Part of the precipitation falling on forested areas moves into the atmosphere as evaporation from the leaves, branches and stems which catch rain or snow, or through transpiration via soil and roots. The other part passes through the surface and ground, flows into rivers, and exits the forest. The water balance between the water entering and leaving a forested watershed fluctuates over time, and is affected by forest conditions such as vegetation species and tree size, and by weather conditions.

  Therefore, the Forestry and Forest Products Research Institute (FFPRI) is continuing to monitor the water balance of forested areas in Japan to clarify the relationship between forest conditions and water balance. The observation data has been published in print in a timely fashion, as well as utilized for research. This database provides the observation data already published in print as electronic files.

  For a brief introduction of seven of our forested watersheds included in this database, some of which began in the 1930s, please see our data note (https://doi.org/10.1002/hyp.14376) published in a special issue of Hydrological Processes entitled Research and Observatory Catchments: The Legacy and The Future.