In the southern part of the South-east Coast division, less than 30% of stream length was found in good condition; only the catchments in eastern Gippsland had more than half their stream length in good condition.18 River health did not demonstrably change over the period 1999–2004. The condition of fish populations in coastal rivers in the northern part of the division was generally poor to moderate, while macroinvertebrate communities in most coastal river catchments were in fair to good condition.19
River health in the South Australian Gulf division, as indicated by macroinvertebrates, declined due to the effects of the prolonged drought. Wetland areas have been extensively modified, filled and drained since European settlement, and close to 90% of those in south-eastern South Australia have been lost. Along the Fleurieu Peninsula, approximately 30% of wetlands existing before European settlement remain, and just 1% of the original extent of wetlands remains in a pristine condition.20
Queensland lost more than 7000 hectares per year of wetlands from 1997 to 2003, mostly in the North-east Coast division. However, the river condition was good at almost 70% of sites monitored, based on macroinvertebrate communities. Northern regions tend to be in better condition than southern regions, with condition generally good in the wet tropics and the central region, and potentially of concern in south-east Queensland. Approximately 27% of the total length of streambank assessed for riparian vegetation condition was in poor condition (based on sampling in three catchments only). The number of native fish species across catchments remained the same as in 2003, but the number of exotic species increased by one in the Herbert, Mary and Warrego catchments. The major pressures on river condition were identified as changes in land-use and land-management practices, and changes to the natural flow regime. The Stream and Estuary Assessment Program report on the central freshwater biogeographic province of Queensland39 concluded that the overall river ecosystems in Central Province are in slightly disturbed condition (as measured by the ecological responses); the same study found that riparian condition was moderately disturbed, partly due to habitat removal and partly due to weeds.
Rivers and wetlands of the Gulf of Carpentaria division are in generally good condition.21
In Tasmania, an assessment of the ‘naturalness’ of inland waters of the Tasmania division17 found 114 175 kilometres (75%) of the state’s river length to be in near natural condition and 24 478 kilometres (16%) to be severely altered from the natural condition. Base levels of stream aquatic health were determined in 2003–04; approximately 49 of the 60 sites (82%) were in good condition (unimpaired), 10 sites (17%) were significantly impaired and 1 site (2%) was severely impaired. There was a small overall change in site condition between 2003–04 and 2005–06.
Assessment of lake naturalness in Tasmania indicated that 580 lakes (43%) are still in a natural or near-natural condition. However, only 6176 hectares (5%) of their total area has not been altered. Up to 110 274 hectares (81%) of the total lake area has been severely altered, and 20 591 hectares (15%) has been significantly altered. The discrepancy between the number and area of lakes altered is related to several large lakes that have been regulated and/or modified for hydro-electricity and/or abstraction.
More than half of Tasmania’s wetlands (12 171 hectares; 59%) and nearly three-quarters of their total area (153 604 hectares; 74%) are still in natural or near-natural condition, 7150 wetlands (35%) and 30 432 hectares (15%) of wetland area have been severely altered, and 1276 wetlands (6%) and 22 754 hectares (11%) of wetland area have been significantly altered.
A number of threatened species were associated with inland waters in Tasmania, including 14 species of freshwater plant, more than 30 riparian plant species and 76 species of freshwater fauna (including 12 native fish and 5 crayfish).
Only about 30% of Western Australia’s major rivers are in good condition, and most of these lie outside the South-west Coast division (Figure 4.11).40 Thirty-two per cent of major river basins (i.e. 12 of the 38 that are monitored) are in a largely unmodified state; most of these are in the North-western Plateau and Timor Sea divisions. Only 17% of remaining wetlands on the Swan Coastal Plain have high conservation significance, and wetland vegetation is being lost or degraded at the rate of more than 300 hectares per year. Information about the condition of other Western Australian wetlands is extremely limited.
The rivers and catchments of the Lake Eyre Basin are in generally good condition. In particular, the low level of hydrological modification means that critical aquatic ecosystem processes remain intact.41