Mt. Fuji, the highest stratovolcano in Japan, has been considered to be a huge water reservoir. Various studies on the water environment of Mt. Fuji have been carried out to understand its scientific characteristics, and for water resource development. However, the mechanism of the water cycle, especially the groundwater flow system in this area, has still not been clarified. The hydrogeological settings and the groundwater flow at the northern part of Mt. Fuji are discussed based on the results of previous studies. Moreover, current issues and prospects are pointed out to further understand the hydrology of this area. Considering the hydraulic conductivities of the layers (e.g. volcanic sand and gravel, lava, volcanic mudflow) of the Shin-Fuji (Younger Fuji) stage and the Ko-Fuji (Older Fuji) stage, it is possible for groundwater to flow in the layers of both stages. At the northwestern foot of Mt. Fuji, three lakes (Lakes Sai, Shoji, Motosu) are mainly recharged not by Mt. Fuji but by the surrounding mountain area. Groundwater at the northwestern foot of Mt. Fuji is considered to be recharged by both water recharged in the northwestern flank of Mt. Fuji and water seepages from these lakes, and to flow toward the western-southwestern foot of Mt. Fuji. To further understand the water cycle in Mt. Fuji, it is essential to comprehensively discuss the results of various studies such as those on the geology, volcanology, geophysics, geochemistry, climatology, and hydrology of Mt. Fuji based on the viewpoints of hydrology and hydrogeology.
