The challenges of hydrological drought definition, quantification and communication: an interdisciplinary perspective

Stahl, Kerstin; Vidal, Jean‐Philippe; Hannaford, Jamie; Tijdeman, Erik; Laaha, Gregor; Gauster, Tobias; Tallaksen, Lena M.

doi:10.5194/piahs-383-291-2020

Cited by 32 publications

(43 citation statements)

References 10 publications

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“…2. Event identification: Floods can be defined as annual maxima events or partial duration series using the peak-overthreshold approach (Lang, Ouarda, & Bobée, 1999), whereas droughts can be defined as annual minimum events (e.g., the lowest flow each year) or defined as events below a given threshold characterized by drought duration and deficit volume (Heudorfer & Stahl, 2017;Stahl et al, 2020) (for an illustration see Figure 2). Based on the latter, either annual maximum series (i.e., largest drought each year) or all events (resembling a partial duration series) can be subject for further analysis.…”

Section: Event Definitionmentioning

confidence: 99%

Challenges in modeling and predicting floods and droughts: A review

et al. 2021

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Predictions of floods, droughts, and fast drought‐flood transitions are required at different time scales to develop management strategies targeted at minimizing negative societal and economic impacts. Forecasts at daily and seasonal scale are vital for early warning, estimation of event frequency for hydraulic design, and long‐term projections for developing adaptation strategies to future conditions. All three types of predictions—forecasts, frequency estimates, and projections—typically treat droughts and floods independently, even though both types of extremes can be studied using related approaches and have similar challenges. In this review, we (a) identify challenges common to drought and flood prediction and their joint assessment and (b) discuss tractable approaches to tackle these challenges. We group challenges related to flood and drought prediction into four interrelated categories: data, process understanding, modeling and prediction, and human–water interactions. Data‐related challenges include data availability and event definition. Process‐related challenges include the multivariate and spatial characteristics of extremes, non‐stationarities, and future changes in extremes. Modeling challenges arise in frequency analysis, stochastic, hydrological, earth system, and hydraulic modeling. Challenges with respect to human–water interactions lie in establishing links to impacts, representing human–water interactions, and science communication. We discuss potential ways of tackling these challenges including exploiting new data sources, studying droughts and floods in a joint framework, studying societal influences and compounding drivers, developing continuous stochastic models or non‐stationary models, and obtaining stakeholder feedback. Tackling one or several of these challenges will improve flood and drought predictions and help to minimize the negative impacts of extreme events. This article is categorized under: Science of Water > Science of Water

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Section: Event Definitionmentioning

confidence: 99%

Challenges in modeling and predicting floods and droughts: A review

et al. 2021

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“…In our study, we used the 20th percentile as drought threshold, meaning that mild droughts are included as well. This could potentially entail that events without clear impacts are classified as droughts, something that was highlighted as a challenge in drought definition by Stahl et al (2020). Despite this, our drought definition still reflects common practices in water management, and we therefore emphasize that this practice is susceptible to a drought frequency paradox.…”

Section: Discussionmentioning

confidence: 94%

Hydrological System Complexity Induces a Drought Frequency Paradox

2021

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Droughts occur as a result of a lack of water compared with normal conditions. Whilst this appears trivial, the exact drought definition of drought is not. Especially as different drought types are present, resulting from the different variables in a hydrological system, each with unique characteristics. We use a common drought definition, the percentile score, and apply the same definition across all drought types, to study whether the actual occurrence of droughts matches the definition. We focus on the data-rich Dutch province of Gelderland, to study droughts from observations across five major components of the terrestrial hydrological cycle. When a percentile threshold of 20% is used as drought definition, corresponding to a mild drought, droughts anywhere in the system occur at least three times more frequently (73% of the time). On the other hand, the situation where drought occurs across all components of the terrestrial hydrological cycle is more than four times less likely than the drought threshold of 20% (namely 5% of the time). This can be attributed by both (1) the different responses across the hydrological system, and (2) the spatial variability present within each component of the hydrological system. With this study, we show the existence of the drought frequently paradox: although droughts are seen and defined as rare from a scientific perspective, when viewed from a societal or operational water management perspective in typical hydrological systems subject to spatial variability and other system complexity, droughts become common, rather than rare. This paradox is a consequence of an inconsistent use of the percentile score drought definition between research and operational water management, and better communication between the two domains is needed in search for a universally accepted drought definition.

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“…Hydrological drought indices provide information that is important for the design and operation of many sectors relevant to the society and the economy of CWA, including domestic water supply, irrigation for agriculture and cattle, hydropower generation, tourism and recreation, and industry. By using hydrological drought indices, it is possible to analyze temporal trends and the influence of climate change, to provide information about drought vulnerability and risk, and to perform large-scale comparative monitoring and forecasting of streamflow and drought conditions (Stahl et al, 2020). The emergence of new hydrological drought indicators during the last years, as well as the new drought definitions like ecological drought (Crausbay et al, 2017) or anthropogenic drought (AghaKouchak et al, 2015), provide evidence for an urgent need to advance hydrological drought research and operational applications (Poshtiri and Pal, 2016), particularly in arid and semi-arid regions that are vulnerable to climate variability and change.…”

Section: Perspectives For Improved Hydrological Drought Monitoringmentioning

confidence: 99%

“…Numerous indices exist for the definition and description of hydrological droughts, which are primarily based on daily or monthly streamflow data (Stahl et al, 2020) and can roughly be divided into threshold-based indices and standardized indices (Van Loon, 2015). Hydrological droughts over CWA were characterized by Rivera et al (2017a) using threshold-based indices for the quantification of drought frequency, duration, and severity for the period 1957-2014.…”

Section: Introductionmentioning

confidence: 99%

A Decade of Hydrological Drought in Central-Western Argentina

et al. 2021

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Most of the water used for the development of the main socio-economic activities in Central-Western Argentina (CWA), an arid to semi-arid region, home to most of the Argentinean wine production, relies on surface streamflow from several snow-fed rivers. During the last decade (2010-2020), reduced snow accumulation over the higher elevations of the Andes mountains triggered the occurrence of hydrological drought over CWA, affecting winter tourism, restricting water use for irrigation and domestic use, and leading to socio-political disputes. This study provides a detailed description of the recent hydrological drought conditions through the use of streamflow records from 15 river basins, which were complemented by precipitation, snowpack, and water equivalent thickness measurements to provide a comprehensive picture of the water losses over the last decade. Hydrological drought indices derived from the threshold level method and the standardized streamflow index allowed characterizing the unusualness of this dry period in the context of the last 49 years. The hydrological deficit over the last decade highlighted the challenges faced by the water managers to provide water for irrigation in the main agricultural oases, with a likely overexploitation of the groundwater resources to supplement the limited surface runoff. The hydrological drought severity increased since 2017, with record-breaking levels in several basins, particularly during the period between July 2019 and June 2020 for the rivers located between 35° and 36°S. We identified the main hydrological drought impacts in CWA, as well as the need for improved mitigation strategies to cope with current and future drought conditions. We also analyzed the current limitations in terms of snow and groundwater observations, highlighting the necessity for an effective hydrological drought monitoring system, together with an improved forecast of snow accumulation in the headwaters, which can contribute to better regional water management plans.

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The challenges of hydrological drought definition, quantification and communication: an interdisciplinary perspective

Cited by 32 publications

References 10 publications

Challenges in modeling and predicting floods and droughts: A review

Challenges in modeling and predicting floods and droughts: A review

Hydrological System Complexity Induces a Drought Frequency Paradox

A Decade of Hydrological Drought in Central-Western Argentina

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