In Brisbane, Sydney, and Melbourne, the volume of rainwater falling on Australia’s urban areas exceeds annual utility water consumption, and it is delivered directly to our buildings. We can capture that rainfall in a rainwater tank connected to our roofs. We don’t have to build dams, chemically treat this water, or pipe it across our cities. Yet most of this resource is discarded as stormwater.
The consequences of not harvesting rainwater are familiar. More stormwater contributes to urban flooding, damages waterways, carries pollutants into rivers and estuaries and places growing pressure on public infrastructure. We are continuing to invest billions of dollars in new water supply and stormwater infrastructure while overlooking the water already falling on our roofs.
That’s unfortunate because rainwater harvesting is one of the few measures that addresses two of our biggest urban water challenges at once. Most urban water policies focus on one outcome or the other. Rainwater harvesting does both.
- It reduces the volume of stormwater
- And it reduces demand for municipal water
Figure 1 shows how, in natural systems, most rainwater becomes groundwater, transpires through plants or evaporates. In our concrete urban systems, this reverses: 80 per cent of rainwater becomes runoff; this is both a big problem and an opportunity.
Rainwater harvesting is a great opportunity.
National rainwater harvesting policy
We need a policy because stormwater risks and water infrastructure costs are rapidly increasing. We need a mix of mechanical and nature-based water solutions for our cites and there is a significant opportunity to widely implement well-established frameworks for rainwater harvesting as a cost-effective part of the solution.
The policy establishes a framework for Australian cities that prioritises small, incremental changes to every building and alignment with the natural water cycle as the first response. Large-scale infrastructure investment can then be pursued where necessary.
The policy objectives are to achieve a 30 per cent reduction in the volume of stormwater runoff at the lot level and a 30 per cent reduction in the volume of residential utility water demand. Professor PJ Coombes has applied award winning systems framework modelling to verify these objectives.
Rainwater harvesting is the practice of capturing rainfall runoff from a roof and storing it for later use. This distinction matters because stormwater – rainfall runoff from urban areas such as streets and industrial areas – carries pollutants and costs much more to treat than rainwater harvesting.
Rainwater harvesting is already a deemed to satisfy response for water sensitive urban design in the South Australia Planning Scheme and is a major component of the NSW Sustainable Buildings (BASIX) land use planning policy.
The rainwater harvesting policy is a performance based standard within land use planning. It provides a deemed to satisfy solution for residential building types. The policy emphasises water volume as the primary factor influencing stormwater impacts and the demand for water infrastructure.
The policy requires specific building outcomes. For example, planning approval for a detached residential home could require:
- 150 square metres of connected roof area
- A 5000 litre rainwater tank
- Connections to all toilets, washing machines and outdoor taps
Feedback welcome to Michael Smit, deputy chair RHA: michael.smit@kingspan.com
The Rainwater Harvesting Association
The Rainwater Harvesting Association is the recently incorporated association for rainwater harvesting in Australia.
Our vision is to harvest rainwater to build sustainable and resilient communities.
The Rainwater Harvesting Association is a peak body representing the rainwater harvesting industry. Our key role is to explain the resilience, water efficiency and stormwater management benefits of rainwater harvesting to this and future generations.
Rainwater harvesting is the only solution that simultaneously delivers demand management, drought response, disaster resilience, flood management, stormwater pollutant and volume controls, and water for urban cooling and groundwater replenishment.
Rainwater tanks are a popular, low-cost, easily sourced, locally made product. Rainwater harvesting for most buildings is a basic building block of resilient cities.
In natural and other disasters, the rainwater tank is a local water source that reduces the severity of natural disasters such as floods and bushfires, cannot be hacked, works without electricity and renews itself every time it rains.
Visit the Rainwater Harvesting Association’s website to download its policy and subscribe for updates.
