CHENNAI: The Water Resources Department (WRD) is set to take up the desilting of the Poondi and Chembarambakkam reservoirs, after nearly seven years, with officials estimating that silt accumulation has reduced the effective storage capacity of three of Chennai's major drinking water reservoirs by 15 to 20 per cent.
The move follows Chief Minister C Joseph Vijay's directive to take advantage of the receding water levels in the reservoirs to fast-track desilting works.
Senior WRD officials said the department plans to remove about 400 mcft of silt from Poondi and Chembarambakkam to restore part of their original storage capacity.
"The proposal is in the preliminary stage and work is expected to begin shortly under a revenue-and-expenditure model," a senior WRD official said.
Officials said the low water levels have created a narrow window for excavation. Poondi is currently holding less than one-third of its capacity of 3,231 mcft, while Chembarambakkam is at around two-thirds of its capacity of 3,645 mcft, making it feasible to deploy excavation machinery.
"A few policy decisions have to be cleared by the State government before field work begins, which should take about a month. If the monsoon is delayed, as speculated under El Niño conditions, it will provide additional time to complete the works," the official said.
The WRD last took up desilting of reservoirs under a 2018 government order, covering Poondi, Chembarambakkam, Red Hills and Cholavaram. While work began at Chembarambakkam in 2019, it remained incomplete, and the Poondi project was stalled following a litigation. Desilting is under way at Cholavaram, while the Institute of Water Studies has completed the feasibility study for Poondi
The proposed exercise comes as storage across Chennai's six drinking water reservoirs has fallen to 5,858.25 mcft, or 44.31% of the combined capacity of 13,222 mcft, providing an opportunity to carry out desilting before the northeast monsoon.
A retired WRD official said desilting of drinking water reservoirs could only be undertaken when water levels recede and should be supported by a long-term maintenance plan.
"Reservoirs supplying drinking water offer only a narrow window for desilting. The department must also have a clear plan for the utilisation of the excavated silt," the former official said.