Combined Hydrological Modelling and Regional Geodetic Estimation of Water Storage Variations in Large River Basins Using GRACE Data

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The goal of this collaborative project between hydrology, geodesy and mathematics, which continues the work of the current funding period is, on the one hand, to improve global-scale hydrological modelling of water storage variations and flows in the different storage compartments by using GRACE data. On the other hand, the determination of the static and temporal gravitational field in these regions from GRACE range and range-rate observations shall be improved by using information derived from hydrological models such as WaterGAP Global Hydrological Model WGHM. The role of the Frankfurt group will be the improvement of the hydrological model WGHM, the Bonn group will be responsible for the improvement of the GRACE analysis and the Potsdam group will develop and improve new estimation approaches that will help to advance project. This project aims at answering important hydrological questions, focusing 1) on the contribution of dynamic floodplain inundation to water storage and flow (continuing the work in the current funding period), and 2) on the impact of continental glaciers at seasonal and longer time scales. Central to the project is the development of a multi-objective calibration tool for WGHM using Ensemble Kalman filter techniques which will be used to exploit GRACE observations of total water storage variations (and river discharge observations) optimally for improved global-scale modeling of water storages and flows. The geodetic objectives comprise the further understanding and improvement of the GRACE level-1B analysis using the Kalman smoother approach resulting in the determination of improved daily GRACE solutions. These daily models will also be applied as de-aliasing product leading to an increase in accuracy of monthly solutions.