The basin that decides how much water goes on
The Kamisaibara Power Station Tenno Channel Settling Basin is a reinforced concrete water structure of 1930 in the Kawamuki district of Kamisaibara, Kagamino, Okayama Prefecture, and it was listed as a Registered Tangible Cultural Property on 29 November 2006. It stands about 240 metres below the Akawase River intake weir, on the Tenno channel that gathers the station's tributary supplies.
Its first job is to settle the sand out of the water heading for the turbines. Its second job is quieter and just as important. An overflow weir along the west side lets surplus water spill away, with a drain gate at the southern end of that weir, so the channel below carries only what the station can use. A conduit that receives more than it can pass will find its own way out of the walls sooner or later, and this is the point where that argument is settled.
Covering 134 square metres, it is roughly twice the size of the smaller basin on the Ikego channel. A slab 20 metres long is cantilevered along the east wall to keep hillside debris out of the water.
Why the basin was registered
Registration number 33-0145 belongs to the Kamisaibara Power Station Tenno Channel Settling Basin, one of nine structures of this station accepted together on 29 November 2006 under the criterion that they contribute to the historic landscape of the country.
Registration dates from 1996 and is written for works that remain in use. The owner notifies the authorities before major alteration; nothing obliges the structure to stop functioning. A Registered Tangible Cultural Property can therefore stay in service, and Okayama Prefecture records all nine of these as facilities currently in operation.
The Tenno channel is the trunk of the tributary system. Water taken from the Akawase enters it from the west, water taken from the Ikego joins it from the north, and the combined flow runs south towards the head tank. Placing the larger of the two settling basins on this channel rather than on either branch means one structure handles the sand from more than one catchment. Kamisaibara Power Station is rated at 2,700 kilowatts, and every litre in that figure passes a basin like this one.
What to look at
The overflow weir along the west side is the element to trace. Its crest sets the working water level in the channel; anything above that level goes over the top and back to the stream. The drain gate at the southern end lets an operator empty the basin completely when the deposit has to be cleared or the channel taken out of service.
Then follow the line of the cantilevered slab. Twenty metres is a long overhang for 1930 reinforced concrete, and the fact that it is still there says something about how carefully the reinforcement was worked out.
The setting rewards a slow look too. The Kamisaibara Power Station Tenno Channel Settling Basin sits low against a wooded slope, its concrete weathered to the grey of the rock behind it, and from the far bank it is not obvious that the water in front of you is already inside a machine.
Visiting
This is a component of an operating power scheme rather than a visitor site. No admission is charged, no opening hours are published, and the basin lies within the operator's fenced land.
Okayama Prefecture asks visitors who want to see the facilities to arrange it in advance with the Tsuyama Power Office of Chugoku Electric Power, on 0868-27-0275. Raise photography on the same call.
Kawamuki is in the northern part of Kamisaibara, reached from National Route 179 between Tsuyama and Ningyo Pass. Without a car, take the JR Kishin Line to Tsuyama Station or Inno-sho Station, then the Chutetsu Hokubu Bus service towards Okutsu Onsen and Ishigoshi; Kagamino town publishes the timetables. Water levels in the channel change without warning when gates are operated upstream, so do not attempt to walk along the conduit.
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Q&A
- What is the Kamisaibara Power Station Tenno Channel Settling Basin for?
- It settles sand out of the water flowing along the Tenno channel towards the station, and it sheds surplus water over an overflow weir on the west side so that the channel below carries only the amount the station needs.
- How large is the Kamisaibara Power Station Tenno Channel Settling Basin?
- It covers 134 square metres and is built of reinforced concrete, with a slab 20 metres long cantilevered along the east wall.
- Where is it in relation to the intake weirs?
- About 240 metres downstream of the Akawase River intake weir, on the Tenno channel that also receives water from the Ikego channel.
- What is the drain gate at the south end used for?
- It empties the basin, which is needed when accumulated deposit has to be cleared or the channel is taken out of service for maintenance.
- Can members of the public go and see it?
- Only by arrangement. Okayama Prefecture gives 0868-27-0275, the Tsuyama Power Office of Chugoku Electric Power, as the contact for anyone wanting to view the facilities.
Basic Information
| Name | Kamisaibara Power Station Tenno Channel Settling Basin |
|---|---|
| Location | Kawamuki, Kamisaibara, Kagamino-cho, Tomata-gun, Okayama Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 1930 structure on 2006-11-29 |
| Quantity | 1 site |
| Dimensions | Reinforced concrete, area 134 square metres; overflow weir on the west side with drain gate at its south end, slab 20 metres long cantilevered on the east wall |
| Owner | Chugoku Electric Power Co., Inc. |
| Public Access | Operating facility. No public entry; viewing of the plant by prior arrangement with the Tsuyama Power Office, 0868-27-0275 |
References
- National Cultural Properties Database, Agency for Cultural Affairs: Kamisaibara Power Station Tenno Channel Settling Basin
- https://kunishitei.bunka.go.jp/heritage/detail/101/00006067
- Cultural Heritage Online, Agency for Cultural Affairs: Kamisaibara Power Station Tenno Channel Settling Basin
- https://online.bunka.go.jp/heritages/detail/171372
- Okayama Prefecture, Cultural Properties Division: Registered Cultural Properties in Okayama Prefecture
- https://www.pref.okayama.jp/page/detail-50777.html
- Okayama Prefecture: Kamisaibara Power Station Facilities (PDF)
- https://www.pref.okayama.jp/uploaded/attachment/260992.pdf
- Chugoku Electric Power Co., Inc.: List of hydroelectric power stations
- https://www.energia.co.jp/energy/general/water/water_all.html
- Kagamino Town: Route buses and public transport
- https://www.town.kagamino.lg.jp/soshiki/22/2132.html
Last verified: 2026.09.08