Estimating extreme dry-spell risk in the Middle Ebro valley (Northeastern Spain). a comparative analysis of partial duration series with a General Pareto distribution and annual maxima series with a Gumbel distribution

Abstract

This paper analyses fifty-year time series of daily precipitation in a region of the middle Ebro valley (northern Spain) in order to predict extreme dry-spell risk. A comparison of observed and estimated maximum dry spells (50-year return period) showed that the Generalised Pareto (GP) distribution combined with partial duration series (PDS) gives better results than the Gumbel distribution fitted to annual maximum series (AMS). Indeed, the classical Gumbel approach underestimated the empirical duration of dry spells. The PDS/GP approach was successfully applied in the study of extreme hydro-climatic variable values. The results reported here could be applied in estimating climatic drought risks in other geographical areas.