Over the last three years, Bengaluru has been struggling between two contradicting situations. While the city was struggling to manage the flash floods, owing to heavy rainfall in the 2021 and 2022 monsoon, this year the city is staring at a possible water crisis. Surprisingly, sometimes both situations occur simultaneously owing to heavy rainfalls in a short duration.
However, a recent report by WELL Labs, a research and innovation centre at the Institute for Financial Management and Research (IFMR), points out a single sustainable solution to both these issues– efficient reuse of wastewater.
According to the report titled ‘How Water Flows Through Bengaluru: Urban Water Balance Report’, Bengaluru is releasing close to 1,040 million litres a day (MLD) of treated water into the lakes, and close to another 659 MLD of rainwater is reaching the lakes as runoff during the monsoons. As a result, most of the lakes in the city are nearly half full all the time.
“Flooding is a problem in many parts since there is no path for the water to flow and reach the next lake. Reuse of treated wastewater is also relevant here because, currently, lakes are full of treated wastewater and cannot act as flood buffers,” the report said.
Explaining the situation, Dr Veena Srinivasan, executive director, WELL Labs, said that the flow of water into the lakes has brought down its capacity to hold floodwater.
“Since most of the lakes are half full due to the inflow of both treated and untreated water, they have a reduced capacity to hold floodwater. Hence, we need to move from a linear water economy to at least a partial circular water economy which will decrease the flow of treated water into lakes,” she said.
She added that the government should also look at policies that allow use of lake water for various purposes.
While the reuse of wastewater could be a solution to the flooding problem, it could also help improve water security and reduce dependency on groundwater and Cauvery water.
“Currently, only one-third of the city’s wastewater is redirected for external reuse, which means it is taken to Kolar, Chikkaballapur, and Devanahalli districts where it is used to replenish both groundwater and surface water sources. The remaining water flows into lakes and runs off land to join rivers downstream. This means the huge quantum of wastewater generated in the city is an untapped resource. Once treated to the required quality, wastewater can significantly mitigate freshwater consumption and can be crucial in making the city water resilient during low rainfall years,” the report said.