## 2 Materials and Methods  
### Study Area Description  
Geologically, the Mornag graben seems to be a large basin, controlled by tectonic events from N-S (Figure 1b) and NW-SE to N160, which have affected the Mio-Plio-Quaternary filling [12]. The Mornag Basin is characterized by the predominance of heterogeneous quaternary sediments, consisting predominantly of conglomerates, sand, gravel, silt, and clay. These deposits are bounded to the northwest by the late Miocene sediments, to the southeast by the paleogenic sediments, and to the east by ancient sediments ranging from the Triassic to late Eocene [13; 14; 15; 16] (Figure 1a). In the eastern part, particularly in Jebel Ressas, there are deposits belonging to the late Cretaceous-Triassic interval, which are composed of marl with thin limestone lenses. Paleocene sediments are found in the south and southeast parts of the basin. The eastern part of Jebel Ressas and the western part of Jebel Boukornine are distinguished by Eocene deposits. Oligocene sediments are found in the south and west-central regions. However, Miocene deposits, which occur in the northwestern part of the study area, consist of gypsum, clay, limestone, marl, and sandstone [16; 17; 18; 19; 20]. The geological formations in the Mornag graben host a complex multi-layered aquifer system [13; 16; 21; 22; 23]. The shallow aquifer, which is unconfined throughout the study area, consists mainly of quaternary alluvial deposits. According to both [23] and [24], this shallow aquifer has a storage coefficient of 6 \(\times\) 10\({}^{-3}\) to 7.3 \(\times\) 10\({}^{-5}\) and a transmissivity of 1 to 80 \(\times\) 10\({}^{-4}\) m\({}^{2}\)/s. The recharge occurs mainly by the infiltration of rainfall at the foot of the surrounding hills, specifically in the regions of Khledia, Ettella, and Rorouf [25]. However, it should be noted that this shallow aquifer has been affected by anthropogenic pressures, which are associated with the growing demand for the agriculture sector, the major activity in the area [2; 12]. The deep aquifers are logged in deposits that extend from the upper Eocene to the Quaternary, with a storage coefficient and transmissivity ranging from 5 \(\times\) 10\({}^{-3}\) to 6 \(\times\) 10\({}^{-3}\) and from 10\({}^{-2}\) to 10\({}^{-4}\) m\({}^{2}\)/s, respectively [21; 24]. This deep aquifer is separated from the shallow one by thin impermeable layers of a clayey nature. However, there are vertical communications between the superimposed hydrogeological units, which have been facilitated by the lateral and vertical discontinuity of the lithological facies and the difference in charge between the aquifer levels [16; 26]. The drainage network consists of the Meliane principal wadi and its tributary represented by the El Hma wadi, which merges to the northwest of the plain towards the Gulf of Tunis. From a hydrological point of view, the study area is divided into three sub-watersheds, i.e., the Oued Meliane basin, the Oued El Hma basin, and the Medjerda Cap-Bon channel. The latter corresponds to the downstream part of the great watershed of Oued Meliane, where the natural outlet is the Mediterranean Sea [23; 27]. Soil types in the study district fall into the category of calcareous brown calimagnesic soils and rendzines [28; 29]. The texture of these soils, which are shallow, often steeply sloping, is sandy to silty in the western and southwestern portions of the plain and silty to sandy clay in the eastern part [30]. However, in the central and northern parts, soils belong to a class that is not highly reactive because of alluvial deposits and have large areas of vertic soils. These are deep, with clay to silty texture, and are moderately adapted to irrigation. The soils of the southern and southwest parts of the study area belong to the class of Mediterranean soils and brown steppes. They are typically deep, with a light texture of sandy to silty and sandy clay to silty (Figure 2).