Does fixing eroding gullies fix nutrient run-off to the Reef?  - Greening Australia FacebookGoogle PlusInstagramLinkedInTwitter
Reef Aid

Does fixing eroding gullies fix nutrient run-off to the Reef? 

Stabilising massive, eroding gullies is one of the best ways to stop sediment pollution at the source, improving water quality for the Great Barrier Reef. A big unknown is how much fixing these gullies can reduce nutrient run-off. In this project, we aim to understand nutrient export from different remediated gullies to identify the best techniques and to improve future gully fixes.

During high rainfall or river flow events, gully erosion causes sediment and nutrients to wash out to the Great Barrier Reef. Excess sediment and nutrients result in poor water quality, impacting the health of the Reef and seagrass beds within the Reef lagoon (read our explainer here). Fixing these eroding gullies and stopping sediment and nutrient run-off at the source is therefore a priority for our community and government.

Greening Australia is already working to remediate gullies in identified priority areas of the Reef catchments. This involves re-working the eroded land using machinery, soil amendment applications and revegetation to stabilise the soil.

Gully remediation projects usually target a sediment reduction, but ideally would also lower nutrient export. The aim of this project is to understand nutrient export from different remediated gullies to identify the best remediation techniques. This will help direct future large scale gully remediation work, to reduce sediment and nutrient impacting Reef water quality.

Researchers from Griffith University and TropWATER at James Cook University assessing water quality sampling equipment.

The Challenge

The impact of excess nutrients on the health of the Reef has been well researched. Nutrients impact the Reef along with sediment run-off. Particulate and dissolved nutrients (e.g. dissolved inorganic nitrogen) are transported with fine sediment during rainfall events, from gullies to Reef ecosystems where they become bioavailable (i.e. the nutrients are in a form that can be consumed and utilised by marine organisms directly).

Most gully remediation methods include the use of erosion stabilisation materials that will initially alter nutrient run-off from the gully system. However, we do not fully understand the impact or longevity of these alterations and what implications they may have on downstream ecosystems (e.g. the Reef).

Previous collaborative research with Griffith University and the Queensland Department of Environment and Science, for example, showed that some gully treatments reduced nutrients in proportion with sediment reductions, while there was no clear trend with other treatments.
 

The Solution

The aim of this project is to better understand nutrient export from remediated gullies in order to identify which remediation methods are successful for reducing both sediment and nutrient export.

We’ll be measuring sediment and nutrient run-off from different remediated gully treatments located at Strathalbyn Station in the Burdekin catchment, across the wet season.

Sediment tracing studies and laboratory experiments will also be conducted to evaluate how different remediation materials may alter nutrients over time.

This project will help inform best practice guidelines for future gully remediation interventions. The project team includes experts from Griffith University, Queensland Department of Environment and Science, TropWATER at James Cook University, and Greening Australia.

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Researchers from TropWATER accessed the site by helicopter to collect water samples after a rain flow event for real-time nutrient assessments. Photo credit: Steve Lewis, TropWATER.

 

This project is part of the $10 million Innovation and Systems Change Program funded by the Great Barrier Reef Foundation’s partnership with the Australian Government’s Reef Trust.

The project builds on previous water quality research and gully remediation projects including Strathalbyn Phase Three (funded by the Great Barrier Reef Foundation) and the Innovative Gully Remediation Project (funded through the Queensland Government’s Reef Water Quality Program).

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