Are Indian megacities forgetting their rainwater endowment?

Bengaluru, Chennai, Delhi mandated rainwater harvesting but are struggling for over a decade to implement the impactful structures on ground

By Mehak Puri, Vivek Kumar Sah
Published: Wednesday 08 May 2024
Photo for representation: iStock

Even as Bengaluru reels from water crisis, other cities in the country have started hitting the headlines for the same reason. It is very clear that the prime reason for the water stress in Bengaluru is that the city did not value its rainwater endowment. Lakes were lost across the years and the city expanded and continued to extract the groundwater. 

Down to Earth analysed the state of rainwater harvesting in Indian cities that took up the movement very seriously initially but eventually lost interest, pushing them towards ‘Day Zero’. 

Bengaluru's efforts

The city of Bengaluru had mandated rainwater harvesting in residential colonies since 2010. In 2021, the Bangalore Water Supply and Sewerage Board (BWSSB) passed an amendment bill making it mandatory for buildings on the sites measuring 60x40 feet and more. Till date, 190,000 properties have installed a rainwater harvesting system says the website of BWSSB. 

“We have also mandated rainwater harvesting for new properties which are 40 feet x 30 feet in size,” Rajiv KN, chief engineer, BWSSB said.

Almost all the buildings — both residential and commercial with mentioned specification — have installed rainwater harvesting systems. Only some 10,000 properties are left out now, he added. BWSSB is penalising citizens for not harvesting rain. 

People who have opted out either have insufficient space or land dispute, the engineer shared. “In the last 2-3 months, we received huge many requests for setting up rainwater harvesting — all this happened due to our awareness campaigns.” 

BWSSB claimed that it has kept no stone unturned for promoting rainwater harvesting across the city. Training programmes for different stakeholders, setting up of demonstration sites, awareness or ‘Abhiyana’ programmes have been regularly conducted, board officials said. 

Over the last 150 days, we have not received any rain, according to Rajiv. This is why the impact of groundwater recharge is not visible, he added. 

Communities are losing interest in rainwater harvesting due to lack of space in their households and high installation cost, said Vishwanath S, founder and director, Biome Environmental Solutions. More of community-level systems should be promoted instead of household-level systems, he suggested.

Few of the rapid actions of BWSSB in April very clearly showed that the the board realised they were falling short of harvesting rainwater in the city. At the end of April, BWSSB announced formation of a task force with the experts from IISc Bengaluru, Central Groundwater Board (CGWB) and Karnataka Groundwater Authority (KGWA), to monitor the groundwater across the city regularly with the help of artificial intelligence-driven groundwater monitoring system. 

But what was the plan all about? A senior scientist, who did not want to be named, said, “Earlier, the monitoring network was managed by CGWB and Karnataka Water Authority (KGWA). But now, BWSSB is planning to have their own monitoring network, to which they have formed the groundwater task force.” 

The board will also instal automatic sensors in a large number of places to make this method successful, the source mentioned. “We will develop a ward-level database that will help us to make better decisions regarding groundwater recharge.” 

Vishwanath had a divergent opinion on this. According to him, the technology is totally new to India and rarely anybody is aware about the AI-based groundwater monitoring process. 

Moreover, absence of a pilot study will make this project incompetent, said TV Ramachandra, scientific officer, Centre for Ecological Sciences, Indian Institute of Sciences (IISc).

The new monitoring systems have been attached to 10-15 borewells as pilot projects, Rajiv noted.

BWSSB also rushed to announce that the extra rainwater from the tech parks and the community buildings will not go into drains but will be used to fill up nearby lakes. The board has planned to recharge 74 lakes, starting with 16 in May and June during the first phase, according to official sources. 

Ramachandra explained that the idea of filling the lake is not new for Bengaluru. This is because, the engineer explained, rainwater from open spaces and parks automatically drains into lakes because of the city’s undulating surfaces. Then, the new initiative is redundant, he said. 

Only time will tell whether these recent endeavours by BWSSB will be benficial or only prove to be white elephants.

Pioneer Chennai slips

Chennai is another city that claims to be a leader in urban rainwater harvesting. Pradheeps Muthulingan, an environmental expert at Chennai Metropolitan Development Authority (CMDA), stated: “In 2002, CDMA mandated the inclusion of rainwater harvesting system designs in building plans as a prerequisite for construction permits. This proactive measure has significantly contributed to sustainable water management in Chennai.” 

Despite seasonal declines in groundwater levels, particularly during summers resulting in water scarcity, the government’s initiative has notably replenished water levels through the implementation of the RWH system, Muthulingan added. Later on, the Tamil Nadu Combined Development Building Rules of 2019, introduced RWH design guidelines for various types of buildings. 

But the city has definitely faltered, said Muthulingan. Weak enforcement by CMDA has somewhat undermined the effectiveness of this visionary plan, he added. Many individuals and residential apartment complexes perceive the implementation of RWH systems as unsuccessful due to inadequate awareness and support for maintenance. 

Though Chennai is probably the first metro to introduce rainwater harvesting and its extension across the state of Tamil Nadu, still a majority of people do not maintain these structures, observed Sivashanmugam Muthusamy, retired chief planner, Chennai Metropolitan Development Authority.

The Department of Town and Country Planning, Chennai focuses on installing the rainwater harvesting structures and granting proper certification. However, there is a lack of monitoring of these structures, public ignorance of the need to improve the design and widespread ignorance of the wider application of these structures, said Muthusamy.

He added that the most recent information on non-governmental organisation’s active participation in providing technical assistance and raising public awareness of rainwater harvesting was provided three to four years ago.

Lakes, ponds and temple tanks are our traditional rain harvesting structures that also need to be rejuvenated using nature-based solutions, said Janakranjan, retired professor of Madras Institute of Development Studies, Chennai. He added that Chennai city receives 1,400 millimetres of annual average rainfall with decline in rainy days. These structures can help prevent the runoff by 95 per cent and save us from the zero-day situation, the expert highlighted. 

At the end of the day, despite a mandate for rainwater harvesting at building level, the city authority and people are losing interest, he said. 

Delhi’s outcome insufficient, unscientific

Delhi, which made rainwater harvesting compulsory for the buildings around this time in 2001, also failed to keep up its motivation. Since June 2001, the Ministry of Urban Development has made rainwater harvesting mandatory in all new buildings with a roof area of more than 100 square metres and in all plots with an area of more than 1,000 sq m that are being developed. 

DJB has made RWH systems mandatory since 2012 and non-compliance attracts a penalty of one-and-a-half times the water bill amount. The Delhi Jal Board, the water utility which looks after the rainwater harvesting systems in the city, also provides financial assistance up to Rs 50,000 depending on the plot size and a 10 per cent rebate on monthly water provided if a resident welfare association / individual has an adequacy certificate. The adequacy certificate is provided by DJB on proper inspection of the installed rainwater harvesting structure, with respect to the plotted area and the size of recharge pit as mandated by the board.

Vandana Menon, independent consultant practicing in the National Capital Region, also feels that the shortage of land has brought household-level rainwater harvesting at a low point. She supported Viswanath’s suggestion of community rainwater harvesting. 

The poor state of the rainwater harvesting systems in Delhi has brought the issue to the green court.  A public interest litigation was filed by a citizen in 2019 to raise a concern on the state of rainwater harvesting in the city. A committee, formed as per the order of the National Green Tribunal, highlighted issues such as the placement of rainwater harvesting structures inside stormwater drains, neglect of routine maintenance and insufficient measures to prevent sewage contamination. 

Recommendations by the committee included stringent guidelines for installation and maintenance, along with the installation of piezometers for groundwater recharge monitoring. In 2023, the same person who filed the PIL in 2019 submitted that the authorities were not complying with the recommendations. DJB, Delhi Development Authority, Public Works Department, New Delhi Municipal Council, South Delhi Municipal Corporation, Central Ground Water Authority and Delhi Pollution Control Committee were pulled up by the tribunal to work as per the recommendations of the committee. 

DJB followed the court’s instructions and built 594 rainwater harvesting structures but none of these structures were located near the stormwater drains, as recommended by the committee. DJB also installed 94 piezometers to monitor groundwater levels and water quality. Others, however, failed to submit reports or provide adequate information, which they have to do by the next date of hearing on May 29, 2024.

All the three mega cities have mandated rainwater harvesting. Then then why are they struggling after more than a decade to implement the impactful structures on the ground? In this climate-risked world, where rainfall is variable and rainy days are fewer, cities should harvest as much as possible – be it through lakes and waterbodies or through groundwater recharge structures. Huge amount of water can be harvested, even if we consider harvesting the built up area of 30 per cent.

City Area (Sq m) as per 2011 data If the city harvests 30  per cent through its buildings (sq m) Average annual rainfall (m) Runoff coefficient RWH potential (cu m) Annual RWH potential (MCM) Annual Demand-Supply gap (MCM) as per 2011 data RWH potential (with 30 per cent of area considered as roof area): Demand-supply gap
Delhi 1483000000 444900000 0.755 0.8 268719600 268 784 34
Chennai 426000000 127800000 1.3 0.8 132912000 132 97 136
Bengaluru 741000000 222300000 0.841 0.8 149563440 149 237 63
Source: Compiled by CSE

There should be both carrot and stick, so that the communities are not only incentivised but also fined for building a faulty groundwater recharge structure. Crunch of space in urban areas in many cases make implementation of household systems difficult. Hence, more of community level projects should be taken up. The authorities should not push for rainwater harvesting and their monitoring, when the cities miss their normal rains and the groundwater reserve is not enough to supplement their surface water sources. Also, monitoring of the structures and their impact need to be done voluntarily by the city water authorities and not only when the court intervenes.

Subscribe to Daily Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.