Journal Article

Global hydrological reanalyses: The value of river discharge information for world‐wide downstream applications – The example of the Global Flood Awareness System GloFAS

Harrigan, Shaun, Salamon, Peter, Prudhomme, Christel, Matthews, Gwyneth, Zuo, Hao, Hansford, Eleanor, Mazzetti, Cinzia, Boisseson, Eric, Garric, Gilles, Grimaldi, Stefania, Melet, Angelique, Zsótér, Ervin

2024

Overview

Global hydrological reanalyses are modelled datasets providing information on river discharge evolution everywhere in the world. With multi‐decadal daily timeseries, they provide long‐term context to identify extreme hydrological events such as floods and droughts. By covering the majority of the world's land masses, they can fill the many gaps in river discharge in‐situ observational data, especially in the global South. These gaps impede knowledge of both hydrological status and future evolution and hamper the development of reliable early warning systems for hydrological‐related disaster reduction. River discharge is a natural integrator of the water cycle over land. Global hydrological reanalysis datasets offer an understanding of its spatio‐temporal variability and are therefore critical for addressing the water–energy–food–environment nexus. This paper describes how global hydrological reanalyses can fill the lack of ground measurements by using earth system or hydrological models to provide river discharge time series. Following an inventory of alternative sources of river discharge datasets, reviewing their advantages and limitations, the paper introduces the Copernicus Emergency Management Service (CEMS) Global Flood Awareness System (GloFAS) modelling chain and its reanalysis dataset as an example of a global hydrological reanalysis dataset. It then reviews examples of downstream applications for global hydrological reanalyses, including monitoring of land water resources and ocean dynamics, understanding large‐scale hydrological extreme fluctuations, early warning systems, earth system model diagnostics and the calibration and training of models, with examples from three Copernicus Services (Emergency Management, Marine and Climate Change). Global hydrological reanalyses are powerful datasets that can fill the observational gap in river discharge observation. They make wide ranging downstream applications possible worldwide, from water resources to ocean monitoring and early warning systems, through earth system model diagnostic, hydrological extreme understanding and model calibration and training. The GloFAS hydrological reanalysis dataset is a product of the Copernicus Emergency Management Service freely available from the Copernicus Climate Data store, offering daily time series from early 1980 until recent, updated daily with a 3‐ to 5‐day delay.

• Publisher: John Wiley & Sons, Ltd,John Wiley & Sons, Inc,Wiley
• Subject: Archives & records / Climate change / climate services / Copernicus / Data assimilation / Datasets / Downstream / Drought / Early warning systems / Emergency communications systems / Emergency management / Emergency preparedness / Environmental monitoring / Evolution / Flood management / Floods / global hydrological reanalysis / Hydrologic cycle / Hydrologic models / Hydrological cycle / hydrological extremes / Hydrology / large‐scale hydrological modelling / Metadata / observational gaps / Ocean dynamics / River discharge / River flow / Rivers / Surface water / Temporal variability / Temporal variations / Time series / Variables / Warning systems / Water discharge / Water resources