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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.
Australian Catchment, River and Estuary Assessment 2002
National Land and Water Resources Audit, 2002
ISBN 0 642 37125 3
Integrated findings: natural resource condition in Australia's drainage divisions
Underpinning the need for integrated and region specific natural resource management
Recognition that natural resource management strategies need to deal with issues from a total system perspective has led to integrated catchment management initiatives. Understanding of the links between physical and ecological processes in both natural- and production-dominated ecosystems allows the causes of natural resource degradation to be more readily identified and strategically managed.
Limited availability of information on the status of natural resources within river basins has constrained the capacity to implement integrated catchment management strategies. Australia-wide natural resource assessments compiled by the Audit provide an unprecedented opportunity to examine patterns of resource condition and change within river basins.
Geographic patterns
Key ecosystem condition drivers have been identified by catchment, river, estuary condition and other Audit assessments. They include climate, landscape and topography, land use intensity, erosion rate, sediment and nutrient loading, native vegetation cover, soil degradation, water quality, water resource use, altered flow hydrology, and exotic biota.
Maps of contextual information from other Audit assessments can be found
in the appropriate report or on the Australian Natural Resources Atlas
at www.environment.gov.au/atlas.
These summaries for each of Australia's 12 drainage divisions are general. They recognise the broad diversity of landscapes and natural resource management issues across Australia and attempt to draw out the key salient points for each division. The intent is to provide an overview of ecological condition and management challenges.
Within each drainage division condition varies immensely. The variation in condition and management needs cannot be detailed in this overview. The reader should refer to catchment management plans, regional strategies and resource appraisals for more detailed information where these are available.
Catchment, river and estuary condition - are they linked?
Using a total catchment management approach, natural resource managers seek to understand how various parts of a catchment interrelate to the overall system and how activities in one part of a catchment may affect the condition of downstream resources. Recognising the biophysical links between component systems within a catchment, it is generally assumed that river condition reflects catchment condition and further downstream, estuary condition reflects both river and catchment condition.
But within estuaries and rivers, there are both internal and external interactions that influence their condition. For example, within the bed and water column of a river, interactions between biota and habitat can alter the relationship between catchment and river condition. Likewise, use patterns within an estuary or external interactions with marine waters affect their relationship to catchment and river conditions.
The Audit's assessment of catchment, river and estuary condition within river basins across Australia enables the assumption that catchment, river and estuary condition are linked and the concept that estuaries are 'the report card of the catchment' to be tested.
A simple correlation technique was used to assess statistical relationships across catchment, river and estuary condition indices at a river basin scale. Although correlation does not demonstrate causality it does serve to highlight expected relationships, similarities and differences between the assessments. Some of the stronger correlations result from shared input variables (i.e. the national land use data). In other instances stronger relationships between independent input variables highlight underlying biophysical linkages between catchment, river and estuary systems. These relationships could be expected to vary regionally.
The relatively high correlation observed between assessed river and catchment condition underlines the need for river management to include catchment management activities.
Correlation of catchment and estuary condition is generally good except between the catchment biota subindex and estuary condition This may be expected as the catchment biota subindex is based on terrestrial biota. The correlation between catchment and estuary condition confirms that estuaries are a useful 'report card of the catchment'. Total catchment management approaches can use these linkages by using the condition of the estuary as an indicator of their effectiveness in improving catchment condition.
Correlation values between river and estuary condition are lower than between catchment and river, and catchment and estuary condition, but still indicative of a positive relationship. The lower correlation between river nutrient and suspended sediment load subindex and estuary condition reflects the differing assimilative capacity of estuary types for sediment and nutrient loads. Further analysis would likely indicate a much higher correlation between wave-dominated estuaries and sediment and nutrient loads, given that such loads stay largely within these estuaries. This is compared to tide dominated estuaries (>0% of all estuaries) where much of the sediment and nutrient load moves through the estuary to the near shore marine environment.
Correlation between catchment and river condition
Catchment condition land subindex versus river environment index: 0.63
Catchment condition land subindex versus river catchment disturbance subindex: 0.65
Catchment condition land subindex versus river nutrient and suspended sediment load subindex: 0.46
Catchment condition land subindex versus river physical habitat subindex: 0.33
Catchment condition land subindex versus river riparian vegetation subindex: 0.41
Correlation between catchment and estuary condition
Catchment condition index versus average estuary condition: 0.54
Catchment condition land subindex versus average estuary condition: 0.5
Catchment condition biota subindex versus average estuary condition: 0.06
Catchment condition water subindex versus average estuary condition: 0.54
Correlation between river and estuary condition
River condition environment index versus average estuary condition: 0.48
River nutrient and suspended sediment load subindex versus average estuary condition: 0.19
River catchment disturbance subindex versus average estuary condition: 0.47
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