Understanding trends in hydrologic extremes across Australia

Wasko, Conrad; Shao, Yawen; Vogel, Elisabeth; Wilson, Louise; Wang, Q.J.; Frost, Andrew; Donnelly, Chantal

doi:10.1016/j.jhydrol.2020.125877

Cited by 50 publications

(28 citation statements)

References 72 publications

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“…Bertola et al (2020Bertola et al ( , 2021 showed that the 100-year flood changed differently than the 2-year flood in some European regions and that these changes can be attributed to different drivers. Similarly, recent studies have shown that small and large floods respond differently to changes in precipitation (Brunner et al, 2021;Wasko et al, 2019Wasko et al, , 2021.…”

Section: Clarifying the Effects Of Temporal Changes On Upper Flood Tailsmentioning

confidence: 91%

Understanding Heavy Tails of Flood Peak Distributions

Merz

Basso

Fischer

et al. 2022

Water Resources Research

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Floods often come as a surprise. Examples of extreme floods that have occurred unexpectedly and have led to disastrous socio-economic consequences abound in the literature (Merz et al., 2015). Figure 1 shows one example time series with such a surprising flood. The 2002 flood peak of the River Kamp, Austria, was about three times larger than the highest flood in the 100-year observational period before and has indeed caused enormous damage triggering desperate emergency measures in the region (Blöschl et al., 2006). From a statistical perspective, the occurrence of such an event is very unlikely if the extreme value behavior conforms to an asymptotically exponential (light-tailed) distribution. However, if the underlying probability distribution has a heavy tail, its occurrence is less unlikely. A heavy upper tail implies that the extreme values are more likely to occur than would be predicted by distributions with exponential asymptotic behavior, such as Exponential, Gamma, and Gumbel distributions (El Adlouni et al., 2008). Because human intuition tends to expect light tail behavior, processes that show heavy tail behavior often lead to surprise (Taleb, 2007).Heavy-tailed behavior of flood peak distributions is of the highest relevance for flood design and risk management. Neglecting heavy tail behavior, if it exists, results in underestimating the probability of occurrence of extremes. This underestimation may result in biased flood management measures, such as underestimated dike

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Section: Clarifying the Effects Of Temporal Changes On Upper Flood Tailsmentioning

confidence: 91%

Understanding Heavy Tails of Flood Peak Distributions

Merz

Basso

Fischer

et al. 2022

Water Resources Research

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“…12-month) is a good indicator of hydrological drought since 12-month SPI shows high correlation with SRI (Shukla and Wood 2008). Moreover, our spatial distribution of long-term drought (longer than 12-month SPI) has similarity with that of Wasko et al (2021).…”

Section: Discussionmentioning

confidence: 53%

“…It should be noted that Taschetto and England (2009) stated a significant decrease in annual total rainfall in southern NSW and VIC with data period covering 1970-2006. Furthermore, one of the latest studies by Wasko et al (2021) reported a decline in rainfall in the south-east of Australia causing a prolonged period of drought. Table 3 illustrates 12-month SPI; the highest intensity (1.64) and second highest magnitude (50.84) were detected between 2017 and 2020 with 31-month duration as an extreme drought.…”

Section: Resultsmentioning

confidence: 99%

“…Besides, long-term drought quantities, duration and magnitude, were higher in the coastal area. It should be noted that Wasko et al (2021) examined trends in hydrological droughts by using standardized runoff index (SRI) at 12-month time scales with data period 1960-2017 and they found a decreasing trend on hydrological droughts in southeast of Australia (especially in coastal areas). Our findings agree with their results in that the longer-term SPI (e.g.…”

Section: Discussionmentioning

confidence: 99%

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Spatiotemporal meteorological drought assessment: a case study in south-east Australia

Yıldırım

Rahman

2021

Nat Hazards

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An understanding on different aspects of droughts is crucial for effective water resources management. Australia has experienced notable droughts in recent years. The present study utilises Effective Drought Index (EDI) and Standardized Precipitation Index (SPI) based on six time horizons (3, 6, 9, 12, 24, and 36 months) to evaluate drought parameters such as magnitude, duration, and intensity with their onset and end in south-east Australia using data from 45 rainfall stations. Maximum drought quantities determined using SPI and EDI, with average data length of 125 years, have been mapped by spline interpolation technique. Furthermore, average drought parameters for each of the SPIs and EDI have been investigated and spatial distributions of drought quantities have been exhibited. In the study area, SPIs based on different time scales (either short term or long term) have detected the maximum drought severity, duration, and/or intensity (at least one of the parameters) between 2013 and 2019. It has been found that south-east Australia had faced one of the most intense droughts during 2013 to 2019. It has also been found that the longest duration of drought has been in southern and eastern coasts of the study area. Generated maps based on average EDI values have depicted that the north-western and central parts of the study area have experienced the longest and strongest drought, whereas higher-intensity drought has been found to be dominating the eastern and southern parts of the study area. Higher frequency of the number of droughts has been found mostly in the east and south of the study area in terms of moderate, severe, and extreme droughts. The generated spatial maps of SPIs and EDI in this study help to identify the most drought-prone and vulnerable parts within south-east Australia. The drought maps developed for south-eastern Australia by this spatiotemporal analysis can be a key tool to policymakers for mitigation, risk assessment, and drought preparedness planning.

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“…Annual potential evapotranspiration is 1,940 mm/year; thus the region is water limited (CSIRO, 2009). There is a steadily increasing trend in total annual rainfall (significant at p < 0.001; Mann–Kendall test) throughout the historical period (Figure 2a) and consequently, evapotranspiration is also increasing due to increased catchment water availability (Wasko et al., 2021). Annual streamflow is closely linked to wet season rainfall, with an average of 94% of runoff occurring during wet season months.…”

Section: Study Area and Data Availabilitymentioning

confidence: 99%

Unprecedented High Northern Australian Streamflow Linked to an Intensification of the Indo‐Australian Monsoon

Higgins

Palmer

Rao

et al. 2022

Water Resources Research

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Streamflow in Australia’s northern rivers has been steadily increasing since the 1970s, most likely due to increased intensity in the Indo‐Australian monsoon. However, because of limited data availability, it is hard to assess this recent trend and therefore contextualize potential future climatic changes. In this study, we used a network of 63 precipitation‐sensitive tree‐ring chronologies from the Indo‐Australian and Asian monsoon regions to reconstruct streamflow in the Daly catchment in the Northern Territory of Australia from 1413 to 2005 CE. We used a novel wavelet‐based method to transform the variance structure of the tree‐ring chronologies to better match the hydroclimate prior to reconstruction with a hierarchical Bayesian regression model. Our streamflow reconstruction accounts for 72%–78% of the variance in the instrumental period and closely matches both historical flood events and independent proxy records, increasing confidence in its validity. We find that while streamflow has been increasing since the 1800s, the most recent 40‐year period is unprecedented in the last ∼600 years. Comparison to an independent coral‐based streamflow record shows regional coherency in this trend. Extreme high flows were found to be linked to La Niña events, but we found no significant relationship between streamflow and El Niño events, or streamflow and other regional climatic drivers. More work is therefore needed to understand the drivers of the recent streamflow increase, but, regardless of the cause, water managers should be aware of the paleoclimatic context before making decisions on water allocations.

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Understanding trends in hydrologic extremes across Australia

Cited by 50 publications

References 72 publications

Understanding Heavy Tails of Flood Peak Distributions

Understanding Heavy Tails of Flood Peak Distributions

Spatiotemporal meteorological drought assessment: a case study in south-east Australia

Unprecedented High Northern Australian Streamflow Linked to an Intensification of the Indo‐Australian Monsoon

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