By Tang Lu, Jamila Najmuddin
Located in the middle of Sri Lanka's capital city of Colombo, is the beautiful and popular Beira Lake. Spread over 65 hectares, the lake offers locals and foreign tourists not just a pleasant and tranquil view, but also a quiet retreat from the hustle and bustle urban life.
Created by the Portuguese rulers of Sri Lanka more than five centuries ago, to serve as a moat to defend their fort, the Beira Lake is today an "urban oasis", a beautiful home for a variety of elegant water birds, the sight of which delights children as well as adults.
The placid waters of the lake attract spotted-billed pelicans, cormorants, herons, colourful storks and many other birds. However, seeing swarms of pelicans on the lake could be a matter of luck.
In the past, the lake was not so pleasant. The Portuguese had put crocodiles in it to deter invaders, and during the British rule, launderers washed clothes there. Sewage flowed into it from slums around the area. It was because of this that during the dry season, the lake gave off an unpleasant odour.
But things have changed now. Seeing the tourism-generating potential of Beira Lake, the Sri Lankan authorities stepped up pollution control measures. A few years ago, they worked with local enterprises to explore the use of Floating Treatment Wetlands (FTW), a technology that uses plants to clean severely polluted water bodies. This is done by the creation of "ecological floating islands" on the water body.
By 2018, researchers were excited to see some dragonflies landing on Vetiver, a plant on the floating wetlands. Vetiver is the Sri Lankan word for Chrysopogon zizanioides, a fragrant grass like lemongrass and citronella.
Dragonflies are sensitive to the environment, and their presence indicates that the water is clean, the researchers told the authorities.
The public too could see the difference. "Since some green eco-floating islands appeared on Beira Lake, pelicans are now coming to the lake in greater numbers than ever before. The lake is so much more beautiful now that you don't have to cover your nose when you walk around," Colombo resident Tissa Perera told Xinhua.
At the end of 2020, the local government began to implement the ecological FTW project in the southern part of Beira Lake. Almost overnight, many floating green islands appeared on the lake. These floating beds of aquatic vegetation were anchored to the water. Some were on the shore, while others were at the centre of the lake. Each of these floating islands was a beautiful, small garden.
Xinhua reporters noticed that the aquatic plants on the ecological floating islands were mainly Iris, Canna and Vetiver grass.
The floating islands gently drift with the wind of the Indian Ocean, and the water birds on the ecological floating island seem relaxed, enjoying the slow ride.
The pelicans are now more numerous than ever, with up to 100 gathering at regular intervals. In the morning, pairs of spotted-billed pelicans "paddle" in search of the first pickings of the day. After feeding, the pelicans swim leisurely towards the floating islands or zip through the sky like a helicopter and land there.
Xu Dong, an expert in the planning and design of constructed wetlands and the ecological restoration of polluted water environment in China, told Xinhua that the floating island is actually a kind of artificial wetland floating on the surface of the water body with suitable wetland plants and aquatic vascular plants, which can purify the sewage entering the lake.
The wetland plants can also reduce the smell of sewage and provide a suitable habitat for aquatic animals and waterfowl. The ecological floating island itself has the aesthetic and leisure tourism effect of a water garden.
As an expert who has done extensive research on Sri Lanka's lakes, reservoirs and lagoons, Xu said, "This is a cost-effective and relatively effective nature-based water pollution solution for Sri Lanka."