As Indian cities confront intensifying and earlier heatwaves, integrating ecologically functional urban water bodies into statutory planning is essential for equitable and sustainable heat mitigation
It is only March, and yet the meteorological department has issued an orange alert for a heatwave in Mumbai, marking an unsettling prelude to the intensifying climate realities confronting the city. The city is literally feeling the heat, with maximum temperatures reaching 40°C. While such conditions are unusual for this time of year, they point to a broader pattern of increasingly early heat surges across western and northwestern India. This trend reflects a global phenomenon in which cities are heating up faster than the global average. A key driver of this phenomenon is the Urban Heat Island Effect, in which dense built environments, limited vegetation, and heat-absorbing construction materials raise urban temperatures, severely impacting urban communities, especially lower-income groups. Studies have shown that extreme heat is already a leading cause of deaths by climate-driven hazards, with 356,000 deaths in 2019. Studies indicate that during heatwave conditions, India experiences approximately 3,400 excess deaths per day. These numbers not only signify an environmental challenge but also an escalating urban public health crisis.
Market-driven technological cooling solutions such as air conditioners raise significant social, environmental, and infrastructural concerns. Such mechanical cooling produces highly uneven geographies of thermal comfort within cities, creating segregated spaces of a cooler inside and a hotter outside.
Market-driven technological cooling solutions such as air conditioners raise significant social, environmental, and infrastructural concerns. Such mechanical cooling produces highly uneven geographies of thermal comfort within cities, creating segregated spaces of a cooler inside and a hotter outside. With only 24 percent of the population having access to air conditioning in India, large segments of the urban population, especially low-income households and workers engaged in informal or precarious occupations, who are bound to spend much of their time outdoors, are the most vulnerable to heat stress. Such stratification in thermal protection along socioeconomic lines makes vulnerable groups disproportionately exposed to heat risks. The use of air conditioners also generates additional heat that is expelled into the surrounding environment during cooling, thereby increasing outdoor temperatures and exacerbating the urban heat island effect. Seen this way, cooling technologies can paradoxically contribute to the very problem they seek to mitigate, and the externalised thermal and environmental costs are disproportionately borne by vulnerable communities. Studies have shown that low-income households spend up to 8 percent of their budgets on electricity for cooling. Further, air conditioners and electric fans already account for nearly 20 percent of the total electricity use in buildings worldwide, a share projected to rise substantially as urbanisation accelerates and global temperatures rise.
Seen this way, cooling technologies can paradoxically contribute to the very problem they seek to mitigate, and the externalised thermal and environmental costs are disproportionately borne by vulnerable communities.
The present approach to urban cooling, based on energy-intensive fixes, is both socially inequitable and environmentally unsustainable. Addressing the urban heat crisis thus requires rethinking urban development strategies by rejuvenating and mainstreaming natural waterbodies as integral components of heat-mitigation strategies.
Research has established that waterbodies significantly influence surrounding microclimates. Through evaporative cooling, lakes and wetlands can reduce adjacent land surface temperatures by up to 3°C, with cooling effects extending up to 800 meters depending on the size, depth, and surrounding land cover. Beyond temperature regulation, waterbodies are multifunctional climate assets, as they enhance groundwater recharge, support vegetative growth and evapotranspiration, reduce dust and improve air quality, and act as flood buffers during extreme rainfall events. But these urban water bodies are increasingly polluted, encroached upon, or hydrologically altered in India. A decline in water quality due to untreated sewage inflows, solid waste dumping, or eutrophication compromises the ecological processes that sustain evaporative cooling and microclimate regulation. The Mithi River in Mumbai continues to receive untreated waste and industrial discharge despite repeated restoration efforts, limiting its ecological and climatic functionality. The Mula-Mutha River in Pune suffers from high biochemical oxygen demand (BOD) levels due to sewage inflows, affecting water flow, oxygenation, and overall ecosystem health.
The Waterbody Census of 2023 in India listed over 2.4 million water bodies, of which only 2.9 percent are in urban areas. Even within this tiny share, about 21 percent of urban waterbodies are either dried up, encroached upon, or polluted. Given high land costs in high-density cities such as Mumbai, urban development prioritises real estate value over ecological preservation. Wetlands, ponds, and low-lying areas, historically natural water retention zones, are reclaimed for construction, reflecting flawed structural governance where waterbodies are not valued for their ecosystem services, including heat mitigation. For example, as Bengaluru’s built-up area increased from 8 percent to over 73 percent between 1973 and 2016, 79 percent of its water bodies disappeared, severely depleting the city’s natural recharge zones. Such rampant concretisation across cities has increased land temperatures by as much as 15°C, particularly in the northwestern, northeastern, and southern regions of India over the past three decades.
The Waterbody Census of 2023 in India listed over 2.4 million water bodies, of which only 2.9 percent are in urban areas. Even within this tiny share, about 21 percent of urban waterbodies are either dried up, encroached upon, or polluted.
In several cities, lake rejuvenation is pursued through bunding, concretisation of embankments, fencing, and installation of tourist infrastructure. While these may improve visual appeal, they often disrupt natural inflow and outflow channels, prevent groundwater recharge, reduce biodiversity, and increase heat absorption through hardscaped perimeters. For example, the development of Hyderabad’s Durgam Cheruvu Lake has given the city a stunning makeover but has been criticised as an exercise that has left it “gasping.” Such development converts ecologically sensitive lakes into enclosed concrete water tanks, reducing their resilience and limiting their ability to regulate microclimates effectively.
Urban heat governance in India has largely been reactionary, focused on early warning systems, emergency response, and public advisories. Their emphasis is on short-term emergency management rather than long-term structural mitigation. Many existing Heat Action Plans conceptualise extreme heat as a temporary hazard, mostly in the form of a heatwave, requiring immediate response measures such as alerts, advisories, and emergency services. While such measures are essential, they do not structurally reduce exposure. A shift toward preventive, mitigation-oriented and intersectoral urban planning is necessary.
Urban heat is shaped by land use, materiality, density, and ecological loss. Therefore, water bodies must be repositioned from passive landscape features to active climate infrastructure, embedded in statutory planning instruments such as development plans, zoning regulations, and environmental clearances. Measurable indicators, such as minimum blue-green coverage ratios, buffer zones around lakes and rivers, protection of natural drainage channels, and heat vulnerability maps, must be integrated into planning approvals.
Many existing Heat Action Plans conceptualise extreme heat as a temporary hazard, mostly in the form of a heatwave, requiring immediate response measures such as alerts, advisories, and emergency services. While such measures are essential, they do not structurally reduce exposure.
Cities can adopt layered strategies for urban heat mitigation, integrating multiple interventions across spatial scales to enhance thermal comfort and resilience. At the neighbourhood level, urban waterbodies can play a complementary role alongside other cooling measures such as shade structures at high-heat intersections, pocket parks, expansion of the urban tree canopy, and the use of permeable pavements. When implemented together, these interventions can create interconnected microclimates that reduce surface and ambient temperatures within dense urban environments. Even small ponds or restored stepwells can create localised cooling pockets, particularly when combined with tree cover.
On a larger scale, urban master plans can adopt Water-Sensitive Urban Design (WSUD) principles, treating water as a central structuring element of urban form rather than a residual utility. Cities can develop interconnected blue-green corridors combining rivers, lakes, wetlands, parks, and tree-lined streets, which could improve air circulation and cooling, reduce surface temperatures, absorb stormwater, and enhance groundwater recharge. By linking water bodies with vegetated buffers, cumulative cooling effects can be amplified through evapotranspiration and shading. Using these methods, Medellín, Colombia, reduced air temperatures by 2°C.
Protecting the peri-urban wetlands, floodplains, and natural troughs is essential. While urban expansion has fragmented these hydrological systems, restoring and conserving them can provide cooling benefits while simultaneously strengthening climate resilience against both heat and flooding. For example, the restored Cheonggyecheon in Seoul has significantly reduced the urban heat island effect, with temperatures around the river 6°C cooler than in other areas.
By linking water bodies with vegetated buffers, cumulative cooling effects can be amplified through evapotranspiration and shading. Using these methods, Medellín, Colombia, reduced air temperatures by 2°C.
Cities can also establish dedicated offices focused on heat management, learning from such practices in Phoenix and Miami-Dade. Miami-Dade was the first to appoint a Chief Heat Officer in 2021. Embedding heat considerations across planning domains, including building codes, transport, urban design, land-use, and environmental clearances, is essential for addressing the structural drivers of urban heat rather than relying solely on reactive response mechanisms.
Urban water bodies can serve as critical climate infrastructures in addressing urban heat, provided they are ecologically functional and integrated through water-sensitive urban design. However, in most cities, urban planning has not been aligned with their natural hydrology. Further, retrofitting the hydrological logic into already urbanised terrain is politically and economically complex. Despite these constraints, embedding these systems within statutory planning frameworks and protecting them from development pressures is essential. Restoring urban water bodies as cooling commons offers a pathway toward more equitable, ecologically grounded, and climate-resilient urban futures.
Soma Sarkar is an Associate Fellow with the Urban Studies Programme at the Observer Research Foundation.
The views expressed above belong to the author(s). ORF research and analyses now available on Telegram! Click here to access our curated content — blogs, longforms and interviews.
Soma Sarkar is an Associate Fellow with ORF’s Urban Studies Programme. Her research interests span the intersections of environment and development, urban studies, water governance, Water, ...
Read More +
PREV
