Regional groundwater flow system in a stratovolcano adjacent to a coastal area: a case study of Mt. Fuji and Suruga Bay, Japan

Groundwater movement through the slope area of Mt. Fuji to the coastal area of Suruga Bay (central Japan) was investigated using spatially dense geochemical data, as a case study for elucidating the groundwater flow system in a stratovolcano adjacent to the coast. Spatial distributions of the hydrogen stable isotope ratio, vanadium concentration, and water temperature in the groundwater showed anomalies at the coastal area of Suruga Bay. The anomalies were characterized as depleted isotope ratio, high vanadium concentration, and low water temperature relative to surroundings. This can be explained as a regional deep groundwater flow from the slope of Mr. Fuji to the coastal area of Suruga Bay because groundwater recharged at higher elevation has a depleted isotope ratio caused by the altitude effect and high vanadium concentration as a result of dissolution from the basaltic aquifer. These characteristics also imply a hierarchical flow system, which is incorporated into a hydrogeological model of the coastal aquifer.