Evidence of hydroclimatic change in the upper Dniester basin, Eastern Europe (1975–2025), based on ERA5-Land reanalysis

Abstract

The increasing climate instability in the Carpathian Region of Ukraine highlights the need for a quantitative as - sessment of long-term changes in precipitation regimes in mountain catchment basins. This study aims to analyse the transformation of the precipitation regime in the Upper Dniester basin (Ivano-Frankivsk Oblast) over 51 years (1975–2025) based on ERA5-Land reanalysis data. The study covers three key aspects: changes in total precipita - tion and temperature regime; seasonal redistribution of precipitation (DJF, MAM, JJA, SON); and transformation of the snow-to-rainfall ratio. The Mann-Kendall non-parametric test with Sen’s slope estimation was applied to detect monotonic trends; sub-period comparisons were conducted for 1975–1999 and 2000–2025. The main re - sults indicate statistically significant warming (+0.058 °C/year, p < 0.001) alongside a non-significant decrease in annual precipitation (p = 0.069). A significant seasonal redistribution was identified: an increase in winter precipi - tation (+0.82 mm/year, p = 0.041) concurrent with a decrease in summer precipitation (−1.87 mm/year, p = 0.013). The winter snow fraction declined from 68.9% to 62.9%, while the annual indicator remains stable (~18–19%). The practical value of the study lies in providing a scientific basis for adaptation measures in the water manage - ment and agricultural sectors of the Carpathian Region.