Several waterbodies dot Outer Ring Road (ORR) between Vandalur and Minjur. The Environmentalist Foundation of India (EFI), a conservation group, has joined hands with the Water Resources Department (WRD) to structurally restore a few lakes along the route.

These waterbodies have been reduced to vacant spaces ridden with vegetation like Prosopis juliflora (seemai karuvelam) and lack proper boundaries. The EFI has taken up restoration works in five lakes in Poonamallee, Kolappancheri, Panayanthangal, Konimedu and Vellacheri this year. The organisation has documented nearly 78 waterbodies along ORR and already rejuvenated those at Konimedu, Minjur and Vandalur.

“We chose to rejuvenate the waterbodies located along ORR as it is easy to structurally restore such lakes before rapid urbanisation occurs in the region. We have started work with the administrative support of the Tiruvallur Collectorate. These lakes also fall in the zone that receive intense rainfall,” said Arun Krishnamurthy, EFI’s founder.

Most of these waterbodies are intermediary storage points and surplus water from these lakes join various rivers, including Adyar, Cooum and Kosasthalaiyar. It was imperative to protect these waterbodies as a source of irrigation, groundwater recharge and freshwater habitat, he said.

Spread over nearly 100 acre, Poonamallee lake is surrounded by arterial roads like ORR and Chennai-Bangalore Highway.

It had only patches of water and was overrun by invasive Prosopis juliflora until a few months ago. Besides creating nesting islands for birds and defining the inlets and outlets, techniques like segmented restoration and dual embankment are being employed as part of the lakes’ restoration.

Cavities have been created at different depths and levels of the lakes to better store floodwater and allow free flow across the lakes’ contour.

Moreover, dual embankment would ensure improved stability. Regulatory trenches were developed in the foreshore area as a natural boundary to prevent encroachments.

In addition, work is under way to plant 6,500 saplings by October in 12 lakes along ORR. Officials of the WRD said both the department and the Tiruvallur district administration had given permission to NGOs for such rejuvenation efforts.