CHENNAI: Despite the sanctioning of funds, desilting of Chembarambakkam lake was not taken up by authorities over the years, and experts opine this was the main reason why water had to be released on Wednesday from the reservoir.
Public Works Department officials confirm that at least 15 per cent of the lake is filled with silt and that deepening works were also not taken up. Following heavy rainfall on Wednesday night, the release of water from the reservoir was stepped upto 5,000 cusecs. The water level stood at 21.5 feet, against the lake’s total capacity of 24 feet.
For the first time since its construction over a century ago, a project was initiated in 2019 to desilt the Chembarambakkam lake and three other reservoirs at a cost of around Rs 36 crore. The project was also expected to bring in additional revenue with the sale of silt collected.
Silt from Chembarambakkam alone was expected to generate Rs 191 crore. The plan was to completely desilt the lake, which has a storage capacity of 3645 mcft, over a period of eight years. As much as 151.80 lakh cubic metres of silt had to be removed.
What actually happened
Despite work orders being sanctioned, the project was delayed by over five months in 2019, due to the onset of monsoon. According to official records submitted last year, silt accounted for 3 per cent of the lake.
When contacted a senior PWD official confirmed to Express on Wednesday that 15 per cent of the lake, which can hold around 550 mcft (6,365 cusecs) of water was filled with silt. Moreover, experts say that deepening of the lake would have increased its capacity by over three times when compared to the results of desilting.
'Not a drop would have been wasted if....'
According to water management expert S Janakarajan, over one third of the Chembarambakkam reservoir is filled with silt. "Firstly, silt survey to find the quantum and quality of silt was never conducted by the government. So, nobody knows the exact amount of silt. The government staff just brought a JCB and picked up silt randomly. This only creates pits inside the reservoir, which is even more dangerous," he said.
"Not even a drop of water would have been wasted if deepening and desilting works were over. If not for desilting, the officials should have deepened the lake to restore it to its original capacity," he added.
Concurring, retired PWD official S Thirunavukarasu said, "One year is enough to desilt a reservoir. We could have saved more water that way. Last year, the reservoir was bone dry. If the depth had been increased, it would have also added up as carryover storage."
"Though cyclone is an unforeseen calamity, Chennai always forgets to desilt its reservoirs and searches for water during summer. If it rains heavily as is forecast, more than 20,000 cusecs of water will have to be released from Chembarambakkam. At least one fourth of that could have been saved," he added.