The Groundwater Drought Initiative (GDI): Analysing and understanding groundwater drought across Europe

Abstract

Abstract. In Europe, it is estimated that around 65 % of drinking water is extracted from groundwater. Worryingly, groundwater drought events (defined as below normal groundwater levels) pose a threat to water security. Groundwater droughts are caused by seasonal to multi-seasonal or even multi-annual episodes of meteorological drought during which the drought propagates through the river catchment into the groundwater system by mechanisms of pooling, lagging, and lengthening of the drought signals. Recent European drought events in 2010–2012, 2015 and 2017–2018 exhibited spatial coherence across large areas, thus demonstrating the need for transboundary monitoring and analysis of groundwater level fluctuations. However, such monitoring and analysis of groundwater drought at a pan-European scale is currently lacking, and so represents a gap in drought research as well as in water management capability. To address this gap, the European Groundwater Drought Initiative (GDI), a pan-European collaboration, is undertaking a large-scale data synthesis of European groundwater level data. This is being facilitated by the establishment of a new network to co-ordinate groundwater drought research across Europe. This research will deliver the first assessment of spatio-temporal changes in groundwater drought status from ∼1960 to present, and a series of case studies on groundwater drought impacts in selected temperate and semi-arid environments across Europe. Here, we describe the methods used to undertake the continental-scale status assessment, which are more widely applicable to transboundary or large-scale groundwater level analyses also in regions beyond Europe, thereby enhancing groundwater management decisions and securing water supply.

Improved understanding of regional groundwater drought development through time series modelling: the 2018–2019 drought in the Netherlands

“…Multiple recent research efforts have aimed at better understanding the variations in groundwater drought and its impacts at national and European scales (Bakke et al, 2020;Hellwig et al, 2020;Margariti et al, 2019;Van Loon et al, 2017;Brauns et al, 2020). The 2018 (-2019) drought in Europe has so far been studied at larger scales from a meteorological perspective (Bakke et al, 2020;Philip et al, 2020;Toreti et al, 2019) as well as from a hydrological perspective in Scandinavia and Switzerland, among others (Bakke et al, 2020;Brunner et al, 2019).…”

Advancing AI-based pan-European groundwater monitoring

“…Fink et al 2004, Stahl et al 2016, Van Lanen et al 2016, Bastos et al 2020, Boergens et al 2020, affecting all compartments of the water cycle. Droughts often affect large areas across national boundaries (Brauns et al 2020). High ambient atmospheric temperature, continuous precipitation deficits, and large evapotranspiration losses translate into delayed and attenuated soil moisture (θ) deficits, which subsequently reduce GW recharge and increase water table depths (wtd) and ultimately, cause low streamflow or dried-up rivers (Tallaksen et al 2009, Van Loon 2015, Hellwig et al 2020.…”

“…The major challenge for pan-European GW monitoring is the sparsity of collated wtd observations, which is attributed to the large spatial gaps and temporal inconsistency in the wtd measurement network (Brauns et al 2020). Sparse wtd measurements pose difficulties in understanding GW dynamics at the continental scale and limit insight into extreme events (e.g.…”

Temporal interpolation of groundwater level hydrographs for regional drought analysis using mixed models

“…The method is illustrated with six GWL hydrographs from various aquifers in the UK (Allen et al 1997). However it is explicitly designed to apply to large-sample problems, such as regional-to continental-scale groundwater drought analysis, where metadata associated with sites may be minimal and may be effectively restricted to gridded meteorological data (Brauns et al 2020).…”