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Australia's rivers are among the most variable in the world and this has been a major challenge in catchments such as the Murray-Darling Basin where management has focused on increasing agricultural production while reducing risks from fluctuating water availability. Pressure for development and over-optimistic assessments of available water have resulted in over-allocation and increasing ecological decline, which has been severely exacerbated by record-breaking drought. In recent years, governments have agreed to radical policies such as the National Water Initiative 2004 and allocated substantial funds in response. Implementation is in gridlock, however, as the socio-economic implications have become clearer. Most debate is focused on the draft Murray-Darling Basin Plan due for release in mid-2010 before finalization in 2011. It will be the first Basin-wide plan and is intended to deal with inequities across borders and risks such as climate change and drought. Climate change scenarios for 2030 foresee a range of potential surface water availability outcomes, ranging from a 7% increase to a 37% decrease, yet greater water scarcity is being experienced in the current (2002+) drought with inflows reduced by 70% or more in extreme years. Contradictory policies are hindering the more open adaptation required to manage a drier future. [ABSTRACT FROM AUTHOR]

Inland recreational swimming sites provide significant social value globally. This study focused on public recreational swimming sites across the Murrumbidgee River and its tributaries in the Australian Capital Territory (ACT) throughout the swimming season (September-April) from 2009 to 2020 to determine whether high intestinal enterococci concentrations could be predicted with flow exceedance and routinely monitored physical and chemical parameters of water quality. Enterococci concentrations were positively correlated with the turbidity associated with high-flow conditions. The predictive accuracy of high enterococci levels during high-flow conditions was good (mean percentage correctly classified, 60%). The prediction of high enterococci levels at low flows was significantly less reliable (mean percentage correctly classified, 12-15%). As the ACT is expected to experience decreases in rainfall overall but increases in extreme rainfall events due to climate change, understanding the drivers of elevated intestinal enterococci under extreme flow conditions remains important from a public health perspective. [ABSTRACT FROM AUTHOR]

Climate change has potentially significant implications for hydrology and the quantity and quality of water resources. This study investigated the impacts of climate change and revegetation on water and salt balance, and stream salt concentration for catchments within the Murray-Darling Basin, Australia. The Biophysical Capacity to Change model was used with climate change scenarios obtained using the CSIRO DARLAM 125 (125 km resolution) and Cubic Conformal (50 km resolution) regional climate models. These models predicted up to 25% reduction in mean annual rainfall and a similar magnitude of increase in potential evapotranspiration by 2070. Relatively modest changes in rainfall and temperature can lead to significant reductions in mean annual runoff and salt yield and increases in stream salt concentrations within the Basin. The modelled reductions in mean annual runoff were up to 45% in the wetter/cooler southern catchments and up to 64% in the drier/hotter western and northern catchments. The maximum reductions in salt yield were estimated to be up to 34% in the southern catchments and up to 49% in the northern and western catchments. These changes are associated with average catchment rainfall decreases of 13 to 21%. The results suggest that percentage changes in rainfall will be amplified in runoff. This study demonstrates that climate change poses significant challenges to natural resource management in Australia. [ABSTRACT FROM AUTHOR]

The Murray–Darling Basin covers parts of four States of Australia and the whole of the Australian Capital Territory. As at 2002, its water management was well regarded internationally. Basin flows are low and variable. The most reliable streams show variations of about 12:1 between maximum and minimum annual natural flows. The longest tributary, the Darling, has a ratio of infinity. It was recognized in the 1980s that extractions from the system, largely for irrigation, had to be constrained. That led to the introduction of the "Murray‐Darling Basin Cap" which limited extractions and recognized the probability of average inflows declining, which was already being predicted by climate change modelling. The "millennium drought" of 2000–2009 was very severe and led to fears that the drop in inflows was happening faster than modelling was predicting. In 2007, the National Government, on the eve of an election, declared that the Basin had been mismanaged for a century by the States and legislated to transfer management powers from the States to the Commonwealth. That transfer has been pursued since then by National Governments of both major parties. Government claims to have "taken the politics out of Basin management and returned to the science." The evidence is that the exact opposite has occurred. The paper traces the history of water management in the Basin. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The relationship between the interannual changes in streamflow, precipitation and temperature of the Murray-Darling basin is investigated by using a two-parameter climate elasticity of streamflow approach. The non-linear relationship between streamflow and both precipitation and temperature indicates a greater streamflow sensitivity to precipitation than to temperature but a more significant impact of temperature change on streamflow than previously reported. The physical mechanisms producing high streamflow sensitivity to temperature change are not well understood, but may relate to concurrent changes in sub-annual precipitation characteristics such as seasonality, spatial distribution and intensity. Thus these characteristics need to be assessed and accounted for when attempting to project how streamflow, and hence water availability, may change in a future warmer world. [ABSTRACT FROM AUTHOR]

Many parts of Australia have experienced their worst single- and multi-year droughts on record over the last decade. These recent climate conditions have severely stressed our water supply systems and the communities that depend on them. With the threat of climate change potentially further exacerbating droughts in the years ahead, Engineers Australia firmly believes that: (i) A national review of the adequacy of drought response plans is urgently required. A recent national overview of long-term water resources planning by the Academy of Technological Sciences and Engineering (ATSE, 2007) revealed large inconsistencies and inadequacies in the standard of that planning. Based on the knowledge of the authors of this paper, similar outcomes are expected in the area of drought response planning. The scope of the review should include assessment of the transparency and defensibility of the timing of implementation of drought response actions; (ii) Continuing investment is needed in climate research to better understand the underlying drivers of our climate variability and their interactions at a range of time scales. The majority of research to date has focused on short -term sea surface temperature or pressure differentials across the globe (eg. the El Niño/Southern Oscillation) without understanding the longer-term drivers behind these temperature and pressure responses, which are being investigated through the Indian Ocean Climate Initiative and, more recently, the South East Australia Climate Initiative. This investment should include consolidation for and communication to the water industry of existing knowledge of links between long-term climate variability and key climate drivers including Earth’s orbital cycles, solar activity, atmospheric chemistry, major volcanic eruptions, surface and deeper ocean circulations (including the thermohaline circulation – the “great ocean conveyor belt”), sea ice, and major bush fires; (iii) Greater collaboration is required between climatologists, paleoclimatologists and water resource engineers to take advantage of recent scientific advances that have direct implications for drought response planning. Engineers Australia proposes that the National Water Commission should conduct a national forum to bring these three industry groups together with the aim of providing meaningful, useful advice to water industry practitioners from the latest climate research and to guide research activities towards more practical outcomes. This will enable water resource planners to better understand natural climate variability in the longer term and appropriately take into account greenhouse gas induced climate change, including an understanding of uncertainties surrounding both current and future climate; (iv) The development of an industry standard end-use demand model for urban areas should be accelerated. The absence of an industry standard tool in this area currently inhibits the ability to rapidly assess the financial costs of imposing restrictions on particular sectors of the community versus supply augmentation costs to avoid those restrictions. Such a tool is needed to make informed decisions about preparedness to pay for new infrastructure to avoid or reduce restrictions; and (v) More sophisticated water products and market mechanisms have a strong role to play in better managing scarce resources between similar types of users during times of drought. This has become increasingly important with demand hardening over recent decades, which has reduced the water savings that are achievable from water restrictions. Any expansion of water markets as a drought management tool must, however, occur within a regulatory framework that seeks to achieve equitable social outcomes by acknowledging the inherent social value of water to communities and the food security value of water to the nation. It is acknowledged in preparing this position paper that our understanding of drought and our responses to it are rapidly changing, particularly in light of climate change. This is particularly the case with the current reviews of aspects of the National Drought Policy, which were being undertaken by several government agencies at the time of drafting this paper. It is hoped that this position paper will encourage both greater dialogue and investment in drought forecasting, planning, adaptation and mitigation to enable Australia to be well placed to cope with future climate conditions. [ABSTRACT FROM AUTHOR]

Anthropogenic warming of the global climate system is beyond doubt. Impacts from a changing climate are already occurring and the latest scientific research suggests that some aspects are locked in for centuries to come. Climate change therefore poses one of the greatest challenges to Australia's environment and water resources. Historical experience and past trends may no longer be a reliable predictor of the future. This article provides a brief overview of the latest scientific research and thinking on the climate change challenge. Observed changes and projections for temperature, rainfall, extreme events and ocean acidification are presented in an Australian context. The impacts of a range of climate change drivers are summarised, expanding upon the well-accepted general warming and drying trend for southern and eastern Australia. Current thinking regarding 'dangerous' climate change is that we are tracking on the higher end scale or above of the worst case scenario predictions reported by the IPCC Fourth Assessment Report (IPCC AR4) released in 2007. The implications for Australia's water resources, and in particular the Murray-Darling Basin, are significant. There appears to be a brief window of opportunity to act and adapt to enhance resilience to climate change; however, this requires an urgent and sustained commitment, and investment in Australia's environmental assets. [ABSTRACT FROM AUTHOR]

Droughts, changing weather patterns due to climate change, unsustainable state and federal government policies and parochial self interest has brought the major irrigated agricultural region of Australia, the Murray-Darling Basin close to collapse. The present state of the Basin together with the predictions of computer modelling of future climate changes over the next few decades is discussed in relation to the existing attitudes of vested interests at all levels and the various policies now being undertaken by governments in an attempt to address the major problems. [ABSTRACT FROM AUTHOR]

This paper introduces a new approach to stochastically generating rainfall sequences that can take into account natural climate phenomena, such as the El Niño–Southern Oscillation and the interdecadal Pacific oscillation. The approach is also amenable to modeling projected affects of anthropogenic climate change. The method uses a relatively new technique, empirical mode decomposition (EMD), to decompose a historical rainfall series into several independent time series that have different average periods and amplitudes. These time series are then recombined to form an intradecadal time series and an interdecadal time series. After separate stochastic generation of these two series, because they are independent, they can be recombined by summation to form a replicate equivalent to the historical data. The approach was applied to generate 6-monthly rainfall totals for six rainfall stations located near Canberra, Australia. The cross correlations were preserved by carrying out the stochastic analysis using the Matalas multisite model. The results were compared with those obtained using a traditional autoregressive lag-one [AR(1)], and it was found that the new EMD stochastic model performed satisfactorily. The new approach is able to realistically reproduce multiyear–multidecadal dry and wet epochs that are characteristic of Australia’s climate and are not satisfactorily modeled using traditional stochastic rainfall generation methods. The method has two advantages over the traditional AR(1) approach, namely, that it can simulate nonstationarity characteristics in the historical time series, and it is easy to alter the decomposed time series components to examine the impact of anthropogenic climate change. [ABSTRACT FROM AUTHOR]