Wanted: A plan to quench Bengaluru's thirst

Managing and utilising Bengaluru’s abundant rain to reduce the city's piped water demand needs a holistic plan

A five-tower apartment complex in Bengaluru’s Hebbal was dependent on 130 ‘loads’ or orders of water tankers every month. Post the installation of a rainwater harvesting (RWH) system, the residents of the buildings have watched this number come down to 30. The city’s dependable rain, coupled with a well-maintained rooftop RWH system meets the rest of its water consumption needs.

A few streets away, at an independent house in the area, the beginning of the summer season brings with it empty sumps and dry taps, despite the full-fledged RWH system the building has. The building’s five residents spend Rs 500 every week to supplement their water supply during the hotter months of the year. While rainwater is collected from the 30x40 sq ft property’s rooftop, a majority of this leaks from the pipes connecting to the filter and storage tank. The runoff rainwater floods the front yard and overflows onto the road, say, residents. Without the required maintenance, the RWH system here lies mostly ineffective.

Tales of defunct, absent or insufficient rooftop rainwater harvesting mechanisms are seen across the city, leaving the city’s rainwater harvesting potential remain untapped.

During an average rainfall year, Bengaluru generates approximately 230 billion litres of water as run-off. “Out of this, only 10% is currently harvested, according to data from the Bangalore Water Supply and Sewerage Board (​​BWSSB),” says Shreya Nath who works on the Urban Water Program at WELL Labs.

According to her team’s estimates, rooftop rainwater harvesting alone can supply over 17% of the city’s total water demand. However, “it is estimated that 67 MLD (million litres per day) of rainwater is harvested daily in the residential context. This accounts for only 3% of the total water needed,” adds Shashank Palur, a hydrologist who is part of the program.

Bengaluru’s water supply comes at a highly subsidised rate. Estimates indicate that BWSSB spends approximately Rs 80/kilolitre (kl), but “the cost to the consumer starts at Rs 7/kl in the domestic context and Rs 50/kl for non-domestic connections,” says Shreya.

As a result, the water supply comes at a constant deficit to the city’s budget, with this year’s projected deficit for revenue alone totalling Rs 1,050 crore.

Promoting water harvesting

According to the BWSSB, a total of 1,84,543 rainwater harvesting connections have been installed in the city so far.

In 2009, new rules were notified, making rainwater harvesting systems mandatory for new buildings measuring 30x40 sq ft and above, and older properties measuring 60x40 sq ft and above. This includes a collection system, a filter and a storage tank, from which the water can either be used directly or transferred to recharge wells that feed into groundwater.

Yet, as of February 2023, more than 50,600 buildings that fall under this criteria are yet to install rainwater harvesting facilities.

In the cases where house owners fail to implement the notified rules, the BWSSB is supposed to serve a three-month warning. Following this, a 50% penalty is charged on the bill. Three more months later, this increases to a 100% penalty.

“We also do not sanction new water connections in homes unless they have installed rainwater harvesting facilities,” says a senior BWSBB official. In 2022, a new notification was released, requiring buildings of 60x40 and above to reuse at least 60% of the rainwater collected. Only up to 40% can be directed to the recharge pit.

The administrative body collects an average of Rs 1.5 crore each month in penalties. In February, the BWSSB collected Rs 1.87 crore in fines from 38,779 connections.

These fines go into awareness programmes, infrastructure and community initiatives, says the official. He cites the example of the rainwater harvesting theme park constructed by the BWSSB in Jayanagar. The facility is home to demonstrations of 26 RWH models. Training sessions for school children, researchers, architects and others are organised here.

The infrastructure

The rainwater harvesting ecosystem has certainly developed over the years, says A R Shivakumar, a senior scientist and water management advisor. “We have come full circle, with the availability of a wide range of products and skilled labourers,” he explains.

Rainwater harvesting is an answer to the need for clean water, he adds. “But for this to work, these systems must become part and parcel of every building.”

For the past 27 years, the former IISc researcher and his family have been deriving their water supply from the rainwater harvesting system set up in their Bengaluru home.

The longest gap between two rainy days in Bengaluru is between 80 to 100 days. “When you take that into account, you need to build a tank with the capacity to store 45,000 litres of water to become self-sufficient,” Shivakumar says.

However, the scientist’s case is a very rare one. The reality is that awareness is starkly low, says RWH consultant Suchethana A R. “Many people just install the pipelines, but never make use of the systems because they do not know how to, and how useful it can be,” he explains.

In reality, only about 40% of BWSSB connections have functional RWH systems, estimates Suchethana. While new houses do have systems installed, many are just for appearance. “In many apartments, they show the RWH system in the planning, to get the plan approval, but it is never used or implemented,” he adds.

Reviewing and addressing the issue is dependent on the particular engineer assigned. “In some areas, an official can sometimes take interest and conduct inspections,” says Suchethana. Then these homes reach out to rainwater harvesting consultants and services to set up the facility.

Upkeep and space are challenges for homeowners, explains water conservation expert S Vishwanath. “Space is a major constraint, especially in buildings not constructed according to regulation,” he says. Keeping the catchment areas, usually terraces, clean is another challenge, he adds.

Government buildings harvest and use rainwater as a standard practice, says the BWSSB official. Most parks in the city also have a mechanism to ensure groundwater recharge, he adds.

Pricing water right

Singular focus on rooftop rainwater harvesting will continue to fall short, says Veena Srinivasan, water researcher and executive director of WELL Labs. She highlights the need for an approach that emphasises stormwater management.

“When high-volume rainfall occurs, there is no place for water to go. The need is not just for rooftop RWH systems. It goes beyond that—we need storage systems, rain gardens where the water can slowly percolate into the ground, and stormwater drains to mitigate flooding,” she says.

Limiting the discussion and regulation to rooftop rainwater harvesting—a largely private investment and endeavour—is not a holistic solution, she adds.

Several experts also point to the low tariff of water supply by the BWSSB as a reason for low motivation among homeowners to use rainwater. “Since water bills are in the range of Rs 300 to 500, people even end up paying double the penalty, instead of installing the system,” says Shivakumar.

The impact it makes on cost-saving is also not very attractive, he explains. Depending on the length of the pipeline, filter and recharge pit, the average RWH installation can cost between Rs 5,000 to Rs 25,000. “The investment cost is high, and the savings are low, which leads to low motivation to install the systems,” Shivakumar says.

However, the investment yields returns within a year, says Suchethana. “While labour charges and product prices have increased over the years, it is still a lifelong investment that requires minimal maintenance.”

While efforts to educate have increased, overall awareness of the benefits and ease of rainwater harvesting varies greatly across the city. “Political will is the real need, and water tariffs need to increase. This would motivate people to save and use rainwater, and derive their water supply needs from nature,” says Shivakumar.

Progressive water pricing, wherein the cost is based on water usage, could prove to be a potential solution. Shashank cites examples of apartment buildings dependent on tankers and borewell water. “Some have moved towards water metering for individual flats, and as a result, units that consume higher than a certain amount are charged accordingly,” he says. This has led to reductions in water usage, with some apartments reporting almost 25% savings on the total water bill.