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Accueil du site → Doctorat → Belgique → Hydrogéochimie et simulation de l’écoulement des eaux souterraines et de la position de l’interface eau douce-eau salée dans la partie est de la Plaine de la Mitidja (Algérie)

Katholieke Universiteit Leuven (1995)

Hydrogéochimie et simulation de l’écoulement des eaux souterraines et de la position de l’interface eau douce-eau salée dans la partie est de la Plaine de la Mitidja (Algérie)

Imerzoukene, Saadia

Titre : Hydrogéochimie et simulation de l’écoulement des eaux souterraines et de la position de l’interface eau douce-eau salée dans la partie est de la Plaine de la Mitidja (Algérie)

Auteur : Imerzoukene, Saadia

Université de soutenance : Katholieke Universiteit Leuven

Grade : Doctor of Philosophy (PhD) 1995

Résumé
Mitidja plain is situated in the North of Algeria. The Eastern part is coastal in its North side and limited by the Atlas Mountains in the South. The region consists on two main aquifers separated in some places by El-Harrach Formation (Calabrian). First and deepest aquifer is Astian (Upper Pliocene). The second and most important aquifer, Mitidja Formation (Tyrrhenian) is alluvial, coastal and unconfined. The groundwater flow and the position of the interface between fresh water and salt water in the Mitidjian aquifer has been simulated with a two-dimensional mathematical model. Groundwater withdrawal has changed the natural flow pattern in some areas. The situation has been approximated by considering the known pumping stations and the main boreholes. Some elements of the global water balance in the aquifer, such as recharge by the rainfall, were calculated. The permeability values have been adjusted during the calibration of the model. The hydraulic head distribution, based on short (dry and humid) periods of simulations, gave a good correspondence between observed and calculated hydraulic heads. The interface is located about 10km from the coast. The simulated groundwater flow in the Mitidjian aquifer is confirmed both by head measurements and hydrochemical observations. The total of 720 groundwater analysis results were classified. Different succeeding water types agree with the general pattern of groundwater movement in the aquifers, which goes from the south to the north, where the Mediterranean Sea is the natural exsurgence. In addition, Mitidja aquifer groundwaters are diluted and became fresh earlier than Astian groundwater because of the depth which is less for the first aquifer. Geographical repartition has given four main water types. In the recharge areas of the south, the F3-CaHCO$\sp3+$-type is the consequence of the dissolution of dolomitic and calcareous sediments from the Atlas. This type reflects the terminal stage of cation exchange. An intermediary stage F2-CaMix$\sp+$-water type between fresh water and fresh-brackish water is localized around recharge areas. In the coastal dunes, this water type occurs because of the topographic elevation which constitutes an additional fresh water supply for the aquifer. For Fb3-CaMix$\sp+$-water type, fresh-brackish water, where marine chlorides are present in non-negligible quantity, there is no predominant anion but the cation exchange is still continuing. The north part, near the coast, groundwater is brackish with B-NaCl$\sp+$-type, the first stage of cation exchange. But in these areas, water quality is mainly determined by a seawater intrusion in the fresh groundwater. The last water type, B3-NaCl$\sp+$ or B3-CaClO is localized in the extreme eastern part of the Mitidja Plain.

Mots clés : freshwater, Hydrology, Earth sciences

Accès au document : Proquest Dissertations & Theses

Page publiée le 10 février 2015, mise à jour le 26 janvier 2017