Within the RU GlobalCDA, the project P5 will provide a comprehensive set of water table elevation time series of all major inland water bodies. This data set is the foundation for the computation of water volumes as well as river discharges that will be used for the calibration and assimilation into the WaterGAP model. Besides providing the necessary data basis for training regions as well as for validation and critical regions, the project will focus on the development of new methods and approaches necessary to ensure the automated and fast derivation of reliable data at highest accuracy for all major water bodies on a global scale. In detail, within the project the following methodologies will be developed: (1) Automated target detection of permanent and non-permanent water bodies, (2) Reliable waveform classification applicable for different surface types (especially for different large and small open water bodies) and consistent for all missions, (3) Refined inland retracking algorithm for inland altimeter data allowing for a consistent multi-mission data combination, and (4) Reliable uncertainty estimation for each estimated water level. All methods developed will be carefully evaluated and compared to existing methods and results as well as to independent datasets if available.