Groundwater levels up in city after rain

According to a release from the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB), the comparative statement of average water levels, studied across 15 areas in the city in November 2016 and 2017, shows that there is a rise in the level – ranging from 0.55 mts to 2.88 mts below ground level. 

The aquifers (water-bearing permeable rock) in the city depend predominantly on the SW monsoon (400 mm from July to September) and the NE monsoon (800 mm from October to December) for recharge. 

Areas such as Perungudi, Alandar and Valasaravakkam show the most rise in water level, with an improvement of 2.88 mts, 2.44 mts and 2.38 mts respectively, below ground level. Thiru Vi Ka Nagar and Manali show the least improvement with a rise of 0.55 and 0.68 mts respectively, below ground level. 

The CMWSSB monitors groundwater level and quality (TDS) every month through a network of 145 observation wells spread across 426 sq.km. In Chennai, the subsoil condition varies - such as sand, clay and hard rock formations - and therefore the percolation rate also varies in these soil types.