Daily rainfall data in five stations Northern Tunisia used to detect the trend and non-stationarity of dry spells. The irregular distribution of rainfall in the growing season for Sidi Abdelbasset station has increased the number of dry spells. The increase of rainy days in Ghézala dam and Sidi Salem stations resulted in a decrease of dry spells in this area. For one year (wet season) return period, dry events occurred from 14 to 27 days constitute an agricultural potential risk for the zone.

This paper analyses a 42 year time series of daily precipitation in Ichkeul Lake Basin (Tunisia) in order to predict extreme dry-spell risk. 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.