CHENNAI: The Water Resources Department (WRD) is keen on commencing work on the sixth reservoir (Mamallan) in the Kovalam basin near Thiruporur amid arguments that alternative options with higher water storage capacity are not being effectively considered by the water resources department. Metro Water officials, however, say that setting up water treatment plants (WTP) near multiple, scattered water bodies will be cost-intensive and finding space to build them within the city will also be difficult.
While local Kovalam fishermen and activists are opposing the Mamallan project on concerns over livelihood and environmental impact, there are others who point to available storage capacity in recently restored water bodies to argue against the project. For instance, Chennai’s recently restored water bodies have a combined holding capacity of more than 2.3 TMC (Thousand Million Cubic feet), about 0.65 TMC higher than the 1.65 TMC capacity of the Mamallan reservoir.
Daniel Robinson, an expert, who worked with Chennai Smart City Limited (CSCL) in restoring 210 water bodies under Smart City Project, opined that creating decentralised water supply systems with locally available sources, such as local lakes, could be a more sustainable option. Apart from the 210 water bodies under the civic body’s control, Chennai has several big lakes like Porur and Retteri lakes.
“There should be a unified authority to maintain water bodies in the city as water bodies are maintained presently by various departments like Greater Chennai Corporation (GCC), Water Resources Department, and Hindu Religious and Charitable Endowments department,” he said.
Meanwhile, a senior Metro Water official said that 210 water bodies were restored with the intention of increasing the groundwater table and not as a drinking water source. “Moreover, drawing water for supply from those water bodies is not viable as setting up water treatment plants (WTP) near the water bodies is cost-heavy and there is also no space,” he added.
When asked if the use of desalination plants could be an alternative to a new reservoir, the official explained that supplying water from desalination plants would cost Rs 50 to Rs. 60 per kilolitre while surface water (lake water) would cost only Rs. 8 per kiloliter. Presently, Chennai has three desalination plants with a total capacity of 360 million liters per day (MLD) and another 400 MLD plant is under construction in Perur. Further, studies have pointed out that three abandoned quarries in Sikkarayapuram can provide 600 mcft of water annually.
Presently, Metro Water lets treated sewage water into Porur lake and supplies the water for drinking needs after treatment in Porur water treatment plant. Work for a similar initiative has been completed in Retteri lake while in five lakes (Perungudi, Narayanapuram, Kovilambakkam eri, Kilkattalai and Ayanambakkam), similar works are underway.
A demand assessment study conducted for the reservoir project has estimated that the present GCC area would require 1,702 MLD (million litres per day) of drinking water by 2035 and 2,178 MLD by 2050. The rest of the Chennai Metropolitan Area (CMA) would require 821 MLD and 1,568 MLD by 2035 and 2050 respectively. On Tuesday, the Metro Water supplied 1,217 MLD using the existing five reservoirs and desalination plants that function at less than half of their production capacity.