Water discharge is an important aspect of the ecosystem services provided by the Soyang Lake to the South Korean population. The water discharge of the lake is tightly linked to the water discharge of the forested catchments covering 85% of the Soyang Watershed area. The general objective of this project is to quantify the annual variability of water flow pathways within a forested catchment and investigate the influence of precipitation amount and intensity, as well as other processes, on this variability. The general research question is: “Under the influence of the monsoon, when does water flow by which flow pathway and in what proportion”? It is hypothesized that the residence time of water within the catchment increases with soil depth and does not vary with lateral distribution, that the contributions of surbsurface and groundwater flow to storm hydrographs increase with antecedent soil moisture conditions and that the runoff ratio of storm hydrographs displays a consistent threshold response to the sum of antecedent soil moisture and precipitation amount. To test these hypotheses, the meteorological, physical and biological conditions leading to water flow and influencing water flow will be studied. Isotope signatures as well as chemical parameters will be derived from water samples in order to separate the hydrograph of the catchment into water flow pathways components. An experimental setup comprising meteorological instruments, piezometers, weirs, water samplers and soil moisture probes will be established. Site, soil and forest characteristics will be measured and related to hydrometric measurements. The results of the project will be presented as a process-based conceptual model of water flow pathways within a forested catchment under the influence of the monsoon. This conceptual model will provide information relevant to the estimation of the Soyang Lake and Watershed water balance with the Soil and Water Assessment Tool. Furthermore, the strong linkages between water flow, nutrient transport and processing and water quality will be studied by integrating the results of this project with those of projects on nutrient elements.