**2.1. Geological setting**

Several geologic studies [4–11] have focused on the stratigraphy, structure, and surficial and subsurface deposits characteristics in the study district. As shown in the geologic map and in the lithostratigraphic column, the geological formations, which outcrop in the study area, are represented by sedimentary series ranging from the Trias to the Quaternary (**Figures 1** and **2**). The Trias deposits, which outcrop in Cherichira Mountain, consist mainly of an alternation of gypsum, clay, and carbonate levels [6]. The Cretaceous units that outcrop in the foot of Trozza Hydrochemical Investigation and Quality Assessment of Groundwater in the BouHafna-Haffouz… http://dx.doi.org/10.5772/intechopen.72173 93

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

Due to rapid demographic growth and agricultural progress, exploitation of groundwater has increased dramatically to provide drinking water to rural community, support irrigation, and maintain ecosystems. During the past 30 years, the exponential increase in water abstraction from Haffouz and BouHafna aquifers has caused ground water depletion, a term often defined as long-term water-level declines, and an increase in salinity of groundwater pumped from wells situated mainly downstream. On the other hand, recent changes in agricultural land use and irrigation may result in groundwater contamination throughout agricultural fertilizers and pesticides applied to fields. Therefore, information about irrigation groundwater quality is critical to the understanding of necessary management changes for long-term productivity [1]. Proper assessment of groundwater sustainability requires understanding and quantification of human effects on water resources using analysis, application

Within this framework, a combined hydrogeological and hydro-chemical data were examined, using statistical methods, to determine (i) natural and anthropogenic processes that control the groundwater mineralization; (ii) the origin of different water bodies and their sources of recharge; and (iii) to assess the suitability of groundwater for agricultural purposes.

The Haffouz study areas, which make up part of the Kairouan plain in Central Tunisia, cover

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

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

Several geologic studies [4–11] have focused on the stratigraphy, structure, and surficial and subsurface deposits characteristics in the study district. As shown in the geologic map and in the lithostratigraphic column, the geological formations, which outcrop in the study area, are represented by sedimentary series ranging from the Trias to the Quaternary (**Figures 1** and **2**). The Trias deposits, which outcrop in Cherichira Mountain, consist mainly of an alternation of gypsum, clay, and carbonate levels [6]. The Cretaceous units that outcrop in the foot of Trozza

and 500 mm/year. The annual total evaporated exceeds 1720 mm Piche [3].

and lie between longitudes 39G 55′ and 39G 70′ north and latitudes 7G 88′ and

of management practices, and revision.

**2. General features**

Kairouan plain [2] (**Figure 5**).

**2.1. Geological setting**

about 1192 Km<sup>2</sup>

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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 depression.

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

#### **2.2. Hydrogeological setting**

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


**Figure 2.** Simplified lithostratigraphic column of the study areas.

300 m. The bedrock of this aquifer is constituted of the Lutetian marly deposits of Souar Formation (**Figure 3**). Nevertheless, the Haffouz unconfined aquifer is constituted of the Mio-Plio-82 Quaternary detrital deposits with a thickness of about 1000 m.

**Figure 3.** Hydrogeological cross section of Haffouz and BouHafna aquifers.

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

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

95

**Figure 4.** Piezometric and sampling map of Haffouz and BouHafna aquifers [12, 13].

The piezometric map (**Figure 4**) shows that the general directions of groundwater flow are N-S, NW-SE, and W-E in the case of BouHafna aquifer, and they are oriented NW and NE in the case of Haffouz aquifer. This may indicate that the recharge of BouHafna aquifer occurs in the Western part of the basin and in the pediment of Ouesselat and Jebil Mountains, where the Oligocene sediments outcrop largely. For the Haffouz region, rainwater infiltrates and recharges the aquifer, locally, in the pediment of Ouesselat Mountain. The hydraulic gradient of BouHafna and Haffouz aquifers varies from 0.009 to 0.003, highlighting the importance of localized recharge in the pediment of mountains, in the northern part, and the linear recharge by the Merguellil Wadi, in the southern part of the region. This variation of hydraulic gradient can also be explained by the lateral variation of lithology caused by abundance of clayey layer, especially in the south of this aquifer.

Hydrochemical Investigation and Quality Assessment of Groundwater in the BouHafna-Haffouz… http://dx.doi.org/10.5772/intechopen.72173 95

**Figure 3.** Hydrogeological cross section of Haffouz and BouHafna aquifers.

300 m. The bedrock of this aquifer is constituted of the Lutetian marly deposits of Souar Formation (**Figure 3**). Nevertheless, the Haffouz unconfined aquifer is constituted of the Mio-

The piezometric map (**Figure 4**) shows that the general directions of groundwater flow are N-S, NW-SE, and W-E in the case of BouHafna aquifer, and they are oriented NW and NE in the case of Haffouz aquifer. This may indicate that the recharge of BouHafna aquifer occurs in the Western part of the basin and in the pediment of Ouesselat and Jebil Mountains, where the Oligocene sediments outcrop largely. For the Haffouz region, rainwater infiltrates and recharges the aquifer, locally, in the pediment of Ouesselat Mountain. The hydraulic gradient of BouHafna and Haffouz aquifers varies from 0.009 to 0.003, highlighting the importance of localized recharge in the pediment of mountains, in the northern part, and the linear recharge by the Merguellil Wadi, in the southern part of the region. This variation of hydraulic gradient can also be explained by the lateral variation of lithology caused by abundance of clayey

Plio-82 Quaternary detrital deposits with a thickness of about 1000 m.

**Figure 2.** Simplified lithostratigraphic column of the study areas.

94 Aquifers - Matrix and Fluids

layer, especially in the south of this aquifer.

**Figure 4.** Piezometric and sampling map of Haffouz and BouHafna aquifers [12, 13].
