Many townships and cities around Australia are experiencing dwindling water resources. Wannon Water’s roof water harvesting project is a leading example of integrated water management, using water from household roofs to supplement existing water supplies and support more liveable and sustainable cities. Wannon Water is an urban water supply corporation serving the south west of Victoria, including the provincial centre of Warrnambool, a fast growing city facing increasing water demand.
The Warrnambool Roof Water Harvesting Project is a leading example of water-sensitive urban design that is sustainable, cost effective and environmentally friendly.
It promotes the use of an alternative water source to help meet the challenges of adapting to climate change without imposing unreasonable requirements on developers.
The project ‘taps’ a new water catchment by capturing water from rooftops in new residential or industrial subdivisions that would otherwise be lost to run-off. This water is then directed for treatment to supplement the urban water supply.
The harvesting of roof water in urban environments has the combined effect of contributing to the city’s water resources, plus reducing the severity of rainfall events on the natural creeks and waterways in the catchment.
The award-winning scheme, which won the ‘Infrastructure Project Innovation Award’ at the Australian Water Association’s Victorian Water Awards in December 2017, is a partnership between developers, Wannon Water and the Warrnambool City Council, and is also supported by the Australian and State Governments.
The core aim of the project is to address a number of the detrimental factors associated with urban development by:
- Utilising the available water in the urban environment – within that urban environment – rather than placing further pressure on rivers and groundwater sources
- Reducing the volume that causes a detrimental impact on the streams downstream of urban development
- Avoiding the need to transport water from up to 100km away
- Deferring the need to augment water supply systems to transport ever-increasing volumes of water over long distances
- Addressing the water quality concerns of accessing the roof water run-off
- Reducing the carbon footprint of the water supply system
Achieving innovative outcomes in the water cycle
Stage one of the Warrnambool Roof Water Harvesting project was launched in the city’s Russells Creek residential growth corridor, at the corner of Whites Road and Aberline Road, in 2011.
The $3.8 million project involved a dedicated pipe network comprising around 2km of trunk mains and more than 2km of smaller collection pipes installed within the new subdivision.
Water from 180 new houses is transported through the pipes to Brierly Basin where it is mixed with other raw water and then treated at the Warrnambool Water Treatment Plant, supplementing the city’s regular drinking water supply.
Property owners still have the option of collecting rain water for their own use such as in gardens. They can install a tank to collect the water and direct any overflow to the scheme.
Alternatively they can have no tank and direct all their roof water to the scheme.
The project has a range of social benefits including:
- Sustainable housing – Connection to the roof water harvesting system satisfies the water conservation/reuse objective of the six star house energy rating requirement. Home owners can meet the water conservation requirements without additional costs. They also save around $5000 by avoiding the need for water-tank-to-toilet and garden tap systems (this can still be
installed if the owners wish)
- Public health and safety – When compared to private water tanks or recycled water options, this concept is superior in that the risk of cross-connections or poor tank water quality is removed
- Liveable cities and amenity – More backyard space is available for other uses if water tanks do not need to be installed or attached to houses. Other amenities in the subdivision are not compromised, as more than half the urban stormwater volume is still available for Water Sensitive Urban Design initiatives such as wetlands
- Lower water bills – A water supply system that provides water without pumping and is assessed as the lowest augmentation cost for water will result in lower prices overall. Better quality water provided from roofs rather than rivers also has lower treatment costs
A long-term strategy for future growth
The scheme will progressively expand as development occurs across the north-eastern area over the next 25 years.
Eventually, roofs on 3000 new homes will form an urban catchment and contribute around 471 megalitres of water a year to supplement Warrnambool’s urban supply.
The project is also expanding to the Gateway Business Park in Horne Road, East Warrnambool.
Wannon Water has worked with the developers to design the industrial estate’s pipe network and pumping station.
Roof water will be collected from sheds built during stage one of the development and piped to the existing Dales Road raw water storage basins. It will be transferred to Brierly Basin and then to the Warrnambool Water Treatment Plant where it will supplement the city’s regular urban supply.
Due to the large roof areas and the flat land in the estate, each industrial site will require above-ground tanks allowing the flow entering the basins to be regulated. The scheme requires a designated buffer volume, dependent on the roof area, but property owners still have the option of installing a larger tank and reserving the extra volume for their own use.
The pipe works are planned for completion in the 2017/18 financial year and, when fully developed, this stage is expected to harvest 25 megalitres per year.