Realities of Stormwater Quality - Singapore vs Small Town Australia

For the purposes of this paper the narrow definition of storm water sourced from man made surfaces, such as city streets and public spaces, entering a dedicated storm water piping /channeling system will be considered.

Man made storm water systems generally run directly to the ocean, to rivers or other publicly accessible ponds/wetlands. It is generally assumed that the water is fit for this purpose. The question posed here will be whether this is really the case and what risk is being accepted using current design and monitoring methods.

The data sets available for flow in storm water systems tend to be comprehensive, while the data sets providing composition or quality data are at best patchy and limited to composite or the occasional grab sample. The lack of significant real time data on water quality has made it hard to evaluate the appropriateness of existing storm water practice and to quantify the inherent risks.

This is not an approach which will be sustainable in the future with an increasingly litigious society with higher and higher expectations with respect to public use of waterways.

This paper focuses on providing a window into what really occurs in storm water drains in real time from a water quality perspective. The data presented will allow a determination of the best management model based on the realistic risks involved for the particular receiving system.

Two separate storm water system case studies will be covered. The first compares multiple storm water channels dealing with run off from Singapore’s city areas. Comparisons can be made between the water quality coming from different drains and within one drain over time. The intent being to allow evaluation of the suitability of the current practice of direct discharge to the ocean.

The second involves a longer term study on a storm water system coming from Mannum in South Australia. Although Mannum is a small town, the drain enters the Murray River just 20 metres from a major intake for Adelaide’s drinking water. Specific work to detect and quantify hydrocarbons w as part of this project.