Poondi Reservoir

Poondi Reservoir, also known as Sathyamoorthy Sagar, is a major reservoir on the Kosasthalaiyar River near Poondi village in Thiruvallur District, Tamil Nadu, about 60 km northwest of Chennai. Constructed in 1944, it is the primary drinking water source for Chennai city. The reservoir is notable for its vast water spread, earthen dam, and the relocated Oondreswarar Temple, and serves as a scenic spot for sightseeing and nature visits.

Visitors can expect a large open water body formed by an earthen dam across the Kosasthalaiyar River, surrounded by flat rural landscape and scrub vegetation. The site offers broad views of the reservoir, dam embankment, and spillway area. Visitors can walk along accessible bund areas, view the water spread, observe birds, and visit the nearby Oondreswarar Temple relocated from the reservoir bed. The area is quiet and primarily visited for sightseeing, photography and picnicking.

Poondi Reservoir was constructed in 1944 across the Kosasthalaiyar River to augment water supply to Chennai. It was named Sathyamoorthy Sagar in honour of S. Sathyamoorthy, Indian independence activist and mentor to K. Kamaraj. The project involved submergence of the original Oondreswarar Temple village, and the 11th-century Chola-era Oondreswarar Temple was dismantled and reconstructed at its present location to preserve it.

The reservoir is associated with the relocated Oondreswarar Temple dedicated to Lord Shiva, which retains Chola architectural features and remains an active place of worship. The reservoir itself is culturally significant as a vital water resource for the Chennai region and is often visited along with the temple.