Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Jonas Ball, Sinclair Knight Merz Pty Limited, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06750 7
Australia is the driest inhabited continent with over 80% of its land having an average rainfall of less than 600 mm/year. Rainfall also varies considerably from year to year, between seasons and across Australia. This large variation in climate and rainfall has resulted in a similar variation in natural environments - ranging from the arid inland areas to the tropical environments of far northern regions to the cooler temperate climates in south-eastern Australia. Australia's inland aquatic ecosystems have also evolved in concert with the variable nature of the continental climate and provide a diverse range of habitats for many unique native aquatic plants and animals, as well as being important for the survival of many terrestrial species. They are integral to the Australian landscape and their health is inextricably linked to their catchments.
Our inland waters are also essential to Australian society and economic wellbeing as they provide freshwater for drinking, agriculture and industry. However, the health of many inland waters has been degraded by the extraction of water for human uses and activities in the catchment such as land clearing, soil erosion, the introduction of exotic species and the discharge of pollutants.
The key findings of Australia: State of the Environment 1996 (State of the Environment Advisory Council 1996) highlighted that Australia's inland waters are under increasing pressure from over-extraction, pollution, algal blooms, catchment modification, habitat destruction and flow regulation. Since 1996, the pressures on many inland waters has increased, with a substantial increase in water extraction, continued clearing of catchment and riparian vegetation, increases in the area of land affected by dryland salinity and increases in pesticide use.
It is difficult to determine whether the condition of inland waters has further deteriorated since 1996 as many environmental changes occur over time scales greater than the five-year reporting cycle. In addition, there are insufficient accurate data to make this assessment, particularly as there exists inherent variability in environmental measurements. Since 1996, our knowledge has increased allowing the geographical extent and seriousness of problems to be better defined. In turn, this provides direction for appropriate management responses to protect and restore inland waters. However, for many aspects there is still not enough information to be able to accurately assess their condition and any changes in their condition.
This assessment of inland waters was based around three key management issues:
- Water resources - Assessing water use and whether the current levels of extraction from surface water and groundwater resources are sustainable.
- Water quality and pollutant sources - The major water quality threats include land and water salinisation; soil erosion, nutrient enrichment and blue-green algal blooms; and pesticides and other contaminants.
- Aquatic ecosystems - The condition of aquatic flora, fauna and habitat that provides a measure of the 'health' of inland waters.
Water extraction has increased substantially over the last 15 years and is unsustainable in many river systems and groundwater basins.
Total water use in Australia for 1996/97 was 24 100 GL (NLWRA 2001a), an increase of 65% from 1985 (AWRC 1987). Seventy-nine per cent of water was extracted from surface waters (19 100 GL), while 21% was extracted from groundwater resources (5000 GL) (NLWRA 2001a). Seventy-five per cent of water extracted is used for irrigation, with irrigation water use increasing by 76% between 1985 and 1996/97 (NLWRA 2001a). Most of the growth in irrigation has occurred in New South Wales and Queensland, with the area of irrigated land doubling in these states over the last twenty years. Urban and industrial water use has also increased by 55% (NLWRA 2001a) between 1985 and 1996/97.
The average volume of run-off from Australia's catchments is 391 661 GL/year (NLWRA 2001a). Only 32% of total run-off can feasibly be diverted for human use and typically consists of baseflows and low to moderate flows that are also important for the health of inland aquatic ecosystems. Based on the sustainable yields determined for 15 river systems in Australia, on average 20% of Australia's total run-off can be sustainably diverted for human uses. Based on current modelling, the impact of the enhanced greenhouse effect on rainfall and run-off remains unclear (see the Atmosphere Theme Report).
With the current level of resource development, 7% of the average annual run-off is able to be captured. However, intensive development of river systems in the Murray-Darling Basin for irrigation and in the coastal river systems near major urban centres for potable and industrial water, has resulted in water extractions exceeding sustainable yields.
In comparison, water use in northern and western Australia is relatively low, but is likely to increase in the future. Diversions have been capped at 1993/94 levels of development in Basin states, with the exception of Queensland which is in the process of implementing a cap on diversions (MDBMC 2000).
Apart from reductions in river flows, other impacts from the over development of water resources include:
- modifications to natural flow regimes due to the regulation of rivers and their use as water supply canals for downstream users. Many wetlands in the Murray-Darling Basin have suffered substantial reductions in area due to changes in flow regimes and inundation areas (Kingsford 2000);
- water quality impacts such as cold water pollution - which may affect up to 3000 km of rivers in New South Wales alone (NSW EPA 2001); and
- barriers to the movement of fish and alienation of habitat (e.g. dams, weirs).
Only 13% of Australian river systems had any operational environmental flow allocations in June 2000 (NLWRA 2001a), but they will be established for most regulated rivers in the next five to ten years. It should be noted that as well as allocating a volume of water to meet environmental needs, it is equally as important to consider the timing of water releases so as to mimic natural flow patterns (or regimes).A number of major reforms were initiated in the 1990s as part of the National Water Reform Framework in response to pressures on the environment and National Competition Policy. Water pricing reforms for urban water are generally on target in all states and territories. Pricing reforms in rural areas have been fully implemented in Victoria and Western Australia and the reform process is under way in other states and territories. All states and territories have put in place processes to separate water entitlements from land entitlements to allow permanent water trading to occur and to separate powers in the water industry to ensure the independence of water resource management, standard setting and regulatory enforcement, and service provision.
|Drainage division||1996/97 Total use (GL/yr)||1996/97 Percentage of water used for urban/industrial||1996/97 Percentage of water used for irrigation/rural|
|1 North-east Coast||2 144||35||65|
|2 South-east CoastA||1 784||74||26|
|4 Murray-DarlingA||11 149||5||95|
|5 South Australian Gulf||272||92||8|
|6 South-west Coast||362||49||51|
|7 Indian Ocean||12||83||17|
|8 Timor Sea||318||14||86|
|9 Gulf of Carpentaria||98||31||69|
|10 Lake Eyre||7||14||86|
|12 Western Plateau||14||93||7|
|13 Island Territories||NA||NA||NA|
A Does not include diversions from unregulated streams in New South Wales.
B Total of drainage divisions is based on state estimates of total water use and is not a summation of drainage division values, which are incomplete.
C NA not available.
Source: NLWRA 2000.
Due to the cap on surface water extractions in the Murray-Darling Basin and the scarcity of surface water resources in other areas, groundwater use across Australia has increased by 90% between 1985 and 1996/97 to approximately 5000 GL/year (NLWRA 2001b). Overall, 33% of groundwater extracted is for urban/industrial use, 48% is used for irrigation and 19% is for stock watering and rural use. South Australia, New South Wales and Victoria use more than 60% of groundwater for irrigation, while Western Australia uses 72% for urban and industrial purposes.
The total volume of groundwater that can be sustainably extracted from groundwater resources is currently estimated to be 25 735 GL/year (< 5000 mg/L TDS); however, many undeveloped groundwater resources are in remote areas. More importantly, most groundwater sustainable yield estimates do not consider groundwater dependent ecosystems or the impact of groundwater extraction on baseflows associated with surface waters. These are major issues that need to be addressed before the intensive development of groundwater resources can be managed sustainably. Some groundwater resources are already overdeveloped including the Great Artesian Basin and many small aquifers in the Murray-Darling Basin and along the east coast of Australia.
The National Water Reforms include various aspects of groundwater; however, in most states and territories groundwater reform is lagging behind surface water reform. The Agriculture and Resource Management Council of Australia and New Zealand has recently begun several policy initiatives designed to improve groundwater management in Australia.
Since the early 1990s the Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) and the Australian and New Zealand Environment and Conservation Council (ANZECC) have collaboratively developed a framework for water quality management. Known as the National Water Quality Management Strategy, this series of water quality policy, benchmark and industry guidelines sets out the agreed processes for identifying and protecting the 'environmental values' of Australia's surface, marine and groundwaters. Of particular relevance to this report, two key strategy papers have been released:
- the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000); and
- the Australian Guidelines for Water Quality Monitoring and Reporting (2000).
In combination, these documents provide a comprehensive approach to water quality issues, such as salinity and eutrophication.
The increasing salinity of Australia's catchments and inland waters is one of the most significant threats to the health of aquatic ecosystems, and irrigation and drinking water supplies. Dryland salinity will be the major contributor to salinisation of the landscape over the next 100 years, with irrigation-induced salinity only having a localised affect. The major cause of dryland salinity is the clearing of deep-rooted perennial woody vegetation and its replacement with shallow-rooted annual crops. In areas that are cleared, water (e.g. rainfall) can 'leak' into the saline groundwater table, raising its level until it reaches the surface. As well as causing soil salinisation, raised saline groundwater tables discharge saline water directly into rivers, streams, wetlands and lakes, and can degrade riparian habitat.
Up to 5.7 million hectares of land are affected by dryland salinity with another 7.5 million hectares at serious risk due to shallow groundwater tables (NLWRA 2001b). Up to 17 million hectares could be affected by 2050. Seventy-six per cent of the land already affected is in Western Australia, with Victoria and South Australia having the next largest areas, respectively. In the Murray-Darling Basin, 300 000 ha of land are affected by dryland salinity (LWRRDC 1998), although potentially up to 5 million hectares are at risk (MDBMC 1999).
Currently, river systems in south-west Western Australia and western Victoria have high in-stream salinities (NLWRA 2001a). River systems in the Murray-Darling Basin where in-stream salinities are predicted to increase substantially over the next 50 to 100 years include: Queensland-Warrego, Condamine-Balonne and Border rivers; New South Wales-Lachlan, Bogan, Macquarie, Castlereagh and Namoi rivers; South Australia-Murray River at Murray Bridge and Morgan; and Victoria-Avoca and Loddon Rivers (MDBMC 1999). Nationwide, 80 important wetlands are already affected by salinity and this will rise to 130 by the year 2050 (NLWRA 2001b). Many riparian habitats (especially wetlands) contain endemic species and communities that are at risk from salinisation (e.g. south-west Western Australia). Loss of these communities will inevitably lead to a reduction in biodiversity in these areas.
The Commonwealth, New South Wales and Victoria released salinity strategies in 2000, but it is too early to judge the effectiveness of these programs. South Australia and Western Australia have had integrated salinity strategies since 1996 and there have been reductions in salinity in some catchments. In-stream salinity mitigation measures such as salt interception schemes and improved drainage will only provide limited relief from salinity. Radical measures such as extensive catchment revegetation and abandonment of highly salinised land will be required. Measures to combat salinity (such as revegetation) will also have a collateral benefit in addressing other problems such as soil erosion. The integration of the management measures for all land and water issues is required to ensure that the maximum benefit from the limited resources available is obtained.
Blue-green algae can produce toxins that affect humans, livestock and native aquatic flora and fauna. They can also have other impacts on water quality and aquatic ecosystems. Blue-green algal blooms occur mostly in storages, lakes, wetlands and stretches of rivers that have reduced flow. They are a significant problem in water storages because of increased costs of treatment, management and/or provision of alternative supplies. In Victoria, 30 to 50 blue-green algal blooms have occurred each year since 1996. In New South Wales, persistent blue-green algal blooms occur in the Hawkesbury-Nepean River and in Windamere, Toonumbar, Carcoar, Lostock and Burrinjuck dams. In Queensland, blue-green algal blooms were present at least 25% of the time in 14 water storages between 1997 and 1999. The Blackwood, Vasse, Serpentine and Swan-Canning rivers in Western Australia have also been affected by regular blue-green algal blooms. Because of the variability in the occurrence of algal blooms and gaps in historical data, it is difficult to determine whether the frequency and size of algal blooms have increased.
New research has shown that aquatic ecosystems exist in one of two dominant states, either clear and macrophyte-dominated or turbid and algae-dominated (Scheffer 1998). The switch from a macrophyte-dominated ecosystem to an algal-dominated system is the result of a complex suite of interactions involving land use change, vegetation clearance, flow regulation and nutrient input. Switching back to a former state requires a large investment of resources and will be slow, if at all possible (Harris 2001). Many inland waters that are subject to regular algal blooms may have already 'switched' to a degraded algal-dominated system and will be difficult to restore.
The major factors that cause blue-green algal blooms are nutrient enrichment and increased periods of low or no flow due to river regulation. Phosphorus levels regularly exceed state and territory water quality objectives in all river systems of the Murray-Darling Basin (except the Condamine River) and some coastal river systems in western Victoria, Sydney, northern New South Wales, south-east Queensland, northern Queensland and Western Australia. Increased periods of low or no flow are common in most regulated river systems.
For most inland waters, the major source of nutrients is diffuse pollution. There is no evidence of any broad scale reduction in diffuse source pollution since 1996. As many of the mitigation measures require widespread changes in land management (e.g. revegetation), changes in diffuse source pollution contributions would not be expected. Land and water management plans contain measures to reduce nutrient pollution and have been or are in the process of being prepared for many river systems. Soils eroded into waterways may provide a source of nutrients for decades into the future and therefore algal blooms will continue to occur despite efforts to reduce point and diffuse source pollution.
Point-source discharges from sewage treatment plants and intensive agriculture also contribute significantly to nutrient levels in some catchments. Strategies for the reduction of nutrients from point sources are being implemented. The volume of wastewater reuse in most states and territories has increased since 1996 and is expected to continue to increase.
As in 1996, there is little nationwide data on the extent and impacts of most pollutants, apart from localised pollution hot spots such as derelict mines. Possibly the most widespread pollutants are pesticides, which are used extensively in agriculture with cotton, rice, sugar cane and horticultural crops the highest users of pesticides. In cotton-growing areas of northern and central New South Wales, the broad spectrum insecticide Endosulfan has been regularly detected in rivers and streams in concentrations known to be lethal to aquatic biota. In the drainage and irrigation canals in southern New South Wales, high concentrations of other pesticides (e.g. Molinate) have regularly been detected. Since 1990 at least 20 fish kills in New South Wales rivers have been attributed to pesticides. Integrated pest management and best management practices for pesticide use are gradually being implemented and a new generation of more selective, less toxic pesticides is also being introduced. However, based on the experience of the past 20 years, pesticide use is likely to increase, potentially causing continuing pollution of inland waters.
Currently, high water acidity is not considered a major problem, but may become a significant issue in the future as the area of land affected by acid soils has increased by 17 million hectares to 47 million hectares over the last decade (see the Land Theme Report). Many rivers in Victoria have shown an increasing trend in acidity over the past 10 years, and this may become more widespread (NLWRA 2001a).
The most widespread known pollutants in groundwater are nitrate and pesticides. Nitrate pollution of groundwater is an issue in rural and urban areas, with concentrations often exceeding Australian Drinking Water Guidelines (LWRRDC 1998a). Pesticides have been detected in over 20% of groundwater samples in some agricultural areas. Other pollutants mainly have a localised effect and can be traced to a specific point source (e.g. leaking underground storage tanks) or are a result of historical contamination of land and groundwater. Overall there is very little publicly available information on groundwater quality in Australia.
There has been an increased focus on protecting Australia's unique aquatic ecosystems, although for many it is too late. Inland waters in the eastern states, north-east coast and south-west Australia are under considerable pressure from water extraction and catchment activities. Based on the limited information available, northern inland waters are generally more healthy as they and their catchments are less developed, although there is likely to be increased pressure on them in the future. Important indicators of aquatic ecosystem health include habitat condition, and the extent and trends in the population and distribution of waterbirds, native fish, frogs and other aquatic flora and fauna. An integrated assessment of river health has also been undertaken using the Australia River Assessment Scheme (AusRivAS). In many areas, these indicators reflect the severe pressures from human activities.
A national assessment of river 'health' using AusRivAS found that at 31% of sites macroinvertebrate communities were significantly impaired, at 8% of sites they were severely impaired and at 1% of sites they were found to be extremely impaired. Generally the degree of impairment was related to land use in the catchment and disturbance of the river system.
One of the major pressures on inland waters is from physical and structural changes such as channelisation of rivers, construction of levee banks to reduce the land areas affected by low to moderate flooding, modification of natural drainage patterns, and vegetation clearing and grazing. These activities especially affect the condition and extent of riparian vegetation and wetlands.
Riparian vegetation is important in maintaining stream bank stability, providing habitat, as a buffer between aquatic and terrestrial systems and in stream metabolism. Riparian vegetation is seriously degraded in many catchments due to clearing, grazing and salinity. Riparian restoration and protection is gradually becoming more commonplace, with successful outcomes being measured in a number of small projects. However, these projects are only a small proportion of the total area affected. Re-snagging of rivers such as the Murray River is also being undertaken to provide habitat for native aquatic species. A national database of riparian vegetation condition and extent is a major information gap.
Wetlands have an important function in Australia's environment and often support high biodiversity. Since European settlement, the condition and extent of many wetlands have decreased substantially (State of the Environment Advisory Council 1996). There is little new information on changes in wetland area since 1996, although the impacts of human activities have recently been quantified for many Murray-Darling Basin wetlands (Kingsford 2000). Many wetlands in the Murray-Darling Basin (and in other areas) have experienced significant decreases in area due to isolation from floodplains, reduced flows and flooding, increased salinity from groundwater inflows and higher in-stream salinities, drainage modifications, grazing and reclamation, and the introduction and spread of exotic species. Programs to better define and map changes in wetland extent and condition are under way. Another 13 wetlands have been Ramsar-listed since 1996 and the new Environment Protection and Biodiversity Conservation Act 1999 has provided additional protection to wetlands. Management plans for many wetlands have been or are in the process of being prepared.
Of the 18 waterbird species listed in the Action Plan for Australian Birds, four species are listed as vulnerable and five species as near threatened, primarily due to habitat loss. Frog populations have been declining in Australia, as in the rest of the world. For most species the cause of decline has not been determined, although the chytrid fungus is known to have infected frog populations throughout Australia. Of the 208 frog species in Australia, 20 are considered endangered and 7 are vulnerable.
Of over 200 freshwater fish species in Australia, 11 are considered endangered and 10 are vulnerable under the Environment Protection and Biodiversity Conservation Act 1999. Thirty-five exotic fish species have become established in inland waters, with eight identified as having a significant impact. In New South Wales, over the last 15 to 20 years many native species have experienced a reduction in range and abundance. Barriers to native fish movement (such as weirs, dams and bridges) have resulted in a reduction in reproductive success and access to suitable habitat. Fishways are being considered for many major barriers; however, effective designs are still being developed. Restocking of mostly native fish is undertaken in all eastern states and territories with a varying degree of success. The loss of genetic diversity and introduction of diseases into wild populations have occurred as a result of restocking in some areas. Fisheries managers are also increasingly recognising that stocking fish is not always the best response to fishery problems and that the maintenance of appropriate environmental conditions is just as critical.
Some of the larger freshwater crayfish species are under considerable pressure from habitat loss and over-fishing; however, there is only limited information on their distribution. Platypus numbers have declined or disappeared in many catchments, but again reliable information on their health and abundance is not available.
Since Australia: State of the Environment 1996 (State of the Environment Advisory Council 1996) there have been some advances in the protection and restoration of aquatic ecosystems. The Commonwealth Environment Protection and Biodiversity Conservation Act 1999 provides greater protection for Ramsar-listed wetlands, threatened aquatic species and migratory birds, although the Act has yet to be fully tested. Most state and territories have legislation in place to protect riparian vegetation and threatened species and to provide for environmental water allocations; however, the application of the legislation is not consistent. National conservation plans for frogs, waterbirds and fish have been prepared. Currently, there is still insufficient data on the condition and abundance of fauna to support or judge the success of these plans. All conservation plans recognise the primary need to establish 'healthy' habitat to support threatened fauna. Pest control programs are having limited success. There have been some localised successes in eradicating pest fish species (such as carp and trout), but many species remain a widespread and intractable problem.