Abstract
Abstract. WaterGAP is a global hydrological model that quantifies human use of groundwater and surface water as well as water flows and water storage and thus water resources on all land areas of the Earth. Since 1996, it has served to assess water resources and water stress both historically and in the future, in particular under climate change. It has improved our understanding of continental water storage variations, with a focus on overexploitation and depletion of water resources. In this paper, we describe the most recent model version WaterGAP 2.2d, including the water use models, the linking model that computes net abstractions from groundwater and surface water and the WaterGAP Global Hydrology Model (WGHM). Standard model output variables that are freely available at a data repository are explained. In addition, the most requested model outputs, total water storage anomalies, streamflow and water use, are evaluated against observation data. Finally, we show examples of assessments of the global freshwater system that can be achieved with WaterGAP 2.2d model output.
Highlights
A globalized world is characterized by large flows of virtual water among river basins (Hoff et al, 2014) and by international responsibilities for the sustainable development of the Earth system and its inhabitants
Global-scale knowledge about water flows and storages on land is necessary to understand the Earth system, including interactions with the ocean and the atmosphere as well as gravity distribution and crustal deformation. Such models are frequently used in large-scale assessments, such as the assessment of virtual water flows for products (Hoff et al, 2014) within the framework of the Intergovernmental Panel on Climate Change and the assessment of impacts based on scenarios for a sustainable future
Less agreement is visible for the separation into groundwater withdrawals and surface water withdrawals
Summary
A globalized world is characterized by large flows of virtual water among river basins (Hoff et al, 2014) and by international responsibilities for the sustainable development of the Earth system and its inhabitants. During the last three decades, global hydrological models (GHMs) have been developed and continually improved to provide this information They enable the determination of the spatial distribution and temporal development of water resources and water stress for both humans and other biota under the impact of global change (including climate change). Global-scale knowledge about water flows and storages on land is necessary to understand the Earth system, including interactions with the ocean and the atmosphere as well as gravity distribution and crustal deformation (affecting GPS) Such models are frequently used in large-scale assessments, such as the assessment of virtual water flows for products (Hoff et al, 2014) within the framework of the Intergovernmental Panel on Climate Change and the assessment of impacts based on scenarios for a sustainable future
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