5.1 Freshwater riverine ecosystem health
Freshwater riverine ecosystems are extensively degraded across NSW
The environmental condition of the majority of NSW rivers has been modified, particularly through vegetation clearing, declining water quality, regulation of waterways, and destruction of habitat. The intensity of land use appears to be a major determinant of the condition of freshwater riverine systems. As a result, rivers in highly urbanised catchments and areas where cropping is the predominant land use show the most signs of ecosystem stress.
Status of Indicator
5.1 River health, as assessed by macroinvertebrate assemblages
The environmental condition of many NSW rivers has been modified, degrading ecosystem health.
Importance of the issue
Freshwater riverine ecosystems comprise rivers and their riparian zones, floodplains and wetlands. Healthy freshwater ecosystems are vital for the maintenance of aquatic and terrestrial biodiversity, water quality, and industries such as aquaculture and fishing. However, these ecosystems are degraded in many parts of NSW, showing some or all of the following problems:
- modified habitats
- removal of riparian vegetation
- sedimentation from the erosion of land and riverbanks
- altered flow regimes
- changes to water quality
- the presence of exotic species.
For more information on freshwater ecosystem health, see EPA 2000c. Information on the status of wetlands in NSW is presented in Biodiversity 6.6.
Status of freshwater riverine ecosystems in NSW
The National Land and Water Resources Audit (NLWRA) has assessed overall riverine ecosystem health in NSW (NLWRA 2002b; Norris et al. 2001b). The assessment was based on macroinvertebrate data from the National River Health Program, as well as catchment and riverine habitat condition, hydrological disturbance and water quality. NLWRA's main findings were:
- NSW has the poorest aquatic biota condition of any Australian State or Territory, with macroinvertebrate communities impaired along 50% of the length of the rivers assessed.
- The environmental condition of 97% of the assessed river length in NSW had been modified resulting in specific forms of degradation including:
– catchment disturbance from land-use changes and clearing in 90% of the assessed river length
– elevated levels of nutrients (especially total phosphorus) and suspended sediments in 97% of the assessed river length
– altered hydrologic regimes in 87% of the assessed river length
– modified aquatic habitat in over 70% of the assessed river length.
The National River Health Program provides information on the patterns of river ecosystem health in catchments across NSW. Between 1994 and 1999, the program gathered macroinvertebrate samples from 994 NSW river sites (including 301 reference sites) and used the Australian River Assessment System (AusRivAS) predictive model to determine the health of the sites sampled. While the sampling data is the same as that used for NSW State of the Environment 2000 (EPA 2000b), this latest assessment used revised heath ratings derived from Turak & Waddell 2001. For more information on AusRivAS and the use of macroinvertebrates as biological indicators, see EPA 2000b.
In its assessment, the National River Health Program classified river sites as:
- reference condition (indicating sites of least disturbance for each region and river type)
- significantly impaired (indicating a loss of 20–50% of macroinvertebrate families)
- severely impaired (indicating a loss of 50–80% of macroinvertebrate families)
- extremely impaired (indicating a loss of 80–100% of macroinvertebrate families).
The study findings on the patterns of river health in NSW are outlined below.
Eastern-flowing rivers of the North Coast
Reference condition sites were located in the relatively undisturbed forest areas of the escarpment and coastal plains of the Clarence, Hastings, Macleay, Bellinger and Manning catchments. Cleared areas, used mainly for crop production and grazing, were characterised by macroinvertebrate assemblages in a significantly impaired condition, with some severely impaired sites also present. This pattern was evident in cleared areas in the tablelands of the Macleay catchment, the coastal plain of the Clarence catchment, and the more extensively cleared Richmond catchment.
Most of the severely or extremely impaired sites were close to urban areas, particularly the larger urban centres on the coast.
Sydney, Hunter and Hawkesbury–Nepean catchments
The largest number of severely and extremely impaired sites were in the urban areas of Sydney, including the Georges, Parramatta and Lane Cove rivers, and the Hunter and Hawkesbury catchments. These were within, or close to, Sydney, Newcastle and Wollongong. Reference condition sites were found in the highly urbanised Georges catchment on undeveloped reserve land.
Away from the urban centres of the coast, sites were generally in better condition and classified mainly as reference condition or significantly impaired. These included the Hunter Valley, the sandstone plateau areas in the west of the Hawkesbury and Hunter catchments, the escarpment slopes of Wollongong, the Royal National Park in the Hacking catchment, and water supply reserves in the south of the Hawkesbury catchment.
Eastern-flowing rivers of the South Coast
In the largely forested far South Coast catchments of Moruya, Bega and Towamba, all but a few sites were classified as in reference condition. Remaining sites in these catchments were significantly impaired, with no severely or extremely impaired classifications recorded. Similarly, in the Clyde, Shoalhaven and Tuross catchments, most sites were classified as in reference condition or significantly impaired. The few severely impaired sites in these catchments reflected localised disturbances associated with dams, poorly constructed forest road crossings or urban centres, rather than indicating catchment-wide influences.
Pristine reference sites generally no longer exist in most lowland river catchments, particularly in western NSW. This means that many of the sites used in this assessment – even some found to be in reference condition – were affected by various human-induced disturbances. Consequently these results need to be viewed in a regional (relative) context rather than as absolute measures of river health.
Most sites in the extensive Murray–Darling Basin were in a significantly impaired condition. Catchments in the north of the basin, such as the Namoi, Condamine–Culgoa, Gwydir, Castlereagh, Border Rivers, Paroo and Warrego, were characterised by significantly impaired or reference condition sites, with few severely impaired sites evident.
Further south, most sites were in a significantly impaired condition, although there were many reference-condition sites along the Lachlan and Murrumbidgee rivers and in the tributaries of the Murray River.
Severely impaired sites were evident in many Murray–Darling Basin catchments and in most cases were associated with agricultural activities such as cropping and grazing.
A detailed assessment of ecosystem health in the Murray and lower Darling Rivers in NSW (Norris et al. 2001a) also highlighted the poor condition of these rivers.
Land use and freshwater riverine ecosystem health
The patterns of river health found in NSW catchments suggest that land use is a key determinant. Figure 5.1 groups the health ratings from the National River Health Program according to the dominant land-use type surrounding each site.
Figure 5.1: Status of AusRivAS sites in specified land-use categories
Source: EPA data, as at 2002
Note: 'Undeveloped and forested land' includes nature conservation and recreation, water storage and supply reserves, forestry and forest reserves areas. 'Grazing' includes limited grazing and grazing on native/improved pastures. 'Cropping' includes cropping and combined cropping and grazing areas.
Sites adjacent to undeveloped and forested land were mostly in reference condition, with relatively few impaired sites. Sites in grazing areas were also mostly in reference condition, but had a higher percentage of impaired sites compared with undeveloped and forested land-use areas. Sites in cropping areas had mostly significantly impaired sites, with more than 10% of these sites rated as severely or extremely impaired. This arises because cropping is a more intense form of agriculture than grazing. Most sites in urban areas were rated as severely or extremely impaired.
Response to the issue
The major responses to degraded freshwater ecosystem health have been to better manage river flow and extraction and reduce the impacts of different land uses. The most significant change in NSW in recent years has been the implementation of new water management rules under water-sharing plans, which are discussed in Water 5.2. Programs to improve land management to reduce impacts on the environment are discussed in the Land chapter.
Other responses to the degradation of freshwater ecosystem health are discussed below including:
- interim environmental objectives
- Government Statements of Intent in response to inquiries by the Healthy Rivers Commission
- Catchment Blueprints
- monitoring programs.
Interim environmental objectives for water quality and river flows were announced in 1999 for 31 NSW catchments. A State Water Management Outcomes Plan, prepared under the Water Management Act 2000, ensures that these objectives are addressed in water management plans (see Water 5.2 for more information).
Environmental objectives, and the strategies to achieve them, are set after independent inquiries into individual catchments by the Healthy Rivers Commission. Coastal catchments have been the focus of the commission's work to date with inquiries completed for the Williams, Hunter, Hawkesbury–Nepean, Clarence, Shoalhaven and Bega rivers, the North Coast rivers, and the Georges River–Botany Bay system. An inquiry into coastal lakes has also been completed. Government Statements of Intent, in response to these inquiries, commit agencies to strategies that will improve river and estuary health.
Following consideration of the commission's Securing Healthy Coastal Rivers report (HRC 2000), the NSW Government has adopted a set of principles to guide decision-making in relation to the protection of coastal rivers (NSW Government 2002). Another key commission recommendation is the development of a State Riverine Corridor Policy, which is currently being drafted. For more information on the status of riverine corridors, see Biodiversity 6.6.
Catchment Management Boards have prepared 21 regional integrated catchment management plans or 'Catchment Blueprints'. These set targets for improving the condition of natural resources, such as water, and reducing degradation processes, such as salinity. They also include management actions to achieve these targets over the next 10 years. Land 4.1 has more information on catchment management.
NSW also has a number of monitoring programs which assess the health of aquatic systems including:
- the interim State Water Monitoring Strategy, developed by the State Water Monitoring Coordination Committee to provide for the monitoring needs and requirements of State and local government
- the Integrated Monitoring of Environmental Flows program, which assesses the physical, chemical and biological impacts of river regulation (see Water 5.2)
- the Monitoring River Health Initiative, which assesses river health across Australia through partnerships between river management agencies, researchers and communities
- community monitoring by schools and community groups who test for macroinvertebrates as an indication of stream health under the Waterwatch and Streamwatch programs
- agricultural industry-based community monitoring, such as monitoring of environmental flows by the Lachlan Valley Water Users' Association and the healthy rivers, landscapes and biodiversity programs of the Ricegrowers' Association of Australia.
A range of other legislative tools, strategies and policies also assist in improving freshwater riverine ecosystem health, such as improving water quality (see Water 5.3), and protecting aquatic habitat (see Biodiversity 6.6) and aquatic biodiversity (see Biodiversity 6.7).
Effectiveness of responses
Many NSW rivers are degraded and under continuing pressure from environmental conditions which have been modified over decades. However, there has been much positive activity in recent years to address this problem.
Previous responses were generally not effectively integrated or focused on priorities. Substantial reforms, such as Catchment Blueprints, are currently being implemented to coordinate agency and community efforts and identify priority actions for management. New water-sharing plans are likely to make a significant contribution to river health over time.
Preparation of the riverine corridor policy is an important priority.
Everyone can play a part in improving the health of riverine ecosystems.
Government needs to ensure there is a comprehensive framework to coordinate the management of river resources and implement the State's objectives for water quality (NSW Audit Office 2003).
Water management plans will identify actions and assign responsibilities for improving water quality and riverside vegetation as well as environmental flows. It will be important that riverine corridors, including tributary streams, are protected from agricultural activities and the urban development process.
Regional service providers need to integrate the provision of water supply, sewerage and stormwater management in order to maximise environmental benefits, including river health, as well as economic benefits to the consumer and the utilities.
Government agencies should assist councils to undertake regional assessments into the capacity of their waterways to sustain desired land uses and integrate them with achievable river health goals. Government Statements of Intent on Healthy Rivers Commission inquiries provide direction and guidance in this area.
Land managers need to retain soil and vegetation on-site. This is particularly important for cropping and extensive grazing activities as well as urban land development. Buffer zones between these activities and river corridors would improve riverine health. Graziers should also manage stock access to streams.
Individuals can do simple things to help reduce water pollution and protect waterways, such as keeping street gutters and drains clear of litter and grass clippings and reducing the amount of fertiliser being used in their catchment. The EPA, Department of Infrastructure, Planning and Natural Resources, Sydney Catchment Authority, Sydney Water and Hunter Water all have more information. Individuals can also get involved in community monitoring programs, such as Streamwatch and Waterwatch.
2.1 Population and settlement patterns
4.1 Land-use changes
4.2 Soil erosion
4.3 Induced soil salinity
5.2 Surface water extraction
5.3 Surface water quality
6.6 Aquatic ecosystems
6.7 Aquatic species diversity
6.9 Aquatic harvesting