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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Land Use - Australia
Australia
Assessment of Australian Catchment Condition
The Audit assessment of catchment condition presents a way to make comparative assessments of catchment biophysical condition. The assessment used an indicator approach and a Geographic Information System (GIS) data compilation system known as CatCon to define patterns of classes of relative catchment condition. This provides insight into the biophysical condition of Australia's more intensively used catchments and a basis for decision support on priorities and opportunities for protective catchment management or remedial action.
Comparisons of catchment condition were made across Australia. The method also has application to smaller numbers of catchments to determine relative ranking within a State/Territory or a drainage division (e.g. catchments draining to the Great Barrier Reef or forming the Murray-Darling Basin).
The assessment of catchment condition was conducted as a partnership between the Audit, the Bureau of Rural Sciences and CSIRO Land and Water with support and involvement of State and Territory natural resource management agencies.
CatCon aimed:
- to develop a classification system that uses biophysical data to define catchment condition and provides an integration and synthesis of Audit data at the catchment scale
- to apply the classification system to provide an integrated Australian-wide report on the relative condition and main pressures operating on catchment condition
- to develop and provide a readily applied and extendable database and presentation framework for compiling, analysing and integrating catchment condition data with consideration to the capacity to integrate data across a range of scales
- to provide catchment specific information that allows decision makers to identify implications for catchment management needs, including information gaps and priorities for more intensive investigation and further research
The determination of catchment condition is ultimately a value judgement that depends on biophysical attributes interacting with social values and economic factors. The Audit's comparative assessment of catchment condition was limited to a biophysical definition with catchment function defined in terms of land, water and biota components.
Selection criteria were developed and applied to 110 biophysical attributes to screen for suitable condition indicators. Fourteen indicators (see table below) were selected and used to generate a five-class condition scale from better to poorer that was used to rank and map relative catchment condition. The result is colour-coded maps for:
- individual indicators;
- composite sub-indices for water, land and biota condition; and
- an overall composite catchment condition index.
Indicators used for the Water, Land and Biota subindices and the Catchment Condition Index
| Indicators | Related Catchment Management Issue |
|---|---|
| WATER | |
| Suspended Sediment Load | Modelled post settlement change in suspended sediment loads |
| Pesticide Hazard | Pesticide use is a surrogate for pesticide pollution risk |
| Industrial Point Source Hazard | Industrial pollution contamination risk |
| Nutrient Point Source Hazard | Nutrient point source loading of waterways |
| Impoundment density | Ecosystem changes associated with altered flows |
| LAND | |
| 2050 high dryland salinity risk/hazard | Modelled risk assessment of salinity impacts |
| Soil degradation Hazard | Soil and land use assessment of soil degradation risk |
| Hill slope erosion ratio | Modelled assessment of changes in hillslope erosion potential from natural conditions |
| BIOTA | |
| Native vegetation extent | Habitat quantity and distribution |
| Native vegetation fragmentation | Deterioration in native habitat |
| Protected areas | Level of habitat protection |
| Road density | Human population and land use intensity pressures |
| Feral animal density | Extent feral animals have impacted on native biota |
| Weed density | Extent weeds have disturbed native vegetation |
Example Catchment Condition Assessment Outputs
Catchments can be presented at a range of scales from subcatchment to total river basin.
For the Audit catchment condition assessment, each indicator and aggregate index was analysed and presented at three scales:
- 5 x 5 km grid
- 500 km2 sub-catchments
- Australian Water Resources Council River Basins
Although maps based on relative rankings are useful for comparing biophysical conditions between catchment or subcatchment areas, they do not convey actual values. However, the probability that an interpretation in relative terms will be meaningful increases at a national scale.
Example outputs for the composite catchment condition index (using 14 indicators) are presented below. For the full range of indicators and land, water and biota sub-indice outputs, link to the CatCon project on-line mapping.
Figure: 5 km x 5 km grid cell scale
When viewed at the 5 x 5 km grid cell resolution the relative biophysical condition of catchments within the assessment area shows a clear pattern of clusters of the grid cells into larger patches.
The most coherent and solid patches with relatively poorer condition occur in:
- the wheat-sheep belt and coastal agricultural areas of Western Australia;
- cropping areas of South Australia;
- western and central Victoria;
- the western slopes and plains of New South Wales; and
- the north-east Murray-Darling Basin in southern Queensland.
Isolated areas of poorer catchment condition also occur in the larger inland-extending basins in central and south-eastern Queensland; and coastal floodplain areas of north, central and south-eastern Queensland and northern New South Wales. The more intensively developed central coastal basins of New South Wales also show poorer condition. In Tasmania the main patches of relatively poor condition match with the more intense cropping and grazing areas of the Tasmanian midlands.
The areas with relatively better condition correspond to conserved lands such as national parks, particularly in the non-tropical, higher rainfall areas. Other clusters of better condition are in the Northern Territory, Cape York and arid parts of western South Australia, corresponding with areas of lower land use intensity.
Figure: 500 km2 subcatchment scale
Aggregation to 500 kmē subcatchment resolution shows a similar overall pattern to the 5 x 5 km resolution but is limited in data variation spatially. There are large, coherent areas with relatively poorer conditions in the wheat and sheep zones of Western Australia, through western and central Victoria and west Gippsland, and onto the western slopes and plains of New South Wales.
In South Australia, Tasmania and Queensland the catchments in poorer condition appear more confined and isolated. In Queensland, these catchments in poorer condition include the upper reaches of the Condamine River in the Murray-Darling Basin, and the more intensively developed, larger river basins in central to south-east Queensland (Fitzroy, Burnett, Mary, Brisbane,) and smaller, coastal basins with developed, coastal floodplains.
Similar to the 5 x 5 km resolution, catchments in relatively good condition lie within the less intensively used parts of the assessment area. In the non-tropical higher rainfall zone, conserved lands have less influence and good condition areas are much more restricted. South-west Tasmania, north-eastern Victoria, the Blue Mountains National Park, parts of the upper Clarence River basin in New South Wales and the south-west of Western Australia are of relatively better catchment condition.
Figure: River basin scale
At the coarse level of aggregation to river basin scale, the poorest condition catchments occur in the Murray-Darling drainage division in south-eastern Queensland, western New South Wales and central northern Victoria. They include the Border Rivers, Namoi, Macquarie-Bogan Murrumbidgee, Murray-Riverina, Goulburn, Campaspe and Loddon River basins. River basins in the more intensively developed south-east of Queensland (Brisbane, Pine, Maroochy), central New South Wales coast (Sydney Coast - Georges River, Wollongong Coast) and central to western Victoria (Bunyip, Maribyrnong, Werribee, Moorabool, Barwon, Lake Corangamite and Hopkins) also fall into the poorest catchment condition class.
River basins in better condition are confined to the less intensively developed parts of the assessment area including, Cape York, the Northern Territory, arid rangelands in South Australia, southern Western Australia and the south-west of Tasmania.
To compare or overlay composite catchment condition data (5 km grid and 500 kmē CRES sub-catchments) with other Atlas data layers link to the Australian Natural Resources Atlas MapMaker.
Informing target and priority setting through comparisons in condition
Target setting occurs at two levels:
- Australia-wide to determine broad priorities for protective management and remedial works; and
- within a catchment or region for the allocation of resources.
As demonstrated by the various aggregations of the composite catchment condition data (above), the patterns of catchment condition vary according to the scale of the assessment framework. Larger comparative frameworks such as entire river basins 'smooth over' the heterogeneity of finer scale patterns of catchment condition such as displayed in the 5 x 5 km grid.
Using river basins as the basis for comparison and for setting Australia-wide or State/Territory target and priorities appears appropriate. Comparisons between entire river basins also inform links between catchment condition and downstream resources (water quality or estuary condition), where the total catchment acts as an integrator for downstream condition.
A finer scale assessment framework is required to identify priorities for catchment management within a specific catchment or region and define localised areas of better or poorer condition. The 500 km2 subcatchments and the 5 x 5 km comparisons used in this project appear appropriate for these applications.
The figure below shows assessed catchment condition at the 500 km2 subcatchment scale in relation to the National Action Plan for Salinity and Water Quality (Commonwealth of Australia 2000) priority catchments. Most catchments in the lower condition classes have been identified as priorities. Notable areas for remedial works outside the National Action Plan for Salinity and Water Quality include the Hunter and Hawkesbury River basins in central New South Wales and smaller coastal river basins in northern New South Wales, southern and central Queensland and coastal Victoria.
Figure: Catchment condition and National Action Plan (NAP) for Salinity and Water Quality priority.
Identifying key condition assessment indicators
Composite indices provide a relative assessment of catchment condition. They help to define priority catchments in need of concerted management effort through either protective management or rehabilitation. Analysis of individual indicator patterns provides a way to examine the relative importance of biophysical attributes or processes contributing to the condition of a specific catchment. Assessments using individual indicators assist in defining the priority management needs within a specific catchment. Assessing how well individual indicators reflect composite patterns of catchment condition also provides a way to identify minimum indicator sets-essential for cost-effective investment in data collection (see below).
Relative performance of indicators used to define composite catchment condition.
| Indicators in order of performance for depicting areas of poorer catchment condition | Indicators in order of performance for depicting areas of better catchment condition |
|---|---|
| Native vegetation extent | 2050 high dryland salinity risk/hazard |
| Native vegetation fragmentation | Nutrient point source hazard |
| Protected areas | Impoundment density |
| Road density | Pesticide hazard |
| Pesticide hazard | Native vegetation extent |
| Sediment load | Native vegetation fragmentation |
| Universal Soil Loss Equation erosion ratio | Industrial point source hazard |
| Soil degradation hazard | Road density |
| 2050 high dryland salinity risk/hazard | Sediment load |
| Industrial point source hazard | Weed density |
| Weeds | Universal Soil Loss Equation erosion ratio |
| Feral animals | Soil degradation hazard |
| Impoundment density | Feral animals |
| Nutrient point source hazard | Protected areas |
Example outputs of the better performing individual indicators for the land, water and biota components are presented below.
Figure: Native vegetation extent for 500km2 subcatchments
Figure: Predicted 2050 salinity extent for 500km2 subcatchments
Figure: Suspended sediment loads for 500km2 subcatchments
Improving catchment condition assessment
Narrowing the window of comparison - State/Territory example
One of the limitations of the method used by the catchment condition assessment is that the condition assessments are relative. This relativity is Australia wide and is not set in the context of any regionally distinct performance thresholds. Australia is yet to develop and agree to performance thresholds for catchment condition.
One approach to address this limitation is to narrow the window of analysis to a specific region or State/Territory. This reduces both:
- the range of variability in compared biophysical settings; and
- the probability that the distribution of condition values will be skewed by patterns external to the area of interest.
The CatCon catchment condition analysis system can readily adjust the window of analysis used for calculating the relative assessments of catchment condition. An example output of the composite catchment condition index for Victoria is shown below.
Figure: Catchment condition for 500km2 subcatchments in Victoria
Narrowing the window of analysis also provides the opportunity to overcome another limitation of the assessment method-the use of finer-scale data sets that might only be available for one region or State. Finer scale data can be loaded into the CatCon system and used to provide analyses that better serve specific catchment management needs.
Improve relevance to regional catchment management clients
Catchment management issues and biophysical responses to similar land uses vary regionally due to differences in climate, land forms, soil types and land use patterns. Social and economic aspirations will also affect regional priorities for catchment management.
Within the Catcon assessment system weightings for indicators can be assigned from zero upwards to facilitate regionally 'tailored' assessments. As more data sets become available, additional indicators can be included, enhancing the query functionality of the system and its regional applicability as a tool for catchment management target setting.
Key steps to achieving this include:
- Incorporating other functional landscape units such as bioregions or land systems into the assessment framework
- Establish agreed regional and catchment management boundaries as a basis for setting priorities, monitoring activities and reporting progress
- Develop minimum and agreed indicator sets, defined reference condition(s) and environmental performance threshold values as the basis for improved comparative assessments of biophysical catchment condition
- Maintain an inventory and quantitative definitions of the catchment management issues across different regions of Australia
- Designing decision support tools for evaluating options for land use change and improvement in land use practices as an input into priority setting at the catchment or regional scale
Improved scenario development
Social values and economic goals have a major influence on the management of natural resources and thus the condition of catchments. Being able to cross-compare patterns of biophysical catchment condition with socioeconomic factors can provide insights on sustainability, development suitability and capacity for particular management scenarios.
Key steps to achieving this include:
- Being able to link social and economic options with biophysical condition to test the likely outcomes of various management actions
- Identifying and applying different value sets for defining catchment condition so that regional groups can select those most appropriate to their community goals and expectations
The figure below presents an example cross-comparison between catchment condition and agri-business flexibility, defined on the basis of biophysical factors associated with soil capability and rainfall.
Figure: Cross comparison of catchment condition and agricultural flexibility
Data sets
Monitoring catchment condition at an Australia-wide scale requires a minimum data set that describes:
- water behaviour in the landscape;
- land cover;
- land use practice; and
- status of natural ecosystems.
It will also take account of social and economic conditions and aspirations.
Data challenges associated with improving catchment condition assessments include:
- Including spatially referenced, land-use practice data to better interpret land use impacts
- Ensuring all Audit Australia-wide data sets are suitable and available for use in catchment condition assessments
- Making other data sets (e.g. climate variability, soil condition, floodplains and wetlands) available
- Collecting social and economic data relevant to catchment based natural resource management to enable comparison of biophysical condition with social and economic opportunities
Further information
View the Australian Catchment, River and Estuary Assessment 2002 report.
Link to the Australian Bureau of Rural Sciences web site to view the CatCon project report
Link to the Australian Bureau of Rural Sciences CatCon mapping facility for the full range of catchment indicators with accompanying interpretations
Link to Atlas on-line mapping for summary catchment condition and other natural resource assessment maps.
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