Observations from the Western Carpathians and Pannonian Plain show that rainfall return levels need to be adjusted to account for rising dew-point temperature

Abstract

Rainfall records from a total of 526 rain gauges located in the western part of the Carpathian Mountains and the adjacent Pannonian Plain were analyzed. Estimation of extreme rainfall totals with various return periods is essential for reliable design of hydraulic infrastructure. The ongoing climate change brings additional challenges to the estimation of rainfall return levels. In this paper, we compared stationary vs. non-stationary generalized extreme value distributions (GEV) for 2-, 5-, 10-, 25-, 50-, and 100-year return levels of 24-h rainfall determined from annual maxima series. The fundamental question we seek to answer in this paper is whether the stationarity-based design concept is adequate under changing climate conditions because the statistical parameters of probability distribution become dependent on dew-point temperature. Our analyses revealed that the projected return levels tend to increase with decreasing return periods. For instance, the 100-year return levels need an adjustment by ~6.64% (CI: -1.03% +14.95%), while the stationary 5-year return periods of 24-h precipitation totals need to be adjusted by up to ~10.5% (CI: -3.61% +21.24%). Our investigations showed that in ~60% of the analyzed sites the current return levels might need an adjustment to account for the rising dew-point temperature. The presented results may have implication for regional water management planning and flood risk assessment.