A stone arch with a plaque reading "Clear Waves"
The Shimonoseki City Waterworks Bureau Utsui No. 2 Reservoir Overflow Tunnel Entrance is a stone-arched tunnel portal built in 1929 at the southern end of Utsui No. 2 Reservoir in Utsuikami, Shimonoseki City, Yamaguchi Prefecture, and was registered as a Registered Tangible Cultural Property on January 16, 1998. It lies just south of the reservoir's intake tower.
The Agency for Cultural Affairs records it as a stone-arch portal 5.4 metres high, with a tunnel 3.0 metres high behind it. The city describes it as the mouth of the tunnel that carries off water overflowing from the reservoir; the Agency calls it a drainage tunnel entrance.
A reservoir needs a safe route for surplus water when levels rise, or the dam itself is put at risk. It is an unglamorous job, and an essential one.
Why it was registered
The portal was registered under the criterion of contributing to the historic landscape of the country. The Agency notes that, together with the intake tower, it forms a handsome waterside scene.
Among the nine Shimonoseki waterworks structures it is the only one classified as a civil engineering work. The others take in, clean, store or manage water; this one protects the reservoir itself, and it completes the picture of the waterworks as a working system.
What to look for
The opening of the Utsui No. 2 Reservoir Overflow Tunnel Entrance is a horseshoe arch of dressed granite. The curve runs a little past a semicircle, so the arch seems to draw in slightly at its feet. Follow the joint lines between the blocks and the care of the masons becomes clear.
Set into the stone above the arch is a plaque incised with two characters, 清波 (seiha), meaning clear waves. Choosing those words for the outlet of spilling water says something about how the engineers of the late 1920s thought about their work.
Take in the domed roof of the intake tower to the north together with this stone arch, and the waterside scene the Agency describes comes into focus.
Visiting the tunnel entrance
The Shimonoseki City Waterworks Bureau Utsui No. 2 Reservoir Overflow Tunnel Entrance belongs to a working reservoir, and the tunnel cannot be entered. The city's advance-application tours cover only the Waterworks Archive Room and the Takao plant, so the portal is seen from outside.
Because this is where surplus water is released, keep well away in wet weather or when water is high. Photograph from places open to the public; a telephoto lens helps to pick out the 清波 characters.
- 📍 Plan Your Visit to Yamaguchi
- Find tours, activities & transport passes near Shimonoseki City Waterworks Bureau Utsui No. 2 Reservoir Overflow Tunnel Entrance
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Q&A
- Can you go into the tunnel at the Shimonoseki City Waterworks Bureau Utsui No. 2 Reservoir Overflow Tunnel Entrance?
- No. It is part of an operating reservoir and is seen from outside only.
- What is the Utsui No. 2 Reservoir Overflow Tunnel Entrance for?
- It is the entrance to the tunnel that carries off water overflowing from Utsui No. 2 Reservoir. The Agency for Cultural Affairs describes it as a drainage tunnel entrance.
- What does the plaque on the Utsui No. 2 Reservoir Overflow Tunnel Entrance say?
- It is incised with 清波 (seiha), meaning clear waves.
- How large is the Utsui No. 2 Reservoir Overflow Tunnel Entrance?
- The portal is 5.4 metres high and the tunnel 3.0 metres high, according to the Agency for Cultural Affairs.
- When was the Utsui No. 2 Reservoir Overflow Tunnel Entrance built and registered?
- It was built in 1929 with No. 2 Reservoir and registered as a Registered Tangible Cultural Property on January 16, 1998.
Basic Information
| Name | Shimonoseki City Waterworks Bureau Utsui No. 2 Reservoir Overflow Tunnel Entrance |
|---|---|
| Location | 1066 Shimoseto, Utsuikami, Shimonoseki City, Yamaguchi Prefecture |
| Designation | Registered Tangible Cultural Property (Civil Engineering Structure) |
| Year Designated | Registered January 16, 1998 |
| Quantity | 1 structure |
| Dimensions | Stone-arch portal; height 5.4 m; tunnel height 3.0 m |
| Owner | Shimonoseki City |
| Public Access | Exterior only (interior closed) |
References
- Agency for Cultural Affairs Database: Utsui No. 2 Reservoir Overflow Tunnel Entrance
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00000487
- Shimonoseki City: Registered Tangible Cultural Properties of the Waterworks (Japanese)
- https://www.city.shimonoseki.lg.jp/site/water/5626.html
- Shimonoseki City: History of the Waterworks (Japanese)
- https://www.city.shimonoseki.lg.jp/site/water/5621.html
Last verified: 2026.09.27
