To detect submarine groundwater discharge (SGD) within 1 km of the coastline on the Kunisaki Peninsula in Oita prefecture, we estimated the spatial distribution of SGD using a radon (²²²Rn)-salinity towed observation system and mixing diagrams, focusing on its relationship with geographic features. The towed observation covered a total distance of 104.7 km, and river water and groundwater surveys were conducted at 14 locations to collect data on ²²²Rn concentrations, electrical conductivity (EC), and water temperature. The results identified notable SGD occurrences, particularly in the southern and northern regions of the Kunisaki Peninsula. In certain southeastern areas, sites with high ²²²Rn concentrations were observed, suggesting the presence of either high SGD activity or recirculated seawater. Coastal areas with abundant SGD were characterized by short distances from upstream regions to the coast and steep slopes, indicating that topographic factors strongly influence SGD formation. Regions with numerous discharge points also exhibited low densities of irrigation ponds, suggesting abundant groundwater availability. However, no clear correlation was observed in the northern and southeastern regions. Future research should investigate factors such as irrigation pond storage capacity, inferred through water balance analyses, to better understand the mechanisms influencing SGD in these areas.

In Japan, the government faces the issue of how to provide a sustainable, stable water supply in the recent context of declining water demand and an increasing number of aging facilities. This issue has led to exploring alternative water supplies in areas where it is difficult for local governments to maintain public water supplies, and small-scale community-based water supplies are drawing attention, often using groundwater as the source. Previous research on groundwater management focused on the concept of governance and revealed the collaborative relationships among various actors in the local community, involving residents themselves who individually install wells. This study clarified groundwater management by local government and residents in an area using a small-scale water supply, in which residents obtain groundwater from individually installed wells. It also examined mechanisms to sustain such small-scale water systems and activities required to maintain them. The study area was the town of Higashikawa in Hokkaido, which is located in part of the Kamikawa Basin and has easy access to groundwater and therefore wells for domestic water are widespread. Groundwater utilization and management were analyzed based on interviews with local government and residents, as well as document analyses. In Higashikawa, the local government once planned public water supply using a dam as source, but the construction of the dam was delayed, and therefore the local government reviewed the project and began managing groundwater quantitatively and qualitatively. Although residents try to prevent groundwater problems, they rely on local government for specialized groundwater management because of the widespread use of wells. Also, although the local government was trying to increase the population, the natural and rural landscape was seen as an attraction to the town, and this led to a balance between population growth policies and landscape preservation. These efforts by the local government and residents led to preservation of groundwater and maintenance of a small-scale water supply. The case of Higashikawa shows that to maintain a small-scale water supply system, local governments need to supplement the management of small-scale water supply by residents and implement policies to sustain not only physical but also social conditions in the region.

This paper investigates how village parishioners and acting chief priests maintain vacant temples, as well as the limitations of their efforts, by examining cases in Hayakawa, a depopulated mountain village in Yamanashi prefecture. The temples in Hayakawa have been vacant since the 1960s due to depopulation. The vacant temples have been maintained and managed by neighboring parishioners, who keep an eye on the temples during their daily rounds, but this situation has become problematic owing to the small, aging population of the surrounding community. Deterioration of the buildings on vacant temple sites are also a cause for concern because if they become damaged by natural disasters, pests, or other causes, the small number of parishioners would be unable to raise the funds necessary for repairs, and the buildings would be left to decay. In the meantime, the acting chief priests tried to maintain temple–parishioner relationships through annual memorial services, funerals, and visits to parishioners, but were unable to attend to parishioners scattered over a wide area and therefore were limited to attending to parishioners in nearby neighborhoods. These case study findings show that the extent to which vacant temples can be maintained is limited.