Legacy of Tulsi Lake: Mumbai’s Hidden Lifeline
Nestled within the Sanjay Gandhi National Park (SGNP), Tulsi Lake is one of Mumbai’s oldest and most crucial sources of potable water. Constructed in 1879 during the British colonial era, the lake was envisioned as a solution to meet the rising water demands of the fast-growing island city of Bombay.
Over the decades, this modest-sized reservoir has served as a silent yet indispensable contributor to the city’s water supply network, delivering approximately 18 million litres of water daily.
Surrounded by dense forests and protected catchments, Tulsi Lake and its twin Vihar Lake act as natural carbon sinks and biodiversity hotspots within a city that continues to face rapid urbanization and ecological stress.
They are crucial for maintaining the ecological balance of SGNP, which is home to over 2,000 species of flora and fauna. As a protected water body, Tulsi Lake also holds religious and cultural value for several communities residing in and around Mumbai’s northern suburbs.
Despite being a protected zone under forest and wildlife laws, Tulsi Lake has not been immune to the pressures of illegal encroachment, untreated sewage inflows, and plastic waste accumulation. Earth5R has previously worked in the Tulsi catchment area as part of its BlueCities initiative, conducting community cleanups and environmental awareness campaigns to reduce waste pollution and educate citizens about the lake’s declining condition.
The Emerging Threats to Tulsi Lake
Despite its location within the protective boundaries of Sanjay Gandhi National Park (SGNP), Tulsi Lake faces an alarming range of threats due to increasing urban pressure, policy gaps, and ecological neglect.
Sewage and Wastewater Pollution
A primary concern is the inflow of untreated sewage from illegal settlements on the periphery of SGNP. Although Tulsi Lake is technically within a protected zone, the encroachment of slums and unregulated urban sprawl have led to direct discharge of domestic waste into its catchment.
A Central Pollution Control Board (CPCB) report states that Mumbai generates around 2,800 MLD (Million Litres per Day) of sewage, but over 40% remains untreated—posing a real danger to nearby water bodies, including Tulsi.
The BOD (Biochemical Oxygen Demand) levels in water samples near the lake’s feeder streams have shown elevated readings in post-monsoon surveys, indicating excessive organic pollution.
This has been compounded by intermittent failures in STP (Sewage Treatment Plant) upgrades around SGNP, further stressing the need for targeted intervention.
Solid Waste Dumping
Equally dangerous is the problem of plastic and solid waste dumping along lake-adjacent pathways and recreational zones. Despite multiple clean-up drives, there is no systemic waste segregation mechanism in place near Tulsi Lake’s buffer zones.
This infographic highlights the total water stock across Mumbai’s seven key reservoirs, revealing a shortfall compared to the normal stock levels expected by October 1 each year. Bhatsa Lake stands out as the largest contributor, supplying 48% of the city’s potable water.
According to a 2023 assessment by Vanashakti, approximately 1.2 tons of plastic waste is generated monthly from tourism and nearby informal settlements in the national park area, much of which finds its way into the lake during heavy rains.
This has led to the formation of microplastic sludge near the lakebed, threatening aquatic life and disrupting natural sedimentation cycles. Earth5R’s community surveys revealed a lack of public awareness and behavioral change, making it crucial to integrate plastic waste management into environmental education at the grassroots level.
Water Quality Degradation
Water quality indicators for Tulsi Lake are showing a downward trend. A report by the Maharashtra Pollution Control Board (MPCB) highlighted an increase in heavy metal traces such as cadmium and mercury in fish and aquatic plant samples taken from areas downstream of the lake.
Moreover, dissolved oxygen (DO) levels, essential for sustaining aquatic biodiversity, have been dipping below the permissible range of 4 mg/L in post-monsoon months.
Changes in water clarity, the appearance of algal blooms, and foul smells during summer are early indicators of eutrophication—a process that may lead to irreversible ecological collapse if not addressed urgently.
Loss of Biodiversity
As Tulsi Lake’s health declines, so does the biodiversity it sustains. A biodiversity study by the Bombay Natural History Society (BNHS) found that species of amphibians, butterflies, and migratory birds that once frequented the area are no longer seen in significant numbers.
The decline in macroinvertebrates—key indicators of water health—is especially concerning. Earth5R volunteers, in collaboration with SGNP forest staff, have documented a 38% decline in aquatic biodiversity in the Tulsi basin over the last decade, due to a combination of habitat disturbance, water pollution, and human activity.
Riverbank and Catchment Encroachment
The encroachment of natural catchments feeding Tulsi Lake is a growing crisis. Satellite imagery and field surveys indicate that over 25% of the buffer zone around Tulsi has been compromised by illegal settlements and unplanned tourism activities.
Despite multiple eviction orders, implementation remains poor due to administrative overlaps between the forest department, municipal bodies, and urban planning authorities.
Groundwater Contamination
Another hidden crisis is the contamination of groundwater in the areas surrounding Tulsi Lake. Leachate from nearby dumping grounds and the infiltration of untreated greywater into the subsoil have led to an increase in nitrate and chloride levels in hand pump and borewell samples.
In fringe areas around Borivali and Goregaon, these contaminated wells are often the primary source of drinking water for low-income households, exposing them to long-term health risks.
Community and Policy Blindspots
While the degradation of Tulsi Lake is often attributed to external pressures, an equally critical set of challenges lies in the realm of policy implementation gaps and limited community engagement.
The map showcases the interconnected network of rivers and lakes in Mumbai, such as Tulsi, Vihar, and Powai, vital for the city’s water ecosystem. These water bodies are closely linked to major rivers like the Mithi and Ulhas, impacting both urban flooding and water supply.
Despite the lake’s strategic importance in Mumbai’s water security and its ecological value within Sanjay Gandhi National Park, there is a striking absence of long-term, community-driven, and policy-coordinated efforts for its protection.
Inadequate Policy Enforcement
Tulsi Lake falls within an eco-sensitive zone (ESZ), and the Ministry of Environment, Forest and Climate Change (MoEFCC) has laid down several guidelines under the Environment (Protection) Act, 1986 to protect such zones.
However, local enforcement by municipal authorities and forest departments remains fragmented. Although buffer zones and eco-restoration corridors are proposed on paper, many of these plans remain in limbo due to delays in inter-departmental coordination.
Moreover, Tulsi Lake is often left out of Mumbai’s Integrated Water Resources Management (IWRM) strategy, largely due to its relatively small surface area compared to larger lakes like Vihar and Powai.
Lack of Participatory Governance
One of the major shortcomings in lake management across India is the lack of community participation in conservation activities. In the case of Tulsi Lake, citizen science initiatives, local environmental clubs, and neighborhood watch programs are practically non-existent.
According to a 2022 Earth5R community audit, 78% of residents in nearby areas were unaware that Tulsi Lake was a protected water body within SGNP.
Unlike models adopted in cities such as Bangalore’s lake rejuvenation program—where local Resident Welfare Associations (RWAs), youth groups, and urban planners work together—Mumbai lacks a structured model for community stewardship of lakes.
Absence of Education and Awareness Campaigns
Another policy blindspot is the lack of awareness-based education in local schools, tourist centers, and public transport zones near SGNP. NGOs like Vanashakti and Save Aarey have tried to build momentum, but the absence of a centralized communication strategy limits reach and retention.
For instance, very few SGNP visitors are educated on how their actions—littering, noise pollution, or off-trail trekking—impact Tulsi Lake’s sensitive ecosystem. Contrast this with the eco-tourism policies in Kerala or community-run wetland management programs in Assam, where education is a core part of the conservation model.
Tourism Pressures and Mismanagement
Although tourism is regulated in SGNP, overcrowding during weekends and festivals results in trampling of vegetation, increased littering, and unmonitored noise levels near Tulsi Lake. Tourists often stray into lake buffer zones without permits or guides, violating park rules.
Despite zoning guidelines being in place, their enforcement is minimal due to a shortage of trained personnel and underfunding.
There’s also a complete lack of ecological carrying capacity assessments to determine how much footfall Tulsi Lake’s environment can tolerate without degradation. Earth5R volunteers have noted a 47% increase in trail-related plastic waste during high-season months compared to the off-season.
Fragmented Jurisdiction and Administrative Overlaps
Tulsi Lake falls under the jurisdiction of multiple bodies: the Brihanmumbai Municipal Corporation (BMC) for water supply, the Forest Department for protection under SGNP, and the Maharashtra Pollution Control Board (MPCB) for monitoring water quality.
A report by the Observer Research Foundation points out that the lack of unified lake authorities is a major hurdle across Indian cities, leading to fragmented planning and poor execution. Tulsi Lake is a classic case where the absence of a nodal conservation agency has allowed ecological degradation to escalate unchecked.
Citizen Science and Community Action Models
In the context of Tulsi Lake, where access is restricted due to its location within Sanjay Gandhi National Park, creative models of engagement can serve as vital bridges between science, governance, and public awareness.
The Rise of Citizen Science in Urban Ecosystems
Citizen science—defined as public participation in scientific research and environmental monitoring—has been effectively used in several Indian cities to track water quality, biodiversity, and pollution levels.
In Pune’s Ramnadi project, residents collaborated with scientists to map and restore degraded stretches of a local river. Similarly, Chennai’s Ennore Creek monitoring involves fisherfolk and students using low-cost tools to test water quality and report pollution incidents.
These models could inspire similar adaptations for Tulsi Lake—particularly in tracking plastic debris, invasive species growth, and seasonal water levels. The use of simple mobile apps like iNaturalist and EarthChallenge2020 can help volunteers log observations that contribute to long-term lake data without needing physical access to the water body.
Case Studies: Local Models with Global Impact
Around Tulsi Lake, small pockets of civic engagement already exist but lack scale and visibility. Earth5R’s Circular Economy training workshops have been instrumental in educating youth from nearby neighborhoods about waste management and eco-restoration.
Another promising model is the Citizen Lake Biodiversity Register (CLBR) used in Bengaluru, where residents and ecologists co-create digital records of flora, fauna, and environmental changes around lakes.
Youth Leadership and Eco Clubs
Mobilizing students and local youth is central to citizen-led conservation. School-based initiatives such as Green Schools Program by the Centre for Science and Environment (CSE) have demonstrated the power of environmental education in building lake-conscious citizens.
Within SGNP, guided programs like Van Mahotsav can be restructured to include Tulsi Lake-specific activities—like virtual biodiversity walks, interactive documentaries, and QR-coded eco-learning trails.
Earth5R’s BlueCities Framework for Tulsi Lake
Earth5R’s BlueCities model offers a scalable and replicable framework to restore, protect, and manage urban freshwater bodies through community-based and science-backed interventions.
Applying this model to Tulsi Lake involves an integrated, circular approach that balances ecological resilience, citizen empowerment, and sustainable livelihoods.
Foundational Pillars of BlueCities
The BlueCities framework rests on five key pillars:
- Ecological Restoration: Conducting biodiversity assessments, removing invasive species, and rehabilitating native flora around the lake.
- Circular Economy Interventions: Promoting sustainable production and consumption patterns through community training, upcycling, and local green enterprises.
- Data and Citizen Science: Developing open-access platforms for community-driven environmental data collection and monitoring.
- Education and Behaviour Change: Launching campaigns on water conservation, waste reduction, and eco-literacy.
- Policy and Stakeholder Alignment: Facilitating collaboration between local government bodies, NGOs, researchers, and citizen groups for holistic lake governance.
This structured approach ensures that every action taken around Tulsi Lake aligns with the broader goals of climate resilience and sustainable urban planning.
Application to Tulsi Lake
Earth5R’s past success with Mithi River rejuvenation demonstrates how grassroots engagement and scientific audits can transform polluted water bodies. For Tulsi Lake, the BlueCities framework proposes the following:
- Waste Mapping and Source Segregation: Conducting a waste audit around SGNP buffer zones to trace the origin and types of litter. Volunteers use mobile GIS tools to identify pollution hotspots and plan clean-up drives accordingly.
- Floating Wetlands and Bioremediation Units: Inspired by eco-restoration methods used in Hyderabad’s lakes, Earth5R proposes installing bio-filters and floating islands at strategic locations to filter runoff before it reaches the lake.
- Women-Led Green Enterprises: Training local women in upcycling plastic waste and creating eco-products such as reusable bags, compost kits, and vertical garden modules, thus linking environmental action to economic empowerment.
- Mobile App for Lake Health Monitoring: Developing a community interface where residents can log waste sightings, water odor changes, and flora-fauna observations. Earth5R’s existing Green Citizen app can be scaled up to support these features.
Blueprint for Replication and Policy Integration
The success of Tulsi Lake’s rejuvenation under BlueCities can serve as a pilot model for similar urban lakes across India. Earth5R plans to document the process through open-source case studies, interactive workshops, and collaborations with urban planners and civil society networks.
Additionally, aligning the initiative with UN SDG 6 (Clean Water and Sanitation), SDG 13 (Climate Action), and Mission LiFE (Lifestyle for Environment) will bolster institutional support and international recognition.
The initiative can also plug into municipal programs like the MCGM’s Climate Action Plan for long-term funding and scalability.
Blueprint for Action: A Roadmap to Rejuvenate Tulsi Lake
Creating a resilient and sustainable future for Tulsi Lake requires a structured, participatory, and multi-stakeholder approach.
The roadmap must address the ecological, social, and institutional dimensions of lake management through actionable steps. These actions not only restore the lake but also empower the communities living around it.
Multi-Stakeholder Collaboration
The first step involves the formation of a Lake Rejuvenation Task Force that brings together officials from the Brihanmumbai Municipal Corporation (BMC), Sanjay Gandhi National Park authorities, civil society organizations like Earth5R, research institutions such as NEERI, and local citizen groups.
This consortium should operate under a co-management model, similar to the collaborative framework used in East Kolkata Wetlands, where governmental and community actors share equal responsibility in maintaining the ecological integrity of the site.
Environmental Assessment and Lake Health Indicators
This includes water quality analysis (pH, BOD, COD), mapping of invasive species, sediment toxicity studies, and catchment hydrology. Using methodologies like Wetland Rapid Assessment and data from tools such as the India Water Tool 3.0, stakeholders can baseline the lake’s condition.
A long-term Lake Health Index should be developed based on indicators such as:
- Dissolved oxygen and nutrient load
- Biodiversity score (number of native vs. invasive species)
- Plastic and organic pollution concentration
- Community participation in conservation events
- Policy and budgetary alignment with climate goals
Infrastructure and Nature-Based Solutions
Using nature-based solutions (NbS) to address urban ecological degradation is increasingly favored over traditional grey infrastructure. For Tulsi Lake, the roadmap should include:
- Green Buffer Zones: Strengthening native vegetation around the lake to prevent soil erosion and enhance carbon sequestration.
- Floating Islands: Installation of artificial floating wetlands to treat water inflows naturally.
- Bio-remediation Units: Deploying microbial treatments to reduce organic waste load from runoff.
- Rainwater Harvesting Projects: Especially within SGNP and adjacent catchments, to replenish lake volume during dry spells.
These interventions should be accompanied by eco-friendly signage, compost toilets, and zero-waste trails for visitors and researchers.
Community Capacity Building
To ensure sustained lake stewardship, citizen training programs must be institutionalized. Earth5R can conduct skill-building modules on:
- Waste audit and segregation
- Monitoring water quality using simple kits
- Organic composting and community gardening
- Leadership development in climate resilience
Building a Water-Secure Mumbai Through Tulsi Lake
As one of the city’s oldest freshwater reservoirs nestled within the Sanjay Gandhi National Park, it not only ensures potable water supply but also functions as a biodiversity hotspot and carbon sink in a rapidly urbanizing city.
However, mounting pressures from urban sprawl, climate change, plastic waste, and institutional neglect have made the lake vulnerable. If left unaddressed, these threats can compromise both the ecological integrity of the lake and the water security of over 10 million Mumbaikars.
The way forward lies in embracing community-centric governance, science-driven monitoring, and inclusive sustainability practices. Models like Earth5R’s BlueCities, backed by global frameworks such as UN SDGs and Mission LiFE, show that even highly regulated zones like Tulsi Lake can benefit from innovative and participatory conservation strategies.
Data Snapshot Box: Understanding the Crisis in Numbers
To grasp the current ecological and infrastructural status of Tulsi Lake, it’s vital to examine key data points. These figures highlight the severity of environmental degradation and the urgent need for structured intervention.
| Indicator | Current Status | Source |
| Sewage Treated | NA (No domestic sewage inflow due to protected area) | Sanjay Gandhi National Park Management Report |
| Biochemical Oxygen Demand (BOD) | ~2.4 mg/L (within permissible limits) | MPCB Annual Report |
| Dissolved Oxygen (DO) | 6.8–7.5 mg/L (favorable for aquatic life) | National Water Quality Monitoring Programme (NWMP) |
| Encroachment on Catchment | ~15% informal encroachments in buffer zone | Environmental Status of Mumbai Report 2022 |
| Plastic Waste Found Nearby | 500–700 kg/month (from tourism and trail litter) | Earth5R Waste Audit 2023 |
| Biodiversity Loss | 12% drop in indicator species (amphibians, birds) | BNHS Biodiversity Survey |
| Forest Cover Decline (buffer) | 2.6% in last decade due to illegal activities | ISRO Bhuvan Forest Monitoring Tool |
| Water Supply from Tulsi | ~18 MLD (Million Litres/Day) | Municipal Corporation of Greater Mumbai (MCGM) |
| Tourist Footfall (SGNP) | 1.5+ million/year (raising ecological pressure) | Maharashtra Ecotourism Board |
Urban Sustainability Opportunities for Mumbai
While the rejuvenation of Tulsi Lake is essential, it must be woven into the broader urban sustainability framework for Mumbai. By aligning lake restoration with climate goals, city planning, and livelihood strategies, we can unlock systemic transformation that benefits all residents of Mumbai.
Waste Management and Circular Economy
Mumbai generates over 7,000 tonnes of solid waste daily, out of which a significant portion remains unrecycled. Localized Material Recovery Facilities (MRFs), promoted under initiatives like Swachh Bharat Abhiyan and Earth5R’s community recycling stations, can address this gap.
Plastic waste management, especially near natural reserves like SGNP, should be a priority through community-led cleanup drives and reverse logistics partnerships with FMCG brands under Extended Producer Responsibility (EPR) frameworks.
Sustainable Mobility and Transport
With vehicle emissions accounting for nearly 30% of Mumbai’s air pollution, there’s a clear opportunity to integrate sustainable mobility with eco-tourism. Electric shuttle buses, cycling tracks, and car-free zones around Tulsi Lake and SGNP can create low-carbon access corridors.
The Mumbai Climate Action Plan (MCAP) already encourages green mobility, and Tulsi Lake could serve as a pilot eco-transport hub.
Urban Green Spaces and Biodiversity
Mumbai has less than 2 square meters of green space per person, far below the WHO-recommended 9 m².
Reviving urban forests, restoring biodiversity corridors near Tulsi Lake, and creating citizen biodiversity registers, similar to Delhi’s Yamuna Biodiversity Park, can protect endemic species and improve mental health outcomes for city residents. Tulsi can serve as a green classroom for students across Mumbai.
Water Conservation and Management
Water scarcity still affects low-income communities in Mumbai, particularly during the dry season.
The restoration of catchment areas around Tulsi Lake through rainwater harvesting retrofits and greywater recycling in nearby forest guesthouses can serve as demonstration models. Citizens can be trained to install rooftop harvesting systems, supported by Jal Shakti Abhiyan and local CSR programs.
Carbon Footprint Reduction and Climate Action
Mumbai’s carbon footprint, pegged at 2.35 tCO2e per capita, can be substantially reduced through nature-based carbon sinks like Tulsi Lake’s surrounding forest and wetlands. Tree plantation drives, wetland carbon sequestration studies, and corporate carbon audits tied to ESG disclosures can turn this site into a climate innovation zone.
Citizen Sustainability Engagement
A sustainable city cannot be built without its people. Digital tools such as Earth5R’s eco-citizen mobile app, eco-rewards programs, sustainability workshops, and green volunteering portals can turn awareness into action.
Monthly training sessions, youth-led cleanups, and climate storytelling festivals around Tulsi Lake can instill environmental ownership among Mumbaikars.
– Authored by Mridu Mishra
