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sur le développement des zones arides et semi-arides

Titre : Field-measurement based recharge assessment in Wadi Natuf, shared Palestinian-Israeli Western Aquifer Basin

Auteur : Messerschmid, Clemens

Université de soutenance : Albert-Ludwigs-Universität Freiburg im Breisgau

Grade : Doctor rer. nat. 2020

Résumé partiel
The main objective of this doctoral research is the determination of groundwater recharge and its spatial distribution in a mountainous karst catchment area of the eastern Mediterranean. The basin was previously almost ungauged and it is characterised by very limited data availability and strong obstacles to any observation of the underground processes (except spring discharge). Therefore the study used the more readily accessible surface features, such as geology in the outcrop, soils and land use and land cover observations. The study area, Wadi Natuf, shows a high spatial variability of these land forms. All lithostratigraphic formations of the regional Western Aquifer Basin (WAB) crop out and most of the land use and land cover (LU/LC) types of the WAB can be found here (with the exception of the arid zone types of the Negev). A dense measurement network for precipitation and other meteorological drivers and for hydrological processes such as surface runoff, spring discharge and soil moisture was established and operated for almost a decade, in order to obtain a data set of empirical field measurements that is unique in this region. The physical characteristics and their classification were comprehensively and intensively recorded and related to each other. The starting point was a detailed description of the WAB’s litho-facies and its spatial distribution. Special attention was paid to the refinement of the conventional regional litho-stratigraphy and especially the hydro-stratigraphy of the catchment area and overall aquifer basin. Previously unknown aquifer properties of the so-called "aquicludes" were detected, measured and described. The location and separation of the different catchment areas within the WAB was studied ; this was a fundamental prerequisite for the spatial differentiation of groundwater recharge. In the Wadi Natuf catchment area, a close correlation between geology and soil thickness, as well as land cover and land use was observed. These patterns were spatially recorded (mapped) and categorized as classes of different recharge potential, they were integrated into a specific basin classification framework of Wadi Natuf. In addition and for the first time in the West Bank, the occurrence of shallow, perched aquifers was recognized and documented. These perched groundwater reservoirs are bound to certain surface landforms in central Wadi Natuf, erosionally isolated hilltop aquifers. Hereby it was noted that these isolated perched aquifers lack any lateral subsurface flow connections. Instead, all recharging groundwater either emerges in the respective measurable spring groups of the hilltops or seeps further downward into the underlying regional aquifers as downward leakage.

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