Cooum River is the shortest river draining into the Bay of Bengal. This river is about 72 km in length, flowing 32 km in the Urban part and the rest in rural part. The river is highly polluted in the urban area (Chennai). Along with the Adyar River running parallel to the south, the river trifurcates the city and separates Northern Chennai from Central Chennai.
Its source is in a place by the same name 'Cooum' or 'Koovam' in Tiruvallur district adjoining Chennai district. Owing to intensive use of surface water upstream for agriculture, indiscriminate pumping of groundwater leading to reduced base flow in the river, formation of sand bar at the mouth of the river, discharge of untreated sewage and industrial effluents and encroachment along the banks, the river, especially the downstream, has been highly polluted.