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Summary

Australian Catchment, River and Estuary Assessment 2002

Assessing the status of Australia's natural resources and the health of its ecosystems is of paramount importance for their wise use, development and management. The National Land and Water Resources Audit (Audit) Australian Catchment, River and Estuary Assessment 2002 is Australia's first comprehensive assessment of catchments, rivers and estuaries. The assessment uses a systemic approach based on surface water catchments to determine the aggregate impact of patterns of resource use on rivers and estuaries (key common property resources).

Benchmarks for the assessments were based on natural conditions and provide a good basis for assessing aggregate impact and change in condition. Nevertheless for many extensively modified catchments, rivers and estuaries, management targets need to be defined in the context of trade-offs between natural condition and the other values provided by uses.

Australia's catchments

The assessment of catchment condition provides a way to compare the biophysical condition of catchments. Using indicators based on nationally available data to assess condition of land, water and biota of river basins and subcatchments, it produced a composite assessment of relative catchment condition. The assessment provides insight into the magnitude of environmental issues being faced in Australia's more intensively used catchments.

The majority of catchments in the poorest condition classes have also been identified as priorities under the National Action Plan for Salinity and Water Quality (Commonwealth of Australia 2000). Important areas for remedial works outside the National Action Plan include the Hunter and Hawkesbury River basins in central New South Wales, smaller coastal river basins in northern New South Wales, southern and central Queensland, and coastal Victoria.

The biophysical condition of a significant proportion of catchments (between 15 and 25%) is likely to continue to decline because of the long-term nature of environmental processes and degree of change in the catchment. These catchments are in the cleared, agronomically marginal rainfall areas, and have soils of relatively poor fertility and structure. They are prone to soil structure decline, soil erosion and salinisation and have low flexibility in terms of profitable land uses.

The assessment demonstrated that spatial pattern and variation in catchment condition can be described by a few indicators - change in vegetation cover, native vegetation fragmentation, sediment and nutrient inputs into rivers, changes to catchment hydrology (particularly the effects of impoundments) and land use intensity. These indicators enable the relative importance of different catchment condition drivers to be identified allowing for more targeted management planning.

The assessment and reporting methods developed can also be used at State and regional scales to examine management scenarios.

Australia's rivers

Rivers provide water for agriculture, industry and domestic use. They sustain ecosystems that provide economic, recreational, aesthetic, social and cultural benefits. The assessment of Australian rivers found that they have been significantly altered by land use and that without informed and strategic management, the condition of Australia's rivers will continue to deteriorate.

The river assessment collated and interpreted data for about 14 000 reaches across the more intensively used catchments. The assessment uses a range of attributes reflecting key ecological processes at the river reach and basin scales and builds on other river assessment initiatives such as AUSRIVAS. Two indices were used:

• an aquatic biota index using macro-invertebrates; and
• an environment index with four subindices - catchment disturbance, hydrological disturbance, habitat, and nutrient and suspended sediment load.

Key findings include:

• one third of the assessed river length has impaired aquatic biota;
• over 85% of the assessed river reaches are classified as significantly modified in terms of environmental features;
• over 80% of the reaches are affected by catchment disturbance;
• with limited data on change of hydrology from natural flows, hydrologic change could be assessed in only 25% of reaches;
• over half of the river reaches have modified habitat, mainly linked to changes in sediment loads that can also alter channel shape; and
• nutrients (mainly phosphorus) and suspended sediment loads are higher than natural loads in over 90% of reaches, with 33% classified as substantially modified.

Management challenges

Protective management. River reaches that were classified largely unmodified in all aspects (habitat, catchment disturbance and nutrient and suspended sediment loads) are scattered throughout the assessed area, especially in far north Queensland, eastern Victoria and Tasmania. They require investment in protective management to ensure their condition is maintained.

Rehabilitation and strategic management. Rivers with the most degraded reaches are located in the Murray-Darling Basin, the Western Australian wheatbelt, western Victoria, and South Australian agricultural basins. These river reaches generally:

• have highly modified catchments;
• high nutrient and suspended sediment loads;
• lost much of their riparian vegetation; and
• dams and levees that disrupt the movement of biota and material into and from the river.

Control of nutrient and suspended sediment loads. Some river reaches have largely unmodified habitat (bed condition, riparian vegetation, connectivity) but very high nutrient and suspended sediment loads. These include the majority of river reaches in Queensland, northern coastal New South Wales, western Victoria and south-west Western Australia. Erosion from hill slopes and stream banks is high and control of nutrient and suspended sediment loads is essential for rehabilitation of these streams.

Environmental flows and longitudinal connectivity. A small group of river reaches in central Tasmania, central Victoria and New South Wales have severely modified habitat following construction of dams. They are otherwise in good condition. These reaches need restoration of environmental flows and longitudinal connectivity (e.g. fish ladders).

Improving management. A key management challenge that follows from this assessment is to implement clearer delineation of institutional and lead agency responsibilities for river management at regional, State and Commonwealth levels.

Building better river assessments

Several areas for improvement were identified, including:

• collection of finer-scale management-relevant data on riparian vegetation - a key component of river condition and rehabilitation works;
• collecting and then using more representative and responsive biotic information, especially fish populations;
• gaining Australia-wide agreement on river reaches, assessment methods and reporting so that changes in condition can be tracked and management activities evaluated; and
• information on changes in river hydrology, especially comparing natural and current flow regimes.

Australia's estuaries

Australia has 36 700 km of coastline and over 1000 estuaries. Estuaries provide highly productive and diverse habitats for fauna and flora. They support fisheries, aquaculture, ports and recreational activities, and are dynamic systems that link catchments, rivers and inshore marine waters. Eighty-three percent of Australia's 19.4 million people live in coastal Australia. The assessment of estuaries has identified that land use impacts are compromising the ecological, economic and social values of Australian estuaries.

The assessment compiled readily available data and used qualitative and quantitative methods within a 'pressure, state, response' assessment framework. The assessment provides detail on the condition of Australian estuaries including:

• amount of modification from the pristine state;
• drivers of change;
• susceptibility to further change; and
• key management needs.

Estuarine geomorphic data were mapped and compiled to classify estuaries in terms of the dominant processes governing their form and function. Detailed site-specific data were collected from a selection of estuaries around Australia and used to develop the Simple Estuarine Response Model. This internet-based decision support tool models the behaviour of estuaries identifying likely consequences of particular management activities.

Of the 979 estuaries and coastal waterways assessed:

• 50% are in near-pristine condition;
• 22% are in largely unmodified condition;
• 19% are in modified condition; and
• 9% are in extensively modified condition.

Most of Australia's near-pristine estuaries are located away from population centres. Some are found around the developed areas of Australia, often within or adjacent to managed public lands such as national parks. The majority of estuaries in near-pristine condition have relatively small catchments (< 15 km²). Protective management of the fisheries and nature conservation values of the near-pristine estuary resource is essential.

Estuaries that have experienced significant change in their condition are those with extensive floodplains that support agriculture, of sufficient size to support industrial ports or with recreational assets surrounded by urban development.

Some of the common challenges facing Australia's modified estuaries are:

• excess nutrients and sedimentation;
• habitat loss;
• changes to natural flows and tidal flushing;
• pathogens and toxicants;
• introduced pests; and
• change to ocean entrances.

Understanding the dominant natural processes in estuaries will assist in developing cost-effective management strategies. Australia's estuaries were classified into six subclasses according to relative influence of the wave, tide and river energies that shape them:

• 17% of estuaries were classified as wave-dominated 'true' estuaries;
• 11% were classified as tide-dominated 'true' estuaries;
• 10% were classified as wave-dominated deltas;
• 9% were classified as tide-dominated deltas;
• 5% were classified as strand plains, coastal lakes and lagoons; and
• 35% were classified as tidal creeks and flats.

Tide-dominated systems are mainly located in northern tropical Australia. Wave-dominated systems are mainly located in southern temperate regions. Their management needs and ecological processes vary.

Sharing information and management approaches

The estuary assessment engaged agencies and groups from around Australia with an interest in estuarine management and has catalysed a number of estuarine specific initiatives including the establishment of a national estuary management network. The groundwork is set for partnerships across Australia to ensure efficiencies in applying research findings, a common level of understanding of management imperatives, publicly accessible information on estuaries and provide for effective involvement of community groups in estuarine monitoring.

Management challenges

The key challenges facing estuarine managers include:

• establishing and maintaining protective management for near-pristine estuaries;
• working to achieve estuarine management targets within catchment management planning processes;
• implementing a clearer delineation of institutional and lead agency responsibilities for estuarine management at a State and national level;
• developing an Australia-wide, estuarine-specific policy and management initiative that builds on the strong industry and community commitment for improved estuarine management; and
• continuing to provide information, training and support to assist local government planning and estuarine management staff.

Natural resource condition in Australia's drainage divisions

Natural resource management strategies need to identify interactions between different resource management issues and deal with development opportunities and degradation issues systemically. Use of an integrated catchment management framework for tackling natural resource issues has been promoted for many years, most recently by the Commonwealth as part of its National Action Plan for Salinity and Water Quality.

Natural resource assessments compiled by the Audit provide an unprecedented opportunity to examine the regional patterns of geographic and resource use drivers of ecosystem condition. Audit findings within Australia's drainage divisions:

• identify climatic, geographic and resource use drivers of catchment, river and estuary condition;
• define the relative importance of these drivers;
• examine relationships between patterns of resource use and the condition of catchments, rivers and estuaries; and
• suggest regionally specific, integrated natural resource management challenges.

Ways forward

The Audit assessment of Australia's catchments, rivers and estuaries reveals that much remains to be done to; understand impacts; improve management practice and fully assess benefits, costs, opportunities and trade-offs.

Key challenges

• Land use. We need to continually re-assess and improve land use patterns and practices, with attention to issues of soil erosion, landscape, nutrient balance, dryland salinity, vegetation and pasture management, water resource sustainability, and water use efficiency.
• Institutional and policy needs. We need to seek a balance between public and private benefits and costs, especially for key public resources - rivers and estuaries - and develop integrated approaches to natural resource management.
• Information provision. We need to ensure monitoring and assessment are cost-effective and provide information to support management decisions and track progress from regional to Australia-wide scales.

Australia has many programs in place and there is widespread community and government commitment to improved natural resource management. Audit findings and information sets are available in the Australian Natural Resources Atlas (Atlas) (www.environment.gov.au/atlas). The Atlas provides insight into key issues and the differences in resource condition across Australia's regions, as well as an information base to assist in setting management priorities. With continued commitment to sustainability, Australia's productive and ecologically diverse landscapes will continue to provide the goods and services the community demands.

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