandran on Sunday

  1. Water levels at major reservoirs are being kept at 3 ft below full capacity

  2. Water being released days ahead of rains based on better forecasting

(With inputs from M Sabari at Salem & R Jeyalakshmi at Madurai)



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