Australia-Wide Assessment of River Health: Northern Territory AusRivAS Sampling and Processing Manual
J. Lloyd and S. Cook
Natural Resources Division, Department of Lands, Planning and Environment
Monitoring River Health Initiative Technical Report Number 19
Environment Australia, 2002
ISBN 0 642 54886 2
About this Manual
Rivers and streams in Australia are accessed and used by people for a variety of activities, ranging from extraction of drinking and irrigation water, industrial uses, stock watering to recreational pursuits. Recently, concern about the degradation of rivers and streams has prompted the introduction of various systems to assess river health. River health is difficult to define, but can be considered in terms of the degree of similarity between a river and unimpacted rivers of a similar type. Levels of impact on a river can therefore be determined by a comparison of the water quality, biological and physical characteristics of impacted rivers and also of rivers in pristine or untouched condition.
Traditional methods for assessment of riverine conditions have largely relied on sampling and monitoring of physico-chemical parameters (such as pH), which didn't necessarily provide an easily interpretable picture of the biological condition of the waterbody. More recently, an integrated approach has been implemented, whereby characteristics of a waterbody and surrounds, such as depth, width, degree of erosion on banks; flow characteristics; available habitats and their condition; water quality and also biological characteristics are measured and assessed. Impacts and stresses on a river system may arise from a number of different sources, for example through riparian vegetation clearing, changes in water quality through pollution inflow and stock access changing bank characteristics.
An impact on a river system may affect not only the physical characteristics and/or water quality of a river, but also the habitats and environment of the many different organisms making up the fauna and flora associated with that river. Each of these biological groups will respond in different ways to stresses in their environment. To assess the condition of Australian waterways, macroinvertebrates (water bugs) were adopted as biological indicators of water quality.
Macroinvertebrates (animals without backbones) live, for at least some part of their life history, in the aquatic system and are usually large enough to be seen with the naked eye. This group includes dragonflies, caddisflies, biting flies (eg. midges), mites, snails, mussels, prawns and crayfish. Macroinvertebrates were chosen because of their abundance and diversity nationally, their sensitivity to changes in water quality, and relatively good taxonomic knowledge. They are also limited in their ability to move from an area of river that is being adversely impacted, and will recolonise quite slowly after pulse pollution events. These animals have been utilised worldwide as good indicators of river and stream health and are increasingly used for rapid bioassessment.
The Monitoring River Health Initiative (MRHI) was developed in Australia as part of the National River Health Program (NRHP). One of the aims of the MRHI was to develop an ability to assess the biological condition of surface rivers and streams in Australia, based on the British model RIVPACS (River Invertebrate Prediction and Classification Scheme). The MRHI has resulted in the construction of a database containing biological and chemical information collected from reference sites - sites that are 'least impacted' by human activities - over a two year period in all states and territories. Outputs from the MRHI program have included the development of a nationally standardised methodology for biological sampling; standard taxonomic identification with quality assurance/quality control protocols and a replicable process to collect comparable data.
AusRivAS (Australian River Assessment Scheme) represents an integrated approach to river assessment combining all facets of the MRHI program and including the generation of mathematical predictive models for individual site assessment. These models enable prediction of macroinvertebrate taxa expected to occur at a site, (in absence of any stress impacting that site), and therefore a comparison between actual collected taxa (observed taxa) with predicted taxa can be made. This allows the site to be categorised relative to reference condition.
This manual describes the methodology used by the Northern Territory (NT) for bioassessment of rivers and streams in the NT, adopted from standard protocols outlined in the River Bioassessment Manual (Davies, 1994). This approach was used for the NT MRHI/AusRivAS programs, and consequent model formulation. The manual is intended as a working guide for groups or individuals wishing to follow the standardised protocol and to collect data that is able to be compared with reference data collected by the MRHI program.
The predictive models are formed from physical, biological and chemistry data collected from surface waters (freshwater). It should be stressed that the sampling and processing protocols specified in this document are not to be used for the bioassessment of wetland, saltwater or estuarine systems.
We are grateful for the assistance of Cyrus Edwards, whose knowledge of the NT AUSRIVAS techniques assisted greatly in the compilation of this manual.