Dry events according a precipitation threshold value in the Mediterranean climate of northern Tunisia

Abstract Dry spells observed in Ichkeul basin Northern Tunisia using daily precipitation data were analyzed. Dry days were defined as having less than a threshold value of accumulated precipitation. Various values of the threshold were investigated. Analysis point dry spells occur randomly during the rainy season. The longest dry spells associated with various statistical recurrence periods are derived on the basis of the fitted Generalized Extreme Value (GEV) distributions. An extreme case (meteorological droughts) was analysed. From the drought return period analysis, the 1 September 1987 drought was found to be the most extreme with a 127-yr return period. The maximum number of seasonal dry events observed is inversely proportional to the threshold value. Longest observed in rainfall event duration is invariant to the rainfall threshold and displays 13 days. This study provides the foundation data for reducing Ichkeul’s vulnerability to future droughts, and investigating the causes of droughts.