The Middle East and the Westbank in particular are widely known for a long-standing competition related to the limited transboundary water resources of the region, resulting the constant threat of intense hydro-political conflict. The Westbank is not per se water scarce but actually shows remarkably high rates of groundwater recharge. Overall, sufficient amounts of water do exist to meet primary water supply needs. Nevertheless, due to strong interannual rainfall variability, high spatial variability of available water resources, high population density, and high water demands for agriculture it is the access to, and share of this essential resource that is of crucial regional importance. Given that the Mediterranean is one of the climate change “hot spots” worldwide and population growth and economic development is expected to further drive up water demand, the conflict on water may intensify even more in the future. The uneven distribution of water resources caused by the particular precipitation patterns in the region is even more pronounced due to the prevailing carbonate lithology with typical effects of spatially concentrated occurrence of highly variable groundwater discharge at karst springs. This particularly complex hydrological setting requires careful consideration when attempting to assess and protect regional water resources, including the investigation of dominant processes in terms of groundwater recharge and runoff generation. The herein presented dissertation aimed to investigate the spatial and temporal distribution of hydrological processes and water balance components in the Lower Jordan region. Special effort has been devoted to the construction of a dense monitoring network under harsh environmental conditions in a data scarce region in order to measure water balance fluxes and interactions of hydrological processes with landscape characteristics. The network consisted of seven runoff gauging stations, a hillslope runoff plot, four meteorological stations, 15 rainfall gauges and several soil moisture plots to monitor the meteorological conditions in high temporal resolution (<10 minutes) over a period of five years along a pronounced climatic gradient. Furthermore, artificial rainfall experiments with dye tracers on ten plots in the headwater region of the study area were realized, soil depth was thoroughly assessed at two hillslopes and samples of undisturbed soil were taken at 35 locations. These were then analysed in the lab for soil-physical parameters in order to characterize processes in the unsaturated soil zone. The collected data set, which is unique in the Westbank and presumably even in the entire Eastern Mediterranean, built the basis for the investigation of hydrological processes. Over the course of this dissertation research, one technical report and three scientific articles were prepared. The technical report presents the experiences from field research realized in the Westbank, including information regarding selection, installation, protection and maintenance of different instruments that were part of the hydrometeorological observation network. Experience shows that beside a careful selection of measurement stations, proper protection against vandalism or other damages is of essential importance for obtaining reliable data with a minimum of gaps. The report emphasises the urgent need for hydrological field data in semi-arid areas in general, and the Westbank in particular, and gives recommendations for researchers and water authority personnel for setting up monitoring networks in semi-arid environments. The first article (study 1) written and published as a part of this cumulative dissertation addresses the question of rainfall redistribution via runoff from rock outcrops and preferential flow pathways at the soil-bedrock interface by means of artificial rainfall experiments and dye tracer. The soil zone plays an essential role for the further partitioning of rainfall into evaporation, surface runoff and potential groundwater recharge. At the same time soil cover, carbonate rock outcrops and vegetation patches are highly variable in the study area, which is expected to have a considerable effect on infiltration and percolation processes. Results from the experiments showed quick and deep infiltration of water from rock outcrops and the presence of preferential flow paths along the soil-bedrock interface. A simple soil water balance model highlighted the effectiveness of rainfall redistribution from rock outcrops and its importance for deep percolation within the soil pockets. The assessment of soil depth along hillslope transects revealed a large variability of soil depths and considerable differences between the two investigated hillslopes with different seasonal rainfall amounts and lithology. Overall, the results of the study indicate a large influence of predominant rock outcrops in the study area on plot scale infiltration, percolation and potential groundwater recharge while its influence on the larger scale still has to be investigated further. In the second paper, long-term of soil moisture observations were analysed in detail and a soil-hydraulic model was developed that served the investigation of the spatial and temporal variability of the soil water balance in general and percolation fluxes in particular. The results confirmed the expected high variability of percolation fluxes and thus potential groundwater recharge, which were also found in study 1. The initiation of percolation at the bottom of the profile was highly dependent on seasonal and event rainfall thresholds. The application of the model to a long rainfall time series confirmed the results gained by modelling the observation period: few rainfall events with exceptionally large amounts are responsible for the bulk of the potential groundwater recharge. Water balance calculation for a set of different conditions identified soil depth as the determining factor influencing percolation rates. This study is the first to provide information on the soil zone, the spatial and temporal distribution and the variability of percolation fluxes in the region. The model can aid assessements of spacially distributed ground water recharge and can serve as input for models of groundwater flow in the region. To take full advantage of the models capabilities, more data on catchment wide soil depths and soil physical characteristics is required. The third study focussed on surface runoff from ephemeral streams in the study area. Observations of Wadi runoff, rainfall and soil moisture in high temporal resolution built the basis for assessing catchment runoff response in terms of event runoff amounts, its temporal and spatial variability. The quantification of spatial heterogeneity of surface cover, land use classes and physiographic characteristics allowed to correlate runoff reactions of individual catchments with their specific catchment characteristics on the basis of single events as well as for the entire observation period. Results show that the general runoff response in the study area is strongly related to high event rainfall amounts with saturation excess overland flow in the headwaters as a dominant runoff process. In contrast, observations on an arid hillslope and on the entire catchment scale that includes arid regions downstream show a distinct runoff reaction that is dominated by Hortonian runoff processes. Analyses of multiple runoff events revealed a strong correlation between event runoff and rainfall amounts and intensities, whereas the antecedent rainfall had only a minor effect. This study represents the first assessment of surface runoff volumes based on observed data in the study area. The identified correlations promise to be valuable to carefully reconstruct long-term runoff coefficients in the investigated catchments using available long time series of rainfall. In conclusion, the overall result of this thesis was a scrutinizing assessment and quantification of water balance components, broadening our knowledge of the influence of soil and surface cover characteristics on percolation fluxes and on dominant runoff processes in the region. The results of all three studies highlight the prominent spatial and temporal variability of water balance components. We found that modelled potential recharge rates from the soil plot model agree with estimations from other studies using different approaches. The assessment and analysis of runoff in contrast, revealed less than one third the amount of water estimated in previous studies. Approaches and observation techniques use in this dissertation research may very well be applicable in other semi-arid areas. The results provide a comprehensive picture of the highly variable water resources in the Eastern Mediterranean and elucidate the strong dependency of water resources on rainfall characteristics, which - according to current projections - are likely to change in the future. The presented observations, methods and results substantially contribute to a better understanding of water resources variability and have important implications for their sustainable management. Finally, this work provides guidance on the challenges of setting up environmental monitoring networks that are urgently needed in the Westbank.