同位体トレーサーと数値モデルを併用した流域滞留時間推定手法の開発とその検証

提出了一种利用带有同位素示踪剂的五层水箱模型来估算时变的MTT值和TTD值的方法，并在日本中部的富士河流域进行了测试。对用于渡越时间估算的水槽模型进行了标定，并通过水平衡和同位素平衡观测结果与模拟结果的对比，验证了该模型的有效性。降水量是控制MTT值时间变异性的主要因素。降水的出现改变了TTD，增加了年轻成分，并缩短了MTT值。长期MTT值与平均坡度、中生代砂岩/页岩盖度、森林盖度、各集水区的蒸发、截留和蓄水有关。所有这些都与地下水的储存量有关，地下水的储存量在山区较小，在平原地区较大。

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.