Warrnambool Roof Harvesting Project
Working demonstration of innovative water management approach to meet the increased water supply demands in urban growth areas
- Wannon Water's Water Supply Demand Strategy 2007-2055 identified the need for new water resources within the 50-year planning period to meet the projected increase in demand.
- The growth areas in Warrnambool provided an opportunity to test innovative ways to save water and secure water supplies by constructing, monitoring and evaluating the roof water harvesting scheme as a pilot to identify risks and barriers and build confidence for other water authorities and councils to establish similar projects in applicable developments.
- The cost per megalitre (ML) was similar to the next preferred augmentation option (groundwater) and had additional environmental and social benefits.
A leading example of integrated water management, collecting and diverting roof runoff for potable uses
- Regional harvesting of roof runoff: A separate collector pipe system has been installed for houses in new developments in the Warrnambool growth area. This pipe network (which includes trunk water mains and smaller collector pipes through the development) flows under gravity into the Brierly Basin where it is mixed with other untreated water.
- Treatment of rainwater: Harvested roof water is treated with other untreated water in the Brierly Basin at the existing Warrnambool water treatment plant to produce drinking water for the City of Warrnambool. Since roof water is generally cleaner than other surface runoff, additional treatment was not necessary.
- Hybrid model: Typically there are discussions around the benefits of centralised versus decentralised water solutions. This project provides a hybrid model that collects water using a decentralised system but treats the water in an existing centralised system, which eliminates many of the public health and safety risks associated with decentralised systems.
- Progressive expansion: The project commenced in 2011 in Warrnambool's northern growth areas with the initial pilot applied to 250 lots across two subdivisions. This will expand to over 3,000 homes and a new industrial estate as development in the growth corridor continues.
- Toolkit: Wannon Water created a toolkit that estimates capital and operating costs of rainwater harvesting schemes. The toolkit can calculate a net present cost (NPC) per ML, which can be used to directly compare the financial viability of rainwater harvesting schemes with other potential water supply solutions across Australia.
- Collaborative management: Collaborative working relationships between project stakeholders were required to overcome management challenges, particularly coordinating the transfer of water from a local government authority and a water retailer.
- Compliance: The regulatory and cultural behaviours of the plumbing industry have been challenging. In particular, several domestic plumbers installed house connections with a 'business as usual' approach and connected the roof downpipes into the regular stormwater system.
- Reducing risk: While no significant risks were identified with the project, Wannon Water will be monitoring the water quality, inspecting connections to ensure there are no cross-connections, and will be responsible for the roof water harvesting network, including screening of leaves and other materials.
Warrnambool, VIC, Australia
Savewater Awards 2011 - Australian Achiever Winner
Australian Water Association (AWA) Victorian Water Awards 2012 - Highly Commended for Infrastructure Project Innovation
Environ Innovation in Sustainability Awards 2012 - Finalist
Tidy Towns Sustainable Communities Awards 2013
Stormwater Victoria 2013 - Award for Excellence
AWA Victorian Water Awards 2017 - Infrastructure Project Innovation Award
Cities providing ecosystem services
- Less urban excess stormwater entering waterways: Reducing stormwater volumes entering local waterways reduces erosion risk and improves waterway health.
- Improved environmental flows: Harnessing local water supplies reduces pressure on the water supply catchment of the Gellibrand River.
Cities as water supply catchments
- Augmentation of water supply system: Each new dwelling is expected to generate 145kL/year.
- Harvested roof water can meet urban demands: In an average rainfall year, the project is estimated to meet approximately 100% of the annual demand of the connected properties. In fact, early monitoring of the system identified more water was generated than used, which would result in excess water being used by other Warrnambool customers.
Cities comprising water sensitive communities
- Informed residents: Flyers are sent out regularly to remind landowners that water is being harvesting from their roof and treated to form part of Warrnambool's drinking water supply. This builds their community consciousness and reduces risk of contamination.
- Toolkit to assist other growth areas: The toolkit has been developed to assist stakeholders in other growth areas to use similar roof water harvesting schemes.
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