An Irrigation Dam Designated for the Way Water Leaves It
The Hakusui Tameike Entei Suiri Shisetsu (白水溜池堰堤水利施設, Hakusui Reservoir Weir Irrigation Facility), an agricultural water complex on the upper Ono River in Taketa City, Oita Prefecture, was completed in March 1938 and designated a national Important Cultural Property on 13 May 1999. Locally it goes by the shorter name Hakusui Dam.
The designation covers a main weir and a subsidiary weir with a culvert, together with an inclined intake, a sluice for sediment, flanking wing walls and a maintenance stair. A stone monument recording the reservoir is included as an attached item. The main weir measures roughly 86 metres long and about 14 metres high; Taketa City gives the more precise figures of 87.26 metres and 14.1 metres. Because Japanese river law reserves the word dam for structures 15 metres and taller, the popular name is a courtesy rather than a legal classification.
What the designation actually rewards is unusual. The Agency for Cultural Affairs cites two criteria, excellence in design and excellence in technique, and its commentary singles out the way each structure was fitted to the shape of the ground so that the water leaving the weir takes on a rare beauty. The engineering brief here included the appearance of falling water.
Why It Was Built
The Fujio Iro canal carries water across the plateau farmland of Taketa and the Ogata district of Bungo-ono. It never carried enough. Building a reservoir on the upper Ono River, close to the Kumamoto prefectural boundary, was the answer settled on in the early 1930s. Ground was broken in April 1934 and the works were finished in March 1938.
Attribution of the design is not consistent between sources. The Agency for Cultural Affairs names Arase Choichi and Ikeda Kakuji, agricultural and forestry engineers with Oita Prefecture, among those involved in the works, and identifies Tetsudo Kogyo Co. as the contractor. Taketa City and several other accounts credit the design and site supervision to Ono Yasuo, a prefectural agricultural civil engineering technician. The two versions have not been reconciled here; the Agency register is the primary record, and the local attribution is noted rather than set aside.
What is agreed is that this was provincial work. No famous name from Tokyo appears anywhere in the file. Prefectural technicians solved a local water shortage with the materials and labour available in 1930s Bungo, and produced something people now drive an hour to look at.
Musha-gaeshi and the Rolling Wave
The main weir is an overflow gravity structure: pure concrete on the upstream face, rubble concrete downstream, and the entire visible surface faced in cut stone. That facing is the first thing worth noticing. It is not decoration applied after the fact but the working skin of the structure, laid with a care that concrete alone would not have required.
The ground beneath the weir turned out to be soft. Falling water would have scoured it. The response was a technique the builders called musha-gaeshi, borrowed by name from the flared upper courses of a castle wall, which breaks the force of the descending water before it reaches the riverbed. Protecting the foundation was the point. The side effect was the pattern of standing ripples across the face that locals call tenpa, a rolling wave.
The wing walls are not symmetrical. The right bank carries a curved projection to guide water, the left bank a stepped one, each shaped to the slope it sits against. Water sheets down over the stonework and separates into a texture that reads more like cloth than like a falling river, which is where the description of a white robe comes from.
The Season Matters More Than the Hour
This is the practical point that catches most visitors out. The weir has been under a repair programme since 2016. Sediment had built up to the point where the sluice gates could no longer be operated, and Oita Prefecture's Hoi Regional Bureau is removing part of it and overhauling the gate machinery.
The work requires the reservoir to be drawn down, so overflow across the weir is stopped from late November until the middle of June each year. That schedule has been in force since 2018 and is projected to continue to 2027. In the most recent cycle, overflow stopped on 27 November 2025, river works were suspended, and water returned to the face on 12 June 2026. A further stoppage from late November 2026 is planned.
Arriving in winter or early spring means arriving at a dry stone wall. It is still a fine piece of masonry, but the thing the place is known for will not be happening. Between mid-June and late November the sheet of water is running. Confirm before travelling: the works office at the Hoi Regional Bureau can be reached on 0974-63-1175, and Taketa City's commerce and tourism section on 0974-63-4807.
Getting There and Where to Stand
The weir is about 11 kilometres from Bungo-Taketa Station, roughly 25 minutes by car. There is no bus. The approach lanes are narrow farm roads, and drivers of larger vehicles should plan for tight passing places.
Two viewpoints exist and they are not interchangeable. The left bank, reached via Shigita in Ogi-machi, puts you below the weir looking up at the full drop of water, and this is the view that appears in photographs. Parking there is split between two lots, the first taking eight cars and three microbuses, the second about ten, with toilets at the first. The right bank, at Tsugikura, looks down from above and holds roughly ten cars. If time allows only one, take the left bank.
Access is free and unrestricted, with no gate and no opening hours, though fencing keeps visitors back from the water itself. Morning light favours the left bank view. The Otonashi Iro circular water divider, another irrigation structure of the same era and about twenty minutes away by car, makes an obvious pairing for anyone interested in how this plateau was irrigated.
Still Working
The weir has never been retired. It continues to supply water to roughly 280 hectares of farmland and is maintained by the Fujio Iro Land Improvement District, the same body that owns it. Designation as an Important Cultural Property did not turn it into a monument; it remains a piece of working agricultural infrastructure that happens to be listed.
That double status explains the repair programme. Removing sediment and restoring the sluice gates is not conservation for display but the upkeep any functioning reservoir requires, carried out under the constraints that a designated structure imposes. The weir was also the first Important Cultural Property designated among Oita Prefecture's modernisation heritage sites, and it reached a wider audience in 2006 through a television commercial for a local barley shochu.
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Q&A
- When can I see water flowing over the Hakusui Tameike Entei Suiri Shisetsu?
- Between roughly mid-June and late November. Repair work requires overflow to be stopped from late November to mid-June, a cycle running since 2018 and projected to continue to 2027. Overflow resumed on 12 June 2026, with the next stoppage planned from late November 2026.
- Is there an admission fee for the Hakusui Tameike Entei Suiri Shisetsu?
- No. The site is outdoors, free to visit and open at all hours, with no gate and no ticket office. Fencing keeps visitors back from the water. Photography is unrestricted.
- How do I reach the Hakusui Tameike Entei Suiri Shisetsu, and where should I park?
- It is about 25 minutes by car from Bungo-Taketa Station, some 11 kilometres, with no bus service. The left bank at Shigita in Ogi-machi has two car parks and toilets and gives the view from below; the right bank at Tsugikura holds about ten cars and looks down from above. Approach lanes are narrow.
- What does musha-gaeshi mean at the Hakusui Tameike Entei Suiri Shisetsu?
- It is the technique devised to weaken the force of water descending the weir face, because the ground beneath the structure was soft and would otherwise have been scoured. The name is taken from the flared coursing of a castle wall. The pattern of standing ripples it produces is known locally as tenpa.
- Is the Hakusui Tameike Entei Suiri Shisetsu still in use?
- Yes. It still irrigates about 280 hectares of farmland and is maintained by its owner, the Fujio Iro Land Improvement District. The current repair programme exists because the sluice gates became inoperable under accumulated sediment, not because the structure was abandoned.
Basic Information
| Name | Hakusui Tameike Entei Suiri Shisetsu (白水溜池堰堤水利施設), commonly Hakusui Dam |
|---|---|
| Location | Tsugikura and Shigita in Ogi-machi, Taketa City, Oita Prefecture (the national register writes the second element as Kashiwabara, Hagi-machi) |
| Designation | Important Cultural Property (Structure); designation number 02369 |
| Year Designated | 13 May 1999 |
| Quantity | Main weir, one unit; subsidiary weir, one unit; attached item, the Hakusui reservoir monument, one unit |
| Dimensions | Main weir about 86 m long and about 14 m high (Taketa City gives 87.26 m and 14.1 m); reservoir capacity about 600,000 cubic metres |
| Owner | Fujio Iro Land Improvement District |
| Public Access | Outdoors, free, no fixed hours; overflow stopped from late November to mid-June during repair works |
References
- Agency for Cultural Affairs, National Cultural Properties Database: Hakusui Tameike Entei Suiri Shisetsu
- https://kunishitei.bunka.go.jp/bsys/maindetails/102/3596
- Cultural Heritage Online: Hakusui Tameike Entei Suiri Shisetsu, main weir
- https://bunka.nii.ac.jp/heritages/detail/177512
- Taketa City: nationally designated cultural properties
- https://www.city.taketa.oita.jp/bunka_rekishi_kanko/bunkazai/siteibunkazai/siteibunkazaigaiyou/4433.html
- Oita Prefecture, Hoi Regional Bureau: notice on the Hakusui reservoir improvement works
- https://www.pref.oita.jp/soshiki/11607/hakusui-info.html
- Taketa City Tourism Association: Hakusui Dam
- https://taketa.guide/spots/detail/52ff4cab-5ddc-4ab6-95bd-bcb537b3c908
- Ministry of Agriculture, Forestry and Fisheries: Hakusui Tameike Entei
- https://www.maff.go.jp/j/nousin/sekkei/museum/m_bunka/jyuuyou3/index.html
Last verified: 2026.08.20
Cultural Treasures in the Same Area
All are within walking distance in the same area, so we recommend visiting them together.
- Shiramizu Reservoir Dam Water Supply Facility Sub-dam 0.00 km
- Shiramizu Reservoir Dam Water Supply Facility Main dam 0.03 km