Pre-operational GloFAS release (v5)

The following is a description of the latest pre-operational release of GloFAS (v5.0), made available on GloFAS Stage Platform from 12 November 2026 00z (UTC). Note that the stage environment does not include all products and is subject to changes as pre-release tests are conducted. The stage environment is aimed for users wanted to familiarise themselves with the new system and monitor in parallel the operational and pre-release systems. Users must be registered to the GloFAS Stage Platform to access the pre-operational products (Registration instructions are available in the website).

For an overview of the previous versions of GloFAS, please see: GloFAS versioning system.

Summary

GloFAS v5 introduces several major changes to the system, including:

Improvements to Model: 

• Major improvements to the open-source hydrological model: OS LISFLOOD v5.0.0
• Improved input dataset, with major revisions to some of the 0.05 degrees resolution input maps (e.g. soil hydraulic properties), and to input datasets for lakes and reservoirs
• A new hydrological model calibration at 5378 in-situ gauging stations. Furthermore, a parameter regionalisation was performed to estimate the parameters of catchments for which in-situ discharge observations were not available.
• A revised return period threshold generation methodology with adjustments for river discharge trends, based on a climatology from 1979–2025. For details see: GloFAS flood threshold generation
• The GloFAS v5 reanalysis dataset is available at the CEMS Early Warning Data Store.

Upgrades to the GloFAS Products/Web:

• Upgrades to the GloFAS evaluation layers. 
  • Upgrades to the Model Performance methodology including; Introduction of JSD, and JDKGE scores; Verification based on all 5,378 GloFAS v5 calibration stations. All changes to methodology are reflected in the Hydrological Model Performance product.
  • Work-in-progress: Upgrades to the GloFAS medium-range Forecast Skill  methodology including; Product name change from 'Forecast Skill' to 'Monthly Forecast Skill' to reflect new monthly skill assessments instead of a single year-round assessment, to reflect seasonal variations in forecast performance; Monthly updates using the latest available reforecasts, to reflect the performance of the current forecasting system; Skill evaluation at all 5,378 GloFAS v5 calibration points. All changes to methodology are reflected in the GloFAS monthly forecast skill product.
• Changes related to the GloFAS Reporting Points. For details on the changes see: GloFAS Reporting Points  
  • 15,513 stations were added to the GloFAS fixed reporting point list, bringing the total to 18,414.
  • The minimum upstream area for fixed reporting points has been reduced from 250 km² to 150 km². The 4,141 fixed points with an upstream area between 150 km² and 500 km² are introduced as small fixed reporting points.
  • To distinguish the small fixed reporting points from the standard fixed reporting points (with upstream area > 500 km²), small fixed reporting points with a flood signal are displayed with only their border coloured according to flood severity, rather than as a fully coloured marker. Their flood signal is derived using the same return-period thresholds and probability criteria as for standard points, but it should be interpreted with additional caution, as forecast skill is generally lower for small catchments at the current model resolution.
• New merged 'GloFAS Reservoirs and Lakes with Reservoir Impact' layer. The ‘GloFAS Lakes and Reservoirs’ and ‘GloFAS Reservoir Impact’ static web layers were merged into this new layer to reflect the large increase in the number of lakes and reservoirs represented in the LISFLOOD model, and the correspondingly revised reservoir impact. For more details see: GloFAS Static Layers Overview
• Change of naming convention for ECMWF NWP ensemble forcing from 'ECMWF ENS' to 'IFS ENS', reflected in title of the Discharge Hydrograph in the Reporting Points pop-up window. The new title is "Discharge hydrograph (IFS ENS)" to reflect the combined forecast ensembles as input. For a detailed description of information in the pop-up windows, see GloFAS Reporting Points.

GloFAS v5.0 Evaluation Results

This upgrade of GloFAS has significant impacts on the GloFAS modelling results. The results of the upgrade are described in the following pages.

Technical details