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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Rivers - Assessment of River Condition - Tasmania
Tasmania River Assessment
Assessment Results
Tasmania, Australia's only island state, covers an area of 67,800 km2, has a coastline of 3000 km, and occupies 0.88 percent of the total Australian area. Tasmania is mountainous; highlands cover two thirds of the state, with much of the State above 1000 metres elevation. The entire south-west corner of the state is protected from development. The climate offers mild summers and cool winters, with much of the mountainous region in the west and south receiving over 3000 mm rainfall annually. In contrast rainfall in eastern parts of the State drop to around 750 mm per annum. The highlands are subject to snowfalls at any time of the year where and the temperature is likely to drop to freezing point up to 100 days a year.
The biological assessment of Tasmanian rivers showed that 76% of the river length assessed was in reference condition; most of the significantly impaired with 20-50 percent of the animal types lost. The environmental assessment found that around 65% of the assessed river length was modified, the majority of this in only moderately modified. This degradation was attributed to catchment disturbance, changes to the hydrological regime and to water quality.
More than half of the river length assessed had disturbed catchments, the majority of this attributable to land use activities. Over 25% of the river length able to be assessed for hydrological disturbance showed change, with a half of this length in substantially modified condition. Most of the four flow regime measures showed change. Only 23% of the total river length had sufficient hydrological data to enable disturbance to be assessed.
Riverine physical habitat has been altered in 41% of the river length assessed in Tasmania, principally as a result of changes to connectivity. Twenty three percent of the river length assessed had severely modified connectivity as a result of the number of dams that have been constructed. Around 40% of the river length assessed in Tasmania had altered water quality with elevated loads of suspended solids and total phosphorus in 36% of the river length.
Comparison of the Biota Index and the Environment Index
Ideally, scores for the two main indices would be similar for each basin. In general, the Biota Index does not demonstrate the same degree of degradation as the Environment Index. Reasons for this may include:
- macroinvertebrates may be insensitive to some environmental changes, including large-scale changes (e.g. changes in connectivity and catchment disturbance), and to changes in some riverine habitat components (e.g. changes in salinity). Other biota, such as streamside and aquatic plants, algae, fish or water birds, in addition to invertebrates would give a more comprehensive assessment of the cumulative effects of environmental change.
- there may be lags between environmental degradation and biotic condition (e.g. nutrient or sediment loads to streams); or
- an environmental component that would explain a biotic response was not measured (e.g. a toxicant).
Environment Index scores compared to Biota Index scores for all basins.
Further Information
- A key point of contact for river management in Tasmania is the Department of Primary Industries, Water and Environment. Information on Tasmanian water resources and their management can be found at http://www.dpiwe.tas.gov.au/inter.nsf/ThemeNodes/DREN-4VH8C4?open
- Exit to more information on the AUSRIVAS for an introduction, models, taxonomy and downloads.
- Assessment of River Condition: and audit of the ecological condition of Australian rivers (by R. Norris, I. Prosser, B. Young, P. Liston, N. Bauer, N. Davies, F. Dyer, S. Linke, and M. Thoms)(PDF 4418 KB)
- View the Audit's Australian Catchment, River and Estuary Assessment 2002
- View the Audit's Australian Agriculture Assessment 2001
- Link to Data Library to download data and metadata
- Link to the Map Maker to make a map using this information.
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