Tamil Nadu govt seeks CRZ clearance for new reservoir in Kovalam

CHENNAI: The Water Resources Department (WRD) submitted a proposal last week to the Tamil Nadu Coastal Zone Management Authority (TNCZMA) seeking Coastal Regulation Zone (CRZ) clearance for building a drinking water reservoir in the Kovalam sub-basin between East Coast Road (ECR) and Old Mahabalipuram Road (OMR). The project, announced by the government in the 2025-26 state budget, will require 4,375 acres of coastal wetlands to build what will be the sixth major reservoir in and around Chennai. Designed to hold 1.655 tmcft of freshwater, it is expected to supply 170 MLD of water to southern Chennai and fast-growing peri-urban pockets. As per the documents available with the TNIE, on June 3, the proposal first came before the State Environmental Appraisal Committee (SEAC) seeking environment clearance (EC). After deliberations, SEAC returned the proposal, stating that the reservoir does not fall under projects requiring prior EC, since it involves no river valley development, hydropower, tunnelling or mining. However, the committee pointed out that the site falls within CRZ-I, II, III (NDZ) and IVB and therefore requires CRZ clearance under CRZ Notification, 2011. It asked WRD to examine treatment technologies such as SBR-UF or MBBR-UF to prevent long-term water quality deterioration once the reservoir is operational. Following this, WRD approached IIT-Madras for a technical feasibility assessment. In its communication dated October 30, IIT-Ms Civil and Ocean Engineering experts concluded that the reservoir is technically feasible. Spread across villages, including Thiruvidanthai, Kalavakkam, Nemmeli, Thiruporur, Thandalam, Krishnankaranai, Pattipulam, Paiyanur, Saluvankuppam and Mamallapuram, the proposed site sits in a natural flood bowl connected to the Kovalam watershed. It receives surplus flows from 69 upstream irrigation tanks. Phase I will cover 1,770.5 hectares and includes excavation of bunds, construction of a foreshore embankment, creation of a peripheral drain to reroute monsoon flows, and formation of a freshwater lake with a 17.71 sq km water spread area. The estimated project cost is Rs 471 crore. WRD officials say the basins topography with a current average bed level of (+)0.35 metres and a proposed Full Reservoir Level of (+)3 metres makes it the only viable large-scale storage site in the sub-basin. The region, dominated by IT corridors and expanding peri-urban settlements, lacks a major reservoir and relies heavily on desalination and groundwater, the latter showing signs of depletion and seawater intrusion. Chennais drinking water demand, now over 1,100 MLD, is projected to surpass 2,500 MLD by 2035. WRD says the Kovalam reservoir will be critical to augment drinking water supply and mitigate chronic flooding in upstream OMR villages. Environmental assessments, however, highlight the ecological cost. The Kazhuveli Wetland Impact Assessment, conducted between October-November, documents that 65% of the site is marshland and 35% saltpans, supporting 102 bird species, including migratory waders that depend on shallow seasonal waters for feeding and roosting. The study warns that converting a dynamic wetland into a three-metre-deep freshwater reservoir will fundamentally alter the local ecology, modify salinity patterns and displace wader population. The consultant has recommended a habitat mitigation plan, including preserving shallow wetlands and creating managed roosting islands. If cleared, the proposal will move to the National Coastal Zone Authority for final approval. A senior WRD official said the project is crucial considering the current average drinking water supply in Chennai is around 700 to 800 MLD, while current demand exceeds 1,100 MLD. This demand is expected to double in the next decade. The water needs of the broader CMA region also remain uncertain and largely unmet, the official said.