Thematic findings: Inland waters
Independent Report to the Commonwealth Minister for the Environment and Heritage
Australian State of the Environment Committee, Authors
CSIRO Publishing on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06745 0
On this page
Water is a critical factor that has shaped the development of Australia. It is scarce in many parts of Australia, yet it is in increasing demand. Some of our water resources are becoming unusable as a result of past and current mismanagement. Australia's inland waters, as well as providing water for human uses (e.g. irrigation and drinking water), provide a diverse range of habitats for many unique native aquatic plants and animals and are important for the survival of many terrestrial species.
These key issues are not independent of each other. For example, increasing river salinity caused by dryland salinity can result in water becoming too saline for irrigation or drinking water and the death of riparian vegetation. In turn, the loss of riparian vegetation can increase the erosion of river banks which can in turn cause further deterioration in water quality and loss of aquatic species. This example highlights the important link between inland waters and their catchments. The health of inland waters often is directly related to land management practices and other human activities in their catchments. A challenge when managing water in Australia is unravelling the complexities of these linkages, which are often beyond the capacity of our management systems.
Unstable stream banks resulting from clearing of riparian vegetation contributes to river silt loads.
Source: Robert Simpson.
Another significant challenge in water management comes from our system of federalism where states and territories largely have the responsibility for water and catchment management. Each state and territory has different approaches to management, to defining environmental needs, and on deciding what is the acceptable health of an aquatic system. This is further complicated when a river, wetland or groundwater resource crosses state and territory boundaries. Cross border natural resource management authorities are striving to achieve more integrated processes and outcomes in the management of their respective inland waters and catchments. However, for some issues state or territory interests have overridden what is environmentally sustainable for the whole catchment.
The COAG Water Reform Framework aims to improve water management and to ensure that the extraction of water is sustainable. Governments have introduced a range of reforms to the water industry (see http://www.ea.gov.au/water/policy/coag.html). These have included charging for the full cost of supplying water, creating a market to allow the reallocation of water to higher value crops or uses, and separating the regulatory and supply functions of water management agencies. Since 1996, there has been some progress in most states and territories. Reforms are not yet fully and equitably implemented, however. For example, users of urban water meet the environmental costs of urban water supply in most states and territories, but the costs of rural water generally do not account for the full environmental cost of extraction.
Successful examples of whole-of-catchment management include the management of the Lake Eyre Basin, part of Australia's arid zone that supports some unique ecosystems. The community decided that upstream-downstream tensions had to be managed effectively, and they established catchment committees that crossed state borders. The community and state agencies have been working together to manage river systems such as the Diamantina River and Cooper Creek (South Australia) in a more integrated way than has been achieved in the Murray-Darling Basin.
The Paroo River is the last unregulated river in the Murray-Darling Basin.
Source: A Tatnell, Big Island Photographs.
The Murray-Darling Basin covers most of inland south-eastern Australia. It includes much of the country's best farm land and nearly two million people. Outside the Basin another million people are heavily dependent on its water (http://www.mdbc.gov.au ).
Australia's water resources are now better understood from integrated assessments undertaken by the NLWRA, SoE reporting programs, and state and territory water management agencies. Also since 1996, indicators for inland waters have been developed (see http://www.ea.gov.au/soe/envindicators/index.html and Appendix 2).
In considering the condition of our inland waters, there are three key issues, also discussed below:
- water resources
- water quality and pollutant sources
- aquatic ecosystems.
A summary is presented in Key findings at the start of this report.
- Water resources
- Water quality
- Aquatic ecosystems
- Surface water resources
- Water use
In an average year, after rainfall, about 391 700 gigalitres (GL) of water runs off Australia's catchments into rivers, streams and wetlands. The highest runoff occurs in northern Australia. As most runoff occurs after large rainfall events (e.g. rainfalls that cause flooding), only 32% of the total runoff can feasibly be pumped from rivers or stored in dams. Much of the water 'diverted' for human uses are the baseflows (see Groundwater) and low to moderate river flows that are very important for river health. After considering environmental water needs, it has been estimated that only about 20% of Australia's total runoff can be sustainably 'diverted' for human uses. The water available for diversion or extraction may decrease if climate variability and change, such as the enhanced greenhouse effect, reduce rainfall and alter runoff patterns.
Only 7% of the total runoff from Australia's catchments can actually be diverted with the current system of dams, weirs, pumps and other infrastructure. Much of Australia's water resource development is concentrated in eastern and southern Australia, where many rivers have been dammed to provide secure access to water for agriculture and for urban areas. Although the construction of new government-funded dams has slowed over the past 20 years, there has been an increase in the number of large on-farm water storages that store water pumped from rivers and/or capture runoff from the land after rainfall.
About 26% of Australia's surface water management areas are close to or have exceeded sustainable extraction limits. However, this assessment is generally based on limited data and a limited understanding of what must be left in rivers to maintain their health. Many river systems in the Murray-Darling Basin and along the east coast of Australia are either overdeveloped or approach full development status (Figure 20). This indicates that that aquatic ecosystems in these river systems are under substantial pressure from water extraction, and the current level of extraction may not be sustainable over the long term. In contrast, the river systems and catchments of northern and western Australia have not been developed to the same extent, so the pressure on the aquatic ecosystems from water extraction in these areas is low. The river systems of northern and western Australia probably will be subject to increased pressure as these untapped water resources are developed for agriculture.
Figure 20: Indicative surface water development status.
Assessments were undertaken by the state and territory water resource management agencies. There are varying approaches to the assessment of sustainable flow regimes.
Source: NLWRA (2001b)
The Ord River dam.
The Ord River diversion dam in north-west Australia was completed and commercial-scale irrigation commenced in 1963. In 1972, the main dam was opened, providing a water storage capacity in Lake Argyle of 10.76 billion cubic metres, several times the capacity of Sydney Harbour.
Source: Cassia Read.
Where surface water is over-allocated (e.g. the Murray-Darling Basin) some states are attempting to reduce extraction. The increasing awareness of the value of water is leading to conflicts in how it should be allocated among different uses, including the maintenance of aquatic ecosystems. One mechanism in the Murray-Darling Basin is a Commonwealth and state/territory agreed limit on water extraction known as 'The Cap', developed after the 1995 audit of water use. The Cap is intended to hold the level of water extraction to that in 1993-94, and has certainly slowed the increase in water extraction. However, Queensland has not yet agreed to set their Cap levels, and New South Wales has not been able to keep within the Cap in the Barwon River system. Capping extraction at 1993-94 levels may stop further deterioration, but will not be adequate to restore damaged river systems. The Cap may have to be reduced to halt the destruction of the Murray-Darling Basin inland river and wetland system.
Trend: Surface water
Pressures are increasing as surface water use continues to increase. The condition is deteriorating and the overall response is adequate in some respects but inadequate in others.
The extraction of water from rivers and groundwater resources reduces the amount of water available for dependent animals, plants and habitats, and also alters the natural patterns of high and low river flows. Since the last review of water resources in 1985, water use has increased dramatically (Table 10). In 1996-97, Australians extracted 24 060 GL from surface waters (79% of water extracted) and groundwaters (21% of water extracted). This is an increase of 65% in fewer than 15 years.
Table 10: Change in mean annual water use (GL) in Australia by water use category Water use category 1985 reviewA 1996-97 reviewB Percentage change Irrigation 10 200 17 940 76 Urban/industrial 3 060 4 750 55 Rural 1 340 1 370 2 Total 14 600 24 060 65
A AWRC (1987); B NLWRA (2001b).
Irrigation now accounts for 75% of water used in Australia. The largest increase in water use was for irrigation in New South Wales and Queensland where the area of irrigated land has doubled. In 1997, 1.472 million hectares of land was irrigated in the Murray-Darling Basin, 71% of the total area irrigated in Australia.
Water use needs to be related to the capacity of the environment to assess whether current levels of water extraction are sustainable (i.e. an estimate of the volume of water that can be extracted without affecting other users and the environment). Preliminary estimates for most surface water and groundwater resources have been made for the NLWRA, but insufficient scientific data and knowledge were available to determine sustainable yields conclusively. More research and data are required urgently to assess the sustainability of current and future water extractions, the water requirements of the environment and the best ways to manage the needs of the environment while providing water for human uses.
Trend: Groundwater use versus sustainable yields
Groundwater available for allocation has reduced substantially in the last decade, and is now overused and over-allocated in many Groundwater Management Units (GMUs).
There has been a 90% increase in groundwater use across Australia between 1985 and 1996-97, to about 5000 GL/year. Overall, 32% of groundwater extracted is for urban-industrial use, 51% for irrigation and 17% 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. Up to four million people in Australia depend totally or partially on groundwater for domestic water supplies.
The total volume of drinking quality groundwater (i.e. with less than 1500 mg/L Total Dissolved Solids) that can be sustainably extracted is estimated to be about 21 000 GL/year. However, many undeveloped groundwater resources are in remote areas. More importantly, most estimates of groundwater sustainable yields do not consider the impact of groundwater extraction on baseflows in rivers, streams, lakes and wetlands. Little is known about groundwater-dependent ecosystems (e.g. caves and aquifers) and their water requirements, although many contain unique or endemic species. Many land and water ecosystems depend on groundwater for at least some of the time, but the interactions between groundwater and these systems are poorly understood. In comparison with surface water, there is relatively little information on groundwater levels, use and quality and increased information is required if groundwater systems are to be managed sustainably.
Some groundwater resources are already overdeveloped, as the rate of extraction exceeds the rate of recharge (i.e. groundwater mining). These include the Great Artesian Basin, many small aquifers in the Murray-Darling Basin, the Perth Basin and aquifers along the east coast of Australia (Figure 21). Although the National Water Reforms Framework include provisions for groundwater, groundwater reform is lagging behind surface water reform in most states and territories.
Figure 21: Groundwater development status.
Source: National Land and Water Resources Audit 2001b
- Eutrophication and algal blooms
- Pollutants and acidification
- Groundwater quality
Trend: Water quality
Pressures are increasing, condition is deteriorating as more land is affected and the overall response is inadequate.
The effect of Australia's natural salinity has been exacerbated by changes in land use since European settlement. The increasing salinity of Australia's catchments and inland waters is one of the most significant threats to the health of aquatic ecosystems and to irrigation. Drinking-water supplies for most of South Australia and many inland towns in New South Wales are at risk from increasing salinity. Adelaide's drinking water is predicted to exceed guidelines for salinity on two days out of five by the year 2020 if there is no action to control increasing salinity in the Murray River.
Nationwide, 80 important wetlands are already affected by salinity and this is predicted to rise to 130 by the year 2050. Many riparian habitats (especially wetlands) can contain endemic species and communities at risk from salinisation. Loss of these communities will inevitably lead to a reduction in biodiversity in areas such as south-west Western Australia.
Dryland salinity, primarily caused by land clearing and rising saline groundwater tables, will be the major contributor to salinisation of the landscape over the next 100 years (see the Land theme report). River systems in south-west Western Australia and western Victoria have high salinities as a result of saline groundwater inflow from areas affected by dryland salinity.
In some catchments, irrigation-induced salinity caused by poor irrigation practices may be a major cause of increasing land and water salinisation (e.g. about 10% of the increased salinity of inland waters in the Murray-Darling Basin).
The Commonwealth, New South Wales and Victorian governments and the Murray-Darling Basin Commission released salinity strategies in 2000, but it is too early to judge their effectiveness. Specific salinity strategies have been developed for some individual river systems and catchments, but most river systems do not have an integrated management strategy for salinity (and other major problems). South Australia and Western Australia have had integrated salinity strategies for some river systems since 1996 and there have been reductions in land and water salinity in some catchments. In many catchments it will take decades for improvements in water quality to be measured (see the Land theme report).
Trend: Algal blooms
Nutrient enrichment and reduced streamflow due to over-extraction of water have increased the frequency and extent of toxic blue-green algal blooms, with some reservoirs being unsuitable for recreation or drinking-water supply over 25% of the time.
Blue-green algae can produce toxins that affect humans, livestock and native aquatic flora and fauna. Blue-green algal blooms can occur in urban or rural areas and are most common in storages, lakes, wetlands and stretches of rivers that have still waters and are enriched with the plant nutrients, nitrogen and phosphorus. They are a significant problem in water storages because of increased costs of treatment, management and/or provision of alternative supplies. Algal blooms also reduce the recreational and visual amenity of water resources and cost Australian water users over $150 million annually.
Although the 1000 km toxic algal bloom that occurred in 1991 in the Barwon and Darling rivers in New South Wales has not been repeated, blue-green algal blooms are common and persistent in many waterways. In Victoria, 30 to 50 blue-green algal blooms have been recorded each year since 1996. In New South Wales, persistent blue-green algal blooms occur in the Hawkesbury-Nepean River, in urban lakes and in many inland 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 since 1996. 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 has increased in recent years.
Nutrient levels are high enough to support algal blooms in all river systems of the Murray-Darling Basin (except the Condamine River) and some coastal river systems in western Victoria, central and northern New South Wales, south-east Queensland, northern Queensland and Western Australia (Figures 22 and 23). Still water conditions are common in most regulated river systems and often coincide with warm water temperatures that are conducive for algal growth.
Figure 22: Tonnes of nitrogen discharged annually.
Source: Data for New South Wales, Victoria, Queensland and Tasmania were obtained from licensing databases supplied by state regulatory agencies. Data for Northern Territory, Western Australia, Australian Capital Territory and South Australia were obtained from the National Pollutant Inventory (2000)
Figure 23: Tonnes of phosphorus discharged by inland sewage treatment plants each year.
Source: Data for New South Wales, Victoria, Queensland and Tasmania were obtained from licensing databases supplied by state regulatory agencies. Data for Northern Territory, Western Australia, Australian Capital Territory and South Australia were obtained from the National Pollutant Inventory (2000)
Based on an assessment of water quality undertaken for SoE (2001), there is no trend showing any broad-scale reduction in phosphorus or soil erosion since 1996, although there have been some improvements on a local level in some catchments. As long-term changes in land management are required to reduce soil erosion, changes would not be expected in the short term. In some catchments, other sources of nutrients such as runoff from fertilised land or intensive agricultural enterprises (e.g. cattle feedlots) may be major contributors to nutrient loads but information is not nationally available.
Catchment plans commonly aim to protect the riparian strips along rivers and drainage lines which (along with wetlands) act as filters for soil and nutrients coming from adjacent farmlands and reduce erosion of river banks and drainage lines. Since 1996, the number and sophistication of catchment management plans and best management practices that have included measures to reduce nutrient enrichment of inland waters has increased markedly. However, there is no nationally available information on the success of these plans. Measures to reduce the nutrient enrichment of inland waters may take decades to have a significant effect.
Sewage treatment plants also contribute significantly to nutrient levels in some river systems. Wastewater reuse in most states and territories has increased from 4.7% in 1993-94 to 6.5% in 1996-97 of total volume of wastewater generated. In New South Wales, Victoria, Queensland and Western Australia, wastewater reuse has increased, while in the remaining states and territories, the reuse volumes have not changed substantially.
Since 1996, there has been a greater focus on managing urban stormwater to ensure that pollutants (e.g. sediments, nutrients and toxicants) do not affect rivers and estuaries. The use of pollutant traps to capture sediment and litter, and constructed wetlands to filter runoff, is now widespread and can reduce the amounts of contaminants entering waterways as long as they are properly maintained. The NHT and state and local government funds have also contributed to improving stormwater management in urban areas.
Trend: Pollutant sources
Diffuse source pollution and especially soil loss from catchments continues to contribute to the widespread nutrient enrichment and turbidity of inland waters. Soil washed into rivers and reservoirs will remain a source of nutrients for decades.
Gully erosion along a creek in Bathurst, NSW.
Source: J Williams.
There is little nationwide data on the extent and effects of pollutants entering inland waters. The National Pollutant Inventory (NPI) provides information on the relative contributions of nitrogen and phosphorus from both point and diffuse source discharges to inland and coastal waters. However, it should be noted that the data for diffuse source pollution is likely to be largely an estimate at this early stage of implementation of the NPI.
Pesticide monitoring is not routinely undertaken in Australia, although spot studies have shown significant contamination in many irrigation areas.
Cotton, rice, sugar cane and horticulture are the highest users of pesticides and pesticide use has increased significantly over the last 20 years (see the Land theme report). There are ongoing concerns with pesticides from agricultural land contaminating the water and sediments of inland waters (e.g. pesticides in high enough concentrations to kill fish have been found in rivers and streams draining agricultural areas in northern New South Wales). There is limited information available of the concentrations or loads of pesticides in inland waters.
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 adopted by farmers and a new generation of more selective, less toxic pesticides is also being introduced (see the Land theme report). However, based on the experience of the past 20 years, pesticide use is likely to continue to increase, potentially causing continuing pollution of inland waters. Although there are many laboratory studies on the effects of pesticides, there is little information about the ecological effects of such chemicals in the river systems.
Other pollutants (e.g. heavy metals) and hydrocarbons (e.g. oil) may have localised effects. Since 1996 in some states and territories (e.g. New South Wales), the management of these sources of pollution has improved. Stormwater management plans have been prepared for all urban catchments in New South Wales and the use of constructed wetlands and other stormwater treatment devices has increased throughout Australia together with improved pollution licencing systems.
Trend: Water acidity
This is an emerging issue in some catchments where increasing trends in water acidity and the area of land affected by soil acidity have been found. Higher water acidity may lead to increased availability and movement of pollutants as well as changes to the chemistry of rivers and streams.
Acidification of inland waters can directly affect aquatic flora and fauna and can increase the leaching of pollutants and nutrients from contaminated sediments back into the river water. Acidification may occur as a result of disturbance of acid sulfate soils, acidic discharge from mine sites or the acidification of soils in agricultural areas. For example, the drainage and exposure of acid sulfate soils in coastal areas of New South Wales has caused high water acidity and localised impacts on freshwater biota. Acidification of inland waters is a localised problem (e.g. some rivers in Victoria have shown an increasing trend in acidity over the past 10 years). Since 1991, the area of land affected by acid soils has increased by 13 million hectares to 47 million hectares (see the Land theme report).
Catchments that have agriculture, industry or urban development increase the risk of contamination of drinking-water supplies. Pathogens of human origin (e.g. viruses, bacteria and protozoa) from sewage, and domestic and native animal wastes can have widespread health effects when poor catchment management allows contamination by these organisms.
In 1998, the Cryptosporidium and Giardia contamination of Sydney's drinking-water supplies followed extensive rainfall that washed pathogens into storage reservoirs (see the Inland Waters theme report). The subsequent independent inquiry recommended a 'whole-of-catchment' approach, with additional legislative and planning powers to ensure that activities in the catchments did not pose any risk to the safety of drinking-water supplies.
There is little information for many aspects of groundwater quality and the information that does exist is extremely localised. The most significant widespread pollutant of groundwater in Australia is nitrate. Groundwater resources in some rural and urban areas exceed nitrate guideline values for drinking water. Pesticides have also been detected in groundwater beneath many agricultural areas indicating that they have leached from the surface into the groundwater.
In urban areas, localised groundwater contamination has occurred as a result of leaks from underground storage tanks, industrial discharges, stormwater runoff and the movement of pollutants from contaminated sites. Although this has occurred in many urban areas, there are very few publicly available data to gauge the extent and effect of the problem.
Trend: Aquatic ecosystems
Increasing salinity of inland waters is a major threat to many aquatic ecosystems, particularly in western Victoria and south-west Western Australia. Eighty important wetlands are already affected by salinity.
There has been an increased focus on protecting Australia's unique aquatic ecosystems. Drainage of floodplain wetlands to allow for agricultural development, and more recently urban settlement, has caused much damage. The building of levees to protect inappropriate development from flooding has often isolated the rivers from their floodplains. Irrigation development, and water-regulating structures (e.g. dams and weirs) also contribute to changes in flow regimes and water character (e.g. temperature) affecting aquatic ecology.
Key pressures on aquatic ecosystems include:
- changes in natural flow regimes as a result of water extraction and supply
- direct modification or destruction of important habitats
- barriers to the movement of plants and animals, for example within rivers and between rivers and their floodplain
- effects of poor water quality
- competition from introduced and exotic animal and plant species.
An example of changes in flow regimes can be found in the Murray River and its tributaries, where the cycle of seasonal flows has been reversed. The river now runs near bank-full in summer as it delivers irrigation water, and runs at low levels in winter as the dams are refilling. Weir pools help distribute water to the floodplain for irrigation and can be an ideal habitat for blue-green algae. The altered flow regime has also assisted pest species like European carp becoming dominant. In May 2001, Commonwealth and state governments introduced a 10-year program to implement water efficiency projects to benefit the environment along the Murray River, the Snowy River and key alpine rivers. One aim is to return flows to the Snowy system from present discharge of 1% of natural flow to 27% by 2010. This plan will restore some of the former aquatic and scenic values of the once 'wild' river.
An aerial view of a lake in the Snowy Mountains.
Source: Environment Australia.
Only 13% of Australian river systems had agreed flow allocations for environmental purposes in June 2000, but at least preliminary environmental flow allocations will be established for many regulated rivers over the next five to 10 years. As well as allocating a volume of water to meet environmental needs (i.e. a sufficient flow of water for the species that inhabit the rivers), it is equally as important to time water releases to mimic natural flow patterns (or regimes). Much more research and monitoring is required to develop and assess environmental flow allocations.
Inland waters downstream of most major water storages are probably affected by cold bottom water discharges from dams. Effects on water quality from cold-water pollution may have significant impacts on ecosystem health in some areas. There are, however, only preliminary estimates of these impacts.
A national assessment of river 'health' using the AusRivAS monitoring assessment system found that at 31% of sites macroinvertebrate communities were significantly impaired, at 8% they were severely impaired and at 1% they were extremely impaired. The degree of impairment generally was related to land use in the catchment and disturbance of the river system. The AusRivAS results provide an important benchmark of river health (Figure 24).
Figure 24: Summary of AusRivAS bioassessment results for all river sites surveyed in Queensland.
Numbers refer to AWRC basins. O, observed number of types of animals; E, expected number of types of animals.
Source: Cooperative Research Centre for Freshwater Ecology 2001, data supplied by relevant state authority
Riparian vegetation is seriously degraded in many catchments as a result of clearing, grazing and salinity (e.g. in some areas of Western Australia over 50% of rivers and creeks have lost their native fringing vegetation and less than 10% of wetlands have healthy fringing vegetation). Riparian restoration and protection is becoming more commonplace, with successful outcomes being measured in some projects. However, these projects are only a small proportion of the total area affected. Resnagging of rivers such as the Murray River is also being undertaken to provide habitat for native aquatic species.
Darling River minus riparian vegetation.
Source: Richard Norris, CRC for Freshwater Ecology.
Wetlands are important in Australia's environment and often support high levels of biodiversity. Since European settlement, the condition and extent of many wetlands has decreased substantially. Since 1996, there is little new information on changes in wetland area. The area of many wetlands in the Murray-Darling Basin (and others) has declined significantly as a result of many physical and biological factors. Programs to better define and map changes in wetland extent and condition are underway. Another 13 wetlands have been Ramsar-listed since 1996 and the EPBC Act could provide additional protection to wetlands. Management plans for many wetlands have been or are being prepared.
Of the 18 waterbird species listed in the Action Plan for Australian Birds (see http://www.ea.gov.au/biodiversity/threatened/action/birds2000/), four species are listed as 'vulnerable' and five as 'near threatened', primarily as a result of habitat loss. Frog populations have been declining in Australia as in the rest of the world. For most species the cause of decline is unknown, although the chytrid fungus has infected frog populations throughout Australia. Of the 208 frog species in Australia, 20 are considered endangered and seven are vulnerable. The Action Plan for Australian Frogs (see http://www.ea.gov.au/biodiversity/threatened/action/frogs/) details conservation measures to protect endangered frog species across Australia. Some states and territories have prepared conservation plans for individual threatened species.
Of over 200 freshwater fish species in Australia, 11 are considered endangered and 10 are listed as vulnerable under the EPBC Act. In New South Wales many native species have been reduced in range and abundance. Barriers to native fish movement (e.g. weirs, dams and bridges) have resulted in reduced reproductive success and access to suitable habitat. Fishways are being considered to overcome many major barriers but effective designs are still being developed. Restocking of mostly native fish is undertaken in all eastern states and territories with varying success. The loss of genetic diversity and introduction of diseases into wild populations have occurred as a result of restocking in some areas. Thirty-five exotic fish species have become established in inland waters, with eight identified as having a significant effect. Many exotic fish species continue to increase in range and abundance. Programs to eradicate exotic fish species are being attempted in some areas.
Fishway in Victoria.
Source: Michael Shirley, Sinclair Knight Merz Pty Ltd.
Some of the larger freshwater crayfish species are under considerable pressure from habitat loss and overfishing. There is only limited information on their distribution, however. Numbers of platypus have declined or disappeared in many catchments but reliable information on their health and abundance is not available.
Since SoE (1996), there have been some advances in the protection and restoration of aquatic ecosystems. Although most states and territories have legislation to protect riparian vegetation and threatened species and to provide for environmental water allocations, the application of the legislation is not consistent and not always legally binding. National conservation plans for frogs, water birds and fish have been prepared. There are 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 (e.g. carp and trout), but many species remain a widespread and intractable problem.
Since 1996, there has been increased research and monitoring of Australia's inland waters and their health, although for many aspects there is still insufficient information to conclusively determine their condition and trend. The information available reveals that the pressures on inland waters have increased and many water bodies in the developed southern and eastern areas of Australia are significantly degraded as a result of activities in the catchments and water extraction for agriculture and urban development.
The Commonwealth, state and local governments along with communities are now appreciating the linkages of river flows, aquatic ecosystems and their catchments.
Important initiatives in the 1990s that indicated that complex water issues needed to be addressed included:
- COAG Water Reform Framework
- ongoing work of the Murray-Darling Basin Commission
- recognition of the importance of environmental flows
- NHT commitments influencing the behaviour of land managers
- increased role for catchment boards and committees
- substantial information collected by the NLWRA
- NAP for Salinity and Water Quality.
Water use continues to increase across Australia. In the Murray-Darling Basin, the volume of water extracted for primarily irrigated agriculture has increased significantly over the past 15 years and is unsustainable in many river systems. Groundwater resources are also increasingly being developed as surface water resources become fully allocated. The effect of increased groundwater extraction on baseflows in surface waters, wetlands and other groundwater-dependant ecosystems is still unknown and requires urgent additional research to ensure that aquatic environment are not further degraded. Other effects of water extraction such as modifications in natural river flow patterns and the construction of barriers to fish movements are also resulting in a declining health of aquatic ecosystems. Although there has been some improvements in the management of water resources, proposed reforms are not yet fully and equitably implemented.
The increasing salinisation of land and water resources is one of the biggest threats to inland waters over the next 100 years. The potential effects are immense and widespread, and will affect both the environment and agricultural and drinking-water supplies in many areas. Many observers are concerned that measures presently in place might not be sufficient to reverse the degradation that has been observed.
Substantial structural changes in land management and use probably will be required in many areas to combat salinity. These changes must also be considered in the context of other issues such soil erosion and eutrophication/algal blooms to ensure that the most benefit is gained from the limited resources available.