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Abstract

Terrestrial Water Storage (TWS) is a measure of the total amount of net-accumulated water in all continental storage compartments. The Global Climate Observing System programme (GCOS) has recently approved TWS Anomalies as an Essential Climate Variable (ECV). With the GRACE/-FO satellite gravimetry missions we have gained the ability to look back on an observable that can be interpreted as monthly TWS change since the year 2002. In the continental water mass budget equation, this change balances the water fluxes from precipitation, evapotranspiration and runoff. Within the framework of the new Collaborative Research Centre 1502 'DETECT', we analyse terrestrial/atmospheric and surface water fluxes and associated budget contributions from model simulations (including free-runs with and without anthropogenic factors), reanalyses, and remote sensing observations for all larger river basins in Europe and combine them with catchment-integrating TWS variability. While, as a first step, we are updating previous budget analyses with latest available data sets, the project's central objective is to quantify to what extent regional changes of land- and water-use contribute to observed budget changes. General budgeting includes the Terrestrial System Modeling Platform (TerrSysMP) and Community Land Model (CLM) at CORDEX- and COSMO-domains over Europe. Here, we introduce our central objectives and show results of our latest analyses of catchment-wide water mass flux time-series over Europe. We discuss our budgeting strategies as well as opportunities and hurdles concerning data availability and uncertainties --- also in view of GRACE successors and the recently launched SWOT mission.