Poondi Reservoir, also known as Sathyamoorthy Sagar, is formed across the Kosasthalaiyar River to augment the water supply for Chennai City. The Kosasthalaiyar River originates near Kaveripakkam in Vellore District and drains into the Bay of Bengal. The total length of the Kosasthalaiyar is 136 km, and it serves as an important water source for Chennai.
Between 1990 and 1996, under the Krishna Water Supply Project, the capacity of the reservoir was increased from 2,750 Mcft to 3,231 Mcft by raising its Full Reservoir Level (FRL) from 33.00 feet to 35.00 feet, thereby aligning it with the Central Water Commission standards. Additionally, the reservoir’s water is supplemented by an interstate agreement to supply 1,000 cusecs of water through the Krishna Water Canal from the Kandaleru Reservoir in Andhra Pradesh. A link canal was formed to carry 1,000 cusecs of water up to Sirugadal, allowing the diversion of water to Chembarambakkam and Redhills through a regulator.
The foundation stone for the Poondi Reservoir was laid by the then Mayor of Madras Corporation, Thiru. S. Sathyamurthy, in 1940, and the project was completed on 14th June 1944.
