The University of Queensland's iconic main lake has been redesigned to support a healthy and self-sustaining ecosystem, as part of the UQ lake and amphitheatre renewal project.
Now that the lake’s construction is complete, the natural environment is beginning to establish. It is expected that some fauna will repopulate naturally and flora will flourish over time.
An independent expert panel, convened by the International River Foundation, set out to improve the lake’s health by creating a more natural system to support an abundance of aquatic plant life and provide a habitat for native fauna species.
Associate Professor Badin Gibbes from UQ’s School of Civil Engineering, who is on the panel, said the complete system re-set was needed to improve the water quality, aquatic ecosystem and aesthetics of the lake.
“After 60 years of sediment collecting into the system, the lake had reached a point where it wasn’t able to recover without some form of intervention,” Associate Professor Gibbes said.
“The approach we took was to use cutting edge, sustainable design practices to redesign the lake in a way that promotes a long-term improvement in the lake ecosystem.”
Creating a natural, in-lake water treatment
To maintain good water quality in the lake, the water should flow regularly from the main lake to the surrounding wetlands and into the Brisbane River.
To achieve higher circulation of water, the lake area was reduced, its depth made shallower and importantly, new 0.8ha wetlands were added to its surrounds.
Wetlands planted at the southern and northern end of the main lake connected by a narrow corridor of wetlands along the western lake edge will provide an ‘in-lake’ treatment system that filters out sediment before it enters the main lake.
“One of the primary drivers of the updated lake design was to change the volume and shape of the lake to try to decrease the residence time of the water,” Associate Professor Gibbes said.
“The wetland system acts as a natural biofilter, stripping out sediment, nutrients and other pollutants before it enters the main lake.
“The residence time – or average time it takes for water to transit through the lake to the Brisbane River – was around 100 days before the lake redesign. We’re hoping these changes bring that number down to the recommended guideline of 15-25 days.”
Curated, native flora for a strong foundation
More than 8,000 trees, palms and shrubs and 66,000 wetland plants have been planted in and around the lake to form a range of habitats, increase the aesthetic appeal and create access points for the community.
A range of sub-tropical habitats have been established to form basking areas for animals to soak up the sun, woody debris, and aquatic and terrestrial native planting.
Floating, submerged and emergent aquatic plants will also attract a variety of insects and bugs to the lake, which will eventually provide a food source for other types of fauna including fish and birds.
Fauna repopulation
It may take around 12-24 months for invertebrates to establish their population in the lake, during which time the lake will be monitored for the opportune time to start re-stocking with fish.
Freshwater lake fish species are likely to be introduced into the lake from hatcheries.
Native species from nearby waterways, which aren’t readily available from hatchery stock, may also be introduced to enhance diversity.
“We will monitor the lake’s natural progression to help us decide when the best time is to introduce fish into the lake,” Associate Professor Gibbes said.
“This includes regular monitoring of the water quality and composition of the ecosystem to ensure the plants, animals, macroinvertebrates and insects are well established.
“Over time, we may see other native species such as freshwater turtles and longfin eels find passage into the lake.”
The future protection of our lake
To ensure the lake continues to thrive well into the future it will require ongoing maintenance and regular health checks.
“Through this project, we can give the lake the best chance that we can envisage for the ecosystem to function well, maintain good water quality and deliver an aesthetically pleasing lake for many years to come,” Associate Professor Gibbes said.