"In Chennai, each of its lakes has a natural?flood discharge channel which drains the spillover. But we have built over many of these water bodies, blocking the smooth flow of water. We have forgotten the art of drainage. We only see land for buildings, not for water," she said.
She said that 'Down To Earth', the science and environment fortnightly that CSE helps publish, had earlier reported on the destruction of wetlands in Chennai.
CSE said that a number of cities including Chennai are both water-scarce as well as prone to flooding.
"Both problems are related excessive construction which leads to poor recharge of groundwater aquifers and blocking of natural drainage systems. While Chennai has been struggling to meet its water needs and has been even desalinating sea water at a huge expense, it allowed its aquifers to get depleted," said Sushmita Sengupta, deputy programme manager with CSE's water team.
CSE's research shows that Chennai had more than 600 water bodies in the 1980s, but a master plan published in 2008 said that only a fraction of them are in healthy condition.
According to records of the state's Water Resources Department, the area of 19 major lakes has shrunk from a total of 1,130 hectares (ha) in the 1980s to around 645 ha in the early 2000s, reducing their storage capacity.
The drains that carry surplus water from tanks to other wetlands have also been encroached upon.