In the recently concluded monsoon session, the Karnataka government introduced the Karnataka Tank Conservation and Development Authority (Amendment) Bill, 2025, which amends the 2014 Act to define graded buffer zones around tanks based on their size, from 0 m for tanks under 0.05 acres to 30 m for tanks over 100 acres. Following this, the Urban Development Department issued a draft notification reducing the buffer zones of storm-water drains.
While there is no universally accepted definition of buffer zones, in many countries they are designated areas around waterbodies intended to minimise the negative impacts of human settlements. From an ecological perspective, buffer zones are considered “protected zones” that help mitigate the effects of human activity and land disturbance, while also providing critical habitats for fish and other wildlife.
Earlier versions of the Karnataka Tank Conservation and Development (KTCD) Act did not explicitly mention buffer zones, instead referring to the areas around waterbodies as “no-construction zones”. Essentially, buffer zones can be understood as no-construction areas or green belts that support vital ecological functions, including nutrient absorption, wildlife habitat preservation, and maintenance of water quality.
The amended Bill
The amended KTCDA Bill was debated in both Houses. It passed the first hurdle, but it failed to receive assent from Governor Thaawar Chand Gehlot after a civic group filed objections, highlighting the negative outcomes of the “unscientifically” drafted Bill. Following this, both moves by the government attracted widespread criticism, with activists calling the amendment “pro-real estate” and a systematic destruction of water bodies at a time when lakes are becoming a part of history.
N.S. Boseraju, Minister of Minor Irrigation and Science and Technology, told The Hindu that the State has 41,800 waterbodies, 90% of which are small. About 22,000 waterbodies under panchayat raj maintenance span less than five to 10 acres, he said.
“As most of these waterbodies are in rural areas, farmers have suffered from the buffer zone rule, especially those who own half an acre or even smaller plots near lakes,” Boseraju said. “Even the opposition has come from urban civic groups in Bengaluru, where there are 220 existing lakes, most of them larger ones, and the buffer zone remains the same for them, essentially meaning no impact,” he added.
However, preliminary assessment of waterbodies data in Western Ghats districts by Nirmala Gowda, activist-researcher, Mapping Malnad, revealed that reducing buffer zones will disproportionately impact smaller lakes due to blanket reduction of safe spaces.
“In the Western Ghats, where developmental projects are in full swing, there is a high risk of lakes filling with silt. These areas have more kattes and kuntes (smaller lakes), which play a crucial role in recharging groundwater levels. If they vanish, it will pose a direct threat to the rich pool of species and to farmers in the area,” Nirmala told The Hindu, adding that it is unclear how the department will prevent encroachments when historical patterns show that water bodies are highly vulnerable.
Adding to Nirmala’s findings, V. Ramprasad of Friends of Lakes questioned whether buffer zones even exist anymore. He specifically pointed out encroachments of stormwater drains in Bengaluru.
Ramprasad’s observations are reflected in records of the erstwhile BBMP Lakes Department and the 2021 Comptroller and Auditor General of India (CAG) report, which reprimanded the civic body for neglecting stormwater drains in the city.
“Bengaluru witnessed large-scale encroachment of lakes and drains and depletion of natural drainage systems. Changes in land use, such as a decrease in vegetation cover and open spaces and an increase in built-up areas, resulted in loss of interconnectivity between waterbodies, impacting effective groundwater recharge and increasing stormwater runoff,” the CAG report said.
A view of accumulated waste in a storm-water drain leading to Hebbal Lake in Bengaluru
| Photo Credit:
ALLEN EGENUSE J.
To illustrate, according to original 1976 documents referred to by the BBMP, Kacharakanahalli Lake spanned 56 acres, but only 16 acres remained when rejuvenation began. Over the years, a temple trust and a sports complex had encroached on the lake, while about 1,200 migrant workers lived in 435 makeshift houses built on the lake area, who are now being relocated to different places.
In addition, the State Economic Survey 2025 highlighted the dependence on underground water for agriculture. In 2015, nearly 37% of agricultural activities relied on groundwater accessed through borewells. By 2025, this number nearly doubled to 60%, highlighting the extent of natural resource depletion.
Moreover, Karnataka is among the top nine States in the country that draw heavily on underground water. On average, 68% of water used in the State comes from underground sources, compared to the national average of 60%. This underscores the dependency on and importance of maintaining groundwater levels, which is closely linked to the preservation of water bodies and, indirectly, to buffer zones.
What is the new rule?
By reducing the buffer zone, the new Act permits the construction of public utility infrastructure such as roads, bridges, water supply lines, electrical poles, pump houses, and sewage treatment plants within tank areas, including the space between full and maximum tank levels, provided that water flow and capacity are not affected. Commercial, recreational, and industrial activities, however, remain largely restricted.
Earlier, Karnataka had a uniform buffer zone of 30 m for lakes and other waterbodies, while storm-water drains (SWDs) had a 50-m buffer, regardless of size. The amendment now introduces different buffer zones based on the size of the lakes.
Minister Boseraju described the Bill as “progressive”, noting that it establishes better buffer zone rules compared to neighbouring States.
“Irrespective of the size of a lake, Tamil Nadu has set a buffer zone of 3 m, and it is 9 m in Telangana. In contrast, we previously had 30 m, and now we have a size-based matrix, which ensures ecological conservation while allowing development,” he told The Hindu.
B.K. Pavitra, Secretary to the Government, Department of Minor Irrigation and Ground Water Development, explained that the amendment was prompted by concerns raised by MLAs from rural areas regarding the “irrational rules” of the previous uniform 30-m buffer for all waterbodies, which hindered potential development.
“An MLA from the Kundapura belt flagged that even Kuntes (smaller water bodies) of 2 acres had a 30-m buffer zone, restricting farmers with nearby land and limiting development opportunities. We compared buffer zones in other states and realised our rules were irrational,” Pavitra said.
He added that following these concerns, Chief Minister Siddaramaiah set up a committee led by Chief Secretary Shalini Rajneesh and heads of line departments, including urban local bodies and civic authorities.
“During the committee meeting, all scientific points were discussed, and buffer zones in different States were compared. We concluded that buffer zones can be reduced based on the size of water bodies,” he said, adding that the reduction of storm-water drain buffer zones was discussed during this meeting.
Minister Boseraju further emphasised that the departments will not authorise any construction in the buffer zones without strict oversight, ensuring vigilance against illegal construction.
Activists raise concern
However, activists argue that this is a weak justification to pass the Bill, as the State has historically been inactive against encroachments.
Nirmala points to a fundamental problem in the government’s interpretation of the law. She stresses that the law should be interpreted in light of its purpose—protecting and conserving lakes—but in this case, it has not been. Public infrastructure projects that do not directly serve the lake, such as its restoration, maintenance, or ecological health, should not fall under the Act.
“For instance, if you’re building a bridge that has nothing to do with the lake, how does the Act allow it? Provisions must be interpreted in light of the law’s core objective, which is lake conservation. Otherwise, these interpretations risk undermining the very purpose of the legislation,” Nirmala explained.
Experts point out that before the government compares States or draws legislative parallels, proper impact assessments are needed. They argue that a fair comparison requires systematic studies of on-the-ground conditions, which the KTCD Act is designed to conduct, but none have been carried out so far.
A government source confirmed that apart from historical documents and interstate comparisons, the department has not conducted any scientific field studies.
Ecological importance
Buffer zones around lakes and waterbodies provide multiple vital functions. They serve as habitats for birds, amphibians, and semi-aquatic species, supporting feeding, nesting, and resting. These green belts help control pollution by filtering surface runoff, trapping sediments, and reducing nutrients and toxins before they enter the water. They mitigate floods by absorbing storm-water surges, aid in groundwater recharge, and prevent soil erosion by stabilising banks. Additionally, buffer zones contribute to microclimate regulation by sequestering carbon and moderating local temperatures.
Scientific studies indicate that the shape and physical features of buffer zones can even predict which lakes or rivers are at risk of nutrient overload, often leading to harmful algal growth.
A review of scientific literature by this reporter revealed a significant gap in studies conducted in India on lake buffer zones and their influencing factors. In contrast, Western countries have extensively studied how increasing and improving buffer zones contribute to lake health and reduce sedimentation.
“Although sediment-trapping capacities are site- and vegetation-specific, and many factors influence sediment-trapping efficiency, the width of a buffer is important in filtering agricultural runoff. Sediment-trapping efficiency is affected by slope,” noted a paper titled ‘A Review of Effectiveness of Vegetative Buffers on Sediment Trapping in Agricultural Areas’.
“Reviewing the relationship between sediment trapping and buffer width showed that wider buffers provide a longer residence time for runoff water and are thus more effective in reducing sediment,” stated Major Factors Influencing the Efficacy of Vegetated Buffers on Sediment Trapping.
In a study titled ‘Tree-climbing Mangrove Crabs of Karwar, West Coast of India’, researcher Pradnya D. Bandekar collected samples from creeks, inlets, and the buffer zones or marginal strips of the Karwar coastline. This underscores the importance of buffer zones, as many aquatic species rely on these strips regularly.
Scientific perspectives
Priyanka Jamwal, senior fellow, Water and Society, explained, “The vegetation in buffer zones serves several crucial purposes. It enhances biodiversity by attracting birds and other species and helps cool the local microclimate. Research has shown that vegetated areas can significantly lower surrounding temperatures.”
“Buffer zones play a vital role in reducing non-point source pollution,” she added. “When rainwater flows into a lake from multiple directions, it passes through these vegetated buffers, which act as natural filters. Through biological and chemical processes, they absorb nutrients and trap pollutants before the water enters the lake. Removing these buffer zones will inevitably degrade water quality, so maintaining healthy buffers around lakes and streams is absolutely essential”.
Shivakumar Magada, professor of Aquatic Biology and limnologist, explained that when excess nutrients enter a lake in the absence of an extensive buffer zone, it disrupts the lake ecosystem, potentially killing aquatic life.
Regarding drains, Inayathulla M., professor and director of the Water Institute at UVCE, said, “Urbanisation has significantly altered natural drainage patterns, reducing the capacity of storm-water systems to handle floods. Reducing drain buffer zones will have a similar effect.” He added that floods are already occurring in the city, and the situation will worsen if buffer zones are reduced.
“Even small modifications to drain systems can alter water volume, flow patterns, and long-term trends. Concrete surfaces around buffer zones increase imperviousness, limiting infiltration and groundwater recharge,” he explained. “Maintaining the natural system is essential for sustainable flood and groundwater management”.
Veena Srinivasan, executive director, WELL Labs, noted that cities like Bengaluru have already lost most of their green cover, as shown in maps where areas that were once predominantly green are now marked red.
“Buffer zones around lakes are among the last remaining green spaces in the city, providing crucial habitats for birds and other species. When these zones are reduced, especially across many small lakes, we’re effectively cutting down trees, urbanising sensitive areas, and further shrinking the city’s green infrastructure,” she added.
Tata Nagar: A case study
Tata Nagar in northern Bengaluru provides an example of these concerns.
Tata Nagar has experienced annual flooding, primarily due to its topography, poorly planned storm-water drains, and lack of maintenance. Even during this reporter’s site visit to Tata Nagar, Kodigehalli, Vidyaranyapura, and Bhadrappa Layout, it was observed that the storm-water drain infrastructure remains below standard.
The Master Plan of Bengaluru 2015 shows only one major storm-water drain in the area, whereas there are actually two, and one of them connects Doddabommasandra Lake and Hebbal Lake. The Tata Nagar drain connects to one of these major drains, which has been encroached upon by houses and apartment complexes. In fact, one of the main roads is built directly over a stormwater drain. Over the years, multiple non-natural drains have been constructed to address flooding in Tata Nagar, but these have only created choke points, exacerbating flooding both locally and elsewhere. Unfortunately, maps of these hasty drain connections are unavailable, and most of these drains lack proper endpoints.
These issues are also highlighted in the 2021 CAG report, which emphasises the substandard storm-water drain network in the city. The report further notes that civic bodies such as BDA, BWSSB, and BBMP themselves have encroached upon storm-water drain networks.
Amidst these challenges, the World Bank is funding the Bengaluru Water Resilience Project, which aims to build a robust storm-water drain network and mitigate floods. Implementing this project, however, will be complicated if the buffer zone law is notified, as there will be no mechanism to address historic encroachments.
Meanwhile, the government is pushing to pass the Bill. On Wednesday, Minister Boseraju affirmed that the buffer zone amendment was based on a scientific study, and the documents and clarifications requested by the Governor following the complaint are being finalised and will be submitted soon.
