Monthly measurements of water dissolved inorganic radiocarbon in Lake Kawaguchi for three years indicating seasonal precipitation-groundwater variations.

Understanding groundwater dynamics is important for projecting water resources of the Lake Kawaguchi, however, the difficulty of observation and the limited number of geochemical tracers are a problem. In this study, we investigated 14C concentration (Δ14C) of lake water for three years and employed a 14C box model to estimate the groundwater contribution. Seasonal variations of Δ14C were also observed in both 2019 and 2020, confirming that Δ14C in Lake Kawaguchi decreases from summer to fall and increases during winter. Heavy precipitation exceeding 300 mm in a few days because of tropical cyclon HAGIBIS (Typhoon#19) significantly increased Δ14C in the lake for one month and it could caused by temporal changes in the surface water pathway. The 14C box model demonstrated that 14C could semiquantitatively evaluate the groundwater flow in the lake. It is needed to add quantative evaluations inflow from rivers and other factors to understand of groundwater dynamics. [ABSTRACT FROM AUTHOR]