Summary 1. AusRivAS (Australian River Assessment Scheme) models were developed, using macroinvertebrates as indicators, to assess the ecological condition of rivers in Western Australia as part of an Australia‐wide program. The models were based on data from 188 minimally disturbed reference sites and are similar to RIVPACS models used in Britain. The major habitats in the rivers (macrophyte, channel) were sampled separately and macroinvertebrates collected were identified to family level. 2. Laboratory sorting of preserved macroinvertebrate samples recovered about 90% of families present when 150 animals were collected, whereas live picking in the field recovered only 76%. 3. Reference sites clustered into five groups on the basis of macroinvertebrate families present. Using seven physical variables, a discriminant function allocated 73% of sites to the correct classification group. A discriminant function based on seven physical and two chemical variables allocated 81% of sites to the correct group. However, when the same reference sites were re‐sampled the following year, the nine variable discriminant function misallocated more sites than the seven variable function, owing to annual fluctuations in water chemistry that were not accompanied by changes in fauna. 4. In preliminary testing, the wet season channel model correctly assessed 80% of reference sites as undisturbed in the year subsequent to model building (10% of sites were expected to rate as disturbed because the 10th percentile was used as the threshold for disturbance). Nine sites from an independent data set, all thought to be disturbed, were assessed as such by the model. Results from twenty test sites, chosen because they represented a wide range of ecological condition, were less clear‐cut. In its current state the model reliably distinguishes undisturbed and severely disturbed sites. Subtle impacts are either detected inconsistently or do not affect ecological condition.

-Fifty-six sites, representing 53 wetlands, were surveyed in the southern Carnarvon Basin in 1994 and 1995 with the aim of documenting the waterbird and aquatic invertebrate fauna of the region. Most sites were surveyed in both winter and summer, although some contained water only one occasion. Altogether 57 waterbird species were recorded, with 29 292 waterbirds of 25 species on Lake MacLeod in October 1994. River pools were shown to be relatively important for waterbirds, while many freshwater claypans were little used.At least 492 species of aquatic invertebrate were collected. The invertebrate fauna was characterized by the low frequency with which taxa occurred: a third of the species were collected at a single site on only one occasion. Patterns of occurrence were not strongly seasonal. Many undescribed species were found and many range extensions were. recorded, reflecting lack of previous aquatic invertebrate work in the region. The level of regional endemicity could not be assessed adequately, although it is probably comparatively low. In terms of their invertebrate fauna, five types of wetlands were distinguished: river pools, rock pools and larger flowing streams; seeps, springs and smaller creeks; freshwater claypans; birridas; and Lake MacLeod. Environmental factors to which invertebrates appeared to respond were ratio of calcium/ alkalinity, total dissolved solids, turbidity, colour, flow, longitude and nutrients, although some factors were inter-correlated.Additional surveys should find extra species of waterbird and, more particularly, aquatic invertebrate using wetlands of the southern Carnarvon Basin. For many invertebrates, occurrences are too sparse for effective protection of species within a nature reserve system and other mechanisms will be required to ensure their conservation. Comparison of site classifications based on waterbird, aquatic invertebrate and plant data showed patterns among sites identified using one element of the biota did not reflect patterns shown by other elements. This suggests that, until further work has identified an element that reflects the whole wetland community, as many biotic elements as possible should be surveyed.

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Many regions across the globe are shifting to more arid climates. For shallow lakes, decreasing rainfall volume and timing, changing regional wind patterns and increased evaporation rates alter water regimes so that dry periods occur more frequently and for longer. Drier conditions may affect fauna directly and indirectly through altered physicochemical conditions in lakes. Although many studies have predicted negative effects of such changes on aquatic biodiversity, empirical studies demonstrating these effects are rare. Global warming has caused severe climatic drying in southwestern Australia since the 1970s, so we aimed to determine whether lakes in this region showed impacts on lake hydroperiod, water quality, and α, β and γ diversity of lake invertebrates from 1998 to 2011. Seventeen lakes across a range of salinities were sampled biennially in spring in the Wheatbelt and Great Southern regions of Western Australia. Multivariate analyses were used to identify changes in α, β and γ diversity and examine patterns in physicochemical data. Salinity and average rainfall partially explained patterns in invertebrate richness and assemblage composition. Climatic drying was associated with significant declines in lake depth, increased frequency of dry periods, and reduced α and γ diversity (γ declined from ~300 to ~100 taxa from 1998 to 2011 in the 17 wetlands). In contrast, β diversity remained consistently high, because each lake retained a distinct fauna. Mean α diversity per-lake declined both in lakes that dried and lakes that did not dry out, but lakes which retained a greater proportion of their maximum depth retained more α diversity. Accumulated losses in α diversity caused the decline in γ diversity likely through shrinking habitat area, fewer stepping stones for dispersal and loss of specific habitat types. Biodiversity loss is thus likely from lakes in drying regions globally. Management actions will need to sustain water depth in lakes to prevent biodiversity loss.

Three elements of wetland biodiversity (aquatic invertebrates, waterbirds and overstorey vegetation of the wetland edge) have been monitored since 1998 at Lake Eganu and Paperbark Swamp in the Western Australian Wheatbelt to provide information about the changes occurring in wetland biodiversity in a landscape that is severely affected by dryland salinization. Changes in extent of wetland vegetation since the 1960s were examined using historical aerial photographs and waterbird use of Lake Eganu during the early 1980s was compared with recent waterbird survey results. Lake Eganu, which is within a major drainage line, started to become salinized in the mid-1960s, about 70 years after land clearing began in the catchment, and its salinity has increased an order of magnitude. The extent of wetland overstorey vegetation and the richness of freshwater aquatic invertebrates have both declined about 80%. Waterbird richness has also declined over the past 20 years, with changes in species composition. Salinization has not occurred at Paperbark Swamp, which is in a small catchment off the main drainage line, and there has been no consistent change in the biodiversity elements monitored.