Odra

Due to the extreme meteorological and hydrological conditions prevailing that summer, several adverse phenomena occurred. In flowing and standing waters, the oxygen content locally decreased, contributing to so-called ‘hypoxia’ and local fish die-offs. In many reservoirs, but also in oxbow lakes and places where the water flows in rivers were, and still are, very low, massive algal blooms were observed, the presence of which can also lead to the deterioration of water parameters and, as a result, fish deaths.

Appearance of the so-called 'golden algae'

Large quantities of so-called 'golden algae' were found in the waters of the Oder River in August 2022, which secrete a potent ichthyotoxin that can directly contribute to the phenomenon of mass fish die-offs in the river. Experts from the Institute of Inland Fisheries Institute in Olsztyn have been analysing samples of the globally rare world Prymnesium parvum, so-called 'golden algae'. Scientists have confirmed that these microorganisms also occur in large quantities in other sections of the Oder River. Further data analysis is currently underway.

The worst drought in 500 years across the continent

According to IMGW-PIB, the situation is extraordinary in Europe. The extreme drought has covered much of Western Europe, Central Europe, the Balkans and the Apennine Peninsula. The extent of the drought is shifting to the east of the continent. The situation in Western and Central Europe is analogous to that in 1921. The effects of that drought were described in a publication by an international team of researchers that appeared in the journal Climate of the Past in 2021. Some areas of the Old Continent are experiencing the most severe drought in nearly 500 years. Europe's major rivers are drying up completely, and entire ecosystems are dying with them. We need to adapt to entirely new climatic conditions and extreme phenomena because climate models indicate that drought periods at our latitude will become increasingly longer, and the scale of the phenomena may grow. This year's August has been the 3rd warmest August since 1991 (the second warmest in the 21st century, after August 2015). The average air temperature is 1.9° higher than the multi-year conditions from 1991 to 2020.

In the Oder River basin, the 2022 hydrological drought started at the earliest. In May, synopticians and hydrologists from IMGW-PIB issued the first warnings against this phenomenon. Lows prevailed in the Oder basin in May-July, mainly due to rainfall deficiency and high air temperature. A significant improvement in the hydrological situation was only brought about by heavy rainfall in the second half of August this year. In the channelised section of the Oder River, more significant fluctuations and increases in water levels related to the regular operation of hydro-technical facilities were recorded. Heavy rainfall associated with storms occurred in south Poland at the turn of July and August and at the end of August. They translated into higher water levels on the upper Oder and its tributaries, especially on the left bank. As a result of precipitation, water levels on the tributaries rose to the high water zone. In comparison, in the Vistula basin, the hydrological drought started slightly later than in the Oder River basin. The increase in the threat of hydrological drought occurred in mid-July. Currently, at the beginning of September, low flow values are recorded, especially in Podkarpacie and Mazovia.

As experts from IMGW-PIB point out, flows and water levels are relatively lower in some rivers compared to previous years. At many stations, water levels have even fallen below the absolute minimum. The last such low water levels and flows were recorded during the 2015 and 2020 droughts.

Extensive research work

Scientists from the Team for the Situation Arising on the Oder River, established by the Minister of Climate and Environment to investigate the causes of the ecological disaster on the river, stress that the specific hydrological and meteorological conditions that prevailed this year may have contributed to the occurrence of the phenomenon. Research analyses are ongoing and are carried out in a multifaceted manner. A preliminary expert report on the situation in the Oder River will be produced by 30 September 2022. In addition to IMGW-PIB representatives, experts from the Inland Fisheries Institute in Olsztyn, the Sea Fisheries Institute - National Research Institute, the National Veterinary Institute - National Research Institute, the General Veterinary Inspectorate, Voivodeship Veterinary Inspectorates, the Chief Inspectorate of Environmental Protection (GIOŚ) and the General Directorate for Environmental Protection (GDOŚ), the Wrocław University of Technology and the Warsaw University of Technology, the University of Warmia and Mazury in Olsztyn, the West Pomeranian University of Technological University in Szczecin and the University of Szczecin also participate in the work of the Team.

The experts' findings will help to identify the boundary conditions under which such phenomena occur, which will help to create a special-purpose algorithm to predict the occurrence of similar events in the future.

Continuous monitoring of water parameters in the Oder River by the Chief Inspectorate of Environmental Protection continues. Subsequent analyses of samples of dead fish and mussels and phytoplankton surveys are being conducted in parallel. Samples will additionally be analysed by laboratories from, among others, Austria, the Czech Republic and the Netherlands. Information can be found on the website of the Chief Inspectorate of Environmental Protection: https://www.gios.gov.pl and on the website: www.gov.pl/web/odra.