Great Barrier Reef case study

 

 

 

Reef rescue plan

One of the jewels in Australia’s ecological crown, the Great Barrier Reef is a vast interlacing web of organisms, all of which have a vital role to play in keeping the ecosystem healthy. Sadly, declining water quality in nearby catchments, much of it brought about by human activity, is now posing a long-term threat to the Reef.

Fertilisers, pesticides, sediments, nutrients, toxic chemicals, sewage, oil, heavy metals and detergents running into the Great Barrier Reef lagoon all endanger those indispensable plants and animals.

Burdekin River flood plume. Image Courtesy of Robert Packett, Queensland Department of Natural Resources and Mines

To address these threats, the federal and Queensland Governments developed the Great Barrier Reef (GBR) Rescue Plan and a Reef Water Quality Protection Plan which aims to dramatically improve the quality of water entering the reef by 2013.

Achieving those goals means both halting and reversing the decline in water quality entering the reef in the next 10 years, as called for in the Reef Plan, and rehabilitating and conserving areas so they can play a role in removing water-borne pollutants.

Fortunately those ambitions are now looking considerably more feasible with the aid of eWater CRC’s Source software.

The Queensland Department of Environment and Resource Management (DERM) has been working with eWater and the Source team to figure out how the targets set in the Plan are achievable using current river conditions and land management efforts.

They are developing a framework that helps gauge how far we are towards achieving the 2020 goal and which forms a key component of an overall 'paddock-to-reef' integrated monitoring, modelling and reporting program.

Professor Gary Jones, CEO of eWater, says protecting the Great Barrier Reef was one of the biggest water quality improvement schemes implemented in Australia and he was pleased eWater CRC was a critical part of the team. He said that the enhancements to Source would tackle the critical issues of sediment and nutrient run-off from local catchments into the GBR lagoon, and identify the best sites for remediation and restoration.

Identifying hotspots

Rehabilitating the Reef begins with identifying the hotspots in the catchment that are the sources for sediment (TSS), nitrogen (TN) and phosphorus (TP), then developing management scenarios in consultation with local landholders and catchment groups.

Runoff after rain is natural and desirable, and a certain amount of contamination in runoff is also natural: any bare ground will lose top soil in heavy rainfall, and Australian rivers experienced turbidity long before the introduction of introduced species. But by tailoring Source to the unique needs of an individual catchment managers can take action – such as revegetation of earthworks – with a high expectation of preventing sediment flow entering stream channels, both urban and rural. This is critical in areas like the GBR where the single largest threat to water quality is the introduction of containments via runoff.

The trial involved monitoring and modelling water quality and management practices across a range of scales including paddock, catchment and marine to estimate the changes to water quality leaving the catchments as a result of the adoption of better land management practices.

Source proved a robust tool for measuring and predicting water quality changes and highlighting and forecasting trends in data in the short to medium term. Those trials have proved so successful that both the Federal and Queensland Government have now recommended that the Source modelling framework be used for whole-of-reef catchment modelling.

This is a hugely significant endorsement of Source and its underlying science, and an Australian first for any catchment modelling product.

Source helps users model the amounts of water and contaminants flowing through a catchment and into rivers, wetlands, lakes and estuaries. The software gives access to submodels, data and knowledge that simulates the effects of climatic characterisations (including rainfall and evaporation) and catchment characteristics (such as land-use, vegetation, topography and soil type) on runoff and contaminant loads.

Linking component models and other ‘plug-ins’ together, users can predict the flow and load of constituents at any location in a catchment over time.

Not only is the product highly adaptable, but it retains all adaptations made to suit local situations and challenges to be used as capabilities when the model is applied elsewhere.

A groundwater prediction module accounts for change of water between surface water (creeks) and groundwater in small upland catchments. This addition greatly enhances the model’s predictions of daily outflows from tributaries into larger rivers to improve water yield accounting.

The product is also highly innovative in focusing on small areas of the catchment. These ‘function unit’ areas are defined by their topography, soil type, rainfall characteristics and land use. Source works on a sort of patchwork of the various types of functional units within a catchment, with each of the runoff, sediment and nutrients generated at each functional unit being modelled as moving to the outflow point.

Source is also useful as a communications tool. It has been used in southern Queensland, for example, to encourage and stimulate landholders who were improving their land management practices at the head of the Darling River. In addition, it helps ensure systems to address declines in water policy are as sustainable as possible. By pinpointing places where erosion must be halted and thus improving paddock sustainability it can help prevent sediment washing off land and out into the reef.

About the plan

In 2003, the Australian and Queensland governments put in place a Reef Water Quality Protection Plan (Reef Plan) to address the issue. The Reef Plan is a framework for the two governments to work together, along with industry, regional natural resource bodies and others to improve the quality of water flowing into the Reef. The Reef Plan was recently updated with a refreshed Reef Plan announced in September 2009. The updated Reef Plan reflects a more concerted and accelerated approach by the governments.

The Australian Government is supporting the Reef Plan through its Caring for our Country initiative, which includes the $200 million Reef Rescue package.

Through Reef Rescue, the government is providing assistance to farmers and land managers in Reef catchments to increase the adoption of improved land management practices that reduce runoff of nutrients, pesticides and sediment from agricultural lands.

Image courtesy of NASA Visible Earth project.

The more northerly coastal area in this image shows the vast extent of sugar cane cultivation, this being the largest sugar producing area in Australia, centered on the city of Mackay.

Other industries in the area include coal, cattle, dairying, timber, grain, seafood, and fruit. The large island off the most northerly part of the coast visible in this image is Whitsunday Island, with smaller islands and reefs extending southeast, parallel to the coast. These include some of the better known resort islands such as Hayman, Lindeman, Hamilton, and Brampton Islands.

River Plumes

In late February 2007, NASA satellite images revealed that even the outer portions of the Australia’s Great Barrier Reef can be bathed in land-based pollution carried far offshore by plumes of river water.

Conventional thinking was that river plumes affected only the lagoon and the inner portions of the reef. But images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite verify a new theory that not even the outer reefs are spared the impact of land-based pollution, which includes excess sediment, fertilizers, and pesticides.

This image from February 9, 2007, shows plumes of sediment flowing into Princess Charlotte Bay, which is about halfway down the east coast of Queensland’s Cape York Peninsula.

Capricorn Print

Coral bleaching may be one of the greatest threats to the Great Barrier Reef. Coral bleaching is a stress response that often occurs when the surrounding waters become too warm for the corals. In the stressful situation, the corals expel their brownish zooxanthellae and lose their color.

Zooxanthellae are unicellular yellow-brown algae that make it possible for the corals to grow and reproduce quickly enough to create reefs. Without the zooxanthellae, the coral cannot obtain sufficient nourishment. If conditions remain difficult, the corals may die. Major coral bleaching incidents on the Great Barrier Reef in 1998 and 2002 led to widespread death of corals in some areas. Researchers in the Barrier reef of Australia are using NASA's resources to help identify troubled coral