[A-HW25] Near Surface Investigation and Modeling for Groundwater Resources Assessment and Conservation

[AHW25-12] Evaluating Mountain Front and Mountain Block Recharge using stable isotopes and Hydrogeological Groundwater Flow Model in Yamanashi, Japan

*Cuong Quoc Nguyen¹、Takashi Nakamura¹、Tatsuki Kimura¹ (1.International Research Center for River Basin Environment, University of YAMANASHI)

キーワード：Mountain Front Recharge, Groundwater Flow, COMSOL Multiphysics, Groundwater Modeling, Hydrogeology

Several studies have pointed out that mountain recharge is a crucial process in groundwater recharge for the alluvial deposit area. However, the attention to this issue is not paid enough in Japan. Kofu basin, Yamanashi prefecture in Japan, is a typical basin surrounded by mountains, with a very high potential for mountain groundwater recharge in this area. Analyzing stable isotopes (δ¹⁸O and δ²H) and chloride concentration in groundwater samples combined with end-member mixing analysis can identify the source of mountain groundwater recharge. The groundwater flow was illustrated using groundwater boreholes and the groundwater flow model simulated by COMSOL Multiphysics. The study found three main sources of groundwater in Yamanashi: mountain front recharge, mountain block recharge, and precipitation/hill-slope recharge, and calculated their contribution in each region. This pilot study in Japan confirms that the groundwater in the basin has a considerable recharge from the mountain’s groundwater source and visualizes the dynamic flow. Sustainable development policies in terms of groundwater use, mountain forest protection, and health risks related to drinking water can be taken advantage of from the study results.