Population
The total population in 1994 was around 151,000 inhabitants. The population of the study zone doubled between 1975 and 2004. This evolution was marked by the migratory movements especially during the period 1975 -1984. Compared to the rural Tunisia, the average age of household head is rather high (53 years). It is higher in the upstream than in the downstream areas (56.2 years in Béni Khedache and 50.8 in Mareth) which confirms the maintenance of a more long-lived patriarchal authority within the framework of large families in mountain and piedmont zones of than in the plains (IRA, IRD, 2003). The average age of the population of the study zone is higher of 3 years than that observed for the province of Médenine and for rural Tunisia (28.8 years with the survey, 25.8 with the census of 1994). This difference is due to the low relative number of young children, mainly in the age group of 0-4 years, and the emigration (Picouet et al., 2003).
