Significance of Wetlands for sustainable Colombo

Published : 9:18 am  January 24, 2018 | No comments so far |  | 


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Untitled-2Being both the commercial and administrative capital of the country, Colombo city is losing its green coverage  day by day due to rapid development and construction of both residential and commercial properties. Colombo once was a complex maze of marshy wetlands now consists of struggling pockets of wetlands. Days ahead of the World Wetlands Day, which is to be commemorated on February 02, Daily Mirror took to the streets to understand the true meaning of wetlands and its functions and how it is connected to day-to-day life of residents in the city.   

According to the Ramsar Convention (an international treaty for the conservation and suitable utilization of wetlands) a wetland is defined as “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plants and animal life.   

Although the hidden contribution of these ecosystems are unfathomable it helps in the mitigation of floods, offers protection from storms, the retention of sediment, to act as a carbon sink, and an excellent purifier of water.   

Importance of wetlands 

Colombo is a city built on and around wetlands. Despite progressive development and degradation, wetlands still cover some 20 km2 of the Colombo Metropolitan Region(CMR).   

The wetlands are fundamental to the well -being of the people of Colombo. All of the wetlands, even the most degraded ones, provide a range of benefits which contribute to human well-being in the city. Of all the benefits provided by the wetlands, over 90 percent of these benefits remain within the Colombo Metropolitan Region.   

The wetlands significantly benefit the urban poor. The income for households in and around the wetlands is less than 40 percent of the average income for the Metropolitan Colombo Region. Over 60 percent of these local households directly benefit from livelihoods and products derived from the wetlands and 100 percent will be receiving indirect benefits from flood mitigation, climate cooling and pest regulation.   

The wetlands assist in delivering food security, such as rice cultivation in the paddy lands, a long established practice in the Colombo Metropolitan Region. However, in addition to rice the wetlands provide a range of other formally cultivated food including vegetables such as brinjal, long yard bean and gourds, eggs and poultry, and milk from cattle, as well as native plants which are foraged. Fishermen are also active in the wetlands across the city. Over 87 percent of all wetland areas currently provide food to the citizens of Colombo.   

The wetlands provide the citizens of Colombo with traditional medicines. The people of Colombo have long benefited from their knowledge of the curative powers of local plants. It is estimated that almost 80 percent of the wetland areas provide local communities with traditional natural medicines which are harvested and foraged for no or limited cost to the individual households.   

The wetlands provide effective protection from flooding. During intensive rainfall events, the wetlands are able to store several millions of cubic metres of water (up to 68 Mm3 for the 100 year return period flood or the equivalent of more than 27,000 Olympic sized swimming pools).   

“City dwellers will be in trouble if these are not protected”
-Dr. N.S.Wijeyarathna

(Deputy General Manager of Wetlands Development – Sri Lanka Land Reclamation & Development Corporation)




  1000Stress levels in urban areas are sky rocketing due to the decrease in the wetland areas in the area. During the past, wetlands had to face the horizontal development and with the present urbanization, sky touching towers and the land reclamation for building those have doubled the risk in these areas.  

According to the rapid development each city dweller faces stressful situations caused by air pollution, floods and several other reasons. The maintenance and development of wetland areas is important to reduce this.   We cannot replace how incredible nature is as it cannot be replaced. City dwellers will be in trouble if the remaining wetlands are not protected. It is essential to invest more on wetlands as we do on mega development projects.   Recently, Delhi in India was severely affected by air pollution. Therefore we should save the remaining wetlands to prevent such a situation in Colombo.   

In this manner public support is important as well as the projects launched by the government.  


The wetlands can reduce extreme air temperatures and make the city more liveable. Due to evaporative cooling, the wetlands can reduce air temperatures, the effect of which can extend into areas up to 100m away from the wetlands’ physical boundaries. This means that over 65 square km, or more than 50 percent of urban Colombo, benefits from this natural air conditioning.   

The wetland soils are mitigating global climate change. Estimates suggest that the wetland soils contain approximately 1.43million metric tons of carbon; the equivalent of almost 90 percent of the annual carbon emissions from CMR.   

The wetlands protect the health of citizens. Four of five of the wetland areas in Colombo buffer the negative impacts of airborne pollutants on air quality. Through the trapping and removal of particulate matter the wetlands are reducing the incidence of cardiopulmonary and respiratory diseases, coughing, bronchitis, and lung cancer, as well as premature deaths from these diseases resulting from elevated concentrations of ambient particulate matter.   

The wetlands contribute to a city rich in biodiversity. Over 250 plant species, including nine endemic, nine nationally threatened and 11 nationally near threatened plant species are present in the wetlands. Almost 280 species of animals, including 32 endemic species, are present in these urban wetlands.   

The wetlands support a critically endangered plant species, the native Critically Endangered plant species, the tree climber Aganope heptaphylla. This plant is only recorded at three sites in Sri Lanka, two of which are the urban wetlands of Beddagana Biodiversity Park and Kolonnawa Marsh.   

The wetlands support endangered animals. Altogether 20 critical species inhabit the wetlands of Colombo. These include four species of dragonfly, two species of butterfly, four species of land snails, two species of freshwater fish, two species of amphibian, two species of reptiles and four species of mammals, including two endangered species: the Fishing cat ‘Prionailurus viverrinus’ and the ‘Otter Lutra lutra’.   

Wetland loss and degradation 

Despite all the benefits that the wetlands provide, it has continued to be completely lost or progressively degraded across Colombo at present. Whilst rates of loss vary across the city, reports suggest that in some areas of the city the rate of loss since the 1980s has been as high as 60 percent.   

Infilling of wetlands with the horizontal development which took place in Colombo for the past year has directly posed a flood risks across the city. According to the Sri Lanka Land Reclamation and Development Corporation (SLLR&DC) the current rate of wetland loss in the Colombo Metropolitan Region is approximately 1.2 percent per annum and the entire wetlands would be reduced by one third by 2038, half by 2070 if the trend continues.   

According to studies conducted by environmentalists the water quality of 64 percent of the wetland areas have been severely affected and is considered to be in bad or very bad condition. Therefore the ecological functioning and consequently the range of benefits being provided would be compromised in at least two thirds of the wetland areas.   

The water quality in the catchments supplying the wetlands has also degraded. At the catchment scale, the water quality is bad or very bad for half of all the sub catchments in the Metropolitan Colombo Region and it would not only be compromising the ecological functioning of the wetlands but will impact on other uses or services such as recreation, crop irrigation or water for livestock.   

The domestic waste water has been identified as significant factor in the degradation of water quality. Accordingly the water quality situation has been critical since 2010; however the degradation has become more widespread and acute during the last five years. The Colombo wetlands have remained resilient but an ecological threshold was crossed in 2010 and the changes in functioning may be permanent.   

Some wetlands are permanently degraded. For instance, Beira Lake is an example of very bad water quality with a permanent algal bloom present and with reports of numerous fish killed. These negative conditions are maintained by a combination of perpetual inputs of nitrogen and phosphorus from the catchment and by the nutrient stock persisting in the sediment water.   

“Colombo wetlands are the critical component of deciding the sustainability of urban development of Colombo”

Ms. W D C T Gunasiri -

“(Environmental Scientist  Surface and Ground Water and Soil surveys)”



Untitled-2The strategy to manage Colombo wetlands is to use them wisely. This can be achieved through integrating Colombo wetlands into city development activities and life styles of urban dwellers to enhance the city livability and human well-being.   

In order to do this many government projects have now been launched and proposed to make wise use of the Colombo wetlands to gain economic benefits and increase social benefits while safeguarding the ecosystem services provided by these precious ecosystems. Colombo wetlands are the critical component of deciding the sustainability of urban development of Colombo. Therefore it should be protected at any cost.  


Canal maintenance activities are degrading the ecological functioning of the wetlands. The routine dredging of sediment from the canals and its deposition on the adjacent banks reduces the ingress of water to wetlands, remobilizes contamination and pollutants and accelerates hydrological conveyance reducing the residence time of water in the wetlands. This in turn can change the abundance and composition of species that inhabit the wetland which can change the usage of these wetlands by more mobile species such as birds that feed on aquatic species. Further increased drainage of wetlands can also make them more susceptible to invasion by alien invasive species such as Annona glabra as has been observed in Talangama tank and Bellanwila Attidiya Sanctuary.   

Alien invasive species present a significant threat to the native biodiversity of the city. Eleven species of alien invasive plants are currently known to be present in the wetlands including Eichhornia crassipes, which is widespread and chokes canals and waterways, and Annona glabra which occurs in almost every wooded wetland in the city and results in significant changes in the native ecological character of the wetlands.   

The impacts on wetlands undermine the well-being of the urban poor. The continued loss and degradation of wetland does not only impact on the native fauna and flora but human well-being suffers significantly. The impacts are most acutely felt by the relatively less well off citizens who live in around the wetland areas and depend on them directly for their livelihood and indirectly for the overall well-being.  

The state of wetlands in Colombo

Despite covering less than 6 percent of the country’s total land area, the Colombo Metropolitan Region houses over a quarter of the nation’s population and accounts for almost 50 percent of national Gross Domestic Product (GDP). However, the CMR is vulnerable to a range of threats which unless addressed will compromise the ability of the nation to achieve its full economic potential and thereby securing the well-being of the population.   

The city is expanding through both formal and informal settlements in order to house the growing population. The growth in the population places pressures on local resources, food production, water demand and the quest for sustainable household incomes. Domestic and industrial developments, along with a proliferation in road traffic generate air and water pollution and increase risks to 
human health.   

Uncontrolled disposal of solid waste further pollutes the soil and water and increases the risk of pests and disease. Invasive species clog up waterways and threaten native biodiversity.   

At the same time, climate change is amplifying these pressures, including increasing urban air temperatures, causing implications for both human health and energy usage through increased demand on air conditioning.   

Flooding is acknowledged to pose a particular threat within the CMR. The people of the CMR are highly vulnerable to flood risks and the city has experienced considerable flood damage in recent years. The triple drivers of climate change, population growth and economic development are all either directly or indirectly exacerbating flood risk to communities and infrastructure.   

All of these land use changes have implications for water and flood risk management, for the governance and institutional structures and the sustainable development of the CMR. At the heart of these issues are the wetlands of the CMR.

Recent projects


According to the Sri Lanka Land Reclamation & Development Corporation many projects have been launched as a means of saving the remaining wetlands. Following are some of the projects launched by the government.   

Development of wetland parks for recreation and education (Eg: Diyasaru Park, Thalawathugoda, Baddagana Wetland Park, Diyatha Uyana)  

Development of jogging tracks and exercise facilities around wetland areas to promote healthy life styles to address urban stress  

Untitled-2Recreational Boat tours (Now operating from Diyatha to Nawala Weli Park)  

Canal based passenger boat transportation projects (Jetty construction has already been started)  

Promoting Paddy cultivation in urban area and suburbs (Eg: Kimbulawala Organic Paddy Farm)  

Proposed wetland based tourist circuit in Colombo  

Proposed wetland based water recreational activities  




Events to commemorate WWD in SL

World Wetlands Day (WWD) observed annually on February 2nd, marking the date of the adoption of the Convention on Wetlands on February 2, 1971. The purpose of establishing to raise awareness about the value of wetlands for humanity and the planet, WWD was celebrated for the first time in 1997 and has grown remarkably since then.   

Ramsar convention member countries and the environmentalists are making arrangements to celebrate the event globally with various kinds of activities and awareness programmes under this years theme of ‘Wetlands for Sustainable Urban Future’.  

Meanwhile, Sri Lanka as a signatory country for the Ramsar convention is to celebrate the day with Sri Lanka’s theme of ‘Wetlands for Sustainable Colombo’ at the Diyasaru Park in Thalawathugoda from January 28 to February 03.  

Sri Lanka Land Reclamation & Development Corporation (SLLR&DC) is organising the event in partnership with the Ministry of Megapolis and Western Development.  
Awareness programmes for school students, public seminars,workshops for professionals, activities related with wetlands, photography and exhibitions have been organised during the period.