Hydrological drought explained

Abstract

Drought is a complex natural hazard that impacts ecosystems and society in many ways. Many of these impacts are associated with hydrological drought (drought in rivers, lakes, and groundwater). It is, therefore, crucial to understand the development and recovery of hydrological drought. In this review an overview is given of the current state of scientific knowledge of definitions, processes, and quantification of hydrological drought. Special attention is given to the influence of climate and terrestrial properties (geology, land use) on hydrological drought characteristics and the role of storage. Furthermore, the current debate about the use and usefulness of different drought indicators is highlighted and recent advances in drought monitoring and prediction are mentioned. Research on projections of hydrological drought for the future is summarized. This review also briefly touches upon the link of hydrological drought characteristics with impacts and the issues related to drought management. How to cite this article:WIREs Water 2015, 2:359-392. doi: 10.1002/wat2.1085 HYDROLOGICAL DROUGHT IN CONTEXTH ydrological drought refers to a lack of water in the hydrological system, manifesting itself in abnormally low streamflow in rivers and abnormally low levels in lakes, reservoirs, and groundwater. 1 It is part of the bigger drought phenomenon that denotes a recurrent natural hazard. 2 Societies around the world are exposed to a multitude of natural hazards, such as earthquakes, volcanic eruptions, hurricanes, storms, tornadoes, floods, and droughts. 3,4 Hydrological extremes (floods and hydrological droughts) are natural hazards that are not confined to specific regions, but occur worldwide and, therefore, impact a very large number of people. 5 Flooding events receive most attention, both in the news and in scientific literature, due to their fast, clearly visible, and dramatic consequences. * Correspondence to: a.f.vanloon@bham.ac.uk School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK Drought events, also called 'the creeping disaster ', 6,7 develop slower and often unnoticed and have diverse and indirect consequences. Hydrological droughts can, however, cover extensive areas and can last for months to years, with devastating impacts on the ecological system and many economic sectors 1,8 (Table 1). Examples of affected sectors are drinking water supply, crop production (irrigation), waterborne transportation, electricity production (hydropower or cooling water), and recreation (water quality) e.g., Refs 1, 6, 8-13. The ecosystem impacts of drought differ between terrestrial ecosystems, in which droughts influence tree mortality due to wild fires, 14,15 and aquatic ecosystems, where they affect e.g., species composition, population density, 16 and food web structure. 17 Examples of drought events in the recent and distant past and their impacts are provided in Box 1.Currently, there is increasing awareness of drought and related hazards (heat waves and wi...

Multiscale evaluation of the Standardized Precipitation Index as a groundwater drought indicator

“…5). This is in accordance with a wellknown phenomenon of the drought attenuation while propagating through subsurface media and the groundwater compartment of the terrestrial water cycle (Hisdal and Tallaksen, 2000;Van Loon, 2015). Notably, the 1996 and 2003 drought events that appeared in the averaged SPI at the Dutch and the German wells, respectively, were not so strongly pronounced in their respective SGI estimates to characterize these events as severe large-scale groundwater droughts.…”

“…It is however noted that such analysis would require a good quality of impact variable data sets and, for many regions for which we need reliable and accurate data sets (e.g., on groundwater drought information), these observations are often not readily available. Nevertheless, the issue of analyzing an appropriate drought timescale is not only specific for the groundwater system, but is also relevant for several other hydrological and ecological systems (e.g., Pasho et al, 2010;Vicente-Serrano et al, 2011López-Moreno et al, 2013;VicenteSerrano et al, 2013;Haslinger et al, 2014;Bachmair et al, 2015;Van Loon, 2015). Figure 5 shows the exemplary time series of the SGI and SPI at 6 and 12 months of the accumulation periods for all wells and grid cells and their respective spatial averages for an overlapping period of 1995-2006.…”

“…The propagation of precipitation signals to groundwater droughts is largely controlled by both catchment and climatic characteristics such as terrain, soil and geological properties, and precipitation seasonality, snowmelt timing, and atmospheric water supply and evaporative demand. This results in a pronounced spatial variation of hydrologic (groundwater) drought characteristics (see, e.g., Peters et al, 2006;Bloomfield and Marchant, 2013;Haslinger et al, 2014;VicenteSerrano et al, 2012;Teuling et al, 2013;Van Loon et al, 2014;Stoelzle et al, 2014;Van Loon, 2015). On the aspect of climatic variables, the SPI that fully accounts for the atmospheric water supply side does not include the effects of the evaporative water demand that could be a determining factor in a hydrologic (groundwater) drought analysis (VicenteSerrano et al, 2010;Teuling et al, 2013).…”

“…Although the SPI is recognized as an effective meteorological drought index (Hayes et al, 2010) due to its relative ease of computation and comparability across climates, some studies have questioned its application for groundwater drought monitoring because the translation of precipitation deficits into hydrologic (groundwater) droughts is nonlinear (Bloomfield and Marchant, 2013;Teuling et al, 2013;Van Loon et al, 2014). Both catchment and climate characteristics such as the differences in underlying soil, terrain, vegetation and geological properties, precipitation seasonality, snowmelt timing, and the availability of atmospheric water supply and demand (evapotranspiration) control the development of hydrologic droughts and the resulting drought characteristics (Bloomfield and Marchant, 2013;Haslinger et al, 2014;Van Loon et al, 2014;Stoelzle et al, 2014;Van Loon, 2015). Recently, Vicente-Serrano et al (2010) introduced the Standardized Precipitation Evapotranspiration Index (SPEI) with a similar multitemporal characteristic to the SPI, but accounting for both the atmospheric water supply (precipitation) and evaporative demand (potential evapotranspiration).…”

Spatiotemporal Characteristics of Groundwater Drought and Its Response to Meteorological Drought in Jiangsu Province, China

“…Furthermore, the relationship between regional groundwater drought and meteorological drought is analyzed based on regional average SGI and SPI. The results are consistent with conceptual dynamics of drought propagation, i.e., attenuation, lag and lengthening [29]. Attenuation is smoothing of the maximum negative anomaly, lag describes the delay in the onset of the drought signal as it passes through the hydrological cycle, and lengthening extends the period of drought.…”