Toyama's Oldest Cylindrical Water Divider
The Akasobu Cylindrical Water Distribution Tank (赤祖父円筒分水槽) is a reinforced concrete cylindrical water divider built in 1949 at Kawakami-naka, Nanto City, Toyama Prefecture, which in 2020 was registered as a Registered Tangible Cultural Property.
The Agency for Cultural Affairs records an area of 29 square metres, owned by the Shogawa Upper Reaches Land Improvement District and registered for its contribution to the historic landscape.
The Agency calls it the oldest cylindrical water divider in the prefecture, which supported the growth of postwar rice farming on the Tonami Plain.
Structure
According to the Agency, it stands at the apex of the fan of the Akasobu River in the Oyabe River system. Water overflowing the inner cylinder, 3.4 metres across, falls into an outer ring and is divided by partitions into three channels.
It was built as part of the Akasobu reservoir works.
What to Look For
Nanto City explains that the Akasobu River had a small catchment and little water, so villages below suffered droughts and water disputes. At local request a prefectural project built the Akasobu reservoir in 1945, and this divider was placed just below it to share the water fairly.
The city notes that five cylindrical dividers survive in Toyama Prefecture, this the oldest. Watch the water spilling evenly from the rim.
Visiting the Akasobu Cylindrical Water Distribution Tank
No official information on visiting conditions could be found. It is a working irrigation facility, so do not enter it.
Enquiries: Nanto City culture section, 0763-23-2014.
Q&A
- When was the tank built?
- In 1949.
- How does it work?
- Water overflowing an inner cylinder falls into an outer ring and is split into three channels.
- How big is it?
- The cylinder is 3.4 metres in diameter.
- Why was it built?
- To end water disputes and share irrigation water fairly, according to Nanto City.
- How is 赤祖父 read?
- Akasobu.
Basic Information
| Name | Akasobu Cylindrical Water Distribution Tank (赤祖父円筒分水槽) |
|---|---|
| Location | 1-19 Terayama, Kawakami-naka, Nanto City, Toyama Prefecture, and other lots |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 2020/4/3 (Reiwa 2) |
| Quantity | 1 structure |
| Dimensions | Reinforced concrete, area 29 square metres |
| Owner | Shogawa Upper Reaches Land Improvement District |
| Public Access | No official visitor information found |
References
- Agency for Cultural Affairs Database: Akasobu Cylindrical Water Divider (Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00013243
- Cultural Heritage Online: Akasobu Cylindrical Water Divider (Japanese)
- https://online.bunka.go.jp/heritages/detail/430552
- Nanto City: Akasobu Cylindrical Water Divider (Japanese)
- https://culture-archives.city.nanto.toyama.jp/culture/bunkazai/%E8%B5%A4%E7%A5%96%E7%88%B6%E5%86%86%E7%AD%92%E5%88%86%E6%B0%B4%E6%A7%BD/
Last verified: 2026.09.28