Droughts have an increasing impact on the entire European continent. As the frequency and intensity of droughts rise in many parts of Europe, the implementation of effective drought adaptation and mitigation strategies becomes increasingly important. However, it is not known how diverse tools are used in drought management with increasing drought severity. This study explores the role of Decision Support Tools (DSTs) in strategic and operational drought management in the Netherlands. Through a survey among national and regional water authorities, this study shows the increasing reliance of water managers on field measurements, Data Information Systems (DISs), stakeholder consultation, and legislation with increasing drought severity. Weather forecasts and expert knowledge remain important throughout all drought management phases. Despite the increased use of DISs with drought severity, the use of hydrological models does not follow the same trend. DISs, which often incorporate hydrological models, reveal a ‘hidden’ use of these models. Rather than serving as ‘key artifacts’ for modelers, they become active ‘participants’ in broader data systems during advanced phases of drought management. All these aspects influence key responsibilities in model use including appropriateness and transferability, reproducibility, and transparency. These factors are critical to consider when aiming to bridge the gap between science and policy in the application and development of DSTs.

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Groundwater depletion is a problem in many parts the world. We developed an approach to investigate the drivers of groundwater depletion in data-scarce regions. The approach combines natural and human-induced drivers, with the latter focusing on the link between human activities and government policies. We tested the approach in Wadi Zabid, Yemen. Forty years of rainfall-runoff data were analyzed, alongside changes in land cover, groundwater abstraction and related policies. No decrease in rainfall was observed, but runoff did decrease slightly. Significant expansion of agricultural lands led to increased demand for irrigation water, which was provided by drilling wells and building water harvesting/diversion structures. In Wadi Zabid, human activities, stimulated by policy measures, were the main drivers of groundwater depletion (water table here fell by 1 m/yr on average over 1972–2016). We conclude that combining natural and human-induced factors is indeed a valuable approach for investigating groundwater depletion drivers.

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Developments such as climate change and a growing demand for drinking water threaten the sustainability of drinking water supply worldwide. To deal with this threat, adaptation of drinking water supply systems is imperative, not only on a global and national scale but particularly on a local scale. This investigation sought to establish characteristics that describe the sustainability of local drinking water supply. The hypothesis of this research was that sustainability characteristics depend on the context that is analysed, and therefore, a variety of cases must be analysed to reach a better understanding of the sustainability of drinking water supply in the Netherlands. Therefore, three divergent cases on drinking water supply in the Netherlands were analysed. One case related to a short-term development (2018 summer drought), and two concerned long-term phenomena (changes in water quality and growth in drinking water demand). We used an integrated systems approach, describing the local drinking water supply system in terms of hydrological, technical, and socio-economic characteristics that determine the sustainability of a local drinking water supply system. To gain a perspective on the case study findings that are broader than the Dutch context, the sustainability aspects identified were paired with global aspects concerning sustainable drinking water supply. This resulted in the following set of hydrological, technical, and socio-economic sustainability characteristics: (1) water quality, water resource availability, and impact of drinking water abstraction; (2) reliability and resilience of the technical system and energy use and environmental impact; (3) drinking water availability, water governance, and land and water use. Elaboration of these sustainability characteristics and criteria into a sustainability assessment can provide information on the challenges and trade-offs inherent in the sustainable development and management of a local drinking water supply system.@en