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Ruhr-Universität Bochum (2019)

Karst water management in semi-arid environments : Central West Bank, Palestine

Jebreen Hassan

Titre : Karst water management in semi-arid environments : Central West Bank, Palestine

Auteur : Jebreen Hassan

Université de soutenance : Ruhr-Universität Bochum

Grade : Doktors der Naturwissenschaften 2019

Résumé
Many populated areas of the world obtain drinking water from karst aquifers, and numerous urban areas are underlain by karstified bedrock. Central West Bank (CWB) transboundary karst carbonate aquifers are of great importance for drinking water supply not only in Palestine. The economic aspirations, rapid population growth and urbanization of the Palestinians exert pressure on the limited available water resources. Limited water availability and accessibility along with the prevailing system of uncoordinated water management will likely prohibit some water users from meeting all of their requirements. Due to their vulnerability to pollution, the exploitation of groundwater from these aquifers requires special strategies for protection and management. For this purpose, a comprehensive field studies, including mapping, hydrochemical, geochemical, mineralogical and microbiological analyses were carried out. Understanding sources and rates of recharge to the CWB is important for assessing sustainability of the areas and its water resources in general. For this purpose, recharge was investigated with the chloride mass balance (CMB) and empirical relations methods, which is presented in chapter 2 of the thesis. The estimated annual recharge of the CWB proves that the amount of annual recharge is a function of many parameters : monthly distribution, quantity and intensity of the rainfall. Therefore, the value of groundwater recharge obtained by the CMB method is comparable to the results of the empirical relations methods, which ranges from 180 to 189 mm/year, representing 31 to 33 % of the long-term mean annual rainfall and seems very reasonable. Water balance models of GIS were utilized to facilitate actual evapotranspiration (AET) quantification. The mean annual actual evapotranspiration was about 66 – 70 % of precipitation. The chemical composition of groundwater of the study area is strongly influenced by rock-water interaction, followed by cation exchange and dissolution of carbonate minerals. Therefore, the second study of this thesis (chapter 3) focuses on the hydrogeochemical and microbial characteristics of groundwater quality in the CWB aquifer, which were utilized to understand recharge mechanisms, geochemical evolution and renewability of groundwater in CWB aquifer. Besides the major chemical compositions, ionic ratios were used to delineate mineral solution reactions and weathering processes. For a sustainable groundwater management in CWB aquifers, knowledge about the influences of the geological structure and the karst system on groundwater composition is required. For this reason, new data on mineral chemistry and geochemistry for sedimentary rocks is examined in the third study (chapter 4) of this thesis. The results overall suggest that the composition of groundwater in the CWB is mainly influenced by source lithology and geology characteristics of the study area. The studied samples are highly homogenous in terms of mineralogical composition with predominance of calcite and dolomite with minor amount of feldspars and quartz. The multivariate statistical analyses have more detailed and comparable results with the traditional hydrochemical and geochemical analyses methods. The Hierarchical cluster analysis (HCA) has classified the groundwater and sediment samples into two major clusters, calcite and dolomite group. The whole-rock geochemical data indicate that the samples have low contents of trace elements and transition metals. In contrast, the concentrations of alkaline earth elements (Mg, Ca, Sr, Ba) and Mn are high in rock and groundwater samples.

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