Stormwater Harvesting

What it is

Stormwater harvesting is the collection, storage and reuse of the flows from urban areas collected in stormwater pipes, channels and lakes.

What we are currently doing

Stormwater harvesting is a major component of the ACT Government's Think water, act water strategy, as it can assist towards meeting our 25% target reduction of drinking water consumption per person by 2023.

It is also factored into the ACT Government’s Water Sensitive Urban Design (WSUD) guidelines. The WSUD target for all new developments and re-developments is a 40% reduction in drinking water use.

In the ACT, sustainable stormwater harvesting is already carried out from most urban ponds and lakes, by the ACT Government, for use on community parks and ovals. Stormwater is also used by golf courses, nurseries, and other large water users.

The ACT Government is currently undertaking the Canberra Integrated Urban Waterways Project with Australian Government Water Fund and Developer assistance. The project will implement stormwater storage, harvesting and reuse of up to 3 gigalitres per year by 2015. The project will cost $17 million (excluding ongoing operations, maintenance and monitoring costs).

Issues with this option

Stormwater is generated by rainfall events through urban areas and usually comes in large volumes over short time periods. Therefore, we need the ability to store and treat this water until it is required for use. Ponds and lakes can be used for the storage of stormwater, but if the water levels vary too much, it can have significant impacts on their amenity and aesthetics for the community, fauna and flora.

Because the stormwater is generally of low quality with a high level of pollutants, it should only be used for irrigation and have secure backflow prevention devices in place.

It is possible to build in mechanisms to divert the first flush and then transport the rest of the stormwater to the surface water storage reservoirs where it is then treated in conjunction with the overall raw water flows. This is in place in Singapore and is an important part of the island’s overall potable water supply.

Findings on a study of stormwater projects across the Sydney region noted that the average cost of treated stormwater was $10 per kilolitre (with a range from $0.52 to $42). Cost is dependant on factors such as existing storage facilities, proximity of irrigation areas and the size of the scheme.

Due to this cost impediment, there is limited opportunity for city-wide stormwater harvesting at significant levels above what is already in place and planned for the Canberra Integrated Urban Waterways Project.

There are limited opportunities for stormwater harvesting but schemes such as the Canberra Intgerated Urban Waterways project present an option for further evaluation and possible expansion into the future.