Planted by the road, they are unlikely to attract even a passing glance. But these plants along the junction of Margaret Drive and Kay Siang Road in the Dawson estate have a special role - they cleanse rainwater before it flows into the Marina Barrage reservoir.
The seven species - including the lalang look-alike pennisitum - form the bio-retention swales, a project by the Housing and Development Board (HDB) to improve the quality of rainwater before it enters the reservoirs. Construction for the project started last year and will end when the swales built along Kay Siang Road to Tanglin Road are completed.
Having plants and soil removing components in rainwater like nutrients and nitrogen before they flow into reservoirs helps to prevent algae bloom, which lowers the cost of treating water.
The project is part of a scheme under the PUB’s Active, Beautiful, Clean (ABC) Waters Programme to include design features, such as bio-retention swales, rain gardens and wetlands, in housing estates and schools, to cleanse rainwater.
The scheme was launched in 2009 and 14 certified projects were started last year. If successful, more projects will be added.
Ms Angela Koh, assistant director of the catchment & waterways department at PUB, said the ABC Waters Programme goes beyond beautifying drains. “We thought it is important to keep water clean and wanted look at different ways to do so,” she said.
Partners like the HDB were engaged for the projects, so they could be extended to more areas, said Ms Koh, noting that the HDB builds 80 per cent of housing in Singapore. The PUB is also engaging private developers and other public agencies to come on board, as well as schools.
“If you think of the over 300 schools in Singapore, as well as private and public agencies it (the water cleansed) can be quite substantial,” she said.
The first rain garden was built in Balam estate in MacPherson in 2008 as a pilot project. Seeing that the project was working “quite well”, the PUB decided to increase the number of projects, said Ms Koh.
Assumption Pathway School is the first school in Singapore to have its own rain garden under the scheme.
An 85m-long rain garden with a boardwalk to provide an outdoor classroom has been built in the school near its entrance.
The rain garden absorbs and treats 12 per cent of the rainwater that falls onto the school’s area.
After the rainwater flows through the ground around the plants, such as the butterfly nectar plant and three layers of soil, it is transferred to roadside canals through underground pipes and then on to the reservoirs.
The PUB is currently in talks with other schools to build such rain gardens, said Ms Koh.
