Monitoring river health using the Australian River Assessment System (AUSRIVAS)
The Australian River Assessment System ((AUSRIVAS) is a Nationally
consistent rapid bioassessment methodology which uses aquatic
macroinvertebrates as a means of assessing the ecological condition of rivers
and streams. AUSRIVAS models have been developed to predict the
macroinvertebrate fauna that would be expected to occur at a site in the
absence of environmental stress such as pollution or habitat degradation. In
Tasmania, this is the main tool used to examine and report on the environmental
condition of rivers and streams.
The main focus of this bioassessment approach is the sampling of aquatic macro-invertebrates.
Aquatic macroinvertebrates (such as insects, snails and worms) are now well recognised as powerful tools for assessing river health. They can - by their presence or absence - tell us a lot about the condition of our waterways.
Aquatic macroinvertebrates are sensitive to changes in habitat and water quality. Some species are known to have particular tolerances to environmental factors such as temperature or levels of dissolved oxygen. Other information can be obtained from the number of species found at a site (diversity), and the number of animals found at a site (abundance).
By sampling aquatic macroinvertebrates from relatively undisturbed rivers, researchers and community groups, can find out the range of species that should be present in undisturbed and unpolluted river habitats.
The basic approach to sampling and assessmentEach site is sampled using a rapid bioassessment technique. This
involves collecting macroinvertebrate
samples from two habitats.
- A sample is taken from shallow, fast flowing areas with a stony or rocky
substrate. This type of habitat is called a riffle. In order to collect a
sample, the stream bed is disturbed by the sampler's feet and dislodged animals
are swept into a net by the current.
Edgewater Sample - A second sample is collected by sweeping the net
along the edgewater or margins of the river and in backwaters and pools which
have slow currents or no flow. Aquatic plants (macrophytes), which provide
additional habitat for aquatic macroinvertebrates, are often found in these
edgewater habitats and are included in the sweep sample.
Physical (vegetation and substrate composition) and chemical (water quality)
properties are also measured. The aquatic macroinvertebrates are sorted on site
and then taken back to the laboratory for identification.
Once the taxa within the sample have been
identified and enumerated, these data – along with additional physical and
chemical predictor variable data – are ready to be uploaded to the AUSRIVAS bioassessment
These are accessible at: http://ausrivas.ewater.org.au/ausrivas/index.php/home/introductionmainmenu,
where details about how to prepare and enter the data are provided.
AUSRIVAS model outputs
The AusRivAS models provide a number of river
health ratings which can be used to gauge the improvements or declines in river
health at a site over time. This can be useful for community groups and NRM
agencies monitoring the condition of their catchments. On a broad scale the
models are useful tools for river managers to assess the environmental benefit
of catchment management practices.