Search

• Estimates of the time of emergence of climate change (ToE) for Australian rivers. • Stochastic data generation helps to better define baseline variability. • Uncertainty in ToE represented by 37 CMIP6 projections and 3 emissions scenarios. • ToE in river flows can precede ToE in precipitation by up to 50 years. • ToE substantially delayed or avoided in a low emissions pathway (SSP1-2.6). Climate change impacts on river flows are leading to substantial changes in water availability for human and natural systems. The significance of these impacts largely depends on the degree of change relative to natural variability. The 'Time of Emergence' (ToE) is the point in time (past or future) when the signal of climate change emerges from the noise of background variability. The ToE has been assessed for some climate variables but rarely streamflows. Here we investigate ToE of changes in streamflow across Australia for various characteristic periods relevant to different water management objectives. We assess the uncertainty in ToE estimates from different emissions pathways and a large ensemble of CMIP6 climate model projections. ToE is likely to occur earlier in hydrologic systems subject to low natural variability than those subject to high variability, and to systems that are vulnerable to failure over longer rather than shorter periods. There are clear regional differences in the patterns of ToE, with changes first emerging in south-west regions of Australia, followed by the south-east, then east and north. We estimate that ToE has already occurred in over 10% of sampled rivers for longer characteristic periods, primarily in south-west Australia. Importantly for planning, the results show that ToE in flows precedes ToE in precipitation by up to 50 years due to compounding effects of changes in annual precipitation, precipitation seasonality, and increasing temperatures. The number of catchments projected to have reached ToE by 2080 is heavily influenced by the trajectory of future emissions. A low emissions pathway generally consistent with aspirational goals of the Paris Climate Agreement (SSP1-2.6) substantially delays the emergence of significant hydrological change by up to 50 years, or negates emergence entirely by 2080, depending on location. Our methods can be applied to catchments globally, and our findings have implications for the prioritisation of climate adaptation efforts across different river systems and the urgency of continued action on climate change mitigation. [ABSTRACT FROM AUTHOR]

The rivers of the south-eastern Murray-Darling Basin (MDB) and the associated irrigation areas of the southern riverine plain (SRP) in south-eastern Australia have undergone major hydrological changes over the last 30 years. These include a period of lower rainfall; a rebalance of surface water diversions between consumptive and environmental water uses under the MDB Basin Plan, improvements in water infrastructure; water trade out of the region; and falling groundwater levels. All these changes increase losses from streams to groundwater systems; potentially leading to the need for greater releases from dams to maintain baseflow in the major rivers. Baseflow is important for conveyance of water, water quality and baseflow-dependent ecosystems during dry periods. Hydrological changes in the SRP will reduce the streamflow by 2029–30 by an estimated 80 to 320 GL/yr. Further hydrological changes by 2029–30 will reduce the streamflow by another 50 GL/yr in the following decade. This is the first assessment of the cumulative stream impacts of the SRP and is relatively lower than previous assessments for single drivers. The current approach of mitigating unexpected losses is to increase conveyance loss budgets as required. This could be extended to mitigate the lower end of potential impacts; but further steps to reduce losses may be required towards the upper end. Further actions include a review of extraction limits for surface water and groundwater, trigger levels, and a greater shift towards conjunctive water management. Groundwater extraction, which has dominated impacts, is increasing from a relatively low proportion of the extraction limit in Goulburn-Murray Sedimentary Plain and shallow aquifers of the SRP. Over time, climate change will become more dominant as a driver. Most monitoring required to support mitigation already exists, but data is not collated or reported in a form relevant for stream impacts. Modelling also needs to be updated with reporting of more relevant outputs. [ABSTRACT FROM AUTHOR]

For over two decades, Australia has sought to address the effects of the over allocation of water resources in the Murray-Darling Basin through implementation of the Murray Darling Basin Plan (2012). It is increasingly apparent that the impacts of climate change on surface runoff and water demand will profoundly impact rivers, potentially negating the Basin Plan's achievements. It will be critical that we use the lessons from the last two decades to inform adaptation to climate change. Environmental water allocations over the last decade have focussed on providing base flows, freshes, and overbank flows, within a Natural Flow Regime paradigm. In a climate-changed world managers have three broad options. The first would be to continue to pursue single loop adaptive management making improvements within the existing framework. The second option would be to adapt the system approach to focus on a subset of sites, akin to maintaining aquatic reserves. The third option would be to move flow management away from the natural flow paradigm to a more functional regime. This approach would invoke the second adaptive management loop by evaluating options for adaptation and developing processes for navigating trade-offs among social, economic, cultural, and environmental values and between protection, restoration, and adaptation. Changes in water availability because of climate change will require more than incremental adaptation (first loop adaptive management) and will necessitate consideration of either protecting a smaller suite of spatial areas or a smaller set of functional outcomes. This requires profound change to some of the Basin Plan's approaches to environmental flow management. The review of the Basin Plan in 2026 provides a rare opportunity to adapt the Basin Plan from a foundation of protect and restore to one that includes adaptation, and this will require substantive changes to the Basin Plan (second loop adaptive management). [ABSTRACT FROM AUTHOR]

This study combined a catchment model and one-dimensional lake model (GLM-AED) to simulate the response of hydrodynamics and water quality of subtropical Advancetown Lake (South-East Queensland, Australia) to future changing climates from 2040 to 2069 and 2070 to 2099 under Representative Concentration Pathway (RCP) 4.5 and 8.5 and increased water demand from a 50% increase in population over current levels. The simulation adequately reproduced water temperature (RMSE of 0.6 °C), dissolved oxygen (DO) (RMSE of 2 mg/L), and other water quality variables, such as nitrogen, phosphorus, and chlorophyll a (Chl-a). Warming temperatures dominated the change in thermal structure and hydrodynamic status of the lake under future climate change conditions. Projected changes in precipitation and hydrological response from the upstream catchment might, however, partly offset the warming temperatures under future climate change. Increased water withdrawal due to population growth, which involved water extraction from the epilimnion, showed antagonistic effects on water stability compared to those from climate change. Under a high emission scenario of RCP8.5 during the 2080s, there is an increased likelihood of winter turnover failure in Advancetown Lake. Nutrient concentrations were simulated to decrease from reduced catchment loads under future climate change conditions. However, Chl-a concentrations were simulated to increase, especially during the period after winter turnover, under these future conditions. The depth of the hypoxia front during stratification is expected to decrease and move towards the water surface, attributable to the warming water temperatures and prolonged thermal stratification, which might affect biogeochemical processes and exchange fluxes between the hypolimnion and bottom sediments. These potential changes may present challenges for water resource management under future conditions of climate change and population growth. [ABSTRACT FROM AUTHOR]

Restoration programmes for degraded aquatic ecosystems frequently focus on flow restoration or reinstatement, including recovery targets for volumes of water to be used for environmental benefit. Australia's Murray–Darling Basin is an example of a major system undergoing substantial water reform to balance the needs of competing users, including the environment, within the constraints of an arid climate. This reform revolves around accounting for finite volumes of water that have been shared amongst water users. We argue that while recovering water will provide good outcomes, as a sole intervention, it is not enough to deliver the desired environmental benefits of the reform given the significantly altered state of the catchment. Here, we present 10 measures that could be used to complement planned water recovery actions. These "complementary measures" integrate recovery actions, which when strategically combined with water delivery would significantly enhance water reform efforts to generate environmental outcomes in a highly modified system. [ABSTRACT FROM AUTHOR]

Australia's water management futures are again under discussion as drought impacts and bushfires hit communities. Water and ecological system limits are being reached resulting in fish kills and dwindling water levels in storages. Awareness is also rising around the inequities in current water governance regimes for First Peoples across the Australian continent and beyond. Here we provide a brief overview and research on: the ingenuity of Indigenous waterscape and landscape knowledge and practices to care for country and community, including the development of agricultural systems and sophisticated fish and eel trapping systems that are thousands of years old; the devastating impacts of colonisation on First Peoples, their country and ability to maintain some cultural practices; and the ongoing contestation over water governance, right from Federation, including the eight waves of water reforms in the Murray-Darling Basin. Current challenges and needs for reform are also presented including: hydrological scientific uncertainties, such as around return flows and their adjustment due to irrigation infrastructure efficiency increases, and new design methodologies, such as for flood estimation inputs to hydraulic models; adjusting current governance regimes of sustainable diversion limits and water markets to provide alternative value to Australia, beyond economic value drivers, that better respond to the benefit of all basin communities in the face of ongoing extreme climate variability and climate change; and determining positive ways forward for truly valuing and allowing First Peoples' knowledge, practices, culture and law to provide a basis for developing the next waves of Australia's water management reform journey. [ABSTRACT FROM AUTHOR]

• The influence of management decisions on water allocations are often overlooked. • Effects of different water management rules were simulated in two Australian rivers. • Changing management rules alone varied long-term water allocations by −6 to +22%. • Influence of drivers varied with river system and reliability of water license. • More systematic and transparent water allocation decisions will be beneficial. A global challenge for water resource management in rivers worldwide is ensuring water supply reliability satisfies consumptive and environmental demands. High variability in water supply, water policy and management decisions, and uncertainty about the effects of climate change compound this challenge. Understanding factors driving water allocations and consequences for water users and the environment is essential. Rainfall and streamflow traditionally drive allocations, yet the influence of water management decisions are often overlooked because they are complex, rarely codified and dependent on the regional context. We compared the relative influences of water management, climate and the river system characteristics including demand and water storage infrastructure on regulated and unregulated water allocations in two regulated rivers with large dams for water supply to towns, irrigated agriculture and wetlands of international significance (Gwydir and Macquarie Rivers of the Murray-Darling Basin, southeastern Australia), using hydrological simulation models and regression-based sensitivity analyses under an historical and drier climate. Water management decisions influenced regulated water allocations (explaining 23% to 52% of the variance) considerably more than unregulated water allocations (explaining 2%). For regulated water allocations, water management decisions and the river system were more important than a plausible change in climate, while for unregulated water allocations, the river system and climate change were dominant drivers. Changing management rules alone could vary long term water allocations by between −6% and +0.1% in the Gwydir River and between −4% and +22% in the Macquarie River. Management rules which allocated future inflows (i.e. credit model) were more likely to fail in a drying environment with projected reductions in runoff, compared to rules where only water in storage is allocated (i.e. debit model). Management rules differed despite both river systems being governed by a single management agency under the same legislative and policy framework. More systematic approaches to justify water management rules and greater transparency in their influence on water allocations are critical for maximizing the benefits to water users and river health, and for managing risks to water supply in a variable and changing climate. [ABSTRACT FROM AUTHOR]

The Hydrologic Reference Stations is a network of 467 high-quality streamflow gauging stations across Australia that is developed and maintained by the Bureau of Meteorology as part of an ongoing responsibility under the Water Act 2007. The main objectives of the service are to observe and detect climate-driven changes in observed streamflow and to provide a quality-controlled dataset for research. We investigate trends and step changes in streamflow across Australia in data from all 467 streamflow gauging stations. Data from 30 to 69 years in duration ending in February 2019 were examined. We analysed data in terms of water-year totals and for the four seasons. The commencement of the water year varies across the country – mainly from February–March in the south to September–October in the north. We summarized our findings for each of the 12 drainage divisions defined by Australian Hydrological Geospatial Fabric (Geofabric) and for continental Australia as a whole. We used statistical tests to detect and analyse linear and step changes in seasonal and annual streamflow. Monotonic trends were detected using modified Mann–Kendall (MK) tests, including a variance correction approach (MK3), a block bootstrap approach (MK3bs) and a long-term persistence approach (MK4). A nonparametric Pettitt test was used for step-change detection and identification. The regional significance of these changes at the drainage division scale was analysed and synthesized using a Walker test. The Murray–Darling Basin, home to Australia's largest river system, showed statistically significant decreasing trends for the region with respect to the annual total and all four seasons. Drainage divisions in New South Wales, Victoria and Tasmania showed significant annual and seasonal decreasing trends. Similar results were found in south-western Western Australia, South Australia and north-eastern Queensland. There was no significant spatial pattern observed in central nor mid-west Western Australia, with one possible explanation for this being the sparse density of streamflow stations and/or the length of the datasets available. Only the Tanami–Timor Sea Coast drainage division in northern Australia showed increasing trends and step changes in annual and seasonal streamflow that were regionally significant. Most of the step changes occurred during 1970–1999. In the south-eastern part of Australia, the majority of the step changes occurred in the 1990s, before the onset of the "Millennium Drought". Long-term monotonic trends in observed streamflow and its regional significance are consistent with observed changes in climate experienced across Australia. The findings of this study will assist water managers with long-term infrastructure planning and management of water resources under climate variability and change across Australia. [ABSTRACT FROM AUTHOR]

Through interviews of 20 sitting politicians and water practitioners in New South Wales, Australia, this article explores the underlying perceptions of the viability of potable water reuse for Sydney in decision-making practices to explore how politics and water management expertise can come into conflict. In particular, politicians' stances on the issue of water reuse are affected by the wider politicized but unrelated issue of climate change. Three key themes emerged as barriers to the implementation of water reuse schemes: existing water governance arrangements, limited community support and the perceived lack of a water crisis. [ABSTRACT FROM AUTHOR]

Climate change affects natural systems, leading to increased acceleration of global water cycle and substantial impacts on the productivity of tropical rivers and the several ecosystem functions they provide. However, the anticipated impacts of climate change in terms of frequency and intensity of extreme events (e.g., droughts and floods) on hydrological systems across regions could be substantially different. This study therefore aims to assess the impacts of climate change on the streamflow of a large river basin located in central Australia (Cooper Creek-Bulloo River Basin). Modified version of the hydrological model Hydrologiska Byråns Vattenbalansavdelning (HBV) was used in this study to generate daily streamflow. This model was first calibrated (2001–2010) and then validated for two independent periods (1993–1997 and 2011–2015). The model depicted a good performance in simulating observed streamflow. Climate projection data from multiple general circulation models (ACCESS1.0, CanESM2, CESM1-CAM5, CNRM-CM5, GFDL-ESM2M, HadGEM2-CC, MIROC5, NorESM1-M, ACCESS1-0, ACCESS1-3, CCSM4, CNRM-CM5, CSIRO-Mk3.6, GFDL-CM3, GFDL-ESM2M, HadGEM2, MIROC5, MPI-ESM-LR, and NorESM1-M) in various forms (raw, statistically downscaled, dynamically downscaled, and bias adjusted) were considered in this study. Results showed that three high resolution dynamically downscaled and bias adjusted models (ACCESS1-3, CNRM-CM5, and MPI-ESM-LR) from Terrestrial Ecosystem Research Network (TERN) dataset (v1.0.2) have better performance than other models considered, that is, in terms of capturing observed precipitation over the basin. Future climate projections of ensemble of these three models forced with RCP 4.5 and RCP 8.5 emission scenarios were then used to generate streamflow for 2050s (2040–2069) and 2080s (2070–2099). Results of the study indicated that mean annual precipitation was projected to decrease by up to −8% in 2050s and temperature was projected to increase by up to 4.66 °C in 2080s under the average and extreme emission scenarios, respectively. Mean annual, mean seasonal (December–February, March–May, June–August, September–November), and mean monthly streamflow were projected to decrease under different emission scenarios in 2050s and 2080s. These results indicate decreased water availability in the future as well as water cycle intensification. These changes in streamflow might have impacts on agriculture, natural ecosystem, and could lead to water restrictions. The outcome of this study can directly feed into frameworks for sustainable management of water resources and support adaptation strategies that rely on science and policy to improve water resources allocation in the region. [ABSTRACT FROM AUTHOR]

As climate change alters flood risk, there is a need to project changes in flooding for water resource management, infrastructure design and planning. The use of observed temperature relationships for informing changes in hydrologic extremes takes many forms, from simple proportional change approaches to conditioning stochastic rainfall generation on observed temperatures. Although generally focused on understanding changes to precipitation, there is an implied transfer of information gained from precipitation-temperature sensitivities to flooding as extreme precipitation is often responsible for flooding. While reviews of precipitation-temperature sensitivities and the non-stationarity of flooding exist, little attention has been given to the intersection of these two topics. Models which use temperature as a covariate to assess the non-stationarity of extreme precipitation outperform both stationary models and those using a temporal trend as a covariate. But care must be taken when projecting changes in flooding on the basis on precipitation-temperature sensitivities, as antecedent conditions modify the runoff response. Although good agreement is found between peak flow-temperature sensitivities and historical trends across Australia, there remains little evaluation of flood projections using temperature sensitivities globally. Significant work needs to be done before the use of temperature as a covariate for flood projection can be adopted with confidence. This article is part of a discussion meeting issue 'Intensification of short-duration rainfall extremes and implications for flash flood risks'. [ABSTRACT FROM AUTHOR]

Despite huge differences in population, household income and development levels, Australia and Brazil have some temporal convergences in their water governance systems. Over the last 20 years, both countries have significantly reformed their water policies and practices by introducing a legal foundation for more integrated and participatory catchment/basin management based on the best information available. A critical test of any water reform is how effective it is in meeting the challenges of extreme and unpredictable conditions of drought and floods, which are expected to increase under climate changes scenarios. This paper compared the contemporary water governance frameworks of Australia and Brazil in relation to three elements of Integrated Water Resources Management (IWRM): integration, participation, and information/knowledge. We focused on insights from Brazil's recent drought and Australia's fluctuating water crises to derive lessons and recommendations for future changes. Among the main recommendations, we stress the need for both systems to improve effective participation and to embrace a more comprehensive approach to cope with water scarcity in future scenarios. Furthermore, water related decisions should be based on a transparent and well informed process, and take into account the lessons from similar situations worldwide in order to avoid unnecessary or ineffective measures. As demonstrated in the Australian case during the Millennium Drought, the most effective initiatives were those involving government, the private sector and society to achieve a more sustainable consumption pattern in all sectors. There is much to learn from the Brazilian and Australia experiences in water reforms and crises, but it is imperative to understand the social, economic and environmental context within which these took place. Continuing to develop the capacity and willingness of researchers and policy makers to work together can make an important contribution towards meeting the growing and spreading challenges in water resource management around the world. [ABSTRACT FROM AUTHOR]

Many countries and regions have struggled to put in place adequate water information systems to assist with sustainable water management. This article describes and assesses the key components of Australia's water information and data systems, with particular reference to rural and regional Australia, focusing on progress with strengthening these systems at a national level since 2007. Through the early part of the period, much of Australia was experiencing a crisis in water availability. The article concludes with ongoing challenges for Australia and lessons from the Australian experience for other countries embarking on upgrading their water information and data systems. Upgrading a nation's water information systems is a long-term task, but an important one in a world of climate change and increased climate variability. Substantial progress is likely to take five to 10 years to materialize. From the outset, upgrading information systems needs to be focused on data series that will facilitate answering key policy questions, assist water users in making significant decisions more effectively, and allow businesses and government to better address risks from water-related events. As always, political support matters. To sustain investments in information, its coverage must facilitate illuminating key questions and issues. Custodians of information systems must ensure that the value proposition is clear to all. [ABSTRACT FROM AUTHOR]

The trend to a hotter and drier climate, with more extended droughts, has been observed in recent decades in southern Australia and is projected to continue under climate change. This paper reviews studies on the projected impacts of climate change on groundwater and associated environmental assets in southern Australia, and describes groundwater planning frameworks and management responses. High-risk areas are spatially patchy due to highly saline groundwater or low-transmissivity aquifers. The proportional reduction in rainfall is amplified in the groundwater recharge and some groundwater discharge fluxes. This leads to issues of deteriorating groundwater-dependent ecosystems, streamflow depletion, reduced submarine discharge, groundwater inundation and intrusion in coastal regions and reduced groundwater supply for extraction. Recent water reforms in Australia support the mitigation of these impacts, but groundwater adaptation is still at its infancy. Risk management is being incorporated in regional water and groundwater management plans to support a shift to a more sustainable level of use and more climate-resilient water resources in affected areas. The emerging strategies of groundwater trade and managed aquifer recharge are described, as is the need for a national water-focused climate change planning process. [ABSTRACT FROM AUTHOR]

Climate change is threatening water security in water-scarce regions across the world, challenging water management policy in terms of how best to adapt. Transformative new approaches have been proposed, but management policies remain largely the same in many instances, and there are claims that good current management practice is well adapted. This paper takes the case of the Murray–Darling Basin, Australia, where management policies are highly sophisticated and have been through a recent transformation in order to critically review how well adapted the basin's management is to climate change. This paper synthesizes published data, recent literature, and water plans in order to evaluate the outcomes of water management policy. It identifies several limitations and inequities that could emerge in the context of climate change and, through synthesis of the broader climate adaptation literature, proposes solutions that can be implemented when basin management is formally reviewed in 2026. [ABSTRACT FROM AUTHOR]

Climate change has emerged as a key threat to river ecosystems. This study presents a generic, conceptual framework for assessing the significance of climate change impact for ecological outcomes. Within the framework, multiple sequences of streamflows with a length that is "critical" to target species are derived under current and future climates; ecological responses are assessed using models that consider the influence of flow sequencing; the ranges of ecological responses under future and current climates are compared to indicate the significance of impact. This framework allows the degree of future climate risks to ecosystems to be assessed with reference to the range of behavior under current conditions. An example application of the approach to the Yarra River, Australia, show that careful use of environmental water rights could provide a similar range of outcomes under future and current climate, where the range of outcomes due to natural variability are appreciably greater than the shifts induced by climate change. This study demonstrates the importance of incorporating natural variability in impact assessments and shows the flexibility of active water management. [ABSTRACT FROM AUTHOR]

Practitioners of environmental water management (EWM) operate within complex social-ecological systems. We sought to better understand this complexity by investigating the management of environmental water for vegetation outcomes. We conducted an online survey to determine practitioners' perspectives on EWM for non-woody vegetation (NWV) in the Murray-Darling Basin, Australia with regards to: i) desirable outcomes and benefits; ii) influencing factors and risks; iii) challenges of monitoring and evaluation, and iv) improving outcomes. Survey participants indicated that EWM aims to achieve outcomes by improving or maintaining vegetation attributes and the functions and values these provide. Our study reveals that EWM practitioners perceive NWV management in a holistic and highly interconnected way. Numerous influencing factors as well as risks and challenges to achieving outcomes were identified by participants, including many unrelated to water. Survey responses highlighted six areas to improve EWM for NWV outcomes: (1) flow regimes, (2) vegetation attributes, (3) non-flow drivers, (4) management-governance considerations, (5) functions and values, and (6) monitoring, evaluation and research. These suggest a need for more than 'just water' when it comes to the restoration and management of NWV. Our findings indicate more integrated land-water governance and management is urgently required to address the impacts of non-flow drivers such as pest species, land-use change and climate change. The results also indicate that inherent complexity in EWM for ecological outcomes has been poorly addressed, with a need to tackle social-ecological constraints to improve EWM outcomes. [Display omitted] • Flow is important for vegetation, but management requires more than just water. • Integrated land-water management is needed to limit impacts of non-flow drivers. • Constraints need to be addressed to improve vegetation outcomes to flow regimes. • Practitioners perceive vegetation management in holistic and interconnected ways. • Building societal understanding of environmental water management is important. [ABSTRACT FROM AUTHOR]