Rainwater harvesting: Is Namma Metro back on track?

A tender floated by the BMRCL to install rainwater harvesting pits on Namma Metro’s purple and green lines is under evaluation. What more must be done to harness water from metro tracks?

Bengaluru: In 2013, Bangalore Metro Rail Corporation Limited (BMRCL) was hailed as the first metro system to install rainwater harvesting facilities. However, this covered just a few kilometres of tracks between Mahatma Gandhi Road and Swamy Vivekananda Road metro stations.

A decade later, the rest of the tracks do not have a solid system to capture rainwater.

“The advantage of metro tracks is that the viaduct on the top is very clean, with no petrol, oil, grease or other pollutants. So the quality of rainwater is extremely good,” points out Vishwanath K, founder of Bengaluru-based Biome Trust. 

This makes capturing clean rainwater a better possibility. In 2012, Biome Environmental Solutions Private Limited proposed a rainwater harvesting system for Namma Metro.

The plan calculated rainfall data for the city and the potential for rainwater harvesting along the metro train track. It looked at the landscaping details and the water requirement in the areas and compared them against the need for and capacity for rainwater harvesting. 

The suggestions also included creating 15KL storage and recharge tanks between three piers (every 56 metres). They included solutions and suggestions for hard rock areas, high water table areas, and weathered rock areas.

“We had suggested that BMRCL install additional storage tanks in rocky areas and not recharge groundwater,” says Vishwanath, founder of Biome Trust.

BMRCL did not act on it fully but tried water harvesting systems between Mahatma Gandhi Road and Indiranagar as a trial in 2013. Pipes carried rainwater from the track through piers, which were either collected or let to recharge on the median. 

“Namma Metro showing us the opportunity for recharging groundwater in Bengaluru, their 50 rainwater harvesting pits constructed in 2012 between MG Road Metro station to Vivekananda Road Metro Station is a good example,” says Raghavendra B Pachhapur, Senior Project Lead working with ActionAid Association, a non-governmental organisation.

However, this was not implemented in all the stretches of the city.

“If we had done this that time itself, we would have been the world’s first metro train system to have a comprehensive rainwater harvesting system,” Vishwanath adds.

The proposal showed that about 8,730 kilolitres of water can be collected per kilometre just on tracks. Today, BMRCL has 73.81 km of operational tracks and 101.74 km of under-construction tracks. The total capacity of operational and under-construction tracks can be estimated at  3729.46 million litres per annum—this is huge.

However, no action was taken to tap into this water. Meanwhile, water splashed onto roads and leaked into underground stations. The BMRCL proceeded with piecemeal temporary solutions whenever problems arose.

For example, data produced in the Karnataka Legislative Council in 2021 shows that in 2018, BMRCL floated many small tenders to make arrangements for arresting rainwater splashing by providing acrylic sheets with mild steel frames, mainly at various stations on reach-1 of Line-1, at a cost of about Rs 19.58 lakh.

The document also includes arrangements to prevent water from entering the infrastructure and accumulating on viaducts.

Focus back on solutions

“The BMRCL website mainly discusses tree planting and compensatory afforestation. We wanted to track the survival rate of trees planted, which took us to various lakes, including Sarakki and Gottiegere. This eventually got us interested in BMRCL’s rainwater harvesting systems,” explains Raghavendra.

His team studied the entire green line and purple line between Magadi Road and Kengeri stations. Between June 2022 and August 2024, they submitted five reports to BMRCL focused on rainwater harvesting systems alone.

“In 2023, we took the findings to BMRCL and told them that we could not find any rainwater structures similar to the ones in the MG Road area. In many areas, water is spilling onto the roads, and patchwork is seen on the roads to fix the damaged areas,” says Raghavendra.

Initially, BMRCL did not respond. “When we asked through an RTI query on actions taken on the previous report, things started rolling,” he adds. In March 2024, the BMRCL floated a Rs 65 lakh tender for installing rainwater harvesting pits below the viaducts in the metro alignment of Line 1 (purple line), Line 2 (green line) and the station areas.

The bids are currently under evaluation. However, the tender document does not provide specific details regarding the kind of work to be done or the infrastructure to be built to store and use rainwater other than “pits.”

Reports say 3,000 litre-capacity underground storages are on both sides of every second metro pillar between M G Road and Baiyyappanahalli metro stations. The tender document does not talk about any of the existing infrastructure.

Solutions plenty, lack of will

“Currently, water gets dumped on the roadside and splashes onto the roads. The median is generally filled with construction debris, and its capacity to absorb rainwater is less. An effective rainwater system will improve the groundwater table, reducing road damage. With the right kind of landscaping between pillars and the right type of plants, they can also reduce the need for water consumption,” Vishwanath explains.

“Stations have huge potential to capture rainwater harvesting, and they should do it,” says Vishwanath. “If there is a dearth of money, corporate social responsibility funds can be tapped,” he suggests.

“Last year showed what can happen if there is no water supply. The groundwater table is drying up. Water crisis will be a norm in the city in future. This year, many lakes have not been filled. If the BMRCL can channel the water collected into nearby lakes, it would be a great solution,” says Raghavendra. 

“Why can’t rainwater harvesting be a part of the original track design? Why does it have to be made separately? Can’t they add it in the tender for constructing the viaducts?” he asks, questioning the measures undertaken as an afterthought.

In fact, the number of kilometres not tendered yet (approved, under approval and proposed) is 251.65 km. The BMRCL has the scope to integrate rainwater harvesting systems into tenders related to these tracks and stations falling under them.

“Namma Metro is a public transport company with investment from state and central governments, so they shouldn’t shy away from rainwater harvesting responsibilities. BMRCL should proactively plan for rainwater harvesting pits in the new lines coming up in the city,” he points out.

A report on harnessing rainwater along the metro line to replenish lakes submitted by Raghavendra and his team explores the opportunity to feed six lakes with rainwater collected from metro pillars.

“All the rainwater collected from the metro tracks and pillars can be directed to lakes,” adds Raghavendra.

“The 2009 BWSSB Act says that storing rainwater is mandatory as part of your infrastructure. This makes it mandatory for metro stations to have a plan for rainwater harvesting. BWSSB has been sleeping. They should plan to use water from metro structures and fund it if needed,” he adds.

The Bangalore Water Supply and Sewerage Board does not seem to have an official plan to tap into rainwater from metro systems. A detailed questionnaire on the topic has been sent to BMRCL but is yet to be answered.