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Accueil du site → Master → Autriche → Charakterisierung der hydrogeologischen Wirkung von Störungszonen im äthiopischen Graben (Gidabo-Flusseinzugsgebiet) mittels regionaler Grundwasserströmungs- und Transportmodellierung

Karl-Franzens-Universität Graz, (2020)

Charakterisierung der hydrogeologischen Wirkung von Störungszonen im äthiopischen Graben (Gidabo-Flusseinzugsgebiet) mittels regionaler Grundwasserströmungs- und Transportmodellierung

Razanajatovo, Njara Nomena

Titre : Charakterisierung der hydrogeologischen Wirkung von Störungszonen im äthiopischen Graben (Gidabo-Flusseinzugsgebiet) mittels regionaler Grundwasserströmungs- und Transportmodellierung

Characterization of hydrogeologic effects of faults on groundwater flow in the Ethiopian rift (Gidabo River Basin) with regional groundwater flow and transport modelling

Auteur : Razanajatovo, Njara Nomena

Université de soutenance : Karl-Franzens-Universität Graz,

Grade : Master Thesis 2020

Résumé
The hydrogeology of the Gidabo River Basin is very complex due to its location in the Ethiopian East African Rift System. The aquifer is marked by a variety of discontinuities and faults, which might considerably impact the groundwater flow. The aim of the study is to improve the knowledge about the hydrogeological properties of the faults, in order to obtain appropriate conceptual models of the region. For this task, regional groundwater modelling of the catchment both flow and transport modelling were carried out by using four alternative models. One is a re-simulated model from the literature, with faults as barrier to horizontal groundwater flow. The three others are newly developed models, having different fault parameters but the same transmissivity zones along each fault zone to simulate the groundwater flow parallel to the fault zones. The same base data are used for all four models to ensure a valid comparison.For the groundwater flow modelling, the field data and the simulation results (groundwater level, baseflow to river) are in good agreement to one another. Similarities in some results are seen in two of the models, although their structures (fault parameters) are completely different. The calibrated transmissivity values of these models reveal that faults deepening to the east, act preferably as hydraulic conduits in the direction parallel to the fault plane in the north of the study area. One scenario shows that the absence of faults can affect the water budget distribution strongly. Using information criteria such as the AICc criterion for model comparison, the model based on the literature was identified as the best model with 87% plausibility. The transport model aimed to simulate the regional distribution of 18O isotopes for each of the conceptual models. The simulated 18O-values differ to some extent from the measured data in the boreholes ; however, the results support different aspects found in the groundwater flow modelling (interaction between river and groundwater, behavior of faults). Furthermore, compared to the simulated groundwater levels from flow modelling, the calculated 18O-values from transport modelling show differences that are caused by model assumptions more clearly. The application of transport modelling might therefore be promising for model selection if the models were refined. More detailed investigation on local scale will be needed to test the models and to determine the hydrogeologic characteristics of the faults more precisely.

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