Climate change and water resources

ABSTRACT

This is a written version of the Munro Oration delivered at the Hydrology and Water Resources Symposium in Sydney on 13 November 2023. The presentation reflects on climate change and water resources, and on decades of research and practice in hydroclimate and hydrological modelling. The presentation highlights Australian contribution to global research and synthesis, challenges posed by Australia’s unique hydrology, key hydroclimate trends and future projections for Australia, and knowledge, opportunities and challenges in water resources adaptation to hydroclimate variability and climate change.

KEYWORDS:

• Hydroclimate
• hydrology
• water resources
• climate change

1. Introduction

I like to thank the National Committee of Water Engineering and the Hydrology and Water Resources Symposium for the opportunity to deliver the 2023 Munro Oration. As a young hydrologist in the 1990s, I watched in awe as the many luminaries of Australian hydrology and water resources deliver the Munro Orations. I am fortunate to know most of the past 20 orators and have learned a lot from many of them. I am humbled and honoured, and daunted, to be giving this oration.

Professor Crawford Munro can be considered as a pioneer of Australian hydrology. His drive and vision led to the establishment of the School of Civil Engineering at UNSW, the formation of Australian Water Resources Council, the development of Australian Rainfall and Runoff, and the start of Hydrology and Water Resources Symposium, all of which are still thriving today. Professor Munro championed and created the visibility and rigour in the science and practice of hydrology, which has allowed many Australian hydrologists to flourish and make significant contributions in Australia and globally. I have not met Professor Munro but am old enough to have heard about his legacy and to learn from later pioneering hydrologists who know Professor Munro, past Munro orators like Tom McMahon, Eric Laurenson, Tom Chapman, Walter Boughton and Russell Mein.

My career in hydrology and water resources was spent largely in two places. I am grateful for the foundation and early and mid-career years at the University of Melbourne, in particular to my mentor Tom McMahon who showed me the exciting world of hydrology. Together with colleagues, like Rodger Grayson, Andrew Western and Murray Peel, and later Jeff Walker and QJ Wang, we worked on just about everything in hydrology, from doing new research to adapting overseas knowledge to apply to Australia’s unique hydroclimate and hydrology. This was also the time when the CRC for Catchment Hydrology was established, led by Emmett O’Loughlin and then Russell Mein, Rob Vertessy and Rodger Grayson. The importance of these research centres is immense, as they facilitate partnerships between science and industry and adoption of research, and they provide the hub for developing the next generation of hydrologists. In many ways, the knowledge, tools, and models developed then are still used today, simply updated and adapted to solve new challenges.

After 15 years at the University of Melbourne, I joined CSIRO in Canberra in 2006. I am grateful to Rob Vertessy who employed and supported me in CSIRO. The pace became more hectic in CSIRO, working with government and industry on large multi-disciplinary and multi-partnership projects. We started with the Murray-Darling Basin Sustainable Yields, where I worked with Tom Hatton, Bill Young, Ian Prosser and Glen Walker. This was followed by more water resources assessments, bioregional assessments, several hydroclimate initiatives and developing water information products with the Bureau of Meteorology. I am proud of the innovations and impacts that we have achieved, and I also learned about the complexities of working with agencies and groups with competing interests, and that science and knowledge is often only a small part informing or driving decisions and changes in management and policy.

In this oration, I will reflect on climate change and water resources, and on decades of research and practice in hydroclimate and hydrological modelling. I will talk about global climate change and global hydrological change and how Australian hydrology is unique. I will show key trends in Australian hydroclimate, discuss hydrological non-stationarity, and present projections of future water resources under climate change. I will talk about efforts and challenges in adapting to climate change in the water resources and related sectors. I will then finish off with some anecdotes and reflections. I have also summarised, as figures for each of the areas discussed here, narratives and pictures and key references from which more information can be found.

2. Global climate change

Global greenhouse gas emissions and atmospheric CO₂ concentration have risen considerably since pre-industrial time. This has caused the global land surface to warm by 1.2°C (and higher in Australia) since 1900, with most of the warming occurring after 1970. We have seen increasingly more climate extremes in Australia and almost everywhere in the world. Ecosystems are at critical thresholds and Australian examples include the tropical coral reefs, kelp forests in the southern ocean and loss of alpine biodiversity. We are all too aware of the increase in flood risk, fire risk, heat stress, and risk to water security, important topics that are addressed here in this symposium. Many of these have been long-standing problems, which are now exacerbated by climate change (Figure 1).

Figure 1. Key climate change risks in Australia and New Zealand and related assessments from the Intergovernmental Panel on Climate Change.

It is heartening to see a lot more adaptation planning across many sectors, particularly over the past decade. The Australian government has also recently developed a national climate risk assessment methodology and is progressing efforts to identify key risks and adaptation options. But progress in implementation has been slow, and gaps in adaptation will only continue to grow. This is partly due to the complexity of the challenge, the aggregated and compounding impacts, and institutions and governance systems themselves being overwhelmed. Governments and society want to address climate change risks, but it is difficult to know exactly how, as this may require a change in the life and systems that we are accustomed to, and some short-term pain to transition to a future that is desired and possible under climate change. There is too much churn in our institutions, staff themselves are directly affected by climate change, and the loss of continuity in institutional and technical knowledge is eroding our capability and capacity to develop and implement effective adaptation actions.

I was fortunate to be a lead author in the Intergovernmental Panel on Climate Change (IPCC) Fifth and Sixth Assessment reports. The IPCC was established in 1988, and there has been six of these assessments. Each assessment cycle is a long process of more than five years and involves almost a thousand lead authors across three working groups assessing the physical science, the vulnerabilities of human and natural systems to climate change, and options for mitigating climate change. These assessments are the biggest peer review process in the world, with over 60,000 references and more than 200,000 responses to review comments by experts and governments in the most recent sixth assessment.

The IPCC assessments provide a robust synthesis of knowledge and have been crucial in informing global mitigation and local and regional adaptation. However, with the monumental effort and cost in producing these assessments, the goodwill of experts working on the assessments, the IPCC reputation and outreach and engagement activities, and the involvement of national governments in the process, one can’t help feeling that there is more that the IPCC can do in driving change.

We are likely to surpass 2°C global average warming in several decades, and hopefully not much more beyond that with global mitigation efforts (albeit slow) underway. The more we can mitigate to reduce global warming, the less we need to spend on local adaptation. We too, as technical experts, must do our part. As engineers, many of us are introverts and are very good at finding solutions to address specific problems. We may need to be more like our passionate colleagues in the social sciences, to communicate the science (and not just to ourselves), to explain the urgency of addressing climate change risk, and to engage with government and industry to help find and action realistic adaptation solutions.

3. Global hydrological change

Averaged across the world, about 1 metre of precipitation falls on the land surface every year. About two-thirds of this evaporates and one-third runs off into the oceans. We presently capture less than 10 percent of the runoff for use. We use about 70% of this for irrigated agriculture, 20% for industries and 10% for human consumption and household water use. This however is a global average. Water is distributed differently across the world because of the Earth’s shape and angle of axis with respect to the sun and the distribution of continents and oceans across the surface.

A warmer climate will intensify the hydrological cycle, resulting in an increase in global precipitation and evaporation rates. Atmospheric water content will increase (this further enhances the greenhouse effect) leading to more intense extreme precipitation (Figure 2b) resulting in greater flood risk in built-up areas and small catchments. The changes in mean precipitation will be different in different parts of the world, with wet regions generally becoming wetter and dry regions generally becoming drier (Figure 2a,c).

Figure 2. Projected change in global precipitation and streamflow under climate change.

Regions that will become drier include the Mediterranean, central America and the Southern Hemisphere mid-latitudes. The drying in the southern mid-latitudes is caused by the expansion of the Hadley cell pushing the winter storm tracks further south into the Southern Ocean. In some way, we are unlucky to be living in a drying region as many parts of the world will become wetter under climate change. The changes in precipitation will be amplified in the streamflow, and more so in the drier regions (Figure 2d). The higher potential evaporation in a warmer world will further enhance the streamflow reduction in drying regions and moderate the increase in streamflow in wetting regions.

The inter-annual and multi-year variability of precipitation is also projected to increase under climate change (Figure 2e). This of course will reduce the reliability of water supply, particularly here in southern Australia where precipitation and therefore water resources are also projected to decrease. We use sophisticated models to assess the combined impact of changes in precipitation, potential evaporation, and inter-annual variability on water security, as well as methods like reservoir yield analysis developed by Tom McMahon and stochastic data approaches of Srikanthan, Rory Nathan and George Kuzcera from many decades ago.

The plots in Figure 2 come from global datasets and global climate and hydrological modelling efforts, which Australian agencies and scientists have contributed significantly to. The connection between precipitation, actual evaporation and runoff through the water balance (precipitation = actual evaporation + runoff) and energy balance (net radiation = sensible heat + latent heat of actual evaporation) can be expressed elegantly using a single Budyko or Fu equation as a function of the aridity index (potential evaporation divided by precipitation) fitted to global or regional datasets. Many Australian scientists, like Lu Zhang, are leading contributors to global research in this area, including extending the simple concept to also predict impact of land use change (in particular vegetation) on streamflow. It is nice to see many younger Australian scientists continuing this tradition, and leading global efforts in exploring and explaining regional and global water and energy (and vegetation) trends under climate change.

4. Australian hydrology is different

We live in the driest inhabited continent. The runoff coefficient in Australia is low, that is, less of the precipitation that falls becomes streamflow here compared to similar semi-arid and temperate regions in the world (Figure 3a). We have amongst the highest per capita water use in the world (Figure 3b), largely because of the food and things we produce and therefore the virtual water that we export.

Figure 3. Australian hydrology compared to the rest of the world.

The inter-annual variability of Australian streamflow is about twice that of rivers elsewhere in the world (Figure 3c). This means that we need larger storages to have the same reliability of supply compared to regions with similar average streamflow. On the upside, there is a strong teleconnection between Australian precipitation and streamflow versus large-scale atmospheric-ocean indices like the El Niño Southern Oscillation (ENSO) (and Southern Annular Mode (SAM), Indian Ocean Dipole (IOD) and Interdecadal Pacific Oscillation (IPO)), in part due to the cause of the high variability. We exploit this teleconnection, and together with the lag in precipitation-streamflow (or serial correlation in streamflow), to forecast streamflow several months or seasons ahead. Our Bureau of Meteorology provides world-class operational seasonal forecast, and we have world leading knowledge in streamflow forecasting (QJ Wang, David Robertson, James Bennett, Narendra Tuteja), and we must use more of this capability to enhance river operations and water resources management, particularly in a drying hydroclimate.

The amplification of precipitation change in streamflow is also higher in Australia compared to other parts of the world (Figure 3d). The precipitation elasticity of streamflow in Australia is about 2–3 (and higher in drier regions), which means that a 10 percent change in mean annual precipitation results in a 20–30% change in mean annual streamflow. This is a useful rule of thumb for estimating the change in streamflow resulting from the change in precipitation.

Our climate and hydrology are unique. This is probably one of the reasons why we punch well above our weight globally in the hydroclimate sciences. The large-scale atmospheric and ocean circulation is unique in the Southern Hemisphere because of the large body of water in the Southern Ocean and much smaller land mass compared to the Northern Hemisphere. As a leading developed country in the Southern Hemisphere, we have some of the world’s best climate and ocean scientists, and global observation and modelling efforts for this region rely on our Bureau of Meteorology, CSIRO and academic and research institutions.

In hydrology, we have a direct need to study and explain our unique hydroclimate, including adapting methods developed in the Northern Hemisphere, to develop knowledge and tools to inform water resources management. I was fortunate to be around some of the best analysis and synthesis of global hydrology from a decade of research around 1990 by Tom McMahon, Brian Finlayson, Andrew Haines and Murray Peel at the University of Melbourne, research that is still very frequently cited today (with more than 10,000 citations of one of the papers). The unique hydroclimate datasets, like the strong ENSO-streamflow teleconnection and the long Millennium drought in southeast Australia, have also attracted many leading hydrologists globally to collaborate with us, further enhancing our knowledge of Australian hydroclimate and significantly contributing to global hydrological science.

5. Observed hydroclimate trend

The most obvious climate signal in Australia is the rising temperature (by almost 1.5°C since 1900) and the declining rainfall trend in southwest and eastern Australia (Figure 4a). The reduction in rainfall is amplified in the reduction in streamflow. For example, in southwest Australia, there is not a single year after 1975 with inflows into Perth Dams higher than the pre-1975 long-term average (Figure 4c). This has led to the practical choice of using only post-1975 data to inform water resources management and planning in Perth, leading to construction of desalinisation plants and much less reliance on surface water.

Figure 4. Observed variability and trends in Australian rainfall and streamflow.

The observed reduction in rainfall across southeast Australia over the past several decades has mainly occurred over the cool season (Figure 4b). The reduction in the cool season rainfall resulted in significant reduction in streamflow, particularly in the southern Murray-Darling Basin and Victoria, where most of the streamflow occurs in winter and spring (Figure 4d).

There is of course high inter-annual, multi-year and decadal variability in the streamflow, where streamflow in a wet year could be 20 times greater than in the drier years. There were three major droughts in southeast Australia in the instrumental record, commonly referred to as the Federation drought (~1895–1902), World War II drought (~1937–1945) and the relatively recent Millennium drought (~1997–2009). Many studies have partly attributed the declining cool season rainfall to the intensification of the subtropical ridge and expanding Hadley cell in a warmer world pushing the winter storm tracks further south into the ocean (Figure 4e). However, it is difficult to quantify the relative contribution of natural variability versus climate change because of the high variability in the hydroclimate.

6. Hydrological non-stationarity

Significant changes have also been observed in the rainfall-runoff data from the Millennium drought. Most catchments in the southern Murray-Darling Basin and Victoria exhibit non-stationarity in the rainfall–runoff relationship, where less annual streamflow is generated during the Millennium drought for the same annual rainfall compared to pre-drought conditions (Figure 5a). For the same reason, hydrological models calibrated to the pre-drought data significantly overestimates streamflow during the Millennium drought (Figure 5b). The hydrological non-stationarity is likely due to changes in surface–groundwater interaction, subsurface water availability and vegetation water use in long dry spells impacting runoff generation. Changes in weather systems and rainfall characteristics can also impact runoff generation. The shift in hydrological response and recovery following the drought can be different in different catchments, and many catchments particularly in the drier areas in western Victoria have not fully recovered from the Millennium drought (Figure 5c).

Figure 5. Hydrological non-stationary and extrapolating models to predict future hydrological and streamflow characteristics.

Understanding the drivers of hydrological non-stationarity and adapting hydrological models so that they can be extrapolated to predict the future under more frequent and severe droughts is important (Figure 5d). Future hydrological predictions may also need to consider changes in the landscape like farm dams and other interception activities, and in conditions not experienced in the historical data used to develop and calibrate the models like higher temperature and potential evaporation and higher atmospheric CO₂ influence on vegetation and ecohydrology. This is an important and complex challenge identified as one of the 23 key unsolved problems by the global hydrological community. It is nice to see many younger and mid-career hydrologists in Australia leading the research in this area.

7. Climate change impact on future water security

The higher temperature and more hot days under climate change will increase heat-related mortality and morbidity for people and wildlife. The higher temperature will impact agriculture through heat stress on crops and livestock and reduced winter chilling for horticulture. The higher temperature also increases potential evaporation and demand for water from people, agriculture and the environment.

The majority of global climate models project that there will be less cool season rainfall in Australia under climate change, particularly in western Australia and southeast Australia (Figure 6b). As most of the runoff in far southern Australia occurs in winter and spring, streamflow and water resources there will reduce significantly under climate change (Figure 6c). The median projection from hydrological modelling informed by CMIP6 global climate models (used in IPCC AR6 assessment) is a 13% reduction in mean annual streamflow in southeast Australia and 18% reduction in far southeast Australia under 2°C global average warming (Figure 6c). The reduction in streamflow is caused by the reduction in rainfall and by the higher potential evaporation.

Figure 6. Climate change impact on future hydroclimate in Australia.

However, there is a large uncertainty or range in the future streamflow projection, mainly due to the uncertainty in the future rainfall projection. The 10th and 90th percentile projections range from little change in streamflow to a 40% reduction in streamflow in southeast Australia. The inter-annual and multi-year variability in streamflow will remain high, and we will continue to have long periods of low streamflow as well as long periods of high streamflow, occurring against a background of long-term declining streamflow trend. Multi-year hydrological droughts will therefore become more frequent and severe, and the reliability of water supply will significantly reduce, and further exacerbated by the projected increase in inter-annual rainfall and streamflow variability (Figure 6b).

The intensity of high extreme rainfall will increase (because of higher moisture holding capacity in the air) (Figure 6b), more so for shorter duration sub-daily rainfall and rarer low exceedance probability events. This will increase flood risk in built-up areas and small catchments, but the impact on riverine floods in large catchments is less certain because of the lag or attenuation in the river flow and the potentially drier antecedent conditions in southern Australia. We have seen major floods in eastern Australia in the recent La Niña years and improving flood warning, managing flood disaster, updating flood design, and flood planning and mitigation will become even more challenging under climate change. These are a major aspect of our profession; it is a key subject of Australian Rainfall and Runoff and are discussed in many sessions in the Hydrology and Water Resources Symposium and other forums. In addition to the excellent coordination of flood knowledge and specification of design guidelines by Engineers Australia, we also lead some of the research globally characterising and explaining changes in rainfall extremes and floods, by experts like Ashish Sharma, Rory Nathan, Conrad Wasko, Seth Westra and Fiona Johnson.

8. Hydroclimate science and modelling informing water resources planning

Water resources management and planning in Australia are informed by some of the best climate and hydrological science. We have access to many types of data (ground observations, interpolated gridded data across Australia, remotely sensed data, palaeo data, reanalyses data), we have well developed models for our water resources systems, and we use sophisticated tools like stochastic modelling and uncertainty analysis to inform and manage the high variability in our systems.

We developed and run the ACCESS global climate model and are well connected to global modelling efforts to understand and model climate variability and climate change globally and in our region. We have several leading regional climate modelling groups funded by the different state agencies running dynamical models to downscale outputs from global climate models to provide high spatial and temporal resolution data to inform local and regional scale planning and adaptation.

The abundance of climate projection datasets and hydrological impact modelling methods highlights the importance and challenge posed by climate change. The different datasets and methods significantly enhance our knowledge and provide us with the opportunity to robustly explore hydroclimate futures and uncertainty in the projections. However, interpreting and communicating the different products can be confusing, to stakeholders, catchment and water resources managers, and decision makers. This sometimes has the unfortunate effect of magnifying the perception of deficit in hydroclimate science, and the need to wait for more certainty in the science and projections before acting on climate change in water resources planning.

Although hydroclimate projections science will continue to improve, the uncertainty in future projections will remain large because of the challenges in understanding and modelling the complex global and regional atmospheric, ocean and land surface processes. We need to accept the uncertainty and plan accordingly, particularly when the majority of climate model projections, and consistently over for the past several decades, as well as understanding of changes in global and regional circulation under a warmer world, have consistently indicated a hotter and drier future in southeast Australia.

Planning in the face of uncertainty is of course not new to water resources practitioners. It is relatively common and good practice to carry out a bottom-up modelling and assessment of the water resource system. This has gained a lot of traction in the scientific literature and is also referred to as scenario neutral, decision scaling or systems approach. Put it simply, this is modelling to understand the system, and the impact on the system under changed climate inputs, as well as water use practice and management decisions. The system can be stress-tested in sensitivity modelling to explore outcomes under different climate inputs (regardless of the projections) and identify the level of change (and types of climate characteristics) that could significantly affect the reliability and resilience of the system. This is particularly useful for complex systems, where desired outcomes for competing uses and values are difficult to ascertain or define. Here, modelling and management can consider several plausible scenarios and adaptation options and the risk versus reward of the different actions (and timing of actions) that acknowledge uncertainty in the future projections.

9. Water resources adaptation to climate change

There has been significant water policy and management change in Australia, particularly in the Murray-Darling Basin, over the past decade. These include government investment to enhance the Bureau of Meteorology online water information, funding to improve agriculture water use and irrigation efficiency, enhancing water supply through inter-basin transfers and upgrading water infrastructure, initiatives to enhance drought resilience, and further developing the active water trading market. The most significant initiative is the more than $15b Murray-Darling Basin Plan which is still being implemented. The Plan includes returning about one-fifth of consumptive water to the environment through the purchase of water entitlements (and managed by the Commonwealth Environmental Water Holder) and water infrastructure projects. All the states and territories have developed climate change adaptation plans, and water utilities across Australia have established climate change adaptation guidelines. Adaptation has also focussed on securing supplies that are resilient to climate change, like desalinised water in all the Australian coastal capital cities and increasing use of stormwater and sewage recycling and managed aquifer recharge.

It is difficult to tell if these initiatives are simply reacting to the recent droughts (in particular the 1997–2009 Millennium drought in southeast Australia and the 2017–2019 drought across NSW) or adapting to projected drier conditions in the future, probably a bit of both. The progress in implementing the MDB Plan has been slow, and whilst there are many climate adaptation plans across Australia it is difficult to find clear examples of adaptation actions. Nevertheless, these initiatives are helping to buffer regions against droughts and facilitate some adaptation to climate change.

There have been plentiful discussions and commentaries, and biophysical and social science literature, on climate change adaptation in the water resources and related sectors. This points to the complex challenge of addressing existing problems (overallocation of water, environmental impact, cultural water, social equity), which will be escalated by climate change, and complicated by the uncertainty in future hydroclimate projections. Some of the initiatives could also be maladaptive because they may perpetuate unsustainable water and land use practice under ongoing climate change.

Climate change impact will be very significant. We need to understand that there will be no winners, and we all need to make compromises to minimise the impact. In addition to managing as best we can for the short-term, we also need to consider longer-term future outlooks that are desirable and possible (which may include changing the way we live and things we are accustomed to, moving out of marginal areas, and/or transitioning environmental systems to different states), and realistic and where possible flexible pathways to get there. This of course is difficult to do in practice.

10. Reflections on science and practice of hydrology and water resources

10.1. Australian hydrology and hydrologists

We are a large country with many different water-related challenges. We are relatively well organised to find solutions to address these challenges. We need to, because Australian hydrology and landscape are unique, and the knowledge developed elsewhere need to be adapted for our conditions. This is probably one reason why we lead many aspects of hydrological science globally.

10.2. Global engagement

We are relatively well engaged globally. This enables us to use the best knowledge for water resources management in Australia. Equally important is our contribution to address global challenges, which is much more significant in many parts of the developing world. We need to be part of the global community to address global problems like climate change and help find solutions to address the impacts on water and related sectors.

10.3. Beyond biophysical knowledge

Positive societal outcomes and changes require more than just biophysical knowledge. We can all learn to better integrate social and economic perspectives and to engage extensively and emphatically, particularly in addressing complex system and transdisciplinary stakeholder challenges.

10.4. Research funding

Our continued success in hydrology and water resources can be attributed to our university and research systems and science-industry partnerships. Institutions like Engineers Australia provide an industry-based focus to address water-related challenges in Australia. The various Cooperative Research Centres from more than a decade ago provide a hub for new research and for translating science to knowledge and tools for the industry, and more importantly the research and applied training for the next generation of hydrologists. Long-term funding for research in hydrology and water resources in Australia has eroded significantly in the past decade, and this must be addressed to ensure continued development of new science capital that is needed to address increasingly complex challenges in water security in a changing world.

10.5. Science to policy

As practitioners in the consulting world, we are pleased to see our work adopted relatively quickly. However, the translation or use of science to inform policy is much more complex. There are often many other drivers of which science is only a small part. Healthy debates around the science and methods can often be seen as deficits in the knowledge delaying management and policy actions (where the appetite for change is already low). We can help by communicating more clearly and simplistically and by better socialising consensus in knowledge (particularly where there is already strong agreement) amongst ourselves, communities, managers and decision makers.

10.6. Leadership and people

A lot of our successes are only possible working with others, either in project teams, or across disciplines and expertise to solve multi-dimensional challenges. Most good outcomes come from socialising our ideas, and compromising and accepting that there are different points of views. It is therefore important to be generous and invest in relationships. We should take time to celebrate the many successes we and the people we work with have achieved, and not dwell too much on setbacks (that we can learn from) or things that we have little control over. We spend a large chunk of our life at work, so we must look after ourselves and our colleagues, and enjoy this journey.

Acknowledgements

Thank you to Engineers Australia for the opportunity to present this Munro Oration. This is also a recognition for the many people I have collaborated and worked with through the years. I thank them for their friendship, their willingness to share knowledge, their passion to make the world a better place, and for the fun we shared along the way. I thank my mentor Tom McMahon and many others that I shared my younger days at the University of Melbourne. I thank Rob Vertessy and others for the opportunity and guidance in CSIRO. I have learned so much from them, and they have helped shaped my thinking in hydrology and life generally. I acknowledge Hongxing Zheng, Jin Teng, Nick Potter, Jai Vaze, Cuan Petheram and many others who are architects of some of the research presented here. I thank David Post, David Robertson and Carmel Pollino for their support in leading some of the recent initiatives in CSIRO. Finally, I like to thank my wife Mei San who is my best friend and strongest supporter and critic, and our beautiful daughters Meghan and Emily who have made my life both professionally and personally all the more rewarding and interesting.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Notes on contributors

Francis H.S. Chiew

Francis H.S. Chiew is a Civil Engineer and PhD graduate from the University of Melbourne. Francis worked at the University of Melbourne for 15 years before joining CSIRO as a Science Leader in 2006. Francis has led the surface water hydrology group in CSIRO for the past 15 years and has worked with governments and industry to deliver knowledge, datasets and tools to inform management and climate adaptation in the water resources and related sectors. Francis Chiew is known internationally for his research on hydroclimate, hydrological modelling and water resources management, and the science outputs from his team and collaborators are widely adopted and cited. Francis was a Lead Author in the Intergovernmental Panel on Climate Change Fifth and Sixth Assessment reports, and the recipient of the 2022 International Hydrology Prize (Volker Medal) from the International Association of Hydrological Sciences for outstanding contributions to hydrology and the application of research for the benefit of society.