Regional frequency analysis for maximum 5-day precipitation totals using L-moments approach in Slovakia

This study presents a comprehensive Regional Frequency Analysis (RFA) of maximum 5-day precipitation totals (Rx5D) in Slovakia using the L-moments approach. The analysis utilized data from 419 precipitation stations across Slovakia, operating continuously from 1951 to 2020. The main objectives were to identify homogeneous regions based on Rx5D, estimate regional frequency distributions, calculate maximum Rx5D for return periods of 5, 10, 20, 50, 100, and 200 years, and map these estimates for Slovakia. The cluster analysis, employing index-flood procedure and Ward’s method, identified 14 reasonably homogeneous clusters. Homogeneity and discordancy tests further refined these clusters. The regional frequency distribution for each Rx5D region was determined using L-moment ratio diagrams, \({Z}^{Dist}\) $Z^{\mathit{Dist}}$ measure and Anderson–Darling tests, resulting in the selection of Gumbel (GUM), Generalized Pareto (GPA), and Generalized Logistic (GLO) as the best-fit distributions for different regions. Specifically, GUM was selected as the best fit only for mountainous regions, highlighting the variability in distribution characteristics across different geographical areas. The analysis revealed significant spatial variability in the Rx5D patterns across Slovakia. Our results indicate that, design Rx5D values expected once every 100 years in lowland regions could occur as frequently as once every 25 years in mountainous areas. The most extreme design Rx5D values exceeding 200 mm were observed in the high-elevation mountainous regions, underscoring the heightened risk of extreme precipitation events in these areas. By exposing these spatial variations, our study contributes to a deeper understanding of precipitation extremes in Slovakia and provides a robust framework for informing water resource management and climate adaptation strategies in the region.