Abstract
Forest management practices influence the availability and quality of water by changing the characteristics of forest site, which in turn affect runoff, infiltration and evaporation rates. Therefore, understanding how forest vegetation impacts the relationship between rainfall and runoff over time is essential for sustainably managing forest for freshwater supplies, especially on remote islands due to their size, locations, geology and topography. However, the tool and /or data for studying a hydrological process of a particular site are/is often not available and even a basic hydrological process of a particular site is often little known. In this study, in the aim of improving our understanding of the hydrological process in an essential watershed on Okinawa Island, we use a simulation model that incorporates a kinematic wave approach to examine rainfall-runoff relationships. We tested the simulation model under various rainfall events to determine its accuracy for projecting runoff discharge. After comparing predicted and observed values, we found the model accurately predicted discharge under moderate and heavy precipitation, but were less accurate for lighter precipitation events. We also explored the modelʼs parameters to identify which values most accurately represent the watershedʼs environmental characteristics. We finally discussed the limitations and the provision for exploring various forest management in using our simulation model and implications for forest management.
