CHENNAI: This month, when the city received heavy rain on two different days, we knew how shallow wells to tap ground water and better maintenance of water bodies are important. Rainwater harvesting structures alone will not save the day anymore.
The civic body and metro water officials need to completely change their strategy in terms of water distribution and usage and relook at the lake restoration projects. There is only 50% rain water harvesting coverage in the city, but almost all areas barring a few locations such as Ambattur, Ayanavaram and Kilpauk Garden had groundwater tables at ground level.
Chithra Kulam in Mylapore did not overflow during 2015 floods. Now it is happening only because the pre-monsoon levels were high and the first spell of rain brought it to ground level. In Karpagam Gardens, Adyar, Palavakkam, it was found that ground water table was actually overflowing. People need to first extract more ground water by digging shallow wells or tubewells inside houses and apartments. They should begin using that. Metro water should charge for water supply. This will encourage people to depend more on wells.
Usually, bore wells are 100-150 feet deep. But open wells and tube wells are 30 feet deep. The latter dug in homes will help in depleting the high water table and enable improved water percolation.
One point that everyone is missing is that the earth was already saturated. Since metro water supply was copious, not much of ground water was extracted. That resulted in the extreme flooding. The rain that fell on Chennai caused all the flooding and not the excess water that was let out from the water bodies as happened in 2005 and 2015.
Also, diverting all storm drain water diverted into existing water bodies located in the extended area of Chennai and excess water into the nearby water ways will help in better recharge of aquifers, besides mitigating floods. For example, on Thoraipakkam – Velachery road, rain water can be diverted to the water bodies, which can then be converted into small reservoirs and supplied to the neighbourhood just like it was attempted at Retteri and Porur.