Estimating extreme dry spell risk in Ichkeul Lake Basin (Northern Tunisia): a comparative analysis of annual maxima series with a Gumbel distribution

Majid Mathlouthi,Fethi Lebdi

doi:10.5194/piahs-383-241-2020

Abstract

Abstract. This paper analyses a 42 year time series of daily precipitation in Ichkeul Lake Basin (northern Tunisia) in order to predict extreme dry-spell risk. Dry events are considered as a sequence of dry days separated by rainfall events from each other. Thus the rainy season is defined as a series of rainfall and subsequent dry events. Rainfall events are defined as the uninterrupted sequence of rainy days, when at last on one day more than a threshold amount of rainfall has been observed. A comparison of observed and estimated maximum dry events (42 year return period) showed that Gumbel distribution fitted to annual maximum series gives better results than the exponential (E) distribution combined with partial duration series (PDS). Indeed, the classical Gumbel approach slightly underestimated the empirical duration of dry events. The AMS–G 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.

Highlights

A proper simulation of precipitation is important
The results obtained have been compared with those obtained when adopting the annual maximum series (AMS)–G approach for the maximum dry event series observed in the study area
The Gumbel distribution is a two parameter extreme values distribution widely used in modelling AMS

Summary

Introduction

A proper simulation of precipitation is important. Precipitation is a very important element of climate that affects both the natural environment and human society. Events ranging from prolonged droughts to short-term, high intensity floods are often associated with devastating impacts both to society and the environment (Hui et al, 2005). Among the study using the wet-dry spell approach one can cite, for example, Bogardi and Duckstein (1993); Wilks (1999); Mathlouthi (2009); Mathlouthi and Lebdi (2008, 2009, 2017); Dunxian et al (2015); Konjit et al, 2016. It is well known that dry spells cause major economic and human losses, and numerous studies have highlighted the need for drought prevention and mitigation plans

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Results

Conclusion