After a year of failed rainfall due to El Nino, Bengaluru is feeling the heat in more ways than one this summer. Stories of water shortage are common, tanker rates have been hiked across the city. Discussions and news reports on water resilience are back after many years of plentiful rainfall when flooding was the main issue the City faced.

Bengaluru and Water

The Bengaluru Water Datajam was held in this background to look at what data says about the state of water in the City, and what can be done to improve the water situation even in dry years. Well Labs, MOD Foundation, Bangalore Apartments Federation and Biome Environmental Trust were the partners for the datajam. The event was held at Cobalt, Church Street, Bengaluru, a space provided by MOD Foundation.

In the day-long event, 32 participants from varied backgrounds, including urban planners, GIS experts,  software developers and other active citizens joined hands to analyse public data in the context of water – groundwater, rainfall, lakes, water supply – in Bengaluru. The participants were split into six teams who dove deep to identify trends and patterns to provide better insights into water supply and groundwater levels, usage and recharge, and wastewater potential in Bengaluru.

Problem Statements

The six teams came up with the following problem statements.

1. Addressing water consumption needs on the outskirts of East Bengaluru.
2. Evaluating the rainwater harvesting potential and costs savings in Bengaluru.
3. Imagining Bengaluru without the Cauvery and the population that could be sustained in such a scenario.
4. Understanding the water supply of RERA-approved projects with over 1000 units from their application forms.
5. Effect of Industrial effluents on the groundwater and water sources in Peenya Industrial Area.
6. Computing a Water Security Index for different parts of Bengaluru.

Outputs

Water consumption needs in East Bengaluru

Abhirami, Biswa, Purva, Sankar and Vidya of Team “Jal Rakshak” looked at the water consumption needs in the outskirts of East Bengaluru and how it compares to the central parts of the city.

What they found is that, while ground water caters to 48% of Bengaluru’s needs, the recharge rates remain significantly lower than the extraction rates. Moreover in the eastern suburbs the depth at which it is available is much more than in the rest of the city. These suburbs are primarily dependent on borewells dug by communities and private water tankers for their water needs.

While BWSSB water lines haven’t progressed too far beyond the central parts of the city, the same is true even for sewerage. They recommend that BWSSB needs to address the needs of these areas in both water supply and sewerage. They also noted a need for a government mandate to increase open areas in newer properties coming up in these areas, which can help increase groundwater recharge pushing up the groundwater levels in parallel with rainwater harvesting.

Potential and economic incentives for Rainwater Harvesting in Bengaluru

Anvitha, Gaurav, Kedaravindan, Namoshi and Sreechand of Team “Water Warriors” looked at the potential for rainwater harvesting in Bengaluru and the economic benefits that could accrue from that.

They estimated the rooftop potential by looking at the rooftop cover in Bengaluru from Google open polygons and the rainfall data of the city. Rainfall was classified based on level of rainfall with a threshold of 30mm. The total harvesting potential was thus calculated as the product of rooftop area, harvestable rainfall and runoff coefficient. Based on rainfall from 2022, they found that 456 Million Litres per Day(MLD) could have been harvested in Bengaluru from the rooftops, which is 25% of the water demand of the city – 1890 MLD.

Bangalore Without Cauvery

Janhavi, Nikhila, Priyanka, Vaibhav and Shubham of Team “Utopia” tried to imagine a Bengaluru without water supply from Cauvery. They tried to compute what could be the population that could be supported with only local sources of water.

They noted that 1450 MLD is pumped up at a cost of Rs. 3 Cr per day to a city that is 350m above the Cauvery in terms of elevation. While Bengaluru’s system of tanks helped with agriculture in earlier days they are also at a lower elevation and it would cost Rs. 2.7 Cr per day to pump up water from them.

While the annual of supply of water to the city from Cauvery and groundwater totals to 2800 MLD, rainfall and waste-water are not considered in this calculation because we are yet to realise the full potential of these alternative, sustainable sources. With rainwater harvesting used to its full potential and treated wastewater available to its full potential, the city could realise close to 4000 MLD which can meet its water demands and sustain a growing population during most years.

Water supply for very large projects in Bengaluru

Malavika, Rohit, Sabarinath, Upasana and Vivek of Team “RERA-vent” looked at the large projects of more than 1000 units coming up in Bengaluru and what their claims for water sources are.

They scraped data from the Karnataka RERA(Real Estate Regulation Authority) website and filtered those projects with more than 1000 units. They found that out of the 19 current projects, 7 lie outside the boundary of BWSSB limits, while 9 are on the boundary. But, 6 of these projects mention “Local Authority” as the water source while 13 mention “Self Development” as the source of water.

The team noted that there are large gaps in how data is presented in the RERA website. There is no geo-code data on where the projects are located, and even the Pin code of the projects is missing in some cases. While the projects mention “local authority” which local authority goes unmentioned. It remains unclear how such large projects will be sourcing water despite having the goal of the regulatory authority to make things more transparent, and this needs to be addressed.

Effect of Industrial Effluents on the Groundwater and Water Sources in Peenya Industrial Area.

Arundhati, Dishant, Mayuri, Namitha and Sanju of Team “Damns” looked at the effect of effluents in water sources of a highly industrialised area like Peenya. While it is known that a lot of industrial effluent dumping happens at Shivapura Lake and Peenya they tried to understand how widely the spread of the effluents happens by understanding the slope characteristics of the area.

According to the land-use maps, most of the area in the ward is given to industries. As per the economic census of 2012 most of the businesses in the area are manufacturing units and garment industries predominate among them.

They found that since the underground drainage from BWSSB is not gridded, most residential and industrial effluents are let out into the stormwater drains which are in turn connected to the streams and lakes. This leads to a direct contamination of the locally present water bodies.

Building a Water Security Index for different parts of Bengaluru

Aniket, Anoop, Chandana, Rithika, Swathi and Vishnupriya of Team “Vrishabhavathi” tried to quantify the water security in different areas of the city and give them a water security index. The index would be calculated based on available water supply, quality of water, consumption in the area, recharge of the water sources for that area and if there’s any reliable authority to resolve water related issues.

They noted that there are large gaps in the data available. For e.g., Cauvery water supply data is not available at a granular level – as to which areas get how much water, potability of water from different sources is also not known.

But with some assumptions on depth of ground water at ward level, rainfall and population, they computed a water security index for the 198 wards in Bengaluru (a lot of data still corresponds to the older wards).

Conclusions

The teams looked at the issues plaguing Bengaluru’s water supply, and one of the key insights was the role rain water could play in addressing the city’s woes.

While one of the teams computed the actual potential of rainwater, others looked at the role it could play in having a city less dependent on faraway sources of water or to replenish heavily used groundwater supplies.

The lack of regulation was seen as one of the important gaps where even data provided to a regulatory authority was missing key parameters, even though the projects were large and would be placing considerable stress on local resources. In other places, industrial areas were polluting local water bodies and the city’s stream network as there was no other sewerage visibly provided to take away effluents from the industrial clusters.

A water security index which can give you a ward-level score of water security was attempted and it revealed important gaps in the data we have on the water in our city, including which areas get how much water. Addressing the gaps identified by the different teams would help us understand the story of water in Bengaluru better and help citizens, researchers or policy makers address the issues better.

Shashank Palur, hydrologist at Well Labs noted that “events like these are great for bringing the community together and helps them understand the problems regarding water scarcity better. It also inspires them to think of possible solutions and test their viability.”

Sindhura VS, urban designer at  MOD Foundation, felt that, “datajams and data visualisations play a crucial role in transforming raw data into meaningful narratives. They facilitate collaboration and engagement, making complex information accessible and actionable by both experts and citizens, enriching the understanding of decision-making processes within a city.”

For the participants, the experience was one of interacting with people with diverse skills and experiences. According to Priyanka Salunkhe, IIHS Urban fellow, “it has been a very valuable interaction across people from various disciplines, with very different skill sets coming together to tackle the problem of water scarcity in Bangalore by leveraging open source data.“

Sankar Venkataraman, a tech professional, noted that, “it was great interacting with people from different disciplines, some from GIS, Urban planners, techies etc, all working to look at specific water issues in Bengaluru, learning about the problems, looking at different dimensions to understand the problem, the causes and brainstorm about it and come up with plausible suggestions. OpenCity.in data has been very helpful in our analysis of the problem we took. Looking forward to more such events.”