Southwestern Sri Lanka Rivers and Streams

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Mahaweli, Sri Lanka.
© WWF-Canon / Mauri RAUTKARI

About the Area

Sri Lanka has an extensive network of rivers and streams that drains a total of 103 distinct natural river basins. However, much of Sri Lanka is arid and has only a few permanent rivers. The southwestern region's "wet zone" is characterised by numerous rivers that arise in the high mountains of the central part of the island. The rivers flow in a radial pattern toward the sea. Most of these rivers are short. The longest rivers are the Mahaweli Ganga (335 kilometers) and the Aruvi Aru (170 kilometers).

The upper reaches of the rivers are wild and usually unnavigable, and the lower reaches are prone to seasonal flooding. These diverse river basins support endemic populations of aquatic plants, bivalves, and fish.

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Size:
15,500 sq. km (6,000 sq. miles)

Habitat type:
Small Rivers

Geographic Location:
Asia: Sri Lanka, an island southeast of India

Conservation Status:
Vulnerable
Local Species
Sri Lanka's known freshwater species include 90 fish (with 26 endemics) and 21 crabs, yet ongoing studies suggest that the number of undescribed species is potentially quite large.

Most of these fish are small and highly specialised to their habitat. Several fish species of an endemic barb genus, Puntius, are considered vulnerable, these include P. cumingii, P. nigrofasciatus, P. martenstyni, P. pleurotaenia, and P. titteya. One species, P. bandula, is critically endangered.

Rare endemic species include the Jonklaas loach (Lepidocephalichthys jonklaasi), Rasporas (Rasbora wilpita, R. vaterifloris), and the spotted Gourami (Malphuhutta kretseri).
Jonklaas loach (Lepidocephalichthys jonklaasi)

Its size is about 6.0 cm. It is a non-migratory fish. Inhabits shallow, slow-flowing rivulets, heavily shaded, with leaf debris. This fish is not visible from the water surface, being concealed beneath leaf debris. It is too rare to be of value to the aquarium trade which in any case exports large numbers of the superficially similar Lepidocephalus thermalis.

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Threats
A majority of the wetlands in Sri Lanka are facing various threats that are posed by harmful human activities. These could be summarized under four major categories; habitat deterioration/degradation, direct loss/exploitation of species, spread of invasive alien species and natural phenomena. Deforestation for fuel wood and agriculture, in stream habitat alteration, introduced species, pesticide use, and collection of fish for aquarium trade has damaged parts of the freshwater ecosystem.

A number of species adapted to still or slow-water environments are threatened by conversion of habitats for rice cultivation.

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WWF’s work

WWF's response to the Tsunami of December 2004
Since the 26 December 2004 Indian Ocean earthquakes and tsunami, WWF has been working to promote green reconstruction - the integration of sound environmental outcomes in all facets of post-tsunami reconstruction.
WWF:
  • Assessed environmental impacts, threats and needs (eg, by participating in the United Nations Environment Programme’s Tsunami Task Force, which published After the Tsunami – Rapid Environment Assessment in February 2005)
  • Developed practical “green reconstruction” solutions to those impacts, threats and needs and has been working with implementing agencies to make positive choices for the environment to underpin the long-term success of reconstruction.
In the longer term, WWF is working to establish sustainable reconstruction as a major consideration in responses to disasters through engagement with affected governments, donor governments and agencies, United Nations bodies and NGOs.

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WWF's response to the Tsunami of December 2004

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Photos and graphics © WWF or used with permission. Text available under a Creative Commons licence.