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Karlsruher Instituts für Technologie (KIT) 2017

Managed aquifer recharge into a karst groundwater system at the Wala reservoir, Jordan

Xanke, Julian

Titre : Managed aquifer recharge into a karst groundwater system at the Wala reservoir, Jordan

Auteur : Xanke, Julian

Université de soutenance : Karlsruher Instituts für Technologie (KIT)

Grade : Doktors der Naturwissenschaften 2017

Résumé partiel
Managed aquifer recharge (MAR) is a promising approach to augment groundwater availability in water scarce regions. Especially in semi-arid areas with a high seasonal variability in water availability the temporal storage of storm water in the underground helps to bridge dry periods and therefore represents a key technology in water management. However, a particular challenge for the technical implementation and operation of MAR is posed by karst aquifers since they usually reveal a strong hydraulic anisotropy and heterogeneity and are therefore highly vulnerable to contamination. The main focus of this work is on the investigation of flood water storage at the Wala dam in Jordan and the managed recharge of the underlying karst aquifer. Of particular interest is the impact on the downstream Hidan wellfield, which contributes to the drinking water supply of the cities Amman, Madaba and small communities in the immediate surrounding. For this purpose a comprehensive hydrogeological conceptual model was developed, which in turn served as the basis for a numerical groundwater model. Based on the simulated water levels and scenarios the main impacts on groundwater levels trends were assessed on the long-term. Furthermore, a combined protection zone concept was developed for the karstic environment of the reservoir and the wellfield considering the interaction of surface water and groundwater. Calculations showed that about 6.7 million cubic meters (MCM) of water infiltrated on annual average (2002-2012) from the reservoir into the underground, which accounts for about 60 % of the annual average groundwater abstraction of about 11.7 MCM in the same period. Tritium data proved the immediate impact of reservoir infiltration on the wellfield, whereas the mean residence time of natural groundwater flow was calculated using the 14C-method to be of several thousand years. An impact on the groundwater chemistry by the low mineralized surface water on the highly mineralized groundwater was observed only in the first years with strong variations in salinity at the wellfield. For the numerical model an "equivalent porous medium" (EPM) approach was used with special adaptation to account for the karst specific heterogeneity and anisotropy of the hydraulic properties. Therefore, the 3-dimensional aquifer geometry was projected onto a 2-dimensional profile along the wadi and further divided into hydraulic zones, which represent both zones of low flow and high flow velocities. Simulations matched the measured groundwater level very well and showed that its declining long-term trend is a result of the sedimentation and the associated decreasing infiltration rate in the reservoir. However, strong groundwater level fluctuations at the wellfield on the short-term are caused by changes in the average pumping depth

Mots clés  : künstliche Grundwasseranreicherung, Managed Aquifer Recharge (MAR), Integriertes Wasserressourcen-Management (IWRM), Jordanien, semiarides Klima, Karst, Hydrogeologie, Hydrochemie, Isotope, Numerische Grundwassermodellierung, Bakteriologische Kontamination, Grundwasservulnerabilität, Grundwasserschutz, Trinkwasserversorgung

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Page publiée le 30 septembre 2017