The Sustainable Rivers Audit (SRA) is a systematic assessment of the health of river ecosystems in the Murray–Darling Basin (MDB), Australia. It has similarities to the United States’ Environmental Monitoring and Assessment Program, the European Water Framework Directive and the South African River Health Program, but is designed expressly to represent functional and structural links between ecosystem components, biophysical condition and human interventions in the MDB. Environmental metrics derived from field samples and/or modelling are combined as indicators of condition in five themes (Hydrology, Fish, Macroinvertebrates, Vegetation and Physical Form). Condition indicator ratings are combined using expert-system rules to indicate ecosystem health, underpinned by conceptual models. Reference condition, an estimate of condition had there been no significant human intervention in the landscape, provides a benchmark for comparisons. To illustrate, a synopsis is included of health assessments in 2004–2007. This first audit completed assessments of condition and ecosystem health at the valley scale and in altitudinal zones, and future reports will include trend assessments. SRA river-health assessments are expected to play a key role in future water and catchment management through integration in a Basin Plan being developed by the Murray–Darling Basin Authority for implementation after 2011. For example, there could be links to facilitate monitoring against environmental targets.

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Microinvertebrates play a critical role in riverine food webs, and recent studies have hypothesized that slackwaters, non-flowing regions associated with the main channel, are important for their reproduction and recruitment. However, little is known regarding the population and community dynamics of microinvertebrate communities in slackwater regions, or how they compare with those in mid-channel regions. This study examined microinvertebrate communities in the epibenthic and pelagic zones of slackwater and mid-channel regions (i.e. four habitats) of an Australian floodplain river in relation to physico-chemical parameters and food availability (as estimated by chlorophyll-a concentration) between September 2005 and November 2006. Results from this study indicate that microinvertebrate abundance and diversity were greater in slackwater habitats than midchannel habitats overall, corresponding with the slower current velocities associated with the former. Nevertheless, communities in all four habitats were most abundant and diverse in late spring (coinciding with an increase in water temperature), and followed similar seasonal trajectories in terms of density, taxon richness and community structure. These findings support the view that slackwaters are important for in-channel microinvertebrate production, and suggest that animals frequently disperse (either actively or passively) among slackwater and other main channel regions year round. Given the critical importance of microinvertebrates in riverine food webs, rivers should be managed with a view to maintaining a natural variety of accessible slackwater regions in order to support the production and survival of microinvertebrate communities.

The regulation of Australian lowland rivers such as the River Murray has resulted in changes to the flooding characteristics of many associated wetlands. It has been suggested that these changes in flooding have changed the pattern of response of many wetland biota. The substantial variability in the size and shape of these wetlands makes limited field observations difficult to interpret. To overcome this variability 16 experimental billabongs were constructed in which factors that may cause changes to populations within billabongs could be manipulated. In this paper we report on experiments that test the hypothesis that changing the pattern of flooding alters the density and diversity of rotifers and microcrustaceans in billabongs. The experimental billabongs were sampled fortnightly for two years. During this time four flood events were imposed. Flooding of the experimental billabongs resulted in increased microcrustacean abundance. Rotifer abundance rarely increased following flooding. Changing the time of flooding did not modify this response. Observed changes in community structure following flooding result from changes in the relative densities of taxa already present rather than changes in the community composition.

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The River Murray, Australia, is a highly regulated river from which almost 80% of mean annual flow is removed for human use, primarily irrigated agriculture. Consequent changes to the pattern and volume of river flow are reflected in floodplain hydrology and, therefore, the wetting/drying patterns of floodplain wetlands. To explore the significance of these changes, macroinvertebrate samples were compared between permanent and temporary wetlands following experimental flooding in a forested floodplain of the River Murray. Weekly samples from two permanent wetlands and four associated temporary sites were used to track changes in macroinvertebrate assemblage composition. Non-metric multidimensional scaling was used to ordinate the macroinvertebrate data, indicating consistent differences between the biota of permanent and temporary wetlands and between the initial and later assemblages in the temporary sites. There were marked changes over time, but little sign that the permanent and temporary assemblages were becoming more alike over the 25-week observation period. The apparent heterogeneity of these systems is of particular importance in developing river management plans which are likely to change flooding patterns. Such plans need to maintain a mosaic of wetland habitats if floodplain biodiversity is to be supported.

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