Encroachments claim Pallikaranai water bodies
The Pallikaranai Catchment, spanning 306.27 sq km, is a key hydrological zone that retains 25 sq km of water bodies with 37.5 mcm storage capacity;
Pallikaranai marshland
CHENNAI: A detailed study conducted by city-based Uvakai Research Foundation has revealed that as many as 165 water bodies, with a combined extent of 7.35 sq km, in the Pallikaranai catchment area have been swallowed by encroachments.
According to the study report titled, 'Hydrological insights from Pallikaranai catchment in Kovalam basin', the 165 lost water bodies include 31 lakes and 134 tanks. Moreover, a temporal analysis of the 185 geocoded water bodies revealed that most of them retained measurable water for fewer than 30 months over the past decade, indicating both reduced retention capacity and hydrological instability.
Interestingly, as many as 116 new water bodies were identified that are not marked in the historical revenue records, of which 45 are abandoned quarries. The study was conducted by using multiple sources such as revenue maps, satellite imagery, RTI records and Google Earth.
The Pallikaranai Catchment, spanning 306.27 sq km, is a key hydrological zone notable for its dense network of water bodies. It comprises three sub-catchments—two draining into the Pallikaranai marsh and one directly into the Buckingham Canal. The catchment retains 25 sq km of water bodies with a combined storage capacity of 37.5 million cubic metres (mcm). The Pallikaranai marsh alone (694 hectares) can store 6.94 mcm of water, as per the report.
"In the Pallikaranai catchment, the existing water bodies and marshlands—if maintained at an average depth of 1.5 metres (about 5 feet) —can store up to 65% of the rainwater runoff during heavy rainfall events like 400 mm. The remaining 35% can flow safely to the sea through natural drains like Okkiyamaduvu and Buckingham Canal, provided they are well maintained and function efficiently," the report said.
It added that the remaining 35% of runoff can be stored with planning, such as deepening existing water bodies, restoring original depths through desilting, and identifying additional storage spaces, the excess water can be saved and used to meet the city's water needs.
Pointing out that the Pallikaranai Marshland lies at a low elevation, the report recommended the government to designate the ecologically sensitive region as no-development zones.