After the Centre for Climate Change in Anna University came out with a report that the annual rainfall in the city may experience a 5% decrease by 2050, the university’s Department of Geology has initiated a study on how a change in rainfall pattern would affect groundwater resource.
At present, the annual rainfall in Chennai remains at 140 cm.
The prediction of decrease in rainfall over the next three decades was arrived using precis, a climate modelling system, and taking into account several weather parameters, including sea surface temperature, and rainfall data for 100 years.
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Alarmed by this data, the Department of Geology has started a study on how the change in rainfall pattern and rapid urbanisation would affect groundwater resources and lead to seawater intrusion.
“We found that at least 15 waterbodies have vanished between Washermanpet and Saidapet over the decades as they were developed into residential localities,” said Samurembi Chanu, a research scholar, Anna University.
The team is now studying the small waterbodies that were found in a city map of 1893. L. Elango, Department of Geology, Anna University, and vice-president of the International Association of Hydrogeologists (Indian chapter), said the area of the waterbodies in the city and suburbs has shrunk from nearly 12 sq.km in 1893 to about 6.4 sq.km. in 2015, mainly due to urbanisation.
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With intense rainfall in short spells predicted in the years to come and with the decreasing open space, it is likely that more rainwater may drain into the sea than percolate down the earth.
Check-dams needed
The study aims at assessing the impact of variation in rainfall pattern and vanishing waterbodies on groundwater resource in the next few decades.
“We found that groundwater resources can be significantly improved if more check-dams are constructed in Araniar-Kosasthalaiyar river basin in the next 10 years. Besides, a reduction in groundwater extraction in Tiruvallur district could help. Also, a link channel may be created between Araniar and Kosasthalaiyar river to improve groundwater resource and arrest seawater intrusion,” he said.
Different methods of rainwater harvesting need to be adopted to conserve maximum rainwater that the city may receive in a short spell.