Hydrological analysis of the Oder droughts for the period 1950‒2022 in the context of the 2022 river disaster

The study aims to analyze the droughts of the Oder from 1950 to 2022 at three water gauge profiles located in the upper (Chałupki), middle (Połęcko), and lower (Gozdowice) reaches of the Oder. The subject of the analysis was the temporal variability of the lowest annual and monthly flows of the Oder, the durations of lows characterized by a flow lower than the adopted threshold criterion (average annual minimum flow, SNQ), and the trends of their changes in the analyzed period. We identified decreasing trends of the lowest annual river flows in the middle and lower reaches of the Oder. The lowest monthly flows of the Oder exhibit statistically significant trends in the months of April–September (Połęcko) and May–September (Gozdowice). The summer drought of 2022 was exceptionally long and severe (the discharge deficit amounted to more than 1.8 Mm³ in the Gozdowice profile) and is unlikely to be reduced to the SNQ level through any existing or planned reservoir. Changes in the drought indicators occur as a result of the course of hydrological processes taking place in the Polish part of the Oder basin.