National Wetlands Update February 2013
Issue No. 22, February 2013
Working Wetlands - bringing the lakes back to life
Royal Botanic Gardens Melbourne
The new bio-remediation wetland area on Lily Lake.
A four-year, $6.5 million project to improve water quality and provide a sustainable water supply for the Royal Botanic Gardens Melbourne was commissioned in August 2012.
The Working Wetlands project includes infrastructure for stormwater collection, treatment, storage and reuse for irrigation at the Gardens' 38 hectare inner-city site - of which a key component was the construction of two bio-remediation wetlands at either end of the Gardens' lake system, on Nymphaea Lily Lake and Ornamental Lake.
The neighbourhood surrounding the Gardens provides an area of about 20 hectares from which stormwater is harvested and diverted into the Gardens' newly-constructed wetlands through underground pipes and gross pollutant traps. The water is then filtered through the constructed wetlands and into the lakes system. In addition to the two permanent wetlands, floating island wetlands were installed on Ornamental Lake and Guilfoyle's Volcano, a historic water storage reservoir at the Gardens.
Water is circulated through the system improving the quality of both the incoming stormwater and the water already in the lakes, keeping temperatures low, increasing oxygen levels and reducing the risk of algal blooms in the lakes in warmer months.
The wetlands serve to 'clean up' the harvested stormwater using a bio-remediation process. The wetlands have been planted with indigenous species, and aquatic and semi-aquatic plants take up excess nutrients such as nitrogen and phosphorus and convert them into foliage. The constructed floating wetlands allow the mass of plant roots to be suspended in the water aiding this process.
Floating island wetlands on Guilfoyle's Volcano.
The final component of the Working Wetlands project has seen the installation of a separate pumping system, which transports water from Ornamental Lake to a water treatment shed. Here the water undergoes a three-stage treatment process, bringing it up to 'A' class quality. The water is filtered for sediments, pH tested and adjusted, and treated with UV light to kill off any pathogens. The water is held in the four storage tanks, which have a capacity to store a total of 500 kiloliters of treated water for irrigation.
The primary aim of the Working Wetlands Project was to revitalise the Gardens' lake system and reduce the Gardens' reliance on potable water for irrigation by up to 40 per cent. However, for the many species of waterbirds, frogs and other aquatic fauna at the Gardens, the constructed wetlands have provided valuable new habitat at this inner-city site.
The Working Wetlands project is supported by the Victorian Government, Australian Government, The Myer Foundation and Sidney Myer Fund 2009 Commemorative Grants Program, Melbourne Water, South East Water Corporation, Friends of the Royal Botanic Gardens, Melbourne Inc., Royal Botanic Gardens Foundation Victoria, The Calvert-Jones Foundation, Ken and Jill Harrison, P. J. Jopling QC and many generous individual donors.
Further information on Working Wetlands is available at Royal Botanic Gardens Melbourne .
Floating wetlands have been installed on Ornamental Lake and Guilfoyle's Volcano, a historic water storage reservoir at the Gardens.
(Royal Botanic Gardens Melbourne)