K. Lakshmi travels to the origin of what was once known as the Thames of South India but now enters Chennai as a sewage carrier. First of a three-part series that will examine how the river went on to become an embarrassment for the city — and what is being done about it

The very mention of the name Cooum conjures up images of a degraded river — stinking and highly polluted. But the waterway, once called the Thames of South India, still serves as a source of groundwater recharge and even irrigation in neighbouring Tiruvallur district.

The slow, meandering 65-km long river, originates in a sleepy village called Cooum in the district. People like Sriram V, who know the history of Chennai, say that the name of the village — and that of the river —may have been derived from ‘coopam', which means a well or a deep pit from where the water comes. “It was also known as Triplicane river and Poonamallee river since it travels through these localities,” he adds.

The big tank in Cooum village gets its inflow from the Old Bangaru Channel, which branches out of Kesavaram anicut, located about 80 km from Chennai. A rickety ride on the long winding road from Tiruvallur town leads to the historic anicut, which diverts the surplus water from Kaveripakkam in Vellore district through a regulator to Cooum tank. The paddy fields and green pastures on either side of the road stand testimony to the fresh water source. The river bed is dry as it is a seasonal river and depends on nearly 60 tanks en route to feed it. Its width varies from 120 m to 40 m outside city limits.

Located in Arakkonam panchayat union, the Kesavaram anicut is the decisive point of the flow in the two rivers — Kosasthalaiyar and Cooum, which branches out of it. A lone irrigation assistant — called laskar — has been deputed to monitor rainfall and flow in the rivers and operate the regulator for water distribution.

A plaque with its paint peeling off reads that the regulator with 16 vents was constructed in 1914 and operated since 1945. The regulator is opened whenever the Poondi reservoir, a source for Chennai's drinking needs, does not need water. “It has not been opened after 2007,” said an official of Water Resources Department, a wing of Public Works Department.

The Cooum river has not been spared of abuse even at its source. Encroachments along its banks are common in several localities such as Kesavaram, Narasingapuram and Sivapuram. Illegal sand mining is also rampant. The Cooum tank near Perambakkam itself has lost much of its water retention capacity due to excessive removal of soil from the water body. The mushrooming of brick kilns around the area has led to the misuse of the tank, say villagers.

D. Manickam, a farmer at Cooum village, said: “Many of the 2,500 families in our village depend on the tank for agriculture. I cultivate paddy or groundnut. When the channels go dry, I source groundwater through rented borewells. Agricultural activities have dropped by 40 per cent over the years due to water shortage. The government must arrest illegal earth removal from the tank that caters to 18 villages.”

Farmers also underline the need for constructing more check dams to store and recharge the water table. R.P. Adhiseshan, a resident of Perambakkam, said that many farmers cultivate less water-intensive crops like brinjal and also flowers to tide over the shortage. Construction of check dams at every five km would improve depleting groundwater table, they say.

The river is the first to be affected owing to rapid urbanisation and lack of solid waste management. According to Water Resources Department sources, the river travels 25 km through nearly 20 villages such as Ekatur and Satharai to reach the Korattur anicut. As the Cooum tank does not have a defined course, the river takes a shape only near Perambakkam-Mappedu Road, they say.

The stretch near Aranvoyal and Manavala Nagar provides a visual treat with water stagnating in the river. A number of packaged-water units have sprung along the river to reap its rich benefits. Officials of Water Resources Department WRD say that the water from Krishna river received in Poondi reservoir is often diverted either to Chembarampakkam reservoir or to flush the Cooum river through the new Bangaru channel. The flow of river would also increase groundwater in a radius of 10 km.

The department is now in the process of rehabilitating tanks in the Cooum sub-basin and providing more check dams in the river. Downstream from Paruthipattu, the waterway gets reduced to being a sewage carrier.