Over-exploited groundwater, neglected lakes: Here’s why Bengaluru is facing a water crisis

Several areas in Bengaluru face a water crisis due to drying borewells. Media reports identify 257 locations at risk. Responding to this, the Bangalore Water Supply and Sewerage Board issued an order on March 8, prohibiting the use of drinking water for washing vehicles, gardening, and construction.

Various factors have contributed to this crisis in the city. The Urban Water Balance report for Bengaluru, released by WELL Labs, a city-based research organisation, highlights some of these concerns. Key aspects include reliance on over-exploited groundwater, limited access to BWSSB pipelines, neglected lake maintenance, and underutilisation of water treatment facilities.

These factors have resulted, among other things, in citizens and housing societies spending inordinate amounts on water tankers – a 12,000-litre private tanker of water now costs Rs 2,850 and more in areas that do not have piped Cauvery water connections and are affected by severe water shortage.

City’s water pipeline mainly serves central zones

According to data compiled by WELL Labs, the city's demand for freshwater stands at approximately 2,632 million litres per day. In addition to the 1,460 MLD of Cauvery water supplied by the BWSSB, the city presently utilises an estimated 1,372 MLD of groundwater, which is almost half of its water requirements.

The report calculates domestic demand based on a projected population of 12.6 million and an average per capita consumption of 150 litres per day. The total domestic demand alone adds up to 1,890 MLD, exceeding the provision from the Cauvery piped water connection. This compels the expanding population in the outer periphery of the city to rely on tankers and private borewells for groundwater access.

The BWSSB’s public water supply is primarily concentrated in the central areas of the city, where the population is lower compared to the rapidly growing suburbs. The 1,460 MLD is exclusively available to core and urban-local-body areas, as per the report. In areas lacking public infrastructure, consumers – including a majority of commercial entities – resort to groundwater extracted from private borewells, tankers, and open wells.

The number of private borewells in Bengaluru at present is difficult to estimate because of the failure of regulatory control on borewell drilling. A Right to Information response said there are 108 borewells in the city, but it does not account for the thousands of private borewells that have been dug by housing complexes and private residences, as also tech parks and other workspaces, all of which are technically illegal.

The situation is alarming as groundwater recharge rates significantly lag extraction rates. According to Central Groundwater Authority data for 2023, all six assessment units – Bangalore City, Anekal, Yelahanka, Bangalore East, Bangalore North and Bangalore South – in urban Bengaluru are overexploited. Natural groundwater recharge through green spaces and water bodies is as low as 148 MLD, one-tenth of the daily consumption. Rapid urbanisation is diminishing the remaining green spaces in the city, which is essential for aquifer recharge. The city’s green cover shrunk from 28 percent in 2010 to 2.9 percent in 2023.

In light of the crisis, the Bruhat Bengaluru Mahanagara Palike has earmarked Rs 131 crore for digging new borewells in affected regions. However, this initiative may prove ineffective due to the already depleted groundwater levels and inadequate mapping of these levels. In both the short- and long-term, such a measure could falter.

“It would be more prudent to source water from unaffected areas in central Bengaluru and distribute from there,” says Shashank Palur, a researcher at WELL Labs and a co-author of the report.

Neglected city lakes unable to retain rainfall runoff effectively

Groundwater experts at WELL Labs emphasise the impact of insufficient rainfall in Karnataka in 2023. About 45 percent of this rainwater becomes runoff, entering rivers and lakes. However, these lakes, filled with treated and untreated wastewater, lack the capacity for rainwater storage or flood buffering.

Within the BBMP, 173 lakes span three valleys in cascading chains. This lake network is pivotal for urban flood management, designed to handle surpluses by allowing water to cascade from one lake to another.

Initially, these seasonal lakes filled entirely during monsoons, acting as flood buffers in periods of heavy rainfall. Urbanisation altered the inflow composition; roughly half the water entering lakes is wastewater, both treated and untreated. Consequently, most city lakes consistently remain full, leaving little room for monsoon rain. This is also responsible for urban flooding during the monsoon. Average runoff during monsoons (June to December) is around 982 MLD – 73 percent more than dry season runoff (568 MLD), states the report.

Additionally, rampant construction has resulted in the channels between lakes getting severed, with the result that overflows do not flow to other lakes but, instead, cause urban flooding and water loss.

“The issue lies in the structure of lake management. Multiple institutes oversee operations, resulting in a lack of coordination and planning for addressing concerns,” says Palur. “The Bangalore Development Authority handles lake rejuvenation and transfers maintenance responsibilities to the BWSSB. Although funds are available, transparency regarding their usage is lacking.”

“These resources might be allocated for beautification, which may not effectively address underlying issues,” adds Rashmi Kulranjan, a researcher at WELL Labs and a co-author of the report.

The researchers told IndiaSpend that regular desilting of lakes, to maintain storage capacity, lacks oversight and authority. It occurs sporadically for select lakes, without a systematic monitoring or decision-making process. For instance, Jakkur Lake underwent desilting between 2009 and 2011, a process that lasted several months. In contrast, desilting of Bellandur Lake has been going on for over five years.

High rate of non-revenue water losses

Bengaluru’s water supply network consists of 6,000 km of pipelines, 60 booster pumps, 84 ground-level reservoirs and over 52 overhead tanks. It pumps about 1,520 MLD water, of which about 448 (nearly 30 percent) is “lost”. This includes unaccounted-for losses of water through pipeline leakages and unauthorised connections. The report estimates “real losses”, i.e. losses caused by poor infrastructure, to be about 331 MLD. The rest is considered “apparent losses”, i.e. losses caused by unauthorised connections, dysfunctional water metering, etc.

In 2016, Bengaluru had the second highest rate of non-revenue water among Indian cities, IndiaSpend reported in September that year. “Reducing losses cannot occur immediately; it requires the overhaul of the entire infrastructure. The NRW rate decreased from 50 percent in 2017 to the current estimated 30 percent,” says Kulranjan.

At the same time, such losses serve as a primary source of groundwater recharge. Introducing NRW reduction schemes could actually lead to a decline in groundwater recharge. To counterbalance this, the city must prioritise investments in rainwater harvesting. This option proves more viable, both in terms of economics and prudent energy use, compared to importing additional surface water.

Although rainwater harvesting is mandatory, the vast majority of buildings harvest rainwater for recharge rather than direct use. A small but growing number of residents and institutions have invested in sub-surface or on-surface storage to enable them to use a substantial amount of rainwater for direct use.

Only 30% of wastewater is reused

Of the city’s net wastewater, 24 percent remains untreated. Among treated wastewater, 63 percent undergo centralised treatment, and 13 percent through decentralised plants. But only 30 percent of the city's total wastewater is reused. There is a substantial potential to expand the treatment infrastructure. This could support various activities, including construction and enhancing public spaces, and relieving pressure on freshwater sources.

The vast amount of wastewater is an untapped resource, capable of reducing freshwater consumption and enhancing water resilience during periods of low rainfall, the report points out. Sectors like watering the city’s green spaces, the construction industry, and aquifer recharge can substitute freshwater with treated wastewater.

“Using treated water instead of fresh water for non-essential activities is a positive measure, which should be sustained in the long term,” says Palur. “The government is also advocating for the utilisation of the BWSSB portal to request tertiary water plants, facilitating water procurement for needy areas of the city. Until recently, this resource had been underutilised.”

Most city treatment facilities perform only secondary treatment, the report says. This is not sufficient to significantly reduce the nutrient concentration in wastewater, which contributes to lake eutrophication (the process in which a water body becomes overly enriched with nutrients, leading to plentiful growth of plant life). Algal blooms in city lakes are evidence of this issue.

In response to the crisis, the Karnataka government announced plans to assume control of water tankers and cap prices. However, Palur suggests that this approach may not be sustainable.

“The escalating prices stem from suppliers having to fetch water from increasingly distant locations. Unless the state absorbs these additional costs, supplying at capped rates would be unsustainable for tanker operators,” he says.

Furthermore, Palur notes that the only long-term solution announced by the government, the Vrishabhavati lift irrigation project, lacks clarity regarding its potential benefits for the city.

IndiaSpend has reached out to BBMP and BWSSB to inquire about the implementation of crisis mitigation measures, such as borewell drilling and tanker-price capping. Additionally, we’ve inquired about their future strategies for lake management and the Vrishabhavati project. This story will be updated when we receive a response.

This report is republished with permission from IndiaSpend.org, a data-driven, public-interest journalism non-profit. It has been lightly edited for style and clarity.

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