Chembarambakkam, Chennai’s largest drinking water reservoir, held 1,254 million cubic feet on 15 October against a full capacity of 3,645 mcft, DT Next reported. That is about a third full, and well below the 2,056 mcft it held on the same day last year.
The city draws on six main lakes and reservoirs, plus Krishna water from Andhra Pradesh and desalination plants. Here is what each one holds, why the numbers matter in both drought and flood, and where to follow them during the monsoon.
The six reservoirs at a glance
Chennai’s piped supply draws mainly on Chembarambakkam, Puzhal (Red Hills), Poondi (Sathyamoorthy Sagar), Cholavaram and Kannankottai Thervoy Kandigai in the districts around the city, and on Veeranam lake in Cuddalore district, which is linked to Chennai by pipeline. Krishna water from Andhra Pradesh reaches the system through Poondi, and the desalination plants on the coast add a supply that does not depend on rain at all.
Two capacities are worth remembering. Chembarambakkam, the largest, holds 3,645 million cubic feet (mcft) when full, and Poondi holds 3,231 mcft. Chembarambakkam spills into the Adyar and Poondi into the Kosasthalaiyar, which is why these two matter most when the city floods. We have not listed capacities for the other four here because we could not confirm them against an official source this week. Chennai Metro Water publishes them alongside daily storage on its website.
The lakes do not all play the same role. Some are drawn on heavily through the year, while others act as a buffer that is topped up during the monsoon and used through summer. That is why a low figure at one lake in October is less alarming than low figures across all of them in April.
Where things stand now
A low figure at Chembarambakkam matters less for daily supply than it sounds, because the city does not rely on one lake. It does mean the northeast monsoon has more work to do than usual this year to refill the largest reservoir before summer.
The state has sought extra Krishna water from Andhra Pradesh. Under the inter-state arrangement, Chennai is entitled to 8,000 mcft between July and October and a further share between January and April, South First reported last year, though actual deliveries usually fall short and the Kandaleru to Poondi canal is shut for maintenance at times.
We could not verify current storage for the other five reservoirs from an official source today. The heavy rain over north Chennai and Tiruvallur district on 17 October should bring some inflow into Puzhal, Poondi and Cholavaram.
Longer term, the state laid the foundation on 14 October for a ₹3,108 crore drinking water Ring Main System at Sholinganallur, intended to move water between sources across the city.
For comparison, in late September 2025 the department reported Red Hills at 91%, Kannankottai Thervoy Kandigai at 90%, Poondi at 78% and Chembarambakkam at 43%, with the major sources including Veeranam together holding 9,169 mcft, nearly 70% of their combined capacity, South First reported. Chembarambakkam’s position this year is weaker than that.
Reading the units
- mcft: million cubic feet, the standard unit for Chennai’s lakes. One tmcft (thousand million cubic feet) equals 1,000 mcft.
- Level in feet: the depth at the gauge. Storage does not rise in a straight line with depth, because lakes widen near the top.
- Cusecs: cubic feet per second, used for inflow and releases. A release of 500 cusecs is substantial for the Adyar.
Why levels matter in a flood
Low levels worry people in summer. High levels worry them in November. When Chembarambakkam nears its full level, the Water Resources Department releases surplus water down the Adyar. In October 2025, with the lake at 20.84 ft and a safe limit of 21 ft, releases were raised to 500 cusecs and localities such as Kundrathur, Sirukalathur and Thiruneermalai were alerted, The News Minute reported. Poondi releases go down the Kosasthalaiyar towards Manali New Town and Ennore.
The department now prefers early, smaller releases to keep buffer space, rather than large late releases.
Where to check daily data
- Chennai Metro Water publishes lake levels on its official website and handles water supply complaints on 1916 or 044-4567 4567, as listed on its complaints page.
- Water Resources Department figures for storage, inflow and outflow are reported daily by city newspapers during the monsoon.
- District administrations of Tiruvallur and Kancheepuram issue flood warnings before major releases.
- IMD rainfall data on the RMC Chennai page shows how much fell in the catchments.
When you read a report, check three numbers: storage in mcft, level in feet and inflow in cusecs. Inflow tells you where the level is heading.
Quick answers
What is Chembarambakkam’s capacity?
3,645 million cubic feet when full.
How full is it now?
About 35% in mid-October 2026, at 1,254 mcft on 15 October.
Which reservoirs matter most in a flood?
Chembarambakkam, which releases surplus water into the Adyar, and Poondi, which releases into the Kosasthalaiyar.
Does a low reservoir mean water cuts?
Not automatically. Metro Water draws on several lakes, Krishna water and desalination, and any change to supply would be announced by Metro Water.
Information checked against official sources on 18 October 2026. Fees, dates and rules can change; confirm on the linked official pages before acting.
Sources
- Chembarambakkam levels dwindle (DT Next, 15 Oct 2026)
- Flood alert as discharge from Chembarambakkam, Poondi increases (The News Minute)
- Krishna water disruption, WRD strengthens Chembarambakkam (South First)
- CMWSSB complaint redressal (Chennai Metro Water)
- Regional Meteorological Centre Chennai (IMD)
