After a parched summer, water levels at Chennai reservoirs begin to rise

Thanks to a generous southwest monsoon and an on-track northeast monsoon, water levels in Chennai’s reservoirs that supply the city its drinking water, have begun to rise once again, after nearly two years. Except for Poondi, the three other lakes had run dry and had not a drop of water in them between July and September this year.

As of Saturday, storage at Poondi stands at 1694 mcft against its full capacity of 3231 mcft. This is 52.43% of its full capacity. Storage this time last year was less than half at 682 mcft.

Cholavaram holds 208 mcft against its full capacity of 1081 mcft (19.24%) while in Redhills it is 863 mcft against 3300 mcft (26.15%). Chembarambakkam currently holds the least at 97 mcft against its full capacity of 3645 mcft (2.66%).

At Veeranam, against its full capacity of 1,465 mcft, storage stands at 1180.40 mcft, just over 80% of its total capacity. Total storage in all four reservoirs put together stands to a quarter of its full capacity. Water levels measure 2,862 mcft (25.42%) against a total capacity of 11,257 mcft. Last year the levels stood at just 1,761 mcft.

Poondi’s inflow is at 915 cusecs a day. The Poondi reservoir has been receiving its share of Krishna water from Kandaleru and Ammapalli reservoirs in Andhra Pradesh. According to a report in Times Of India, water from Poondi is being sent to Red Hills and Chembarambakkam. As on November 2, the 776 cusecs outflow from Poondi is being shared between Redhills with an inflow at 440 cusecs a day and Chembarambakkam with 257 cusecs a day.

This southwest monsoon between June and September, Chennai received 587.8 mm of rainfall as opposed to its normal measurement of 439.6 mm, according to the information provided on Regional Meteorological Centre’s web page. Between October 1 and 30, Chennai received 5% increase in its northeast monsoon rainfall, recording 263.9 mm against its normal measure of 251 mm.

After almost a decade of neglect, desilting works began in these lakes in September this year. According to reports which have quoted sources in the Water Resources Department, the Chembarambakkam lake, which covers an area of 2316 hectares, will be desilted over a period of eight years. Further, 25.30 lakh lorry loads would have to clear 151 lakh cubic metres of silt from the lake to improve storage capacity. 

Desilting is a process which aims to rid the lake bed of accumulated silt to improve storage capacity. Prior to it, the lakes were only four storing water at 80% of its capacity, due to the presence of silt accumulated over decades. 

In Cholavaram lake, at least 70,000 cubic metres of silt has been removed. The Redhills lake was expected to be desilted soon after an order to desilt the lake was issued seven months ago. According to a senior officer in CMWSSB, the last time desilting work was carried out in two of the four reservoirs was in 2008.