Multiple-tracers-aided surface-subsurface hydrological modeling for detailed characterization of regional catchment water dynamics in Kumamoto area, southern Japan

Rahman, A. T. M Sakiur; Hosono, Takahiro; Tawara, Yasuhiro; Fukuoka, Youichi; Hazart, Aurelien; Shimada, Jun

Multiple-tracers-aided surface-subsurface hydrological modeling for detailed characterization of regional catchment water dynamics in Kumamoto area, southern Japan | Modélisation hydrologique de surface-subsurface appuyé par plusieurs traceurs pour une caractérisation détaillée de la dynamique des eaux du bassin régional de la zone de Kumamoto, sud du Japon Modelización hidrológica superficial y subterránea con ayuda de múltiples trazadores para la caracterización detallada de la dinámica hídrica regional en las cuencas en la zona de Kumamoto, sur de Japón 日本南部Kumamoto地区区域流域水动力学详细特征的多示踪辅助地表水和地下水水文模拟 Modelagem hidrológica de subsuperfície e superfície auxiliada por múltiplos traçadores para caracterização detalhada da dinâmica da água de captação regional na área de Kumamoto, sul do Japão

2021

Integrated watershed modeling techniques have been applied in recent years to examine surface and subsurface interactions. Model performance is often evaluated by best fit of the hydrograph, which alone cannot explicitly explain whole catchment dynamics. To overcome this problem, this study incorporated multiple tracers (³H, ⁸⁵Kr, and groundwater temperature) into a physically-based fully distributed modeling framework for characterizing regional-scale hydrological processes in Kumamoto, southern Japan. First, a simulation performed by a hydrometrically calibrated model showed satisfactory performance for river discharge and groundwater level. However, this model showed poor fitting for isotopic composition and temperature due to the structural uncertainty of the model. A new model was established reflecting recent deep bore log data and incorporating tracer data showed acceptable accuracy for hydrographs and tracers. Thus, more reliable estimates of groundwater storage, groundwater age and water flow paths were depicted over the regional catchment. Comparisons between the two models indicate that the model structure of an area with an uncertain lower boundary can be addressed by incorporating multiple tracer data. Tracer-aided models could be applied for a holistic understanding of contaminant transport dynamics besides flow simulation.

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