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Located just a few kilometers away from Colombo, the Thalangama (Talangama) wetlands are an environmental protection area and biodiversity hotspot in a rapidly urbanizing environment. It is the perfect spot for a relaxing afternoon in nature and for those who are passionate about birding.
The wetland is home to two man-built reservoirs (tanks) namely Thalangama tank and Averihena tank, both just 300 meter apart. The Thalangama tank spanning about 28 acres (11 ha) is comparatively larger and much older than the recently constructed Averihena tank (8 acres or 3.2 ha) and serves today mainly as a source of irrigation water supply for about 100 acres (40 ha); maintained by the Department of Irrigation. The tanks are also important for floodwater retention and have a high scenic and aesthetic value, which attracts many visitors. They are particularly rich in biodiversity with a remarkable Avifauna (bird population), which is well-known among local and foreign wildlife enthusiasts. The wetland is also in high demand for educational purposes, fishing, bathing and the collection of flowers and water lily leaves for ceremonial purposes. Both tanks thus constitute multi-purpose urban freshwater resources with different stakeholder interests that govern its use and management. Due to rapid urbanization of the area, the land value has increased significantly leading to excessive land filling and the reclamation of paddy lands for housing, despite the fact that this activity is illegal. This is accompanied by indiscriminate (over-night) garbage and construction waste disposal, next to the volume of litter and bottles left by the daily lake visitors. Given the overall garbage challenges in the country, authorities are struggling with a way to address these issues.
A related challenge is the fast growth of invasive plant species like the Wel Atha trees (Pond or Monkey Apple (Annona glabra)), water hyacinths (Eichhornia crassipes) and Salvinia (a type of watermoss) on the lake surface. The growth of water hyacinths was probably catalyzed by the recent dredging activities, which brought nutrients from the sediments back into circulation, but also benefits from large bird colonies (and their droppings) which rest on lake islands overnight, as well as farmers releasing manure into the lake, or residents their domestic wastewater. While we are keeping the spread of Water Hyacinths under control, other water weeds, like Salvinia or the submerged invasive Coontail and Bladderwort remain a challenge. A particular threat to the ecological balance is the release of non-native fish into the lake.
This practice is very harmful for native fish species of which some are not only endemic to Sri Lanka but also endangered, like the Day’s killifish and Yellow catfish.
Among the endemic and endangered mammals, the Purple-faced leaf monkey is the most noisy and visible around the lake, but also the most chased one by local residents when it moves from roof to roof in groups of 15-30 family members.The western purple-faced langur which is the subspecies living around the lake is one of the 25 most endangered primates in the world.