Assessment of Precipitation Trends in the Bârzava Catchment, Romania

Abstract

Climate change challenges the stationarity assumption which is the base for the traditional hydraulic infrastructure design. This leads to the need to perform analyses of precipitation and temperature trends. This study examines long-term hydro-climatic changes in the Bârzava River basin, western Romania, a flood-prone catchment with cascade reservoir systems, that is critical for flood protection. Using mean monthly precipitation, along with maximum and minimum temperature data from eight meteorological stations spanning 1960–2021, we applied the Mann-Kendall test and Sen’s slope estimator to detect monotonic trends, complemented by Inverse Distance Weighting interpolation to assess spatial variability across the 1,190 km² catchment. Results reveal upward trends in monthly precipitation, with the strongest increases during June-August (Kendall’s τ up to 0.46, Sen’s slopes 0.05–0.07 per year) and additional significant increases from January through May and in December. September-November months showed no detectable trends, indicating non-uniform seasonal changes. Spatial patterns confirm highest precipitation in the Semenic Mountains and lowest in the plains, with June consistently recording peak monthly totals. These findings demonstrate that climate change altered intra-annual distribution rather than uniform annual increases, with implications for intensified warm season flood risk and potential low-flow stress.