Summer sorted in Chennai, courtesy monsoon – Times of India

CHENNAI: At least 479mm rainfall Chennai and surrounding areas received during the two cyclones – Nivar and Burevi – flooded roads, but it also recharged the city’s aquifers and pushed up ground water tables in all zones. And with the reservoirs around the city brimming, Chennai Metro Water Supply and Sewerage Board says it will be able to tide over the 2021 summer without rationing supplies or sending water trucks around the city.
“We expect this water to last till the end of next year,” said Metrowater managing director T N Hariharan. On Sunday, the total water stored in the five reservoirs – Poondi, Choolavaram, Redhills, Kannankottai Thervoykandigai and Chembarambakkam – had nearly doubled to 10,311mcft compared to 5,166mcft on the same day last year. “This water in reservoirs alone will last for 10 months,” he said. Water in Sikkarayapuram and Erumaiyur quarries, which help the city during peak summer of drought years, will be kept as reserve, he said.

In addition, after nearly five years, all the 15 zones in the city have recorded an average increase of 1.65 metres in the groundwater level since October. Official data show that between November 2019 and this year, there has been an average increase of 1.46m in the groundwater table. Even in areas like Sholinganallur, where there is no piped water supply, the water table has seen an increase of 0.54m. The ground water level which was at 3.44 meters in November 2019 is now at 1.89 meters.
The dependence on the two desalination plants in Nemmeli and Minjur, which together can produce 100MLD water, has come down. The production capacity of these desalination units has reduced to 82MLD since November, but will improve, officials said.
Despite being a bountiful year, the city’s water managers say they have contingency plans. While several state agencies including the CMDA are planning for infrastructure to maintain resources for a long-term plan to manage water scarcity, Metrowater is working on solutions for judicious use of water.
Since November 25, Metrowater has increased water supply to 830MLD from 750MLD. Of this, residents in core areas get 653MLD and those in added areas get 112MLD. “People in the core city areas will get water supply every day for about four to six hours. We have planned in such a way that residents will get water every day but for fewer hours. Residents in added areas will get water supply on alternate days,” Hariharan said.
While weathermen forecast the monsoon to bring in more rains, water management experts say the state should take into account the condition of the tanks and water channels before rejoicing. Madras Institute of Development Studies professor S Janakarajan, who specialises in areas of water said: “A majority of the tanks and supply channels are heavily silted. This will reduce their storage capacity by half. Chennai, Tiruvallur and Kancheepuram districts are considered one integrated watershed. Tanks in these districts are interlinked. Surplus water from the tank flows into a downstream tank. With silt accumulation in all these water bodies, the water flows from these tanks even after one or two spells of rainfall,” he said.
Besides desilting and maintenance, water managers should consider “induced water management, say a few scientists. “For instance, the supply should be 750MLD instead of 830MLD for a few more months every day across all areas. This will ensure minimal tapping of groundwater. This will be an ideal time to store water in reservoirs as evaporation and seepage will be less compared to May or June,” said hydro geologist J Saravanan.