Plotting a course to healthy waterways in the ACT

Australian Captial Territory Water Minister Shane Rattenbury has looked back on his portfolio and found a path for healthy waterways across the ACT.

Australian Capital Territory Water Minister Shane Rattenbury has looked back on his portfolio and found a path for healthy waterways across the ACT.

For many Canberrans, summer is a time for rest and relaxation and maybe a trip to a local lake or river for a picnic. Recent ACT Government-funded research has shown that the economic value of the amenity of our lakes (the benefits they offer to us day to day by adding beauty to our city and offering a place to exercise, rest and socialise) is greater than the economic value they provide by trapping pollutants from stormwater, the main purpose for which they were initially designed.

As we know, the ACT’s lakes and ponds trap pollutants well. So well that this regularly leads to poor water quality, particularly during summer. The high nutrient load of stormwater entering our lakes results in blue-green algal blooms and the excessive growth of water plants and attached algae, degrading the amenity of our lakes and ponds and creating health risks.

Healthy waterways essential to ACT happiness

The ACT Government has been working to address these water quality problems since 2014 through the ACT Healthy Waterways program. The initial stage of the program was a joint Australian-ACT Government investment of $94 million that delivered 20 large wetlands, ponds, rain gardens and waterway restorations.

The Lake Tuggeranong catchment experiences the greatest number of algal blooms, often needing to be closed for recreational activities due to high levels of pollutants. As a key focus area, extensive Healthy Waterways research and monitoring has been undertaken in the Lake Tuggeranong catchment on the causes of algal blooms and sources of plant nutrients driving algal blooms in summer.

University of Canberra researchers found that high levels of phosphorus stimulate the algal blooms and that the excessive phosphorus is coming from everywhere in the urbanised catchment rather than from a few point sources. Fertilised sports fields were found to contribute to the problem but are not the primary source of phosphorus.

Monitoring of waterways in other parts of Canberra suggests that diffuse urban waterway pollution may also cause the algal blooms observed in Lake Burley Griffin, Lake Ginninderra and ponds elsewhere in the ACT, and high levels of plant nutrients in stormwater are likely to stimulate the excessive growth of water plants and attached algae in Yerrabi Pond.

This pattern of pollution means that significant investments are needed across the urban catchments to reduce pollution. In recognition of this, the ACT Government has invested $30 million to expand the Healthy Waterways program to improve water quality locally and create evidence-based plans for solving water quality problems.

Healthy Waterways plans are being created for Lake Tuggeranong in 2024 and Lake Burley Griffin, Ginninderra and Yerrabi Pond in 2025. The projects will incorporate the findings from ongoing research, trials of new, innovative wetlands, and pilot programs to prevent the pollution of waterways from occurring in the first place. The plans will provide a strong evidence base to support business cases for further investments in water quality improvements.

Progress of Healthy Waterways program in 2023

This year, the Healthy Waterways program has delivered a set of floating wetlands in Yerrabi Pond and novel roadside drain outlets to green space in Kambah, reconnecting urban runoff from this suburb to its catchment.

A major drain re-naturalisation project that was started in Calwell is nearly complete. It aims to provide amenity, ecological benefits, and improved water quality. Construction has also started on the exciting new wetland at Belconnen Oval that incorporates ponds, surface wetlands, and—in an Australian first for stormwater—a subsurface wetland.

The subsurface wetland intends to help intercept the significant dissolved load of nutrients found in Canberra’s stormwater.

Lastly, we have commenced a project to deliver a recycling system that treats stormwater to irrigate the sports fields in Kambah.

These projects and delivering local benefits aim to test and prove innovative designs for water quality assets so they can be rolled out across Canberra.

ACT Healthy Waterways also funded further development of the Leaf Collective in the Tuggeranong and Yerrabi catchments. This program, co-designed with the local community, supports residents in taking collective action to remove leaves and grass from drains and gutters, which research suggests can be a significant source of nutrient pollution in stormwater. The Leaf Collective autumn 2023 pilot was a success, with residents of Tuggeranong suburbs collecting, on average, 38 per cent more leaf litter and grass clippings per person than residents from the matched control suburbs.

Research in Canberra

Behind the scenes, the University of Canberra was funded to continue to track down the source of excessive plant nutrients in stormwater, and consultants examined fertiliser use by businesses and residents. Recently built wetlands were monitored to evaluate their performance, and water quality models were created to underpin the Healthy Waterways plans and for other purposes like evaluating a proposed sewage treatment plant. A street sweeping experiment began recently to gauge the benefits of increasing the frequency of sweeping during summer in suburbs dominated by Eucalyptus trees.

Healthy Waterways has a smaller focus on rural catchments, and this year funded both planning and restoration activities in the Naas-Gudgenby river system to address the problem of ‘sand slugs’, where soils eroded from catchments are deposited in channels, smothering bed habitats and impacting fish and other plants and animals.

Next year, the government will complete this round of water quality infrastructure and continue efforts to improve its management of road verges and sports fields. The research focus will expand to Lake Burley Griffin to improve our capacity to understand and predict the outbreak of algal blooms in the lake and to understand the sources of faecal coliforms for the lakes and Murrumbidgee River, which can close these waterbodies to recreation.

Further restoration activities will be undertaken in the Naas-Gudgenby catchment, and the feasibility and sustainability of sand mining will be re-examined, building on work completed a decade ago.

Lessons learned from the 9-year Healthy Waterways program will be incorporated into a plan for Lake Tuggeranong, which will then be presented to stakeholders and the community for review before the version is finalised.

The benefits of long-term investments in research and water quality mitigation will be evident in the plan for Lake Tuggeranong and the ones that follow in 2025.

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