**2. General features**

The Haffouz study areas, which make up part of the Kairouan plain in Central Tunisia, cover about 1192 Km<sup>2</sup> and lie between longitudes 39G 55′ and 39G 70′ north and latitudes 7G 88′ and 8G 33′ east (**Figure 1**). This region is bounded by Ouesselat and Jebil Mountains in the north, the Trozza Mountain in the south, and the plain of El Ala in the west. The altitude of the study area ranges from 200 m a.m.s.l. at Haffouz plain to 997 m at Trozza Mountain. The study area has a semi-arid climate with mild, wet winters and warm, dry summers [2]. The average monthly temperature varies between a minimum of 10.15°C measured in January and a maximum of 33.07°C measured in August. It receives an annual rainfall ranging between 300 and 500 mm/year. The annual total evaporated exceeds 1720 mm Piche [3].

Mountain are constituted of the Yprisian limestone of AlagAbiod and El Metlaoui formations. These formations are covered by the Lutetian limestone and clay of Cherahil and Souar formations, respectively. On the Lutetian deposits, the sandy and sandstone units of the Oligocene repose with an average thickness of about 350 m. These deposits belong to the Fortuna formation out crop in the central part of the study area. The Miocene deposits are represented by thick calcareous and clayey layers, which correspond to A in Grab and Mahmoud formations, respectively. These formations are overlaid by the sandy clay of the Beglia Formation and the clay Saouaf Formation. The Quaternary sediments that are represented by sand, clay, and conglomerate deposits occur in the plains of El Ala and Haffouz and in the Merguellil Wadi

Hydrochemical Investigation and Quality Assessment of Groundwater in the BouHafna-Haffouz…

http://dx.doi.org/10.5772/intechopen.72173

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Structurally, the BouHafna basin is bordered to the east by the major fault of Ouesselat Mountain and corresponds to a syncline structure, which consists of the sandy deposits of Fortuna Formation. However, the Haffouz region, which is limited by the faults F1 in the east and F2 in the west, corresponds to a Graben structure filled by the sand, sandstone, sandy

The BouHafna aquifer is lodged in the sand and sandstone deposits of the Oligocene. This aquifer, which is unconfined overall the basin, has a thickness varying largely from 50 to

depression.

clay, and clay of Mio-plio-quaternary (**Figure 3**).

**Figure 1.** Location and geological map of the study areas.

**2.2. Hydrogeological setting**

The drainage network consists of several nonperennial Wadis such as Mourra, 55 Zabbes, and MsilahWadis that drain toward the Merguellil Wadi, the most important Wadi of the Kairouan plain [2] (**Figure 5**).
