GloFAS verification activities are based on GloFAS fixed reporting points with additional quality criteria applied. For GloFAS v4.0 hydrological performance assessment used the following criteria to select the 1949 stations for the analysis:

• At least 1 year of observation within the 1979-2022 reference period (regardless of gaps)
  
• Limited impact of lake, reservoir and human influence on river discharge
• Exclusion of stations with poor observation quality problems (typically observations showing errors that could not be corrected, e.g. truncated peaks, etc.), or stations that could not be mapped onto the GloFAS river network with high enough confidence (i.e. the observed gauge could not be represented by GloFAS, for example because of too uncertain metadata, completely unrepresentative observations)

For reference, in version 3.1 we had 1532 stations. For v3.1, the minimum observation length was set as 4 years, which was relaxed further to only 1 year for v4.0. Even though the scores will not be robust at all for very short availability period, which the users should be aware of, this way users can see the model behaviour with the flood thresholds and can have a first impression on the model performance.