Australian Natural Resources Atlas

Natural Resource Topics

Australian Catchment, River and Estuary Assessment 2002

National Land and Water Resources Audit, 2002
ISBN 0 642 37125 3

Introduction

Assessing the aggregate impact of resource use on key natural ecosystems

Ecological sustainability is the cornerstone of Australian natural resource legislation and management. Natural resources are the natural capital underpinning a strong economy and a healthy society. Assessing the status of Australia's natural resources and the health of its ecosystems is therefore important. Understanding how use of natural resources has changed ecosystem function and health could prevent further resource degradation and reduction of options for future generations.

Impacts on ecosystems occur from a range of causes that operate through links between physical and ecological systems. The natural dynamics of ecosystems, including seasonal and catastrophic events, can mask changes associated with impacts of resource use. To understand the process links and impact drivers operating on natural systems, an integrated natural resource assessment approach is required (Figure 1). Australian Catchment, River and Estuary Assessment 2002 applies a systems approach to undertake its integrated assessment of these key natural resources.

Australian Catchment, River and Estuary Assessment 2002 assesses aggregate impacts of natural resource use on catchment, river and estuary condition and identifies priority management challenges for the maintenance of these natural assets.

Figure 1: Catchment-based integrated natural resource assessment.

Catchments, rivers and estuaries

Catchment. An area that drains all precipitation that falls on it to a single point. A river basin includes all the catchment area that drains to a major river mouth and is named after the river. The Australian Water Resources Council defined 246 river basins that are the subbasins of drainage divisions.

River. The main drainage channel of a large catchment area. Most Australian rivers have seasonal flow patterns and some are intermittent. Australian Catchment, River and Estuary Assessment 2002 defines 246 river basins by name and by the 1:250 000 scale mapping of Australian drainage patterns.

Estuary. A semi-enclosed coastal body of water where salt water from the open sea mixes with freshwater draining from the land. This management-based definition was formed to ensure that all types of estuaries and embayments identified by the Australian community were included in the assessment.

Australia's diverse landscapes

Australia is a diverse continent and this is reflected in its vegetation, biota, landscapes, riverine habitats and estuaries.

Differences in catchment and river function across Australia reflect regional climatic, geological and land use patterns (e.g. water quality and flow characteristics of a tropical river fed by monsoonal rain and draining savanna rangelands are very different to those of a temperate river draining wet rainforests).

Australian estuary form and function is also diverse being governed by a combination of river, tide and wave energies. Around Australia the relative dominance of these energies varies, forming a range of estuary functional types (Figure 2).

Although we do not yet fully understand the causal links and relationships in ecosystems, we do understand key drivers of ecosystem function and dysfunction (e.g. processes such as water flow, sediment movement, nutrient cycling and fire regime). We can use information on these drivers within the biophysical frameworks provided by catchments, to assess ecosystem condition and examine the importance of process-based links between component ecosystems.

Figure 2: Process drivers of the form and function of Australian estuaries.

Assessment concepts

Assessment of Australia's catchments, rivers and estuaries is based on two key related concepts: ecosystem health and condition. These concepts are difficult to define in absolute terms.

Definitions of health consider the status of the whole system rather than individual components and are usually made by reference to attributes that assess ecosystem vigour, organisation and resilience (Rapport 1998). The ecosystem health paradigm can be applied to natural ecosystems and to ecosystems dominated by human production. It recognises that agricultural lands and even cities are ultimately 'ecosystems' that can occur in a range of states of health. Difficulties in applying this paradigm lie in:

Assessing the condition of a natural system usually involves measuring the distance of that system from some ideal state or benchmark. Benchmarks differ for different systems and value judgements by sectors of society. A desirable condition is governed by the pattern of resource use and acceptable trade-offs between economic development, biodiversity, aesthetics, and cultural, spiritual and recreational values.

An objective benchmark for rivers and estuaries - concerned with the maintenance of natural values - is the pristine or pre-European settlement state. In the case of extensively modified systems (e.g. river impoundments or shipping ports) a pristine state only represents a useful reference point rather than a realistic or desirable management goal.

While it may be desirable to manage rivers and estuaries to maintain natural values and characteristics, catchments that are highly modified by human settlement and industry cannot be realisitically managed to a natural state target.

Benchmarks for good catchment condition need to reflect an ideal balance between a natural and modified productive state that is capable of maintaining or mimicking near-natural biophysical processes, supplies goods and services required by the community and minimises impact on downstream riverine and estuarine ecosystems. Such benchmarks have not yet been defined for Australian catchments. The approach adopted in this assessment has been to produce a relative condition assessment across catchments.

Biophysical assessment and reporting frameworks

Port Melbourne: developed for urban and industrial uses.

Port Melbourne: developed for urban and industrial uses.

Photo: Department of Natural Resources and Environment, Victoria.

Catchments

The water cycle and hydrology are major drivers of many ecosystems. Catchments provide examples of natural systems where links between system components can be readily identified (e.g. soil erosion on the land surface in the upper catchment may ultimately affect the quality of water that flows to the lower catchment and in turn the ecology of biological communities living within the estuary at the bottom of the catchment).

Catchments are therefore an appropriate biophysical framework to assess the status of natural resources (land, water and vegetation) that affect the condition of river and estuary ecosystems.

River basins

River basins represent the total catchment of a river system and are the primary basis for reporting in Australian Catchment, River and Estuary Assessment 2002. For finer scale reporting of river condition, rivers have been divided into 'reaches' representing sections of river with relatively uniform physical characteristics. Each designated reach is about 5 km in length.

River basins are aggregated to form 12 drainage divisions and have been used to provide overview summaries for Australia-wide integrated findings.

Floodplains support high value industries.

Floodplains support high value industries.

Photo: Jim Tait

Estuaries

Estuary condition reporting is by reference to individual estuaries and to a classification system of physical processes that classes the estuary in relation to the dominant geomorphic processes governing its form and function. Recognising the importance of contributory catchments in determining the status of estuaries, each estuary has also been identified in relation to the river basin within which it occurs.

Landscape units within catchments

Catchments and river basins contain a range of landscape units (e.g. alluvial floodplains, colluvial slopes, upland tablelands), usually having distinct characteristics in terms of biophysical elements (e.g. soil, vegetation, biota) and processes (e.g. soil formation, water balance, erosion) and consequently resource use suitability and land use.

Landscape units provide an appropriate framework for assessing the status of terrestrial biota and drivers of ecosystem condition. They are also a more appropriate framework than catchments for the large arid proportion of Australia (~ 40%) that lacks surface drainage to well-defined catchments.

Landscape units called subregions were used in the Audit assessment of landscape health (NLWRA 2001a), and are used to provide additional ecosystem condition context in the integrated findings section of this report.

Irrigated agriculture requires high quality water.

Irrigated agriculture requires high quality water.

Photo: Murray-Darling Basin Commission

Ecosystem condition - what drives it?

Ecosystem condition drivers include biophysical elements and processes, and socioeconomic factors (e.g. market prices; profitability; and aesthetic, recreational and cultural values). Socioeconomic factors are recognised to be drivers of ecosystem condition since they affect the behaviour of individuals and communities, but their role as condition drivers was not considered in this assessment.

Biophysical elements and processes that determine the patterns of and change in biota, material and energy within ecosystems are considered condition drivers in that changes to these biophysical processes or elements 'drive' the ecosystem to a different condition state. We can distinguish condition drivers associated with the geographic context of an ecosystem (climate, rainfall, topography, soil type) and those associated with resource use and degradation patterns (vegetation cover, water quality, soil degradation). Intensive land and water use has the greatest impact on ecosystem condition. However, not all ecosystems are equally susceptible. Geographic context (including climate, topography, and soil type) is important in determining ecosystem resilience and also affects the extent to which drivers associated with resource use and degradation patterns impact on ecosystem condition.

In modified ecosystems, particularly those in stressed landscapes, the influence of an individual driver (e.g. soil erosion) may dominate. This can result in irreversible changes that undermine the resource capital (e.g. soil fertility, structure, carbon content) of the system and lead to an ecosystem condition with reduced structural complexity, biological diversity and primary productivity.

This contrasts with unstressed natural ecosystems where condition drivers operating at varying scales or rates (e.g. climate seasonality and decadal climate variability) maintain a dynamic, often cyclical, ecosystem condition equilibrium.

The condition of a natural ecosystem can be considered a function of:

While condition drivers can be described individually, they usually operate collectively to generate change. Rainfall intensity, for example, is a primary driver of soil erosion mediated by vegetation cover, soil type and topography. Soil erosion drives surface water quality (turbidity and nutrient loading), and this drives instream primary productivity, which in turn drives aquatic biotic community composition. These drivers of condition are all interlinked and may in turn impact on each other.

This presents challenges when seeking to discover the primary causes (and therefore key management priorities) for maintaining ecosystem health.

The suite of ecosystem condition drivers operating in any particular basin is dependant on the pattern and intensity of land use and its geographic characteristics. Australia's river basins have a broad spectrum of geographic and land use settings. Figures 4 to 6 illustrate some of the land use patterns in river basins and associated key drivers of ecosystem condition.

Figure 3: Conceptual relationship of natural ecosystem condition determinants.

Figure 3: Conceptual relationship of natural ecosystem condition determinants.
Figure 4. Land use patterns within Australian river basins and associated drivers of ecosystem condition - coastal basins with lower intensity use.
Figure 5. Land use patterns within Australian river basins and associated drivers of ecosystem condition - coastal basins with higher intensity use.
Figure 6. Land use patterns within Australian river basins and associated drivers of ecosystem condition - inland basins.

Geographic drivers

Ecosystem characteristics - climate, topography, soil properties and vegetation type - are important determinants of resilience to impacts of resource use (Table 1). They affect the extent to which condition drivers such as erosion and landscape water balance can act under different land use patterns.

Table 1: Geographic drivers of ecosystem condition.
Climate and rainfall
  • Climate affects primary productivity, nutrient cycling rate, soil moisture and evaporative potential, soil formation, types of erosion, and water oxygen concentration.
  • Rainfall affects water balance, vegetation cover, erosion rates (and types), surface water flow, fire regime.
  • Ecosystems that have moderate climates in terms of evenly distributed medium rainfall and limited extremes in temperature, rainfall intensity or aridity are considered more resilient to resource use impacts because they are more likely to maintain ground vegetation cover and have higher rates of nutrient cycling and soil formation producing better-structured and more fertile soils.
  • Key input to modelling of soil erosion, nutrient loading and landscape water balance (NLWRA 2001b).
Topography
  • Affects erosion potential, stream flow gradients, water balance, size of catchments, and potential land use intensity.
  • Generalisations concerning influence are difficult as topography interacts with climate and soil types. Steeper landscapes generally have a greater potential for soil erosion and higher gradient streams have greater flow velocities and sediment transport capacities. Larger catchments associated with less dissected landscapes usually have lower stream flow rates and lower sediment transport capacity.
  • Topography is often one of the primary determinants of land use intensity.
  • Key input to Audit modelling (NLWRA 2001b).
  • Geomorphic landscape units form assessment framework for the Audit landscape health project.
Soil properties
  • Affect landscape water balance, nutrient leaching, catchment hydrology, vegetation type, primary productivity, wind and water erosion potential and downstream water quality.
  • Deep well structured fertile soils are the most resilient in terms of resource use impacts.
  • Properties that make major Australian soil types susceptible to impacts include:
    • low reserves of organic matter (e.g. Tenosols, Rudosols)
    • dispersiveness (e.g. Sodosols)
    • proneness to compaction (e.g. Vertosols, Organosols)
    • proneness to waterlogging (e.g. Podosols)
    • proneness to slaking (e.g. Dermosols)
    • proneness to hardsetting and crusting (e.g. Chromosols, Kandosols, Sodosols)
    • proneness to acidification (e.g. Kurosols, Ferrosols, Hydrosols)
    • low fertility (e.g. Tenosols, Rudosols, Podosols, Sodosols, Calcarosols)
    • low water retention capacity (e.g. Calcarosols, Tenosols, Rudosols, Sodosols)
    • proneness to water erosion (e.g. Sodosols, Organosols, Ferrosols, Kandosols)
    • proneness to wind erosion (e.g. Calcarosols, Podosols, Tenosols, Rudosols)
  • Distribution of soil types and properties (NLWRA 2001b).
  • Key input to modelling and soil condition assessments (NLWRA 2001b).
Vegetation type
  • Affects water balance, erosion rates, soil structure and fertility, nutrient cycling, primary productivity, and fire regime.
  • Susceptibility to use impact is dependent on interactions with climate and soil type. Characteristics that favour resilience include high percentage ground cover, low palatability to livestock, fire resistance, and capacity to grow in nutrient poor soils.
  • Native vegetation types and extent compiled and mapped (NLWRA 2001c).
  • Key input to assessment of agricultural productivity and sustainability (NLWRA 2001b) and assessments of landscape water and nutrient balance and erosion rate.

Land use-associated drivers

Intensity of land and water use determines the potential for impacts on ecosystem condition. Intensity ranges from maintenance of essentially natural ecosystems to the complete alteration of land surfaces and ecosystem biophysical processes. Land use has been summarised into nine classes (Table 2).

Table 2: Land use-associated drivers of ecosystem condition.
Nature conservation
  • Usually contains ecosystems in pre-settlement condition.
  • Condition drivers (e.g. exotic biota, altered fire regime, altered water balance and modified stream flow) may still be operating in areas used for nature conservation.
  • Extent of nature conservation area used as an indicator in catchment condition and landscape health assessments (NLWRA 2001a and this report).
  • Incorporated into catchment disturbance index of the river condition assessment (this report).
Other protected areas and indigenous use
  • Areas with indigenous land uses usually contain ecosystems in good condition. Indigenous use includes traditional hunting, and in some instances livestock grazing, forestry and other primary production uses.
  • Ecosystem condition drivers include exotic biota, altered fire regime, grazing pressure and erosion.
  • Incorporated into landscape health assessment of extent of conservative land tenure (NLWRA 2001a).
Minimal use
  • Includes a range of crown lands where use of resources does not greatly affect ecosystem condition. Exceptions are in localised areas used for more intensive purposes (e.g. military use and transport corridors).
  • Ecosystem condition drivers include exotic biota, altered fire regime, grazing pressure and erosion and in some cases complete loss of the ecosystem as occurs with road and rail construction.
  • Incorporated into landscape health assessment of extent of conservative land tenure (NLWRA 2001a).
Livestock grazing
  • This land use class is the most extensive in Australia.
  • Impacts on ecosystem condition depend upon landscape resilience, grazing pressure and the level of pasture improvement such as tree clearing and exotic pasture sowing. Livestock grazing on native pastures is less intensive than agriculture or built environments. Ecosystem condition impacts can be intensive within susceptible landscapes.
  • Most of this class represents uncleared native pastures or rangelands.
  • Cultivated improved pastures are included within the dryland agriculture land use class.
  • Key condition drivers include grazing pressure, vegetation cover and condition, fire regime, soil erosion and compaction, exotic biota, altered water balance, changed catchment hydrology, nutrient loading and water quality degradation.
  • Extent of total grazing pressure is used in the Audit's Landscape Health in Australia assessment (NLWRA 2001a).
  • Also incorporated into catchment disturbance index of the river condition assessment (this report).
  • Key attribute for rangeland monitoring and assessment (NLWRA 2001d).
Dryland agriculture
  • Dependent on rainfall for crop growth. Includes land that has been cleared and where surface form and soil properties have been modified by land levelling, cultivation and addition of ameliorants and fertilisers.
  • Includes improved pastures and cereal and grain crops.
  • Ecosystem condition is dependent on suitability of the landscape and soil type for agriculture and management practices in place.
  • Key ecosystem condition drivers include loss of vegetation cover, soil erosion, compaction, and acidification, altered water balance, dryland salinity, changed catchment hydrology, nutrient loading, water quality degradation, exotic biota, and fire regime.
  • Key input to the Audit assessment of agricultural productivity and sustainability (NLWRA 2001b) and assessments of landscape water and nutrient balance and erosion rate.
  • Input to assessment of catchment condition (this report)
Forestry
  • Includes both native production forests and plantation forestry.
  • Where native forests are only selectively logged, many ecosystem process drivers maintain their function. Some processes operating at the species and community level may be affected.
  • Plantation forestry is a more intense land use as it includes clear felling of natural vegetation and produces significant changes to biophysical processes and ecosystem conditions. While plantation forests are growing, they contribute to the stability of many catchment scale ecosystem condition drivers.
  • Key condition drivers affected by forestry land uses include exotic biota, altered fire regime, grazing pressure, erosion, altered water balance, changed catchment hydrology, and water quality degradation.
  • Incorporated into landscape health assessment of extent of conservative land tenure (NLWRA 2001a).
  • Incorporated into catchment disturbance index of the river condition assessment (this report).
Irrigated agriculture
  • Has the capacity to affect all the condition drivers also affected by dryland agriculture.
  • Increases potential for a range of degradation issues associated with soil and landscape water balance.
  • Generates ecosystem impacts through drivers associated with river regulation, construction of dams and tail water discharge (i.e. aquatic habitat connectivity, flow regime change and associated water quality changes).
  • One of the more intensive forms of land use.
  • Key input to the Audit assessment of agricultural productivity and sustainability (NLWRA 2001b).
  • Input to assessment of catchment condition (this report).
Built environment
  • Includes urban and industrial development and is the most intensive land use in terms of resource use impacts. Only larger cities and industrial complexes are mapped.
  • Key ecosystem condition drivers operating in built environment areas include vegetation cover loss, soil erosion, altered water balance, dryland salinity, changed catchment hydrology (especially hard panning), nutrient loading, toxicant pollution, water quality degradation, exotic biota, and fire regime change.
  • Incorporated into catchment disturbance index of the river condition assessment (this report).
  • Input to assessment of catchment condition (this report).
Water bodies
  • In eastern Australia, many water bodies mapped in the national land use coverage are constructed impoundments and reflect river regulation and water resource use associated with irrigated agriculture or urban development.
  • Majority of mapped water bodies are inland drainage terminal evaporative basins and saline lakes. Other types include coastal mangrove and saltpan wetland complexes (northern tropical Australia), floodplain wetlands (Murray-Darling basin), coastal (south-eastern Australia) and inland lakes (e.g. Lake George in New South Wales).

Resource use drivers

Patterns of resource use and degradation are important drivers of ecosystem condition.

Table 3: Resource use and degradation drivers of ecosystem condition.
Native vegetation extent and condition
  • Extent of native vegetation cover is determined by the intensity of current or past land uses.
  • An important determinant of landscape water balance, nutrient cycling, soil structure, erosion rates, catchment hydrology, fire regime, and habitat availability.
  • Riparian vegetation is particularly important for the stability of catchments and their ecosystems. It provides habitat, stabilises stream banks intercepts nutrients and sediment, and moderates instream temperature by shading.
  • Where vegetation has not been cleared, its condition can influence the operation of key ecosystem condition drivers.
  • In developed catchments, exotic vegetation cover including crops and plantation forests can perform some of the biophysical roles important for maintaining catchment condition stability.
  • Incorporated into riparian vegetation index of the river condition assessment (this report).
  • Extent of native vegetation used in the Audit landscape health (NLWRA 2001a) and the catchment condition assessment (this report).
  • Recommended attribute for rangeland monitoring and assessment (NLWRA 2001d).
Fire regime
  • Fire has played an important role in the evolution of Australian ecosystems and many Australian landscape mosaics are mediated by fire.
  • Key driver of vegetation cover and structure, soil fertility (and structure), erosion potential, biota and habitat availability.
  • In areas of more intensive land use, fire is seldom used as a management tool, except for specific production or risk reduction goals.
  • Current fire regimes are often far removed from pre-settlement conditions. In areas of extensive land use, fire regimes are often determined by production goals (i.e. pasture management).
  • Assessment of changes to fire regime is limited by availability of Australia-wide data. Qualitative information compiled for the Audit assessment of landscape health (NLWRA 2001a).
  • Recommended attribute for rangeland monitoring and assessment (NLWRA 2001d).
Landscape water balance/catchment hydrology
  • Rainfall infiltration rate is a key determinant and is governed by topography, type and extent of vegetation, and soil type and condition.
  • Modified by water use patterns including irrigation and groundwater use.
  • Primary driver of ecosystem processes including groundwater discharge to stream surface flows and wetlands.
  • Governs catchment hydrology and the distribution of vegetation and groundwater dependent ecosystems.
  • An unstable landscape water balance is the basis for dryland salinity.
  • Catchment hydrology is affected by water resource use patterns and patterns of land development including land levelling, wetland draining and levee and dam construction.
  • Hydrology changes incorporated in the Audit assessment of landscape health (NLWRA 2001a).
  • Impoundment density used as input to the catchment condition assessment (this report).
  • Hydrology changes incorporated into the river condition assessment (this report).
Dryland salinity
  • Driven by landscape and catchment water balance.
  • Salinised soils lead to the death of native vegetation, soil and riverbank erosion and habitat loss.
  • Input into the Audit assessment of dryland salinity (NLWRA 2001e).
  • Input to assessment of catchment condition assessment (this report) and landscape health (NLWRA 2001a).
  • Basin salinity exceedances incorporated into the river condition assessment (this report).
  • Surface water quality salinity exceedances input into the Audit assessment of water quality (NLWRA 2001f).
Nutrient loading
  • Many Australian ecosystems have evolved in nutrient limited conditions because of the naturally low nutrient status of soils.
  • Surplus nutrient sources include agricultural fertilisers and discharges from point sources such as sewage treatment plants.
  • Nutrient loads derived from diffuse sources such as water-borne soil erosion are the most significant sources in terms of total quantities contributed.
  • Landscape features that help reduce nutrient and sediment loads exported from catchments include wetland detention basins and riparian vegetation. These features are often degraded or lost with intensive land use. This loss can act as a secondary driver for nutrient loading problems.
  • Ecosystem impacts associated with nutrient loading include water quality deterioration (e.g. algal blooms and dissolved oxygen decline), and changes to the composition of aquatic biota communities in wetlands, rivers, estuaries and coastal environments.
  • Landscape balance for nitrogen and phosphorous input to the Audit assessment of agricultural productivity and sustainability (NLWRA 2001b).
  • Phosphorus and nitrogen load incorporated into the river condition assessment (this report).
  • Nutrient point source hazard incorporated into the catchment condition assessment (this report).
  • Water quality measures, point source discharges and ecological integrity measures associated with nutrient loading used in estuary condition assessment (this report).
Soil erosion
  • Australia's climate and soils make landscapes particularly prone to soil erosion.
  • Associated with a range of land uses and drivers.
  • Significant driver of ecosystem condition causing soil structure and fertility decline, altered catchment hydrology, change in vegetation community, surface water turbidity, benthic habitat smothering, stream channel bed aggradation, and nutrient loading and changes in aquatic biota community composition.
  • Water-borne soil can be transported beyond the mouth of a river basin affecting water quality in near-coastal marine environments (e.g. fringing coral reefs of the Great Barrier Reef Marine Park).
  • Wind erosion is a significant degradation driver particularly for ecosystems containing infertile and poorly structured sandy soils.
  • Ratio of current soil erosion to natural rates has been assessed by the Audit assessment of agricultural productivity and sustainability (NLWRA 2001b).
  • Hill slope erosion used as input to the catchment condition assessment (this report).
  • Suspended sediment and bed load data incorporated into water quality and physical habitat indices of the river condition assessment (this report).
Soil degradation (see Table 1 for degradation issues)
  • Key affected processes include landscape water balance, catchment hydrology, soil erosion, primary productivity, and downstream water quality.
  • Soil acidification is usually associated with structural and fertility decline which can provide prerequisite conditions for changes in rainfall infiltration rates and changes in landscape water balance.
  • Soil degradation hazard used as input to the catchment condition assessment (this report) .
  • Acid soil lime requirements and soil management input into the Audit assessment of agricultural productivity and sustainability (NLWRA 2001b).
Water quality
  • Processes such as loss of vegetation cover and soil erosion are often related to land use intensity and may be primary drivers of water quality deterioration.
  • Water quality issues include turbidity, salinity, nutrient and organic loading, low dissolved oxygen, acidity, heavy metals and pollutants.
  • Impacts caused by these include change in instream metabolism (temperature and primary productivity), algal blooms, smothering of benthic habitats, and loss of aquatic biota.
  • Surface water quality exceedances for turbidity, total nitrogen, total phosphorus, pH and salinity input to the Audit water resources assessment (NLWRA 2001f).
  • Suspended sediment, nitrogen, phosphorus and salinity incorporated into the river condition assessment (this report).
  • Pesticide, industrial point source and nutrient point source hazard and suspended sediment load incorporated into the catchment condition assessment (this report).
Surface water and groundwater use
  • Ecosystem condition is related to volumes available to maintain environmental flows or groundwater dependent ecosystems and the design, construction and operation of water supply infrastructure such as impoundments and weirs.
  • Surface water and groundwater use can affect seasonality of flows, water temperature, water quality, habitat connectivity, distribution and reproduction of aquatic biota, stream channel and estuarine geomorphology, and catchment hydrogeology.
  • Input to the Audit water resources assessment (NLWRA 2001f).
  • Impoundment density used in the catchment condition assessment (this report).
  • Hydrology change and habitat connectivity incorporated into the river condition assessment (this report).
  • Recommended attribute for rangeland monitoring and assessment (NLWRA 2001d).
Exotic biota
  • Include wild stock, feral vertebrate pests (e.g. foxes, rabbits and cats), exotic plant species and invertebrates.
  • Many have been accidental or incidental introductions and may be more appropriately considered ecosystem degradation rather than resource use.
  • The ecosystem pressures associated with domestic stock and exotic species introduced to the wild for recreational purposes (e.g. trout) are patterns of resource use.
  • Can affect biophysical process drivers such as catchment hydrology and soil erosion through physical impacts on native vegetation and landscapes (e.g. trampling, increased grazing pressure, soil disturbance and the exclusion of ground cover). Exotic biota can compete with native biota for habitat and food resources, and can be predators.
  • Exotic vertebrates and weeds of national significance used as input to the catchment condition assessment (this report) and the Audit assessment of landscape Health (NLWRA 2001a).
  • Recommended attribute for rangeland monitoring and assessment (NLWRA 2001d).
Dryland salinity is caused by rising groundwater mobilising salt in the soil.

Dryland salinity is caused by rising groundwater mobilising salt in the soil.

Photo: Murray-Darling Basin Commission.

Australia-wide assessments: context for regional action

Natural resource management decision makers need to be able to place specific issues within an informed, broader context, to be able to strategically target investment. This requires operating over a range of scales and setting strategic directions at larger scales while defining specific on-ground activities at regional scales.

The Audit's Australia-wide resource assessments use consistent, integrative approaches based on an understanding of key biophysical process drivers to compare natural resource systems and management issues. This comparability provides an appropriate broad scale context for setting natural resource management program and policy priorities.

Those involved in onground activities and regional planning processes can use the Audit's information as an input for setting regional priorities. To complete the analysis at regional scales, information on social and economic benefits and costs is essential. This ensures explicit trade-offs are made to deliver the most cost-effective and regionally appropriate set of works and activities.

Assessment extent and limitations

Availability of data is the primary limitation on the coverage in this assessment.

The area of assessment for catchments and rivers includes all river basins with intensive land use (Figure 7) and selected river basins (in the Northern Territory and the western division of the Murray-Darling Basin) that do not contain intensive land use, but for which resource data were available. Whole river basins were used so that processes such as hydrology, and sediment and nutrient movement could be modelled and balanced over entire river basins.

The estuary assessment has an Australia-wide coverage. In more remote areas the limited availability of data has resulted in a greater dependence on qualitative assessment methods using expert opinion and remotely sensed data. Estuary condition also provides an indicative, integrated measure of catchment and river condition.

The Audit landscape health report (NLWRA 2001a) includes Australia-wide assessments of the condition of bioregions and component subregions including more remote areas. These findings have been used to provide context for the integrated findings section of this report.

Uniform assessment frameworks that use comparable data are needed to produce Australia-wide assessments. State and Territory data has been compiled using consistent standards and unit protocols. Where not available, assessments have used national data sets.

Data limitations include:

Figure 7. River basins that contain areas of intensive land use. The area represents 40% of the continent (3 million km2).

Before you download

Most publications are downloadable as PDF files. Adobe Acrobat Reader  is required to view PDF files.

If you are unable to access a publication, please contact us to organise a suitable alternative format.

Key

   Links to an another web site
   Opens a pop-up window