Spotlight: Projects investigating potential for wetlands as a water quality management tool

11 August 2025

Spotlight: Projects investigating potential for wetlands as a water quality management tool

A wrap-up of wetland projects funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation.

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Wetlands can be part of the solution to help improve water quality in agricultural landscapes. They are widely recognised for their potential to hold back, slow and treat water before it flows into rivers and downstream marine ecosystems – converting and breaking down nutrients and trapping organic matter like leaves and vegetation, and sediment particles along the way. However, the effectiveness of each wetland varies, and depends on their individual characteristics, including size, shape, vegetation and soil type.

Here, we explore a selection of Great Barrier Reef Foundation funded projects that have investigated the key factors that influence a wetland’s ability to treat agricultural runoff. These findings are adding to the evidence and data to inform the development and refinement of models, and will guide future design and maintenance of natural and constructed wetlands managed for water quality improvement.

Component 1: Synthesis of evidence and identification of gaps

Overview: This project looked at global and local research on wetland effectiveness as a water quality treatment tool. It summarised evidence on what characteristics drive the ability of different wetland types (e.g. natural and constructed) in their ability to convert and break down nutrients and trap sediments.

What it involved: Researchers synthesised evidence from more than 350 studies globally relating to wetlands and water quality, with only 17 studies in the Great Barrier Reef. The team reviewed studies to understand the effectiveness of wetland systems as a water treatment tool, the characteristics that maximise water quality improvements, and the cost-effectiveness of wetland construction, rehabilitation or restoration.

Outcome: The synthesis found wetlands vary widely in their size, shape, water depth, vegetation, and soil carbon levels – which influences their ability to treat water. Given this variability, it is extremely difficult to know exactly how effective the systems are in water quality improvement. Gaps in our understanding remain and there is a need for long-term data collection in the Great Barrier Reef catchments.

How this will be used: This report has identified a need for more field-based measurements to build confidence in our understanding of how well wetlands work to achieve water quality improvement. We also need better information on the cost-effectiveness of constructing and maintaining wetlands, and how to design them for maximum water quality outcomes in specific locations. Wetland design depends on the local landscape, especially water flow, the amount and type of plant cover and how well the wetland can hold and treat water.

This project was led by C₂O Consulting.

The final report can be viewed here: Waterhouse, J., Molinari, B., Star, M., Weber, T., Waltham, N., Motson, K. (2024). Synthesis of evidence of the effectiveness of wetlands in water quality improvement, costs and cost-drivers in the Great Barrier Reef catchment area. Report prepared for the Great Barrier Reef Foundation. Brisbane, Queensland. 110 pp.

Component 2: Gathering data to assess wetland treatment performance

Overview: These projects monitored constructed wetlands in the Tully-Johnstone and Mackay catchments to help build stronger evidence around wetland ability to improve water quality. Another key focus of the projects was to measure water balances – how water enters the system, how long it stays, and how much water leaves a wetland. The longer a wetland holds water, the more time it has to convert and break down nutrients, and trap organic matter and sediment particles. Results will inform better design and function of constructed wetlands to improve water quality.

What it involved: Over two wet seasons, teams conducted detailed field monitoring to measure water, nutrients and sediment flows in and out of the constructed wetlands. These wetlands were chosen by landholders and stakeholders. The teams recorded vegetation cover, rainfall, hydrology, groundwater interactions, water temperature and other physical characteristics that could influence the capacity to treat water.

How this will be used: Data from these projects have informed the wetland hydrology and water quality model for the Great Barrier Reef (component 3). The findings offer insights into nutrient processing (denitrification), sediment trapping, and groundwater interactions within wetlands. They also show the effectiveness of different vegetation types and the importance of ongoing maintenance and actively managing the wetlands to enhance wetland treatment performance.

Projects:

Tully Landscape wetland monitoring led by Terrain NRM with contributions from Griffith University and the Queensland Government Department of Primary Industries. The wetland monitoring was designed with input from a panel of science advisors.

https://terrain.org.au/monitoringfarmwetlands/

Sandringham wetland monitoring led by JCU TropWATER and Reef Catchments NRM.

https://reefcatchments.com.au/biodiversity/early-mornings-in-sandringham-water-quality-monitoring/

Component 3: Building a wetland model for the Great Barrier Reef

Overview: This project focussed on developing computer models tailored to Great Barrier Reef freshwater coastal wetlands – simulating some of the core characteristics of the ability of wetland systems to improve water quality.

What it involved: The model simulates the amount of nutrients that can be removed by different wetland types depending on water balance, hydrology and individual characteristics, such as location in the catchment, their size and the different types of vegetation cover. The model also captures the multiple physical, biological and chemical processes that drive the break down and conversion of nutrients, and removal of particles in wetlands. This work has been informed by the wetland synthesis (component 1) and preliminary results from the monitoring projects (component 2).

How this will be used: This model will provide critical support to decision makers for the future design, management and prioritisation for investment in wetlands at the catchment and wetland scale.

Alluvium led this consortium project (Griffith University, James Cook University, FlowMatters) with oversight from a Technical Advisory Committee.

Collectively these projects greatly build on existing evidence to inform how we can design, construct, maintain and manage wetlands to support water quality improvements for the Great Barrier Reef and its catchments as well as local biodiversity.

These projects were funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation.

Other useful links: