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At a glance 
The issue Aquatic health looks at the condition and functionality of aquatic ecosystems of inland waters. A healthy aquatic ecosystem supports the biological, chemical and physical processes that are essential for maintaining good water quality, habitat and biodiversity. Monitoring aquatic health provides a way in which to assess changes from a baseline condition and to highlight the pressures on the systems arising from activities in the catchment. The aquatic health of Tasmania's inland waters is assessed by looking at the associated aquatic biota. This provides an integrative measure of a stream's condition, because aquatic biota respond to all aspects of water quality and quantity as well as habitat condition. Ideally, several biological measures would be useful in assessing aquatic health (e.g. fish, water plants, algae, and riparian vegetation) but the most extensive dataset available in Tasmania is for aquatic macroinvertebrate communities from the National River Health Program. This 'At a glance' section provides an overview of the aquatic health issue in Tasmania. More detailed information is available in the Aquatic Health Issue Report. Two indicators are included in the main report: River Health (AUSRIVAS) and Assessment of River Condition (ARC). A number of recommendations that are relevant to aquatic health issues are also provided. Favourable news - Tasmania has a higher percentage rate than most other States of unmodified river length based on environmental habitat and catchment criteria (NLWRA 2001).
- Sites in the World Heritage Area covering a large part of the south-west of the State are considered to be in pristine condition (Krasnicki et al. 2001).
- Tasmania is committed to monitoring the aquatic health of rivers as part of the National River Health Program and through the State of the Rivers reporting program.
- The large majority of regions in the State have been sampled through the National River Health Program, with the exception of the South-West Wilderness area.
- The development of a strategic framework for improved management of the environmental protection of freshwater ecosystem values has commenced in Tasmania. This is part of the implementation of the Water Development Plan for Tasmania. This framework includes a program to identify freshwater ecosystem values in Tasmania and the development of a conservation system based on comprehensive, adequate and representative principles.
Unfavourable news - The aquatic health of rivers in many parts of the State has been subject to degradation from land use and in-stream management practices.
- When both AUSRIVAS reference and test sites are considered, the macroinvertebrate communities (as indicators of aquatic health) in 30% of the riffle habitat sites, and 20% of the edgewater habitat sites, were found to be impaired relative to minimally disturbed and pristine conditions. Not all rivers and streams within the State were considered in the assessment.
- As part of testing the AUSRIVAS river health models in Tasmania, an assessment of selected test sites across the State with known or suspected impacts found that the macroinvertebrate communities were impacted at nearly half of the sites.
- The broader Assessment of River Condition (ARC) conducted at the river basin scale indicated that approximately 24% of the river length assessed across the State was biologically impaired (5,587km of river reaches were assessed out of a total of more than 166,000km of natural water courses in Tasmania-see Water Quantity and Water Use Issue Report).
- In comparison, approximately 63% of the river length assessed has been environmentally modified to varying degrees based on ARC habitat and catchment measures. Environmental data was available for 98% of the total river length assessed, with some sub-indices particularly lacking input data (e.g. hydrology). Data was not available for all rivers and streams within the State.
- There has been an increase in the number of small dams which affect aquatic health as a result of their cumulative impacts at catchment and regional scales. More information is contained in the Water Quantity and Water Use Issue Report.
- There are some gaps in the management of environmental issues associated with water management and development that affect aquatic health in Tasmania. These include the absence of a State conservation policy for rivers, wetlands, estuaries and groundwaters, and limited progress in determining environmental flow allocations for catchments across the State.
Uncertain news- Identifying the type and extent of changes requires comparisons with rivers that share similar environmental characteristics but are relatively undisturbed. However, there are limited minimally disturbed/pristine sites available to provide adequate baseline data for aquatic health measures in some heavily degraded river catchments (e.g. through urbanisation and/or agriculture). This is causing uncertainty in assessing the degree of aquatic health degradation for some rivers.
- As the primary objective of the AUSRIVAS river health assessment was to develop and test river health models, the study focused upon sites that were considered to be of regional concern. Test sites were generally chosen because a problem was known or suspected at the site. The Biological Index in the Assessment of River Condition (ARC) was also primarily based on these AUSRIVAS test sites. As a result the data available and presented here may potentially bias the assessment of aquatic health toward a poorer overall level of condition for the State.
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