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Accueil du site → Doctorat → Allemagne → Concepts and models for the characterization of the West Gedaref hydrogeologic system, Sudan

Technischen Universität Berlin (2001)

Concepts and models for the characterization of the West Gedaref hydrogeologic system, Sudan

Mirghani, Muna

Titre : Concepts and models for the characterization of the West Gedaref hydrogeologic system, Sudan

Auteur : Mirghani, Muna

Université de soutenance : Technischen Universität Berlin

Grade  : Doktorin der Ingenieurwissenschaften 2001

Résumé
The purpose of this research was to apply concepts and techniques, which with limited data lead to a better understanding of the west Gedaref groundwater system. Classical quantitative hydrogeology has been used to provide local estimates of hydraulic properties and averages of hydrogeologic conditions. Then conceptual models are used to allow spatial characterization of aquifer properties, namely : the aquifer configuration, the heterogeneous hydraulic parameters T and S, the hydraulic head as well as the recharge rate. Following deterministic and stochastic approaches a conceptual framework for analysis was defined. Contrary to the concept of unique model parameters, geostatistical methods are based on the random function concept where multiple realizations exist. The random function hypothesis allowed for the characterization of the heterogeneous transmissivity field, an important input to the flow model. Based on the adopted assumptions a finite element numerical simulator was used to calibrate quasi three dimensional flow parameters conditioned against steady and transient head measurements and a tentative water budget estimate. The results of the inverse solution and the forward solution of the flow model showed the ability of geostatistics to identify aquifer heterogeneity within the targeted range. The transmissivity distribution indicates considerable spatial heterogeneity probably caused by the complex tectonic structural pattern in the area. The mean transmissivity ranges between 0.0003 to 0.002 m2/s, with a regional average of 0.0004 m2/s. The average storativity is estimated at 0.002. The study results showed that the main source of recharge to the Azaza-Abu Naga sandstone aquifer is the vertical leakage and underflow from eastern basalt aquifer. The adopted flow model lead to a maximum safe yield of 10,000 m3/d (around 18% of the potential recharge estimated for the Gedaref basin) from the Azaza Abu Naga middle sandstone aquifer. This amount is partly drawn from vertical leakage (about 4,000 m3/d), and partly from boundary inflows. Additional development is expected to jeopardize the limited aquifer storage and convert the flow into unconfined conditions. The study indicated that the most favorable areas for the development of groundwater in the west Gedaref are the Azaza, Abu Naga and the area around the valley of Al-Laya wadi system.

Mots clés : al- Kadarif  ; Grundwasserleiter ; Hydrogeologie ; Mathematisches Modell

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