Multiannual and seasonal variability of Vistula River flows from 1953 to 2022 in the context of meteorological conditions

Abstract

The aim of this study is to analyse the variability of the average annual flows of the Vistula River in the hydrological years 1953–2022, divided into two sub-periods: 1953–1987 and 1988–2022. The analysis was conducted at eight hydrological stations located along the Vistula River. Long-term trends were calculated using the nonparametric Mann–Kendall test. Changes were noted in the distribution of mean annual and monthly flows between the periods 1953–1987 and 1988–2022, but this trend was not statistically significant. The analysis showed that the 1988–2022 period was warmer than 1953–1987, as observed at four meteorological stations. However, no trends were observed in annual precipitation totals. Mean annual flows in 1988–2022 were lower than in 1953–1987, while minimum annual flows in 1988–2022 were higher than in 1953–1987. The study highlights the changing timing of minimum average monthly flows recorded in the middle reaches of the Vistula. In the years 1953–1987, the lowest average monthly flows occurred in September, whereas, in the period 1988–2022, the lowest occurred in October.