Hydrological drought severity explained by climate and catchment characteristics

Abstract

s u m m a r y Impacts of a drought are generally dependent on the severity of the hydrological drought event, which can be expressed by streamflow drought duration or deficit volume. For prediction and the selection of drought sensitive regions, it is crucial to know how streamflow drought severity relates to climate and catchment characteristics. In this study we investigated controls on drought severity based on a comprehensive Austrian dataset consisting of 44 catchments with long time series of hydrometeorological data (on average around 50 year) and information on a large number of physiographic catchment characteristics. Drought analysis was performed with the variable threshold level method and various statistical tools were applied, i.e. bivariate correlation analysis, heatmaps, linear models based on multiple regression, varying slope models, and automatic stepwise regression. Results indicate that streamflow drought duration is primarily controlled by storage, quantified by the Base Flow Index or by a combination of catchment characteristics related to catchment storage and release, e.g. geology and land use. Additionally, the duration of dry spells in precipitation is important for streamflow drought duration. Hydrological drought deficit, however, is governed by average catchment wetness (represented by mean annual precipitation) and elevation (reflecting seasonal storage in the snow pack and glaciers). Our conclusion is that both drought duration and deficit are governed by a combination of climate and catchment control, but not in a similar way. Besides meteorological forcing, storage is important; storage in soils, aquifers, lakes, etc. influences drought duration and seasonal storage in snow and glaciers influences drought deficit. Consequently, the spatial variation of hydrological drought severity is highly dependent on terrestrial hydrological processes.

The effect of climate on timescales of drought propagation in an ensemble of global hydrological models

“…Another limitation of the evaluation is that the sites with observed data are not spread evenly across the globe, as most sites are located in the United States or Europe, with scarce data in Africa and Asia. Differences between the models and observations can be attributed to several types of errors (Van Loon, 2015). The first type of error concerns errors in the model meteorological forcing data, but also in the GPCC 10 precipitation data used to create the validation dataset.…”

“…However, we examine the relationship between drought propagation and specific model characteristics to identify areas for further study. First, we examine the relationship between SPI-n and average soil moisture 20 storage, as previous work has suggested that water storage plays an important role in drought propagation (Barker et al, 2016;Van Loon and Laaha, 2015). In addition, we examine the effect of model structural choices on drought propagation in an exploratory analysis.…”

Impact of meteorological drought on hydrological drought in Toruń (central Poland) in the period of 1971–2015

“…The catchment's reaction to the precipitation shortage is diverse and primarily depends on physiographic catchment features (soil permeability, topography, land use and land cover), climatic conditions (mainly precipitation and evaporation) and water management [GÓMEZ GÓMEZ, PÉREZ BLANCO 2012; TOKARCZYK, SZALIŃSKA 2014; VAN LOON, LAAHA 2015;WEN et al 2011]. According to LORENZO--LACRUZ et al [2013] the most severe hydrological droughts do not always occur in areas with the intense meteorological droughts, because their severity is also influenced by other factors, like amount of water consumed by the industry and society, effectiveness of water management and meteorological conditions in river's upper course.…”

“…The influence of climatic factors (precipitation, high air temperature, high evaporation) and diverse external conditions may mitigate or aggravate hydrological drought as well as delay it in the relation to the beginning of meteorological drought. VAN LOON and LAAHA [2015] claim that as much as 30 various factors may influence water level and discharge in the main water current. TOKARCZUK and SZALIŃSKA [2014] compared the influence of meteorological drought on hydrological drought in highland and lowland regions of Poland and came to the conclusion that it is different.…”

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“…Drought events are stochastic in nature. A drought event is considered to be a 'creeping hazards' because it develops slowly, it is not easily detected, covers extensive areas and it lasts for a long period of time with adverse impact on water resources, ecological systems, and socio-economic development [1,2]. The term drought has been defined differently in numerous applications [3].…”