GloFAS verification activities are based on GloFAS fixed reporting points with additional quality criteria applied. The gneral GloFAS v4.0 hydrological performance assessment used the following criteria to select 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)

This general model performance analysis excluded some stations that show clear lake or reservoir influences. This is also why the number of stations can be lower than the 1995 stations used in the v4.0 calibration, where good quality stations were used even with noticeable lake or reservoir influences, which were not included in the general model performance analysis. The reason for this is that these catchments are lot more difficult to model and sometimes improvements could come for the wrong reasons, and thus especially any comparison results between models, such as v4.0 vs v3.1, becomes harder to interpret. 

For reference, in version 3.1 we had 1532 stations. While for v4.0 1987 stations could be used and for the v4.0 vs v3.1 comparison 1949. The number is lower for the comparison, as some stations could not be mapped in v3.1 due to the lower resolution (or other issues) of the river network. The generally lower number of 1532 originally used stations for the v3.1 analysis was partially due to the longer minimum observation length of 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. In addition, numbers also incresed for v4.0 as extra stations were added to the GloFAS observation network since the v3.1 implementation in 2021.