Waterbird synchrony across Australia's highly variable dryland rivers – Risks and opportunities for conservation

The world's freshwater biotas are declining in diversity, range and abundance, more than in other realms, with human appropriation of water. Despite considerable data on the distribution of dams and their hydrological effects on river systems, there are few expansive and long analyses of impacts on freshwater biota. We investigated trends in waterbird communities over 32years, (1983-2014), at three spatial scales in two similarly sized large river basins, with contrasting levels of water resource development, representing almost a third (29%) of Australia: the Murray-Darling Basin and the Lake Eyre Basin. The Murray-Darling Basin is Australia's most developed river basin (240 dams storing 29,893GL) while the Lake Eyre Basin is one of the less developed basins (1 dam storing 14GL). We compared the long-term responses of waterbird communities in the two river basins at river basin, catchment and major wetland scales. Waterbird abundances were strongly related to river flows and rainfall. For the developed Murray-Darling Basin, we identified significant long-term declines in total abundances, functional response groups (e.g., piscivores) and individual species of waterbird (n=50), associated with reductions in cumulative annual flow. These trends indicated ecosystem level changes. Contrastingly, we found no evidence of waterbird declines in the undeveloped Lake Eyre Basin. We also modelled the effects of the Australian Government buying up water rights and returning these to the riverine environment, at a substantial cost (>3.1AUD billion) which were projected to partly (18% improvement) restore waterbird abundances, but projected climate change effects could reduce these benefits considerably to only a 1% or 4% improvement, with respective annual recovery of environmental flows of 2,800GL or 3,200GL. Our unique large temporal and spatial scale analyses demonstrated severe long-term ecological impact of water resource development on prominent freshwater animals, with implications for global management of water resources.

Is fish biomass in dryland river waterholes fuelled by benthic primary production after major overland flooding?

Aim To investigate the phylogeographic structure of the widespread freshwater prawn, Macrobrachium australiense, within and between major Australian drainage basins using mitochondrial sequence data. This will enable the investigation of historical connections between major drainages and examination of hypotheses of biogeographic associations among Australian freshwater basins.Location Inland, eastern and northern Australia.Methods Sequencing 16S rRNA and ATPase 6 protein coding mitochondrial DNA genes from M. australiense from 19 locations from inland, eastern and northern Australia.Results Within drainage basins, haplotype trees are monophyletic, with the exception of the Finke River from the Lake Eyre Basin. Macrobrachium australiense from the two main inland drainages, the Murray–Darling and Lake Eyre Basin are divergent from each other and do not form a monophyletic group, instead the Murray–Darling Basin haplotypes clade with eastern coastal haplotypes. Haplotypes from neighbouring eastern coastal drainages were found to be quite divergent from each other.Main conclusions The phylogeographic relationships among M. australiense suggest that the two major inland drainages, the Murray–Darling Basin and the Lake Eyre Basin, are not biogeographically closely associated to each other. Instead the Murray–Darling Basin is more closely allied with the eastern coastal drainages across the Great Dividing Range. Despite their proximity the neighbouring southeast Queensland coastal Mary and Brisbane Rivers are also biogeographically divergent from each other. The results also indicate that the Finke River appears to have been isolated from the remainder of the Lake Eyre Basin catchment for a significant period of time.

The viviparid snail Notopala is distributed throughout the rivers and other waterbodies of the northern tropical regions of Australia, extending south into the Lake Eyre and Murray-Darling Basins. Despitearecentexarnination of the WesternAustralian viviparids the taxonomy of a number of species, especially those from the Lake Eyre and Murray-Darling Basins, is unclear. Principal Components Analysis was used on seven shell measurements to determine which morphometric characters best delineate the species. Umbilicus width and aperture lip length explained most of the variation. The results suggest that there are four species of Notopala in Australia: N. waterhousii andN. essingtonensis in the north and northwest, N. sublineaca in the Lake Eyre and Murray-Darling Basins and N. hanleyi in the Murray-Darling Basin. With lheapparentextinction of both species ofNotopala in the natural environment of the Murray-Darling Basin, the population of N. hanleyi surviving in a Murray irrigation pipeline and the ...

Water is scarce in the Lake Eyre Basin in the heart of Australia. The region goes through natural cycles of boom and bust, and the flooding of the basin rivers is accompanied by spectacular responses from wildlife and vegetation. However, the Lake Eyre Basin faces the threat of diversion of water from rivers and wetlands and development of floodplains for irrigation and mining. Around the world, such water resource developments have caused widespread degradation of rivers and loss of habitats. Lake Eyre Basin Rivers outlines the environmental, social and economic values of the rivers from a diverse range of perspectives, including science, tourism, economy, engineering, policy, Traditional Owners and pastoralists. It describes the current state of the environment and the past and ongoing threats to the river systems, drawing on stories from the Murray-Darling Basin. It also provides direction for ensuring that the rivers remain free-flowing to service the environment and future generations. This book is a valuable reference for environment and government agencies, industries and policy-makers concerned with the region and will be of interest to the communities of the Lake Eyre Basin.

Climate change threatens water resources from local to global scales. However, there are significant challenges in assessing climate risk for large river basins, especially those with multiple jurisdictions and competing management objectives. Traditional methods follow a top-down approach, where the impacts of climate projections by climate models are simulated using hydrological and water resource models. While these methods can provide a detailed snapshot of how rivers are impacted under a small number of projected future climates, their computational burden, and challenges in linking water resource models owned by different jurisdictions mean it is difficult to robustly explore the implications of aleatory (from hydroclimate variability) and epistemic (from hydroclimate change) uncertainty. Unlike top-down approaches, bottom-up approaches can be used to better understand vulnerability under a range of possible future climate. Bottom-up approaches begin with a sensitivity analysis of important management objectives to multiple hydroclimate stressors. Unfortunately, bottom-up approaches are constrained when using complex system models in large river basins, as their methodologies typically require many times more simulations than top-down approaches.The Murray Darling basin (MDB) is Australia’s most significant river basin. Irrigation in the basin supports over $30 billion (AUD) in agriculture and livelihoods for the 2.4 million residents. The MDB has significant environmental values, with RAMSAR wetlands, many endemic and threatened species, and it is the traditional land of over 50 first nations groups. We assessed the impacts of climate change on basin-wide inflows and key indicator sites using both top-down and bottom-up approaches. We stochastically generated multiple sequences of future hydroclimate conditions, which helps separate the influence of climate variability from climate change. We deliberately traded-off detail in our assessment by deriving simple functional relationships between sub-basin inflows and 21 key indicator sites using existing scenarios from the complex jurisdictional water resource models. This allowed us to assess far more replicates of stochastic data, more climate scenarios, and conduct a more rigorous stress test within the bottom-up framework than would normally be permitted using complex models.The top-down approach provides a scenario-based assessment of likely conditions for water resources in the MDB, and spatially coherent projections of future inflows and river management metrics. The bottom-up approach provides more insight into spatial differences in sensitivity across the river catchments that make up the MDB, and can be used to both augment and help interpret outcomes from the top-down approach. The bottom-up approach also yields important thresholds in hydroclimate conditions which compromise basin-wide objectives (assessed through flow at the Murray River mouth which prevents the important lower lake system from becoming too saline). We consider top-down and bottom-up approaches to be complementary in assessing and adapting river systems to the impacts of climate change.The simple methods used here are complementary with other more detailed impact models. The ease of undertaking simulations and computational efficiency means simple methods can filter down the range of possible conditions or stressors that contribute to uncertainty, allowing a more targeted set of simulations to be undertaken using detailed, but costly, water resource models.

AimMajor knowledge gaps exist regarding the evolution of arid zone organisms. For freshwater species with high dispersal potential, little is known if historical aridification influenced connectivity across drainage divides and impacted on their divergence and diversification. We tested the hypothesis that the historical aridification of Australia promoted the isolation and influenced the demographic histories and evolutionary divergence of a migratory group of freshwater obligates.LocationCentral and eastern Australia; Murray–Darling Basin (MDB), Lake Eyre Basin (LEB), Fitzroy Basin (FIT).TaxonThree lineages of golden perch (Macquaria ambigua), a widespread fishery resource from inland Australia.MethodsWe obtained genome‐wide data for golden perch sampled throughout their range. Phylogenetic relationships were reconstructed using maximum likelihood. Species distribution modelling was used to predict contemporary and past distributions for the three lineages and to develop hypotheses regarding their biogeographic and demographic histories. Hypotheses were independently tested using coalescent simulations in fastsimcoal and DIYABC with the genomic dataset.ResultsWe found evidence for three reciprocally monophyletic lineages that have experienced little to nil genetic connectivity since divergence. Coalescent models suggest that the coastal (FIT) and inland (MDB and LEB) lineages diverged ~103 thousand years ago (ka), followed by the split of MDB and LEB lineages ~58 ka. These timings agree with reductions of large freshwater environments in Australia during the late Pleistocene. Species distribution models show an extreme decrease in habitat during the Last Glacial Maximum ~21 ka, consistent with inferred demographic contractions in coalescent tests.Main conclusionsWe reveal that aridification of Australia during the late Pleistocene has driven and reinforced the divergence of a migratory freshwater obligate. Our findings are important for informing the conservation management of aquatic organisms under climate change. This work further demonstrates the value of using species distribution modelling to formulate diversification hypotheses and to improve interpretation of coalescent analyses.

Alluvial floodplain gully erosion in dryland rivers – An overlooked source of sediment with implications for river condition and management

Water quality, along with hydrology, plays an important role in the spatial and temporal dynamics of a range of ecological patterns and processes in large rivers and is also often a key component of river health assessments. Geology and land use are significant drivers of water quality during flow periods while during periods of no-flow, local-scale factors such as evaporation, groundwater influence and the concentration and precipitation of compounds are important. This study explored the water quality changes in two Australian dryland rivers, the Cooper Creek (Lake Eyre Basin) and the Warrego River (Murray–Darling Basin), across different hydrological phases over several years. Water quality varied both spatially and temporally; the greatest spatial variability occurred during the no-flow phase, with temporal changes driven by flow. Concentrations of major anions and cations also varied spatially and temporally, with an overall cation dominance of calcium and magnesium and an anion dominance of bicarbonate. This bicarbonate dominance contrasts with previous data from inland lentic systems where sodium chloride was found to dominate. Such extreme spatial and temporal variability hampers successful derivation of water quality guidelines for these variable rivers and suggests such guidelines would need to be developed with respect to ‘flow phase’.

The proliferation of alien fish in dryland rivers potentially obstructs the maintenance of river health. Modified flow regimes are hypothesised to facilitate invasions by alien fish but in unregulated dryland rivers, large floods provide a recruitment advantage for native over alien species whereas droughts favour alien species. We tested these hypotheses by using data from a 3-year study (2000–2003) of fish populations in the unmodified rivers of the Lake Eyre Basin (LEB) of Australia. Results from a lower reach of Cooper Creek were compared with those of an earlier study (1986–1992). During both periods, large floods occurred, with return periods ranging from >1 in 5 to >1 in 25 years. In the lower Cooper, decreases in the abundance of alien species relative to native species, and dramatic increases in recruitment of native species, were observed during a 1–3-year period following large floods. In two other rivers in 2000–2003, there was no statistically significant change in the already low abundances of alien species. We suggest that the naturally variable hydrological regimes and native-dominant fish assemblages of the unregulated LEB rivers afford some resistance to the establishment and proliferation of alien fish through flood and drought conditions.

ABSTRACTShell shape varies markedly in freshwater mussels in the order Unionoida. Freshwater mussels belonging to the genus Velesunio (Family Hyriidae) are distributed widely in the rivers and wetlands of Australia, with recent molecular evidence suggesting at least three more species within the genus Velesunio than previously described using shell morphology. This study explored differences in shell morphology between and within two major Australian drainage basins: the Murray–Darling and Lake Eyre. Differences in shell shape among the species were difficult to detect with variability in morphology, showing the greatest difference between drainage basins. For all species, there were significant differences in morphology between rivers within basins; Shells from the Lake Eyre Basin, showed small differences in shell morphology among with greater species level differences in morphology at the site scale in the Murray–Darling Basin. Extreme flow variability of Lake Eyre Basin rivers means they spend considerable time as lentic waterholes. In contrast, the rivers of the Murray–Darling Basin, while still highly variable, spend a far greater time under flowing conditions. Thus, the variability in shell morphology among sites may reflect local hydraulic variability rather than large-scale flow variability.

The Lake Eyre Basin, one of the world's last unregulated wild river basins, covers almost one sixth of the Australian continent, with large areas of connected wetlands (73 903 km2), including floodplains, lakes, waterholes and river channels. Few data existed and so we used literature and government biotic and abiotic data and anthropogenic impacts to assess the conservation risk of the ecosystem as Least Concern (IUCN Red List criteria for ecosystems, version 2.0). This was based on limited distributional change and low levels of degradation or anthropogenic threatening processes. The approach could be applied to ecosystem assessments of other large river basins around the world, given the Lake Eyre Basin occupies one extreme (unmodified) while the Aral Sea (collapsed), previously assessed, occupies the other extreme (highly modified). River flow analysis with available biotic data is critical for risk assessment as well as identification and tracking of long‐term threats. Assessment was possible at this large basin scale and appropriate, given the critical importance of connectivity but could also occur at finer spatial scale. Increased diversions for irrigation, mining impacts on floodplains and projected increased temperatures threaten the current status (Least Concern) of the connected wetlands of the Lake Eyre Basin ecosystem.

ABSTRACTDryland rivers are differentiated from other rivers by high flow variability. They are also particularly important for river regulation to secure supplies for irrigation agriculture and to meet other human demands. The dilemma is that river regulation not only has considerable benefits for human societies in achieving water security and providing flood protection but also represents perhaps the greatest cause of hydrological interference by humans. In Australia, the Murray–Darling basin with only 21 mm of run-off had committed over 90% of the exploitable yield to consumptive irrigation use as early as the late 1970s. Here, perhaps more so than in any other country, there arose an imperative to advance a new river science to support the environmentally sound management of regulated dryland rivers and Keith Walker was at the heart of that endeavour. In this short opinion piece, I offer observations on how his search for a “general model” has advanced over the past two decades.

ABSTRACTManaging large river basins for sustainability is a contentious social–ecological arena challenging traditional scientific and rational planning approaches to water and related natural resources governance. “Crises” are inevitable but double-edged: creating threats and uncertainties, but also new opportunities to shape trajectories of change and avoid adverse consequences. A case study of the large remote cross-border Lake Eyre Basin (LEB), in arid central Australia, shows how over two decades a series of social–ecological and political–administrative “crises” emerged, posing significant environmental and social dilemmas for water governance, while also opening up opportunities for institutional change. This article examines the role of crises in the emergence and evolution of water governance in the LEB, how they were perceived, the challenges and opportunities posed, social and institutional responses, and governance capacity outcomes. Finally, it reflects on emergent crises as opportunities for more systemic and adaptive change in large river basins.

Holocene palaeoclimatic variations as recorded offshore south-western South Africa