Simulation of groundwater flow and evolution of the fresh-/salt-water interface in the coastal aquifer of the Mitidja Plain (Algeria)
Imerzoukène, S.; Walraevens, K. (1999). Simulation of groundwater flow and evolution of the fresh-/salt-water interface in the coastal aquifer of the Mitidja Plain (Algeria). Natuurwet. Tijdschr. 79(1-4): 249-262
In: Natuurwetenschappelijk Tijdschrift. L. Walschot/Natuur- en Geneeskundige Vennootschap: Gent. ISSN 0770-1748, more
Also appears in:
De Breuck, W.; Walschot, L. (Ed.) (1999). Proceedings of the 15th Salt-Water Intrusion Meeting Ghent (Belgium), 25-29 May 1998. Natuurwetenschappelijk Tijdschrift, 79(1-4). Natuurwetenschappelijk Tijdschrift: Gent. 307 pp., more
The Mitidja Plain is situated in the north of Algeria. The eastern part (575 km² lies by the sea in the north and is limited by the Atlas Mountains in the south. The region has two main aquifers separated in some places by the El-Harrach Formation (Calabrian). The Plaisancian marls (Lower Pliocene) are the substratum of the whole area. The deepest aquifer is an Astian formation (Upper Pliocene). The second and most important aquifer, Mitidja Formation (Tyrrhenian), is alluvial, coastal, and unconfined. The prevailing horizontal intergranular flow in the Mitidja aquifer is characterized by heterogeneity in the vertical direction. Locally salt water occurs at a depth of a few metres. The thickness of the two aquifers near the coast, including in some places clays of the El-Harrach Formation, varies between 20 to 100 m under the beach and between 150 to 240 m at about 15 km to the south. The study of some hundreds of boreholes, 700 groundwater analyses, and several hundreds of hydraulic measurements from 1983 till 1989, allows the authors to describe the groundwater flow and the evolution of the groundwater quality. A few resistivity profiles in the coastal zone illustrate the relation between the fresh-water and the salt-water flow in natural conditions (in 1968 and 1978). At present conditions are very much influenced by human activities such as pumping, and exceptionally by long dry seasons. A 2D mathematical finite-element model has been applied to these phenomena in a reduced area of the region (178 km²). This model is based on the Badon-Ghyben-Herzberg equation. It simulates the evolution of salt-/fresh-water distribution. The thickness of the salt-water layer is less than 20 m near the coast and decreases progressively to the south.
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