A multi-purpose modelling framework for improved prediction of hydrological extremes at the European and global scale

OS LISFLOOD is an open-source, spatially distributed, physically-based hydrological model. Notably, it is used in the operational set-up of the Copernicus Emergency Management Service (CEMS) to generate flood forecasts for the European and Global Flood Awareness Systems (EFAS & GloFAS) and drought indicators for the European and Global Drought Observatories (EDO & GDO). Being part of an operational set-up, OS LISFLOOD and its European and global model domain set-ups benefit from regular upgrades, with the release of EFAS version 6 (1 arcmin spatial resolution, 6 hours temporal resolution) and GloFAS version 5 (3 arcmin spatial resolution, daily temporal resolution) planned in 2026.

In a multi-purpose framework, developments included in EFAS v6 and GloFAS v5 aim to improve the representation of all key hydrological states and fluxes, with specific attention to high and low flows, soil moisture, snow cover, total runoff, and total water storage. For example, improved representation of physical processes (e.g. a diffusive river routing and a revised reservoir routine) enables more accurate simulation of river flow dynamics; updated model inputs (such as meteorological forcings and soil properties) and revised model routines (model state initialization, snow melt, and water losses to the deep groundwater) support more realistic representation of snow cover, soil moisture and total water storage dynamics. Moreover, model parameter calibration used a novel objective function, the Joint Divergence Kling–Gupta Efficiency (JDKGE), designed to optimize performance on both high and low flows.  

This contribution presents the quantitative evaluation of EFAS v6 and GloFAS v5. OS LISFLOOD calibration utilized 2,318 in-situ discharge time series for Europe and 5,230 globally, with an increase of 22% and 162%, respectively, over previous versions. Median modified Kling Gupta Efficiency (‘KGE) exceeds 0.7 for both systems, representing an improvement of +0.08 and +0.21 for the European and global domains, respectively. Examples of high and low flow simulations for different climate zones and socio-economic landscapes allow to uncover the outcomes of modelling choices, explain challenges, and share open questions. European and global set-ups comprehensive evaluation also entails comparisons with relevant hydrological variables for water resilience such as soil moisture and total water storage.

EFAS and GloFAS hydrological reanalysis datasets are available from the Copernicus Early Warning Data Store. In compliance with FAIR principles, OS LISFLOOD source code (with v5 incorporating all recent model improvements) is freely accessible alongside its pre- and post-processing tools, input maps, and calibrated parameter maps. By providing open access to these datasets and modeling tools, we invite the wider community to benefit from the recent developments, collaborate in model evaluation, and contribute to the ongoing evolution of the system.