New reservoir for Chennai will get delayed as green nod application returned

CHENNAI: The construction of sixth reservoir near Tiruporur to augment the city’s drinking water needs will get delayed as the State Level Expert Appraisal Committee (SEAC) has returned the application for environmental clearance directing the Water Resources Department (WRD) to avail Coastal Regulation approval.

The project came up for discussion in the SEAC recently when the Committee advised to submit the proposal before the concerned Coastal Zone Management Authority (CZMA) for appraisal and recommendation as per the provisions of the CRZ Notification, 2011 and subsequent amendments.

“The proposed reservoir project does not fall under the purview of Environmental Clearance under the EIA Notification, 2006 and its subsequent amendments, as it involves neither major river valley development nor any hydroelectric generation or tunnelling/mining activities. However, the project is located in a Coastal Regulation Zone and therefore attracts CRZ clearance as per CRZ Notification, 2011,” the minutes of the meeting said.

Also, the Committee observed that the proposed diversion canal to carry existing drains and natural storm water channels in the surrounding villages carrying greywater from nearby habitations may not be sufficient to handle the untreated inflows and may ultimately affect the reservoir’s water quality adversely, reduce effective storage capacity, and pose long-term risks to sustainability and public health. Following this, the Committee suggested the WRD to explore the feasibility of treating such water using appropriate technologies such as the Sequential Batch Reactor (SBR) in combination with Ultra Filtration, or the Moving Bed Biofilm Reactor (MBBR) coupled with Ultra Filtration in order to safeguard the reservoir from potential contamination and to ensure compliance with applicable environmental quality standards.

A few weeks ago, the WRD applied for Terms of Reference (ToR) for Rs 471 crore reservoir that would fall under the Kovalam sub-basin. The reservoir will have an overall catchment area of 414.08 sq km and have total storage capacity of around 1.655 TMC with an annual yield of 2.25 TMC. The new reservoir will have a storage depth of 3 metres and a water spread area of 17.71 sq km.

As per WRD document, the water stored from reservoir will be supplied to extended Corporation areas like Sholinganallur, Medavakkam, Pallikaranai, Siruseri, Kelambakkam, Mamallapuram and others. The reservoir to be built close to the shore between East Coast Road and Old Mahabalipuram Road.

The reservoir will indirectly augment groundwater recharge, check seawater intrusion, and directly supplement the Chennai city water supply with up to 170 MLD for nine months each year. The reservoir will contribute to 17.17% of the present water demand of the city, once completed, as per the document.

The department has clarified that instead of storing water in mountainous dams, which capture runoff from limited portions of the catchment, coastal reservoirs allow for the storage of water in estuaries, capturing excess floodwaters from the entire catchment area.

NEW RESERVOIR

· Total water spread – 17.71 sqkm

· Depth of the project – 3 metres

· Total storage capacity – 1.655 TMC

· Total annual yield – 2.25 TMC

· Cost of the project – Rs 471 crore

WATER DEMAND ASSESSMENT (IN MLD)

Area - 2015 - 2020 - 2035 - 2050

GCC - 922 - 1333 - 1702 - 2178

Rest of CMA - 214 - 387 - 821 - 156

TOTAL - 1,136 - 1,720 - 2,523 - 3,746