Last updated: May 2025
The Thalangama wetlands are part of a network of wetland ecosystems around Colombo city that spread over 20 km2 and provide critical life support to the city. These ecosystems keep people safe from floods, cool the air, filter polluted water, provide food and medicines, and fight climate change (10). These wetlands have become an environmental protection area and a biodiversity hotspot in a rapidly urbanising environment, as they host an array of plants and animals, including the endangered fishing cat and otter (5, 10). In 2007, Thalangama Lake and its surroundings were declared an Environmental Protection Area (EPA) under the National Environmental Act (4, 5). This protected area covers approximately 118 hectares (4) and includes two man-made reservoirs: Thalangama Tank (11 ha) and Averihena Tank (3.2 ha), located just 300 meters apart (5). The area hosts floating and rooted plants, scrublands, and trees that provide habitat to up to 100 species of migratory, resident, and endemic birds throughout the year. In addition, the area supports 30 species of dragonflies, 12 species of reptiles, 10 species of mammals, and 15 species of freshwater fish (1, 4). Since the lakes and their surroundings were declared an EPA, only limited uses are permitted, such as traditional fishing and rice cultivation (4, 5). The lakes are also important for floodwater retention and have high scenic and aesthetic value, attracting many visitors, and scientific and educational activities (5, 13). However, due to the area's rapid urbanisation, land values have increased significantly, leading to excessive landfilling and the reclamation of paddy lands for housing. This is compounded by the indiscriminate disposal of garbage and construction waste and the spread of invasive species (5). These challenges have also led to the engagement of surrounding communities in managing and maintaining it (11).
Removal of invasive plant species
Thalangama Wetlands Watch
Overview
Nature-based solution
- Blue infrastructure
- Lakes/ponds
- In-land wetlands, peatlands, swamps, and moors
- Parks and urban forests
- Large urban parks or forests
Key challenges
- Climate action for adaptation, resilience and mitigation (SDG 13)
- Climate change adaptation
- Environmental quality
- Waste management
- Green space, habitats and biodiversity (SDG 15)
- Green space creation and/or management
- Habitat and biodiversity conservation
- Water management (SDG 6)
- Flood protection
- Improvements to water quality
- Inclusive and effective governance (SDG 16)
- Inclusive governance
- Disaster-risk reduction
- Social justice, cohesion and equity (SDG 10)
- Environmental education
- Sense of community and community engagement
- Economic development and employment (SDG 8)
- Economic development: agriculture
Principal problems in Functional Urban Area (FUA)
- Climate-Related Hazards
- Urban flooding (stormwater)
- Environmental Degradation
- Biodiversity loss
- Invasive alien species
- Physical water retention and availability
- Land use and Socio-economic change
- Rapid urbanization
Key priorities
Climate action (adaptation and/or mitigation), Biodiversity (conservation and/or restoration)
Focus
Maintenance and management of urban nature, Maintenance or upgrade of exisiting green spaces (e.g. parks), Ecological restoration of ecosystems, Restoration of wetlands (other types than peatlands and mangroves, e.g. seagrass), Restoration and protection of ecosystems (including water ecosystems), Protection of natural ecosystems, Protecton and enhancement of wetlands (other types than peatlands and mangroves, e.g. seagrass), Expansion of protected areas, Habitat restoration, Habitat conservation, Creating nature reserves, wildlife sanctuaries, or biodiversity hotspots to conserve unique ecosystems, Knowledge creation and awareness raising, Educational and awareness raising programs, Scientific research of biodiversity or ecosystems
Project objectives
- To establish the area as an environmental protection zone (4, 6)
- Protect the wetland to increase its capacity to store water and absorb floods (10)
- To work closely with institutional stakeholders and community members to safeguard the wetland and its biodiversity (12)
- To ensure the flood retention capacity as well as reduce the water deficit for nearby plantations (13)
- To support research from local universities and NGOs related to environmental sciences (11)
- To control the spread of invasive species on the Thalangama lake (11)
- To protect the wetlands to promote agriculture, fisheries and recreational activities (8)
Implementation activities
A law was passed and approved in 2007 to protect the wetland, recognising it as a biodiversity hotspot, highlighting its ecological importance and the need for its conservation (6). This law aims to control the activities carried out in the area and to establish certain functions to be fulfilled by the managing body (6). Permitted activities include rice cultivation, fishing, nature trails, construction of bird-watching towers (6)
The World Bank funded Metro Colombo Urban Development financed the selective partial dredging of the lake in 2017 following extensive stakeholder consultations and scientific study using a transdisciplinary approach (9, 10, 13). Through these efforts, patches of invasive vegetation were identified and suitable areas were left undisturbed for wetland inhabitants (10)
Additionally, some community members have been involved in lake maintenance activities by cleaning the lake, picking up litter, removing invasive species and caring for the flora and fauna present in the lakes (4, 11). They have also promoted stakeholder dialogue facilitation, supported research and environmental education and established a waste management system in the wetland (11)
As of July 2022, some members of the Thalangama Wetlands Watch are monitoring about 4000 meters of streets and waterways with the blue and yellow lines being cleaned twice every day. The water surface is being monitored once a week by boat for trash and water hyacinths (11)
Climate-focused activities
Climate change adaptation:
- Restore mangroves, marshes, reefs and wetlands to dissipate the effects of storms and floodwaters
Biodiversity conservation or restoration-focused activities
Biodiversity conservation:
- Protect and enhance urban habitats
- Preserve and strengthen existing habitats and ecosystems
- Protect species
- Control and clean invasive alien species
- Means for conservation governance
- Public engagement
Main beneficiaries
- Researchers/University
- Citizens or community groups
- Food producers and cultivators (i.e. farmers, gardeners)
Governance
Management set-up
- Co-governance with government and non-government actors
Type of initiating organisation
- Local government/municipality
- Public sector institution
- Citizens or community group
Participatory approaches/ community involvement
- Co-management/Joint management
- Citizen monitoring and review
Details on the roles of the organisations involved in the project
Ministry of Environment and Natural Resources: declared the area as Environmental Protected Area (6)
Central Environmental Authority (CEA): management agent (6, 8)
Thalangama Wetlands Watch: A self-financed, non-profit community initiative of citizens living in the vicinity of the lake. They work closely with institutional stakeholders and other community stakeholders to protect and maintain the wetland (11)
Irrigation Department: EPA maintenance agent, activity alignment and approval (5)
Stakeholders involved in the management of the EPA: CEA, Irrigation Department, National Aquaculture Development Authority, Sri Lanka Land Development Corporation, KMC, Field Ornithology Group, Road Development Authority (11), Environmental Society of Colombo International School (12), Urban Development Authority, Agrarian Development Department and Local Authorities (6)
Local universities and NGOs (Not specified): research in the area (11)
Schools and community members: volunteering actions (11)
Project implemented in response to ...
... an EU policy or strategy?
Unknown
... a national policy or strategy?
Unknown
... a local policy or strategy?
Unknown
Type of enablers
NGOs/Community groups driving the implementation, City network or regional partnerships focused on climate change, sustainability, GI or NBS in the city
Financing
Total cost
Unknown
Source(s) of funding
- Public local authority budget
Type of funding
- Earmarked public budget
Non-financial contribution
Type of non-financial contribution
- Provision of labour
Who provided the non-financial contribution?
- Citizens (e.g. volunteering)
Impacts and Monitoring
Environmental impacts
- Water management and blue areas
- Increased protection against flooding
- Achieved increased protection against flooding
- Green space and habitat
- Increased green space area
- Achieved increased green space area
- Increase in protected green space areas
- Achieved increase in protected green space areas
- Increased number of protection areas
- Achieved increased number of protection areas
- Increased number of species present
- Achieved increased number of species present
- Increased presence and recovery of wild species
- Achieved increased presence and recovery of wild species
- Increased protection of threatened species
- Achieved increased protection of threatened species
- Improved prevention or control of invasive alien species
- Achieved improved prevention or control of invasive alien species
Economic impacts
- More sustainable tourism
- Achieved more sustainable tourism
- Increase in agricultural production (for profit or not)
- Achieved increase in agricultural production (for profit or not)
Socio-cultural impacts
- Social justice and cohesion
- Improved access to urban green space
- Achieved improved access to urban green space
- Increased involvement of locals in the management of green spaces
- Achieved increased involvement of locals in the management of green spaces
- Increased sustainability of agriculture practices
- Achieved increased sustainability of agriculture practices
- Health and wellbeing
- Gain in activities for recreation and exercise
- Achieved gain in activities for recreation and exercise
- Cultural heritage and sense of place
- Improvement in people’s connection to nature
- Achieved improvement in people’s connection to nature
- Increased awareness of flora and fauna as culturally and historically meaningful
- Achieved increased awareness of flora and fauna as culturally and historically meaningful
- Increased appreciation for natural spaces
- Achieved increased appreciation for natural spaces
- Education
- Increased support for education and scientific research
- Achieved increased support for education and scientific research
- Increased knowledge of locals about local nature
- Achieved increased knowledge of locals about local nature
Type of reported impacts
Presence of formal monitoring system
Yes
Presence of indicators used in reporting
Yes
Presence of monitoring/ evaluation reports
No evidence in public records
Availability of a web-based monitoring tool
No evidence in public records
Potential risks of implementation and trade-offs
Ecosystems and biodiversity, Habitat destruction, fragmentation, or alteration (e.g. use of monocultures), Social justice and conflicts, Gentrification
References
1.
Lakpura LLC (n.d.). Talangama Wetland. Accessed on October 9, 2024, [Source link];
2.
Rathnayake, Z. (2024). From wastelands to wetlands: The fight to save Sri Lanka's natural flood buffers. Accessed on October 9, 2024, [Source link];
3.
Sri Lankan Safari (n.d.). Talangama Wetland. Accessed on October 9, 2024, [Source link];
4.
Thalangama Wetland Watch (n.d.). The Thalangama Area WILDLIFE AND PROTECTION STATUS. Accessed on October 9, 2024, [Source link];
5.
Thalangama Wetland Watch (n.d.). The Thalangama Area LOCATION AND ITS CHALLENGES. Accessed on October 9, 2024, [Source link];
6.
Sri Lanka's Government (2007). Gazette Extraordinary No. 1487/10, dated 5th March 2007. Accessed on October 9, 2024, [Source link];
7.
Dahm, M., Amerasinghe, P. (n.d.). 15 Ways Wetlands Are Vital for Cities, Food and People – A Photo Essay from Sri Lanka. Accessed on October 9, 2024, [Source link];
8.
Central Environmental Authority (2018). Talangama Environmental Protection Area. Accessed on October 9, 2024, [Source link];
9.
Thalangama Wetland Watch (n.d.). 9-thalangama-wetland-watch.pdf. Accessed on October 10, 2024, [Source link];
10.
Rajapakse, N. (2021). Urban wetlands breathe life into Sri Lanka’s capital city. Accessed on October 9, 2024, [Source link];
11.
Thalangama Wetland Watch (n.d.). Our Activities ABOUT US AND OUR WORK. Accessed on October 9, 2024, [Source link];
12.
Environmental Society (2022). The Environmental Society's Thalangama - 2022 Clean up Operation Report. Accessed on October 9, 2024, [Source link];
13.
Clean Nation (2018). Unlawful Construction at Thanagama Wetland Tank. Accessed on October 9, 2024, [Source link];
14.
Environmental Foundation LTD (2022). Illegal Construction at Thalangama Wetland. Accessed on October 10, 2024, [Source link];
Endangered species present in the Thalangama Wetlands
Thalangama Wetlands Watch
Information about this nature-based solution was collected as part of the Naturescapes project funded by the European Union under Grant Agreement No 101084341.