Adyar River

Adyar River is one of the two rivers that flows in Chennai. It originates near the Chembarambakkam Lake, Kanchipuram district.The 42.5-kilometre (26.4 mi) long river contributes to the estuarine ecosystem of Chennai. Despite the high pollution levels, boating and fishing take place in this river. The river collects surplus water from about 200 tanks and lakes, small streams and the rainwater drains in the city, with a combined catchment area of 860 square kilometres (331 sq mi). Most of the waste from the city is drained into this river and the Cooum River.

Adyar river starts from Malaipattu tank near Manimangalam village in Sriperumbudur Taluk at about 15 kilometres (9 mi) west of Tambaram near Chennai. It starts to appear as a stream only from the point where water from Chembarambakkam lake joins the river. It flows through Kancheepuram, Tiruvallur and Chennai district for about 42.5 kilometres (26.4 mi) before joining the Bay of Bengal in Adyar, Chennai. Here it forms an estuary, which extends from the Adyar Bridge to the sandbar at the edge of the sea, with some small islets in-between. The estuary attracts a wide variety of birds. The estuary covering an area of about 120 hectares (300 acres) was made a protected wildlife reserve in 1987. The river forms a backwater near the mouth, known as the Adyar creek, due to the formation of sand bar at the mouth. This creek is a natural channel which carries tidal water back into the sea.

The river is almost stagnant except during the rain season. Rapid industrialisation and urbanisation has led to severe contamination of this river. However, the river gets just 10 per cent of the untreated sewage being let into the three principle waterways of Chennai daily, with the other two, namely, the Buckingham Canal and the Cooum River, taking the major share (60 per cent and 30 per cent, respectively). The problem of sedimentation was not severe as the Adyar's width near Thiru.Vi.Ka. Bridge is nearly 480 metres (1,570 ft) that enabled tidal effect into the waterway for about 4 kilometres (2.5 mi). However, it was essential to provide groynes to keep the river mouth open for adequate width and prevent inundation during monsoon. In 2011, the Water Resources Department (WRD) proposed to construct groynes to reduce formation of sand bars near the mouth the river.In 2012, the state government allotted ₹ 3,000 million towards construction of 337 sewage cleaning systems in the waterways in the city, including 49 locations in the Adyar river. Others include 105 points in Cooum river and 183 locations in the Buckingham Canal.