Contribution of soil water and its flow path to stormflow generation in a forested headwater catchment in central Japan

Hydrometric observations and natural tracer analysis were carried out in a small forested headwater catchment in central Japan in order to clarify the source component in stormflow generation and the actual flow path of the main component. The storm hydrograph produced by a total rainfall of 45.9 mm was separated into two and three physically-based source components. For the storm event, soil water contributed around 36% of the event discharge and nearly 52% of the peak discharge. Successive potential distribution maps of both soil and groundwater zones confirmed the now path of soil water contributing to stormflow generation. The results show the important role of soil water in stormflow generation and illustrate the important place near the stream, maybe the riparian zone, for considering the mechanism of stormflow generation and the process by which the stream-water quality is formed.