CHENNAI : The rainfall in Chennai is likely to reduce by 5 per cent by 2050. However, there will be an increased frequency of catastrophic rainfall, said professor L Elango from the Geology department of Anna University. Speaking at ‘Urban Ecology and Resilience’, a conference on climate change here on Thursday, he said, “We used the global climate change model, which studies the climate change pattern across the globe in grids of 25 sq km. We down-scaled it to study the grid in which Chennai fell to predict this pattern,” he said.
At the event organised jointly by the UN Human Settlements Programme and AARDE Foundation, Elango said while the overall rainfall would come down by 5 per cent, the number of days in which the precipitation falls would also get reduced. “Therefore, the number of massive floods and storms and other weather extremities may be more frequent,” he observed. Apart from studying 13 decades of rainfall pattern, factors such as wind velocity, surface temperature and ocean currents were also studied carefully to arrive at the results, he said.
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Since Chennai falls on a terrain formed on a hard sediment, rain water will not get stored as ground water unless there’s a robust system of reservoirs, Ilango said, adding that during heavy rains, the run-off into the ocean would be greater, if storage capacity of the landscape was lower.“We studied 17 wells in Chennai that were completely submerged under water during the 2015 floods. The study of water samples showed that the water in these wells had high composition of not only pollutants but also microbes,” he said, pointing out that the declined quality of ground water was a definite consequence of such catastrophic floods.
“To mitigate this problem, we are now studying different waterbodies across the city and State to see how they can be made more resilient to natural calamity,” he said. Building check-dams and creating percolation zones in waterbodies are some of the solutions that are emerging through this research, said Elango.
Need to store rainwater
Since Chennai falls on a terrain formed on a hard sediment, rain water will not get stored as ground water unless there’s a robust system of reservoirs, Ilango said