Chennai is composed of a blue-green infrastructure – a composition of wetlands (blue) and vegetation patches (green) of areas such as Guindy National Park, Vandalur, Madras Theosophical Society and educational campuses such as IIT-M and Madras Christian College.
Wetlands perform an important hydrological function by acting as sponges — “soaking up water during wet periods and releasing it during dry periods” — and the Greater Chennai Corporation area has an estimated total of 474 wetlands (Bhaskar et al, 2017). Wetlands of Chennai play an important role in the hydrology of the city – they help in collecting floodwater and in recharging groundwater.
The most critical wetland in Chennai’s drainage system is the Pallikaranai Marsh, a freshwater Marsh which, along with its satellite wetlands, forms a large part of the floodplain on which South Chennai is located. The Pallikaranai marsh drains an enormous area of about 250 square kilometers and over the years, its size has drastically reduced from 6000 hectares in the 1990s to 593 hectares at present (Bhaskar et al, 2017).
Pallikaranai marshland is an inland freshwater marsh. A marsh is an area, where water covers the ground for a longer period and is dominated by grasses and herbaceous plants. These grow in waterlogged, but rich soil deposited by rivers. Marshes are also common in deltas, where rivers empty into a larger water body. They possess unique features buffer stormy seas, slow shoreline erosion, offer shelter and nesting sites for migratory water birds, and absorb excess nutrients that would lower oxygen levels in the sea and harm wildlife. As marshes are drained for industrial and agricultural development, this protective layer gets diminished. It is one of the last remaining wetlands of Chennai city. It is unique because being a coastal wetland that is largely freshwater offers multiple properties and functions. Historically, a large part of South Chennai was a floodplain and comprised Pallikaranai marsh and surrounding satellite (smaller) wetlands, along with pastureland and dry forest patches. It served as the only water source for irrigation and groundwater source for a major portion of Chennai. It had a spread of 60km2 (6000 ha), around the early 19th century and drains an area of 250 km2 through two inlets viz., Okkiyam Madavu and Kovalam creek, before falling into Bay of Bengal. The distortion to the system came in the form of laying of Buckingham Canal for navigation in 1806.
The marsh has witnessed a steady 90% decline in the past 50 years. In 2002, it had shrunk to the size of 593ha (Care Earth 2002, Central Ground Water Board, M. o. 2017). It used to receive copious volumes of freshwater. However, currently much of the runoff water has been diverted through narrow channels and closed storm- water drains, offering less scope for free oxidation as the water flows. The dynamics of sedimentation has also affected water-land ratio leading to shifts in vegetation and creating new niches for invasive species. It is also the only largest urban wetland in Southern India, falling under Kanchipuram district. Kanchipuram district is situated on the northern East Coast of Tamil Nadu. Pallikaranai is one of the 94 identified wetlands under the National Wetland Conservation and Management Programme (NWCMP) of the Government of India. It is also a Key Biodiversity Area as well an IBA (Important Bird Area).
Pallikaranai is a heaven for diverse flora and fauna, supporting about 188 species of birds, 10 species of mammals, 10 species of amphibians, 50 species of fishes, 21 species of reptiles (endangered Russell’s Viper), and 7 species of butterflies and close to 114 plant species. Many migratory birds use the area as a stopover site during migration and to spend the non-breeding season.
Lack of understanding about the significance of the marsh in an urban environment as a flood regulator and environmentally a highly productive habitat has resulted in the marsh being reduced to around one-tenth of its original size, due to unplanned urbanization, destructive reclamation and dumping of solid and liquid waste.
One of the decisive steps in the protection of the Pallikaranai Marsh was when the Tamil Nadu Pollution Control Board in 2002, commissioned a study to map the extent of the Marsh. The landmark study by Care Earth Trust indicated that the Marsh had lost over 90% of its original area. The 2002 floods led to increased citizen interest in the conservation of the Marsh, leading to the Save Pallikaranai Forum, led by Resident Welfare Associations. Increased attention to the Marsh led to multiple studies on the Marsh, resulting in an increased momentum in the demand for protection. In 2005, a High Level Committee chaired by the Chief Secretary was constituted to discuss a remedial plan and after a series of deliberations, 317 Ha of the Marsh was declared a Reserve Forest in 2007 (Vencatesan, 2007).
With the primary goal of protecting, restoring and conserving wetlands for the cause of biodiversity conservation and human well-being, The Conservation Authority of Pallikaranai Marshland was formed in 2012. This body is registered under the Tamil Nadu Societies Registration Act 1975 (TN Act 27 of 1975) and acts as the key technical advisory body for developing and maintaining the Marsh Lands in a self-sustaining manner.The Authority is chaired by the Principal Secretary to Government, Environment and Forest Department.
