We have achieved a better understanding of how sediments and nutrients reach the Great Barrier Reef and offered ways to mitigate their impact.

The challenge

A more vulnerable Great Barrier Reef

The condition of the Great Barrier Reef is in decline. While climate change is considered the most serious long-term risk to coral reefs, in recent decades agricultural pollution has had a major impact on their condition, reducing their resilience to bleaching and cyclones. In particular, fine sediment and associated particulate nutrients reduce water clarity, slowing coral growth, impairing coral recruitment and making coral more vulnerable to disease.

Between 2008 and 2017, the Australian and Queensland governments spent an estimated more than $600 million on improving land management with the aim of improving the quality of water reaching the Great Barrier Reef World Heritage Area (the Reef). About half of the investment is allocated to reducing river loads of fine sediment and particulate nutrients through improved land management. The area draining to the Reef is vast (>420,000 square kilometres), and the investment is not enough to manage all areas. Therefore, locating the major sources of anthropogenic sediment (and nutrients) and understanding how to remediate these landscapes is critical for maximising the return on investment.

Our response

Working with partners to find solutions

Our material fluxes research team identifies the major sources, drivers and dynamics of sediment and particulate nutrient fluxes in river basins, and defines land management options for modifying those fluxes. Our strengths are in automated field instrumentation in agricultural landscapes, rivers and coastal waters; sediment source tracing and geomorphic assessment; and modelling erosion and sediment transport processes. We have experience working with rangeland ecologists and the grazing industry to develop practical and effective management solutions.

Alluvial gully erosion in the Upper Burdekin catchment, Queensland.  ©CSIRO, Rebecca Bartley

To integrate our science across disciplines, we collaborate with research institutions such as James Cook University, the Australian Institute of Marine Science (marine systems expertise), the Australian National University (cutting-edge laboratories), the University of the Sunshine Coast (hydrology expertise) and Griffith University (optically stimulated luminescence lab and geomorphology expertise)

The results

Science delivers

With our partners, we have defined the system of erosion and sediment transport processes connecting agricultural land with receiving water bodies. We did this by:

Runoff from sugar cane in the Mossman catchment, Queensland.  ©CSIRO, Tony Webster

  • measuring sediment sources and transport to identify primary sediment sources, material fluxes and land use impacts
  • modelling river basin sediment yields, with cross-disciplinary links to develop hybrid process/statistical models including estimates of uncertainty
  • trialling and evaluating land management effects on sediment and nutrient yields.

Based on this research:

  • We have developed conceptual models of river network sediment supply and delivery (that connect land management practices with river loads) to support the evaluation of the effectiveness of the Reef water quality investments.
  • We have developed conceptual frameworks linking land management changes to marine ecosystem's response.
  • We have provided advice to governments on more effective and targeted remediation programs for the Reef.
  • We have led the sediment source and management sections of successive Scientific Consensus Statements on Reef water quality.
  • Our research has directly informed the location of the Queensland Governments Major Investment Projects in the Reef catchments, which are part of $90 million spending package from the Ministerial Water Science Taskforce.
  • The research has supported regional water quality improvement plans and associated investment strategies.
  • The research supports the current Reef 2050 Long-Term Sustainability Plan, through the draft Reef 2050 Water Quality Improvement Plan 2017–2022.

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