What is a bioretention system?
A bioretention system is a vegetated depression also known as rain garden that captures stormwater runoff from urban areas, like roofs, driveways and walkways. Runoff that travels through the rain garden is briefly detained and cleansed via filtration through the soil before entering nearby reservoirs or lakes. In this way, it not only helps to improve water quality in nearby waterbodies but enhances aesthetics and biodiversity.

Why install bioretention systems in Singapore?
Singapore is highly urbanized. Owing to its geographical location, Singapore experiences an abundant rainfall average of 2,340 mm in a typical year. Severe thunderstorms develop during the monsoon season, with frequent cases of flash floods occurring island wide. In addition, the recent trans-boundary pollution from Indonesia due to the slash and burn of forest has worsened our air quality. As our catchment area increases from 2/3 to 90% by 2060, nonpoint source pollutant removal is important to provide for pristine waterways. With more contaminants being introduced into our rainwater and runoff, the need for bioretention systems surges.

Novel Bioretention Systems Development for Sustainable Stormwater Management in Singapore
In order to seek for a solution for sustainable stormwater management, Prof Hu Jiangyong and her researchers from NERI have embarked on a project funded by PUB to study bioretention systems that are suitable for Singapore’s landscape. So far, they have developed a patented engineered soil and installed a number of bioretention testbeds for the testing of the removal efficiency pollutants using the engineered soil media and plants. The engineered soil was developed through rigorous laboratory testing, with specified soil components that are easily available in Singapore. By adopting the specified engineered soil mix, consistent soil properties can easily be attained by landscape contractors. The team will also be testing at least 50 plant species (including native species) for their potential to improve water quality. The project will help establish a list of plants that is suitable for Singapore. Outcome of the project could then help to establish improved design of rain gardens and bioretention swales suitable for implementation in Singapore. These bioretention systems will significantly help to reduce the amount of pollutants entering the waterways and reservoirs, providing for improved quality of life for Singaporeans.

Article contributed by Prof Hu Jiangyong and Dr Guo Huiling.
For more information, please contact Prof Hu Jiangyong (ceehujy@nus.edu.sg)