Project: coastDat - Regional Water and Matter Fluxes at the Land-Ocean Interface - In order to better understand the global coastal systems and the dangers and risks associated with them, it is important to examine the atmosphere, the land, hydrology, the ocean and especially their interactions and feedbacks. In this project, we provide data on water and matter transport at the land surface. Currently, contributions were made by Umweltforschungszentrum Leipzig (UFZ) and the “Regional Land and Atmosphere Modeling” department of the Institute of Coastal Systems - Analysis and Modeling at Helmholtz-Zentrum Hereon as well as from NIOZ and IOW. Our aim is to quantify the associated cycles of water and matter and their changes, mainly for the transition from land to the ocean. Our work contributes to GCOAST (Geesthacht Coupled cOAstal model SysTem) --> https://www.hereon.de/institutes/coastal_systems_analysis_modeling/research/gcoast/index.php.en Summary: ERA5 is the fifth generation of atmospheric reanalysis (Hersbach et al., 2020) produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). It provides hourly data on many atmospheric, land-surface, and sea-state parameters at about 31 km resolution. It is frequently used to force regional climate models (RCMs) or ocean models. However, it lacks crucial information on riverine freshwater inflows at the land-ocean boundary. The latter is an important flux in ocean model or Earth System model applications, as it is affecting salinity and marine stratification in coastal areas. Therefore, we extended ERA5 with high-resolution river discharge from 1940-2024. Analogous to Hagemann and Stacke (2022), the global hydrology model HydroPy (Stacke and Hagemann 2021) and the Hydrological Discharge (HD) model (Vs. 5.2, Hagemann et al. 2023; Hagemann et al. 2020) were used to simulate daily discharge time series over the whole globe at 1/12° horizontal resolution. HydroPy was driven by daily ERA5 forcing data from 1940-2024 to generate daily input fields of surface and subsurface runoff at the ERA5 resolution. In order to initialize the storages in the HydroPy model and to avoid any drift during the actual simulation period, we conducted a 30-years spin-up simulation by repeatedly using year 1940 of the ERA5 dataset as forcing. To generate river runoff, the HD model was operated globally at 5 arc minutes horizontal resolution. First, the forcing data of surface and sub-surface runoff simulated by HydroPy were interpolated to the HD model grid. Then, daily discharges were simulated with the HD model. This work used resources of the Deutsches Klimarechenzentrum (DKRZ) granted via the Hereon part of the Helmholtz shareholder resources budget. Moreover, ERA5 datasets provided by DKRZ DM via the DKRZ data pool were used.