Longest dry spells phenomenon in Northern Tunisia: risk assessments using daily rainfall observations

Código

I-EBHE0006

Autores

Majid Mathlouthi, Fethi Lebdi

Tema

WG 1.14: Droughts in Mountain Regions

Resumo

It is likely that climate change increases the frequency and duration of droughts. This contribution focuses on dry event analysis from series of observations of the daily rainfall. The approach has been illustrated on a case study catchment localized in Northern Tunisia where the average rainfall is about 600 mm. The dry events are constituted of a series of dry days framed by the rainfall event. Rainfall events are defined themselves in the form a uninterrupted series of rainfall days understanding at least a day having received a precipitation superior or equal to a threshold value. The rainfall events are defined by depth and duration, which are found to be correlated. An analysis of the depth per event conditioned on the event duration has been undertaken. The negative binomial distribution appears the best overall fit for the depth per event. The duration of the rainfall event follows a geometric distribution while that the dry event follows the negative binomial distribution. The length of the climatically cycle adjusts to the Incomplete Gamma. Event based analysis was used to study of the effects of climate change on water resources and crops and to calibrate precipitation models with little rainfall records. Adaptation measures in response to long droughts in the basin adopt a drought management system based on three phases: (i) before drought, preparedness and early warning; (ii) drought management, mitigation in the event of drought; and (iii) subsequent drought, when the drought is over. During each of the three phases, different measurements are applied and executed.