During 2020, the CEMS Hydrological Data Collection Centre welcomed the “Icelandic Meteorological Office” and “Confederación Hidrográfica del Júcar” as two new hydrological data providers to the CEMS hydrological data collection network. Together with the “Slovenian Environment Agency”, who increased the number of stations providing real-time hydrological data to the HDCC, a total of 193 new real-time stations were received by the HDCC. This brings the number of data providers and stations actively providing data by the end of 2020 to a total of 48 and 1990 respectively, with an increase of 4.3% and 11% compared to 2019.
In additional, Poland, Ukraine, Serbia, Ireland, Norway and Romania provided in 2020 new historic data sets. With a total of 12,357,356 new historical data values, the volume of the historical database has increased in 2020 by 10.9% compared to 2019.

This report contains an analysis of the hydrological data received by the CEMS Hydrological Data Collection Centre (HYDRO) for the year 2020 in terms of:

1. the general hydrological conditions across Europe, focusing on important deviations of average discharge;
2. gaps and outliers, including a classification according to causes, duration, length and distribution; and 
3. high flow events, looking at the duration, magnitude, number and distribution of exceedances according to the threshold levels.

The EFAS team, and particularly HYDRO, would like to thank the EFAS Partners and Data Providers that contributed to the CEMS hydrological data collection. We would like to acknowledge their dedication to the EFAS project, their commitment and the sharing of their hydrological data. We thank them for their cooperation with the HDCC, both in the provision of data and for their proactive role in responding to the questions and solving issues. Without their collaboration, the delivery of this report would not be possible.