Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Hydrogeophysical and hydrogeochemical characterization of volcanic aquifers in Northwest Ethiopia.

Auteur : Fenta Mulugeta Chanie

Université de soutenance : University of Szeged

Grade : Doctoral thesis (PhD) 2022

Résumé
The pursuit of meeting the critical needs for clean water of Ethiopia’s citizens depends on groundwater resources. However, the geology, rainfall, physiography, and other factors make it challenging to manage resources without conducting intensive, efficient investigations. The variable physiographic area surrounding the town of Dangila in northwest Ethiopia has been occasioned by incessant borehole failure and low yield over the past four decades. The Oligocene – Miocene and the recent Quaternary timing of volcanic eruption yielded a highly complex groundwater reservoir. The variable groundwater reservoir of rainfall causes variations in groundwater occurrence, quality, quantity, and aquifer parameters within hundreds of meters. Volcanic aquifers supplying freshwater in Ethiopian highlands have imposed various challenges on sustainable management that have prompted groundwater research. In my study, the intricate nature of volcanic aquifers demands a multi-investigation approach that uses survey data and information from diverse sources. Numerous investigative approaches have been utilized, comprising analysis of existing boreholes, rock outcrops, and hydrochemistry as well as water-stable isotope analysis, surveys of near-surface geomagnetic and vertical electrical sounding, and pump test analysis techniques. Additionally, the extent of the possibility of utilizing new fiber optical technologies to understand the complex geometry of aquifers systems has been assessed. As a result, in this study, the aquifer’s groundwater reservoir characteristics, hydraulic parameters, water quality, and suitability for drinking and irrigation use have been investigated. The influencing factors for groundwater chemistry, the sources of ions in the groundwater, the rock–water interactions, and groundwater evolution have been examined. Furthermore, the sources of precipitation for recharge, the recharge and discharge areas, the potential areas for further borehole drilling, and the governing features for groundwater occurrence and movement have been investigated. Finally, the conceptual groundwater flow model has been developed for the sustainable utilization of the groundwater resource in the future.

Mots Clés : Hydrogeophysics. Hydrochemistry. Water isotope. Volcanic aquifer. Groundwater flows conceptual model. Northwest Ethiopia.

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