Monthly maps for discharge anomalies and Lowest alert level exceedance with a summary of the monthly hydrological situation.


Hydrological situation for May 2021

Figure 1. Exceedance of lowest discharge threshold level for May 2021.
Figure 1. Exceedance of lowest discharge threshold level for May 2021.
Figure 2. Exceedance of lowest water level threshold level for May 2021.
Figure 2. Exceedance of lowest water level threshold level for May 2021.
Figure 3. Classification of stations according to discharge historical data average percentile ranges for May 2021.
Figure 3. Classification of stations according to discharge historical data average percentile ranges for May 2021.

by EFAS Hydrological Data Collection Centre,

In May, the highest concentration of stations exceeding their first threshold level is located in central Europe. Analysing the relationship between the number of stations in each basin and the number of stations with exceedances, the Soca-Isonzo river basin in Slovenia is the most affected with 38% of its stations overpassing threshold levels. The next is the Dnieper river basin with 32 % of stations with exceedances throughout Ukraine and Belarus. Many stations exceeded their thresholds in the Danube basin in Slovenia, Austria, Serbia, Slovakia, Czech Republic, Hungary, Romania, Croatia, Germany, Ukraine, Kosovo, and Bosnia and Herzegovina. Also notable is the concentration of stations in the basins of the Po and Dnieper rivers (Italy and Ukraine/Belarus respectively). Finally, there are some isolated stations distributed throughout Norway and Sweden and three stations in Spain (one in the Minho-Limia basin in the north and two in the east).

Regarding stations registering values above the 90% quantile, a tiny number of stations (78) exceeded this value in May, just over twice as many stations that last month (32). A considerable number of these stations (roughly 26%) were located in southern Britain. Another considerable number of stations also surpassing the 90% quantile (just over 24%) can be found in the Danube basin in stations across Slovenia, Slovakia, Croatia, Serbia, Ukraine, Czech Republic, Romania, and Serbia. To a lesser degree, other stations can be seen in the Oder basin on the Lusatian Neisse river (Poland) and on the Oder river through Germany. To a minor extent, values exceeding the 90% quantile can be found in stations in the Vistula basin (Poland) and Elbe basin (Germany and the Czech Republic). A handful of stations over the 90% quantile occurred in several basins in the south of Sweden, France (Rohne basin) and dispersed stations in Spain. Other scattered stations can be seen in the Dnieper basin through Ukraine and Belarus. Two isolated stations are in the Daugava basin (Latvia) and Soca/Lsonzo (Slovenia).

Finally, and according to those stations registering values below the 10% quantile, the highest concentration of them corresponds to the north of Spain with the presence of 11 stations along the Ebro and Minho basins. The rest of the stations fulfilling this criterion are isolated stations located on the Thames river (England), Rhine river (Germany), Oder river (Poland), Verde river (Spain), and the Danube river along its course through Romania.