Chennai, 25 October: Sustained rainfall over nine days has delivered a significant fill-up to the six reservoirs that supply drinking water to Chennai, with combined storage increasing by 984.98 million cubic feet (mcft) between 15 and 24 October, official figures show. Total storage in the reservoirs rose from 4,485.68 mcft to 5,470.66 mcft, equal to 41.38 per cent of their combined capacity of 13,222 mcft.
What the gains mean for supply
The reported increase — amounting to about 27.89 billion litres — has strengthened the city’s short-term water outlook as the northeast monsoon intensifies. The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) supplies 1,237.71 million litres a day (MLD), of which reservoirs currently provide 968.41 MLD or roughly 78 per cent of the total.
- Reservoir water contribution: 968.41 MLD
- Total daily supply (including desalination, quarries, wells): 1,237.71 MLD
- Desalination at Nemmeli: 200 MLD (combined)
CMWSSB numbers indicate that the additional rainwater stored in the reservoirs is equivalent to nearly 29 days of current withdrawal from those reservoirs alone, or about 23 days of Chennai’s total daily supply when all sources are included. Other contributors to urban supply include two desalination plants at Nemmeli, quarries, wells, borewells and smaller local sources.
Reservoir-wise changes
Among the six waterbodies, Red Hills (Puzhal) recorded the largest rise, accounting for more than half of the overall gain. Its storage climbed by 539 mcft, from 1,876 mcft on 15 October to 2,415 mcft on 24 October, reaching 73.18 per cent of its capacity of 3,300 mcft. Other reservoirs also showed improvements.
| Reservoir | Storage on 15 Oct (mcft) | Storage on 24 Oct (mcft) | Capacity (mcft) | Percent full |
|---|---|---|---|---|
| Red Hills (Puzhal) | 1,876 | 2,415 | 3,300 | 73.18% |
| Chembarambakkam | 1,319 | 1,497 | ||
| Veeranam | 526.68 | 677.56 | ||
| Poondi | 412 | 490 | ||
| Cholavaram | 120 | 144 | ||
| Kannankottai–Thervoy Kandigai | 232 | 247 |
Other notable changes included Chembarambakkam rising from 1,319 mcft to 1,497 mcft, and Veeranam increasing from 526.68 mcft to 677.56 mcft. Poondi, Cholavaram and Kannankottai–Thervoy Kandigai also registered gains.
"The nine-day spell has materially improved reservoir levels, particularly at Red Hills, which remains a key water source for the city," the official figures showed.
Context and consequences
Chennai depends on a mix of reservoir water, desalination and local ground sources. The present boost reduces immediate pressure on the desalination plants and groundwater, but officials caution that monsoon patterns remain variable. Continued rainfall would further bolster stocks, while a premature dry spell could quickly undo the gains.
The CMWSSB figure for non-reservoir supply includes 200 MLD from the two Nemmeli desalination units, 28 MLD from quarries, 16 MLD from wells and borewells, 14 MLD from sources in added areas, and 5 MLD from Porur. Taken together, these sources underpin Chennai’s daily distribution network alongside reservoir deliveries.
Residents and civic groups welcomed the improved storage but said prudent water use should continue, particularly in peri-urban and newly added areas where service gaps persist. Water managers will monitor inflows and withdrawals closely over the coming weeks to calibrate supply schedules.
With the northeast monsoon still active, the extra storage offers breathing space. Officials will track reservoir behaviour and catchment inflows to plan releases and maintain distribution across the metropolitan area.
