DELWP’s Hydrology and Climate Science team hosted a series of VicWaCI webinars from May to October 2020. These virtual sessions detailed some of the research findings by our researchers that ultimately helped form the Victoria’s Water in a Changing Climate (PDF, 10.5 MB) (accessible version (DOCX, 2.7 MB)) document.
A playlist of these webinars is available here. Alternatively, you can learn more about each presentation and watch individual videos by finding the topic you are interested in from the menu below. The views and opinions expressed in these videos are those of the presenter. They do not necessarily reflect the department or its work. These videos feature optional closed captions.
Presenter: Michelle Ho (CSIRO)
Length: 51 min (inc. Q&A)
Topic: A system’s approach to understanding climate change impacts on water
The Victorian climate has always been variable. Now and into the future shifts in the climate resulting from global climate change will exacerbate the challenges faced by water managers and users. While projections of temperatures under climate change are highly certain across a large number of climate models, projections of rainfall and evaporation are less certain. A lack of certainty in climate projections does not, however, preclude the assessment of future climate impacts provided an appropriate method is used. A systems-centric approach to assessing climate impacts is explored here. It provides a framework for assessing climate impacts that accommodates climate uncertainties and provides context for projections of climate under different scenarios of change. A systems approach also allows for climate sensitivities and breaking points in the system to be identified. In addition, the robustness of alternative management rules and investments may be analysed to inform plans to adapt to a changing future.
Michelle Ho is a Research Scientist in the Hydrological Prediction Under Change team within the CSIRO Water program and is a contributor to the Victoria Water and Climate Initiative. Michelle has a background in civil engineering and research exploring flood and drought periods informed by paleoclimate data in the Murray Darling Basin. As a postdoc and research associate at the Columbia Water Center, Columbia University, she analysed water at a continental scale in the context of the food, energy and water nexus and more recently has been exploring ways to support decision making under climate uncertainty and unknowns.
Presenter: Acacia Pepler (Bureau of Meteorology)
Length: 42 min (inc. Q&A)
Topic: Which weather systems cause Victoria's rainfall, and how are they changing?
The majority of rainfall in Victoria can be attributed to thunderstorms, cold fronts, and low pressure systems, and days where these interact often cause the heaviest rainfall totals. This presentation will show how the most important weather systems vary across Victoria and throughout the year and highlight how recent declines in cool season rainfall can be linked to changes in the weather.
Acacia Pepler is a research scientist in the Climate Research Section at the Bureau of Meteorology. She is interested in all aspects of Australian climate change and variability, with a particular focus on extreme events. She received her PhD from the University of New South Wales in 2017, where she studied the severe low pressure systems known as East Coast Lows.
Presenter: Margarita Saft (University of Melbourne) and Tim Peterson (Monash University)
Length: 72 min (inc. Q&A)
Topic: Does catchment runoff always recover from droughts? A state-wide natural experiment that challenges our assumptions.
The Millennium Drought provided a natural experiment to challenge the assumption that catchment streamflow always recovers from droughts. Statistical analysis of annual and seasonal streamflow and precipitation was undertaken using Hidden Markov Modelling. Seven years after the drought, the rainfall-runoff dynamics had not recovered in 35% of catchments, and the number of recovered catchments is not increasing. Seasonal analysis produced similar results and suggests that reduced Autumn precipitation does not explain the non-recovery. For those catchments not recovered, ~80% show no evidence of recovering soon, suggesting that the catchments are persisting within a low-runoff state. The precipitation post-drought that is missing from the stream is not going to groundwater recharge, vegetation interception or unsaturated zone storage and is likely going to increased transpiration per unit of precipitation. These findings and more are the first empirical evidence of catchments having multiple co-existent states and a finite resilience to transient disturbances and suggest hydrological droughts can persist indefinitely after meteorological droughts.
Dr Tim Peterson is a senior lecturer in the Department of Civil Engineering at Monash University. His research focuses on using observational data to quantitatively understand socially relevant long-term change in groundwater and streamflow, including hydrological resilience, and the development of tools to allow others to identify such changes.
Topic: Hydrologic shift during and after the Millennium drought: explanatory factors and changes in subsurface storage and flow regime.
Catchment hydrologic response to rainfall has changed since the start of the Millennium drought, and in many cases has not returned to the pre-drought state. In 2010–2016, following the end of the drought, the average annual rainfall was close to the pre-drought norm across our study catchments, yet streamflow deficits were still ~-21% on average. This was a direct consequence of drought-induced shift in catchment behaviour. A simultaneous assessment of a large range of factors representing climate, vegetation, soils, groundwater, and human impacts allows us to identify the factors related to streamflow anomalies during and since the drought. A complimentary analysis of low flow and cease-to-flow conditions demonstrates widespread changes in catchment storage and transition of many Victorian catchments towards a higher degree of flow intermittency.
Dr Margarita Saft is a Research Fellow in the Department of Infrastructure Engineering at the University of Melbourne. Her research focuses on shifts in rainfall-runoff response associated with long droughts, long-term changes in catchment functioning and its implications for hydrological modelling, and impact of subsurface processes on runoff generation. She received her PhD from the University of Melbourne in 2017, where she investigated the changes in hydrologic behaviour during multiyear droughts in South-Eastern Australia.
Presenter: Luke Osburn (Bureau of Meteorology)
Length: 39mins (inc. Q&A)
Topic: The weather systems that produce extreme rainfall in Victoria and how hourly rainfall intensity is changing
Luke Osburn’s research has focused on extreme precipitation events, precipitation processes and how they are being affected by climate change. His PhD was on orographically driven precipitation over the Snowy Mountains and he then went on to investigate how precipitation in California was being affected by climate change.
Luke is currently specialising in sub-daily extreme precipitation events and is particularly interested in how those events are being influenced by climate change. He has focused on using rain gauge observational data and has used extreme value modelling theory to estimate 1 in 100-year precipitation events in Victoria. He has also been investigating how extreme precipitation events are being affected by different storm types.
Presenter: Peter Van Rensch (Bureau of Meteorology)
Length: 34 mins (inc. Q&A)
Topic: The contribution of changing weather systems to the reduced streamflow response during the Millennium Drought
Rainfall from various weather systems in Victoria changed during the Millennium Drought. This coincided with a reduction in streamflow in many catchments that was below expectations from the rainfall received. A large proportion of the reduced streamflow has been attributed to internal catchment characteristics, however the question of what influence the changes in weather systems had on the lower than expected streamflow remains. In this presentation, results from the weather system dataset developed at the Bureau of Meteorology will be shown. The dataset is used to determine if the rain that fell was different during the drought in the catchments that experienced the greatest change in streamflow response. Analysis of changes post drought will also be shown.
Peter van Rensch is a Climate Processes Specialist at the Bureau of Meteorology. He is currently focusing on understanding how changes in weather systems influences streamflow. Previously, while at CSIRO, he researched the influence of climate drivers, such as the El Niño-Southern Oscillation and the Indian Ocean Dipole, on Australian rainfall. He recently completed a PhD at Monash University specifically looking at El Niño and east Australian rainfall.
Presenter: Surendra Rauniyar (Bureau of Meteorology)
Length: 52 mins (inc. Q&A)
Topic: Defining a climate baseline: separating climate change from climate variability in recent rainfall
Cool season (April to October) rainfall is important for agriculture and replenishing reservoirs across Victoria. However, it has been unusually low (~12% below the 20th century average) since the beginning of the Millennium Drought in 1997. This persistent drying condition has challenged the underlying assumption of stationarity used in defining the baseline climate for future planning and management of water resources over Victoria. If the baseline is changing, it is helpful to understand the causes of that change and whether there is now the need to allow for the influence of climate change in future planning. This presentation will show how much of the observed drying is driven by external forcing, and what is the expected combined impact of both external forcing and internal variability on Victorian rainfall over coming decades.
Surendra Rauniyar is a research scientist in the Climate Change, Variability, and Extremes group at the Australian Bureau of Meteorology. Surendra's research interests include understanding southern Australia's climate variability and change, and associated drivers and attribution of the observed change. Surendra has a background in civil engineering and received his PhD from the University of Melbourne in 2015, where he examined the spatiotemporal variability of rainfall over the Maritime Continent and northern Australia caused by three major modes of climate variability.
Presenter: Steve Charles (CSIRO)
Length: 54 mins (inc. Q&A)
Topic: Hydroclimate projections and baselines
Climate model simulations (projections) show a range of plausible future changes, which will be amplified in changes to runoff and hence water supply for Victoria. This Webinar will provide an overview of the currently available projections of these changes. Steve will outline sources of uncertainty, recent regional climate modelling at finer spatial scale than global climate models, and the resulting hydrological projections. The projected changes will be discussed within the context of recommended hydroclimate baselines, given the observed drying experienced by the region in recent decades. Climate science continues to evolve, with the next generation of climate models providing new projections for the Intergovernmental Panel on Climate Change Sixth Assessment Report (IPCC AR6) due next year. Some preliminary results from these new projections will also be shared.
Dr Steve Charles is a Senior Research Scientist at CSIRO Land and Water, with over 20 years of experience in hydroclimate research. In recent years he has worked on projects on climate downscaling, seasonal forecasting and climate changing projection at regional scales, focusing on the impacts of climate variability and change on hydrology and water supply systems.
Page last updated: 09/12/20