Will the Kelani River Pollution Ever End?

By: Sachini Perera

Water is a vital resource for life, with flora and fauna species, including humans, dependent on it for food, energy, shelter, agriculture and much more. The value of water requires the recognition of the vast environmental, economic, and social services it offers, such as purifying air, storing carbon and enhancing biodiversity (IUCN, 2021).

Globally, freshwater habitats account for rich biodiversity. Rivers, such as the Amazon and Mekong, are vast ecosystems for floral and faunal species and are primary sources of drinking water for global populations. Too often, the complete value of rivers has not been recognised and thus, are under threat from a wide range of anthropogenic activities, such as pollution or poor water management.

The Kelani River is the fourth longest and second largest water body in Sri Lanka and is one of the most critically important rivers. Home to over 25% of the nation’s population, the river is the primary source of drinking water to 4 million people living in the Colombo & Greater Colombo areas (Rebert & Sathananthan, 2017).

Additionally, a considerable proportion of Sri Lanka’s industries, such as the manufacturing sector and other small, medium, and large-scale businesses are dependent on the river for the environmental and economic services it provides. Industries and businesses require an Environment Protection Licence (EPL) according to the National Environmental Act of 1980 and under the provisions of Section 23 (a) for the discharge of effluent and other industrial wastes.

According to a 2014 report by the Central Environmental Authority (CEA), agricultural runoff, domestic waste, sewage, and industrial waste discharges are the most impactful pollution sources. Despite many of the industries operating within the Kelani River basin having obtained the EPL, river pollution continues to increase at a rapid rate as observed through water quality assessments conducted in the river.

Though there are mandatory regulatory frameworks and policies in related to discharge of industrial effluents, there are concerns that certain industries have failed to adhere to the requirements of the EPL given the lack of monitoring of industrial activities, while several may lack the capacity for adequate effluent treatment and discharge, and the overall accumulative treatment capacity of the central treatment plants in the industrial zones.

In consideration of the importance of the Kelani River and associated ecosystems, it is concerning that the anthropogenic activities threatening the river will result in it becoming entirely unusable in the future which will directly impact the people and nature dependent on it for survival. Therefore, it is a national responsibility to regulate conservation measures and protect its ecological, economic, and hydrological importance.


Impact of Pollutants

Discharge of untreated sewage, chemicals, pharmaceuticals, municipal waste, and other pollutants cause an accumulative pollution load which directly results in a reduction of overall

water quality of the river. This then has severe consequences on the biodiversity of the river ecosystem.

The biological alterations in the river through the change of watercolour, an increase of Escherichia coli bacteria and other microorganisms and bad odour has been observed in water samples. The discharge of chemicals interrupts the clarity of the water, whilst also encouraging the onset of eutrophication. This leads to other environmental issues where Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) increase and disrupt the food webs via a decrease of dissolved oxygen in the water bodies which is a sign of habitat degradation.

A significant extent of the deforestation on the riverbanks has resulted in an increase in run-off and discharge of effluents to the river. The plantation of tea, rubber, coconut, and rice is a common type of land use within the river basin and observed in areas near the river. This then is responsible for low forest cover and agricultural runoff, which result in the discharge of inorganic chemicals from fertilizer usage into the river.

Direct discharge of sewage and municipal waste from the urban development and domestic residential land usage along the riverbank has also caused the Kelani River to become a dumping ground for a wide variety of untreated toxic waste and thereby an increase in BOD levels (Surasinghe et al., 2019).

Ecological Significance

The biodiversity of Kelani River basin cannot be fully evaluated since detailed research has not been conducted. However, small scale research studies conducted provide valuable insight on the ecological importance of the river and its habitats. The Kelani River basin is a nationally important habitats for a wide variety of endemic, point endemic, threatened and common species. As it flows from the mountainous region through Sri Lanka into the coast at Modara, the range of flora and fauna is varied across three different forest covers and floristic regions in the country (Mallawatantri et al., 2016). Research has indicated that the species Balanocarpus kitulgalensis is critically endangered as its habitat is restricted to the riparian forest of the Kelani River basin. Other ecologically important species found within the Kelani River ecosystems are endemic species such as the plant Vetica luwesiana, and the fish species Pethia bandula, and Systomus asoka.

Image credits: Nalinda Pieris

Image 1: Critically endangered plant- Balanocarpus kitulgalensis

Image credits: Sampath Goonathilake

Image 2: Endemic fish species- Pethia bandula

Other recorded point endemic invertebrates listed on the IUCN’s National Red List for their narrow distribution include the damselfly species Archibasis oscillans and three freshwater crab species Ceylonthelphusa nata, Clinothelphusa kakoota and Perbrinckia cracens. Table 1 outlines the threatened species within the Kelani River basin together with their conservation status (Mallawatantri et al., 2016).

Total Number 
Critically Endangered (CR) 
Endangered (EN) 
Vulnerable (VU) 


16  8  7  1 
Butterflies  23  1  10 


Freshwater Fish 

27  8  15  4 
Amphibians  9  0  6 



11  1  6 



25  0  10 


Mammals  28  1  14 


Table 1: Threatened species of Kelani River basin 

There is a high possibility that some biodiversity may not be discovered and may already be extinct due to the high rate of pollution occurring. Once the river basin is contaminated, it is possible for this to spread to its tributaries and canals and result in bioaccumulation and biomagnification. It is necessary to take the required precautions to protect and conserve the recorded and unrecorded biodiversity amid increasing pollution.

Years ago, conservation activities, strategies, and a sustainable approach to the Kelani River Basin began, and the actions and measures used to combat pollution have centred on ecosystem service resilience. The role and input of the Environment Foundation Limited (EFL) towards reducing and mitigating the Kelani River pollution commenced in 2015 following funding by Asia Foundation and conducted under two phases. Through that, workshops, and training programmes regarding the pollution impact of domestic waste sources were conducted for community-based organizations. Additionally, a comprehensive map of pollution sources in a 40km area of the Kelani River was created to aid government and other agencies in ongoing and future conversation strategies.


No comments yet.

Leave a comment

Your email address will not be published.