Characterization of homogeneous regions for regional frequency analysis of heavy daily precipitation in central Tunisia

The Sebkhet El Kalbia and Sidi El Hani catchment is the second largest watershed in Tunisia, which represents a typical semi-arid area localized in the central region. Characterized by a high risk related to the high spatio-temporal rainfall variability, this region represents one of the most vulnerable zones where hydrologists try to assess and predict the behavior of such a climatic component. The regional frequency analysis of annual maximum daily rainfall can help enormously in the estimation of the expected rainfall at high return periods. Eventually, the principal objective of this research is to determine the regional statistical distribution for homogeneous regions in the Sebkhet El Kalbia and Sidi El Hani catchment. The Sebkhet El Kalbia and Sidi El Hani catchment was selected to represent semi-arid regions in Tunisia as it covers a large area in addition to the availability of rainfall data. The data was analyzed using multiple frequency analysis methods and was subjected to various statistical tests including Akaike information criterion (AIC), Bayesian information criterion (BIC), and the khi-square test (khi 2 ) in order to determine the best regional statistical distribution and define the homogeneous regions using regional analysis. The study concluded that the GEV distributions were the best model to describe the distribution of the annual maximum daily rainfall in the central region of Tunisia. The Sebkhet El Kalbia and Sidi El Hani catchment was sub-divided into three homogeneous regions. The contour maps for the 10, 20, 50, and 100 years rainfall associated to other components (the slope and the sea effects) were produced to predict the behavior and dynamic of heavy rainfall events in the study area.