Excessive drawing of groundwater from water bodies in and around the Pallikaranai marshland will have a serious impact on the landscape, a study has warned. It has also cautioned against excessive extraction by water tankers during summer.
The study, commissioned by Conservation Authority of Pallikaranai Marshland, began in February 2012 and was completed in February 2014. The study area covered a five-km radius of the marsh.
It said excessive pumping could lead to groundwater depletion where groundwater is extracted at a rate faster that it can be replenished. The impact of groundwater depletion could vary. The first and foremost direct impact was the the loss of base flow. This could result in negative impact to various components of the landscape including increased magnitude and frequency of floods, loss of wetland changes in channel morphology, loss of wildlife habitat and reduction in biodiversity, drying up of wells and salt-water intrusion, the study warned.
Three forms of water extraction (both surface and ground water) were noticed during the study period – totally commercial, partly commercial and domestic/household level use. On an average, 700-800 tankers with a capacity of 10-12,000 litres each were filled every day from the western and south western peripheries of the marsh. These activities were carried out by private parties that have contracted erstwhile agricultural bore wells or wells, and the cost of drawing water is about Rs 190/- to Rs 200/- per tanker. There is no regulation or control for extraction. It was observed that surface water from the Narayanapuram and Pallikarnai wetlands was also drawn by lorries at night.
The presence of seasonally-filled wetlands is higher, 6 in east side, 10 in west, 8 in north and 5 in the south side of the marsh. This includes the lakes of Velachery, Adambakkam, Perumbakkam, Perungudi, Kilkattalai, Muvarasapattu, Madipakkam, Puzhudivakkam, Nesavalar Nagar Lake and Narayanaparam. The total number of small ponds in and around the marshland is 13. Their number is higher along the western side of the marsh.
The study also suggested the introduction of a licensing system for establishing commercial extraction units, as well as evolving norms for sustainable extraction by tankers. Regulation and monitoring of unsustainable extraction of water from borewells in the water bodies is ncessary, it added.
