Geomorphology
The study site is drained by two main wadis (dry streams): Oum Zessar (367 km2) facing east while the Hallouf Dahri (530 km2) is facing west. The average runoff is estimated at 8.74 mm3/year (Fersi, 1985).
The SS is made of three major geomorphologic landscapes; the Dahar plateau, Jebel (mountain) Matmata and the Jeffara plain. Djebel Matmata crosses the region from the northwest to the southeast the range becomes less massive and is divided into a number of hills of an average height of 400 meters, whereas in the north altitudes reach more than 600 m (Jebel Mzenzen culminates at 690 m). The Djeffara is the coastal plain coming from Gabès, clears into the south at the level of Mareth, into the Djeffara, which also stretches NW-SE, forming the coastal area. At highest it reaches an altitude of 100 meter above sea level, and it ends in the sea (or lagunes/sebkhas). The geological formations are of alternating continental and marine origin. The oldest submerging layers are represented by a marine, superior Permian, and the most recent ones are of the recent Quaternary. In between appear strata of different age, which is generally declining in northward direction.
