| 研究実績の概要 |
An approach to estimate the time-variant MTT and TTD using a five-layer tank model with isotopic tracers was proposed and tested within Fuji River catchment, central Japan. The tank model used for the transit time estimation was calibrated and then validated by comparing observed and simulated results of not only water balance but also isotope balance. Predominant factor controlling temporal variability of MTT is precipitation amount. Occurrence of precipitation alters TTD, with increases in younger components, and shortens the MTT. Long-term MTT values correlated with mean slope, coverage of Mesozoic sand stone/shale, coverage of forest, evaporation, interception and storage for each catchment. All of these are related to the amount of groundwater storage, which is smaller in mountainous areas and greater in plain areas.
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