A new study on Bengaluru’s groundwater crisis exposes a contradiction at the heart of the city’s water management: the city can receive intense rainfall and experience flooding while extracting groundwater at more than twice its estimated annual resource. The finding is not simply about borewells running dry. It shows how rapid construction, shrinking permeable land and weakened connections between lakes and drainage corridors are changing the way Bengaluru stores, moves and retains water.
The study, titled From Crisis to Resilience: Rethinking Urban Flooding and Groundwater Recharge in Bengaluru City, was published in World Water Policy in 2026. It examines 27 years of rainfall data from 1997 to 2023, along with long-term groundwater records, to assess the relationship between urbanisation, land-use change, flooding and aquifer recharge.
Its central finding is stark. Groundwater extraction in Bengaluru was estimated at 4,627 hectare-metres in 2023, against an annual extractable groundwater resource of approximately 2,128 hectare-metres. This placed the stage of groundwater extraction at around 217 per cent, meaning that estimated extraction substantially exceeded the volume considered available for annual withdrawal.
The research was authored by Dr S Biswas of the Central Ground Water Board under the Ministry of Jal Shakti, SV B. Patel of the Irrigation and CAD Department in Hyderabad, and Distinguished Professor Basant Maheshwari of Western Sydney University in Australia. Their work links the extraction imbalance to increasing dependence on borewells, particularly in peripheral areas where municipal water supply is inadequate.
That dependence has grown alongside Bengaluru’s physical expansion. According to the study, the city’s built-up area increased from about 42 per cent in 2000 to 86 per cent in 2020, while vegetation declined sharply. Open soil, unpaved roadside verges, vegetated areas, natural drainage corridors and other surfaces that could absorb or slow rainwater have increasingly been replaced by roads, buildings, concrete and paving.
This change has altered the city’s water cycle. Rain falling on an open or vegetated surface can be temporarily stored, move slowly and infiltrate the ground. Rain falling on a paved surface is more likely to become rapid runoff. The study found that runoff from built-up areas increased by about 105 per cent in 2020 compared with 2000.
The result is Bengaluru’s apparent water paradox. Water arrives during intense rainfall but moves quickly across the surface, contributing to flooding, instead of remaining in the landscape long enough to replenish groundwater. At the same time, residents, institutions and businesses continue to draw from aquifers to meet demand, especially in locations where piped municipal supply has not kept pace with urban growth.
The researchers found that Bengaluru’s groundwater system still responds to rainfall. Dr Biswas said the long-term analysis showed that groundwater levels often responded most clearly one to two months after rainfall, particularly in some wetter years. This suggests that rainfall remains capable of contributing to recharge, but that the city’s changing surface conditions are reducing the opportunities for that recharge to occur.
The decline is visible not only in large lakes or formally protected water bodies, but also in the smaller spaces that collectively influence local hydrology. The study identified gardens, vacant plots, roadside verges, bioswales and other vegetated patches as areas that can slow runoff and create opportunities for infiltration. Their individual contribution may be limited, but their combined loss reduces the number of places where rainwater can enter the ground.
Between 2000 and 2020, runoff contributions associated with vegetated areas declined by approximately 82.4 per cent, while those associated with open areas declined by 67.6 per cent, according to the research. These figures describe more than a change in land cover. They indicate a shift in the city’s capacity to manage rainfall at neighbourhood level.
Bengaluru’s lake system provides the larger institutional and physical context. The researchers note that the city’s lakes historically functioned as an interconnected system of tanks, catchments and rajakaluves that broadly followed the natural topography. Lakes stored monsoon runoff, slowed water moving downstream, reduced flood peaks and, where local geological conditions allowed, created opportunities for groundwater recharge.
This system depended on connections beyond the lake boundary. A lake could not perform all these functions if its catchment was blocked, its buffer was built over or its connecting drainage corridor was narrowed. The study therefore cautions that protecting lakes alone will not be sufficient without safeguarding their surrounding catchments, buffer areas, drainage links and permeable land.
That finding has implications for how urban infrastructure is defined. Flood management is often approached through drains, culverts and channels, while groundwater management is treated as a matter of borewell regulation or artificial recharge. The evidence in the study indicates that these are not separate systems. The same land-use decisions that increase surface runoff can reduce the recharge available to aquifers.
The governance challenge is especially significant because the functions involved are distributed across the urban system. Municipal water supply, groundwater assessment, lake management, stormwater drainage, road construction, building permissions and land-use planning may involve different departments and agencies. The study’s reference to fragmented governance highlights the difficulty of managing water when the catchment, drainage network and aquifer are treated as separate administrative subjects.
The numbers also show why a narrow focus on annual rainfall can be misleading. Bengaluru continues to receive rainfall, and groundwater levels can respond to wetter periods. But rainfall totals alone do not determine water security. The timing, intensity and movement of rainfall matter, as does the amount of land available to retain and absorb it. A city may therefore experience both waterlogging during storms and declining groundwater availability over the longer term.
The 217 per cent extraction figure provides the clearest measure of the pressure on the resource. It does not mean that every borewell is drawing water at the same rate or that every part of the city has identical geological conditions. It does show, according to the study’s estimates, that aggregate extraction is far above the annual extractable resource. Continued dependence on groundwater under those conditions places greater importance on recharge, demand management and reliable municipal alternatives.
The study does not present lake restoration as a complete solution. Its findings instead point towards a broader water landscape in which lakes, catchments, rajakaluves, open plots, roadside edges, gardens and built surfaces interact. The condition of each affects how rainwater moves through the city. When these elements are disconnected, the city loses both flood-buffering capacity and opportunities for local recharge.
For residents, the consequences appear in different forms. In one part of Bengaluru, intense rain can overwhelm roads and drainage corridors. In another, households and establishments may rely on borewells or private water supply because piped water is unavailable or insufficient. These experiences can look unrelated at street level, but the study connects them through the changing urban water cycle.
The larger urban question is whether Bengaluru’s expansion is being planned around the movement and retention of water. The research suggests that the city’s water security cannot be addressed only by finding new sources or building additional drainage infrastructure. It also depends on whether urban development continues to remove the surfaces and corridors that allow rainfall to remain within the landscape.
The evidence confirms three linked trends: groundwater extraction exceeded the estimated annual extractable resource in 2023; built-up land expanded substantially between 2000 and 2020; and runoff from built-up areas increased while runoff contributions from vegetated and open areas declined. What remains to be established from the supplied material is how these pressures vary across individual neighbourhoods and how existing agencies are implementing corrective measures. Those are the next questions for Bengaluru’s water governance, but the study’s core message is already clear: flooding and groundwater depletion are two outcomes of the same urban transformation.
