This collection gathers papers that describe and/or apply the global water resources and use model WaterGAP.

WaterGAP is a global freshwater model that calculates human water use as well as water flows and storage on all continents (except Antarctica), taking into account the human influence on the natural freshwater system such as climate change, water abstractions, and dams. As one of the pioneers in the field of global hydrological modelling, it supports our understanding of the global freshwater system since 1996 for historical periods and the future. The model is continuously being improved to answer scientific questions driven by societal demands. WaterGAP is applied to assess water scarcity, droughts, and floods and to quantify the human impact on, for example, groundwater, wetlands, streamflow, and sea-level rise.

This collection gathers papers on innovative approaches and methods that limit the impacts of wet and dry hydrological extremes on society and ecological systems.

With climate change, the frequency and intensity of heavy-rainfall events, floods, and droughts are increasing in many parts of the world, causing high levels of damage to people, property, and ecological systems. Managing these water extremes, in particular rapid changes between contrasting hydrological conditions, poses a challenge for regional and local decision-makers. This collection includes articles on innovative approaches and methods for the development of adaptation strategies that limit the impacts of wet and dry hydrological extremes on society and ecological systems. It covers (but is not limited to) topics related to new methods for monitoring, forecasting, and the communication of water extremes on different spatial and temporal scales, as well approaches integrating flood protection and drought mitigation.

This collection was initiated by the BMBF (German Federal Ministry of Education and Research) funding measure "Water Extremes" (WaX) (in German, Wasser-Extremereignisse).