A fantastic water conservation project at the Royal Botanic Gardens in Melbourne proves that reservoirs and tanks, not just ponds and lakes, can be things of beauty and landscape features in their own right.
Over the past few years, ‘Guilfoyle’s Volcano’ has been restored as a functioning water storage body and now forms a key part of the Gardens’ strategic water management plan, along with a series of constructed wetlands and a complex reticulation and treatment system.
This structure was the main water supply for the Gardens from the mid 1870s until the site was connected to mains water in the 1930s. Unfortunately, the reservoir then fell into a state of disrepair and relatively little is known about Guilfoyle’s original design.
The new design aims to evoke a volcanic eruption via swathes of colourful and contrasting plants and hard landscaping that mimic lava flows pouring down the slope and extending into the lawn and pathways.
Paths wind through plantings of cacti, succulents and other low water use species mulched with rocks and pebbles and spiral up the volcano to viewing platforms surrounding the crater lake, that also offer views across the Gardens and beyond.
Stormwater is diverted from nearby residential drains, filtered through gross pollutant traps and gravity-fed to wetlands with sediment ponds before entering two ornamental lakes. Pumps circulate the water between the lakes via a shady creek, or to large water tanks for UV treatment, pH adjustment and chlorination, or up to the Volcano for storage until it is needed for irrigation.
In addition to the wetlands, fourteen small floating islands in the crater lake and the Ornamental Lake also help to filter and treat the water using natural biological processes.
The islands are made from recycled PET plastic that has been injected with polyurethane and covered in coconut fibre. They are planted with semi-aquatic plants whose submerged roots and a variety of microorganisms filter out sediments and excess nutrients. The plants are harvested regularly to remove the nutrients from the system.
This is an impressive project made possible by a wide range of government and private donations. Given the low cost of water and the high cost of engineering works and landscaping, it’s hard to imagine that this project would have stacked up under a traditional cost benefit analysis – even taking into consideration the many environmental, heritage, educational and other benefits.
These attractive works have restored a really important part of the Gardens’ history, reduced the site’s dependence on potable water supply, improved the water quality of the lake system, and reduced the risk of algal blooms. They have also put the Gardens in a much stronger position to withstand the next drought (which is far more likely than a volcanic eruption).
Photo credits: Pip Marks