Three Structures Built to Harness the Kiso River
The Yomikaki Power Station Facilities (読書発電所施設, Yomikaki Hatsudensho Shisetsu) are a group of Taisho-era hydroelectric structures in Yomikaki, Nagiso Town, Nagano Prefecture, built in 1922 and 1923 and designated an Important Cultural Property in 1994. The designation covers three parts: the Yomikaki Power Station itself, a reinforced-concrete main building with a head tank above it; the Momosuke Bridge (桃介橋, Momosuke-bashi), a timber-stiffened suspension bridge over the Kiso River; and the Kakizore Aqueduct Bridge (柿其水路橋, Kakizore Suirokyo), which carries the station's water channel across a tributary.
None of this sits inside a single compound. The power station stands southwest of Nagiso Station, the Momosuke Bridge crosses the river upstream within sight of the station, and the aqueduct lies farther up the valley in the Kakizore district. What was protected in 1994 is a working sequence, intake to turbine, strung out along a few kilometres of river.
The name is a small puzzle for anyone who reads Japanese. The characters 読書 normally mean "reading," which is why automated translations sometimes turn the name into "Reading Power Plant." Here they are pronounced yomikaki. Nagiso Town records that the village of Yomikaki was formed in 1874 when Yogawa, Midono and Kakizore merged, and the name is said to string together the first sounds of the three: yo, mi and kaki.
The builder was Daido Electric Power, a company later absorbed into today's Kansai Electric Power. Kansai Electric still runs the power station and the aqueduct, while the Momosuke Bridge belongs to Nagiso Town and serves as a municipal footpath.
Why the Yomikaki Power Station Facilities Were Designated
Japan's national database of designated cultural properties lists two grounds for protecting the Yomikaki Power Station Facilities: excellence of design and excellence of engineering. Both apply. The power station has a carefully composed facade, and the two bridges solved hard structural problems with the materials of their day.
The driving force was Fukuzawa Momosuke, the adopted son-in-law of the educator Fukuzawa Yukichi and later nicknamed Japan's "king of electric power." As president of Daido Electric Power he set out to dam and divert the fast, steep Kiso River for a chain of plants. According to the Nagiso tourism association, Yomikaki was built between November 1921 and December 1923 and opened with a maximum output of 40,700 kilowatts, making it a landmark among run-of-river stations of the Taisho period.
A run-of-river, or channel-type, station works by diverting water upstream, sending it along a gently graded channel to a point high above the powerhouse, and then dropping it through steel penstocks onto the turbines. The Kakizore Aqueduct Bridge is where that channel crosses the Kakizore River. The head tank and penstock behind the Yomikaki powerhouse are the final drop. At Yomikaki the links of that chain survive together, and they still work.
Nagano Prefecture's official tourism site presents the Yomikaki Power Station Facilities as the first operating hydroelectric plant to be named an Important Cultural Property. In 1960 a fourth generating unit was added, fed from the new Yomikaki Dam through a channel of about 8 kilometres that delivers an effective head of 112 metres. A Kansai Electric document from 2007 gives the station's maximum output as 117,100 kilowatts.
What to Look For at Each Site
The Powerhouse and Head Tank
The Agency for Cultural Affairs records the power station as a main building and a head tank. The main building is reinforced concrete with a building area of 970.6 square metres and comes with one set of penstocks; the head tank is plain concrete.
Look at the semicircular windows, the clerestory lantern that rises from the roof, and the band of ornament along the top of the walls. Nagano's tourism site describes the style as Art Deco and credits the design to Sato Shiro, an architect Daido Electric brought in. It is an industrial building that was clearly meant to be seen from the river and to look good doing it.
Above the powerhouse, the penstock runs straight down the slope from the head tank. The pipes are reported to be the originals, and the front and side walls of the head tank still carry their original detailing.
Momosuke Bridge
The Momosuke Bridge was finished in September 1922. Official records describe it as a timber-stiffened suspension bridge 247.8 metres long and 3.0 metres wide, including a central stair and 9 anchorages. The Nagiso tourism association and a Ministry of Land, Infrastructure, Transport and Tourism report round it to 247 metres long and 2.7 metres wide, which probably reflects a different point of measurement.
It was built to carry construction materials to the Yomikaki site, with a narrow-gauge rail line down the middle of the deck. In 1950 it became a village road and for decades served as the everyday crossing between the two banks, used by students walking to the local junior and senior high schools. Decay closed it in 1978. Nagiso Town restored it in 1993 as part of the Tenpaku Park project, and the designation followed the next year.
As you walk across, watch the centre of the deck: the restoration marked where the old rails ran. Under the walkway is a continuous wooden stiffening Truss, best seen from the riverbank where hangers and truss line up in profile. The midstream tower has its own stair down to a sandbar, a feature the national record includes in the protected structure.
Kakizore Aqueduct Bridge
The Kakizore Aqueduct Bridge, completed in 1923, is part of the channel that feeds the power station. The national record describes a reinforced-concrete twin-arch bridge 142.5 metres long with reinforced-concrete side spans at each end. The tourism association gives its length as 142.4 metres and calls it one of the largest prewar aqueduct bridges surviving in Japan.
Two broad arches leap the Kakizore River, and short girder spans tie the ends into the slopes. Nagano's tourism site puts the deck at 6.8 metres wide; the open channel runs along the top, and water flows through it whenever the station is generating. The weathered concrete has the texture of something that has been working for nearly a century.
Visiting: Walk the Bridge, View the Rest from Outside
Only one of the three parts is open to walk on. The Momosuke Bridge is a public town road, free and open year-round, about 5 to 10 minutes on foot from Nagiso Station on the JR Chuo Main Line. Tenpaku Park at the bridge end has parking and toilets. By car, allow about 30 minutes north on National Route 19 from the Nakatsugawa interchange of the Chuo Expressway.
The Yomikaki Power Station is an active Kansai Electric facility and does not accept visitors. You cannot enter the grounds, so the powerhouse and penstock are seen from outside the fence. The Kakizore Aqueduct Bridge is likewise part of the live water channel and cannot be walked on; it crosses the river beside the road up to the Kakizore Gorge, and you view it from there. As of October 2026 the Nagiso tourism association notes road works near the aqueduct, with construction vehicles and equipment on site.
No official notice restricts photography, but both the powerhouse and the aqueduct are operating plant, so stay out of fenced areas. Beside the Momosuke Bridge, the Fukuzawa Momosuke Memorial Museum occupies the villa he used as his base in the valley and displays photographs and papers connected with the man behind the Yomikaki Power Station Facilities.
Q&A
- What is included in the Yomikaki Power Station Facilities Important Cultural Property?
- Three structures in Nagiso Town, Nagano: the Yomikaki Power Station (main building and head tank), the Momosuke Bridge and the Kakizore Aqueduct Bridge, designated together in 1994. One set of old suspension-bridge timbers and one commemorative monument are also included as attached items.
- Can you tour inside the Yomikaki Power Station?
- No. It is a working Kansai Electric plant and tours are not offered. The grounds are closed, so the powerhouse and penstock can only be seen from outside.
- Can I walk across the Momosuke Bridge in Nagiso, and is there a fee?
- Yes. The Momosuke Bridge is a town road, free and open year-round with no set hours. It is about 5 to 10 minutes on foot from Nagiso Station.
- Why is 読書 in Yomikaki Power Station read "yomikaki" and not "reading"?
- It is a place name. The village of Yomikaki was created in 1874 by merging Yogawa, Midono and Kakizore, and the name is said to join the first sounds of the three villages.
- Where can I see the Kakizore Aqueduct Bridge, and can I walk on it?
- It spans the Kakizore River beside the road toward the Kakizore Gorge and is viewed from that road. Because it carries the power station's water channel, the bridge itself is off limits.
Basic Information
| Name | Yomikaki Power Station Facilities (Power Station, Momosuke Bridge, Kakizore Aqueduct Bridge) |
|---|---|
| Location | Yomikaki, Nagiso Town, Kiso District, Nagano Prefecture |
| Designation | Important Cultural Property (Structure) |
| Year Designated | Designated 1994/12/27 (Heisei 6) |
| Quantity | 3 structures (power station 1 site, Momosuke Bridge 1, Kakizore Aqueduct Bridge 1); attached items: old suspension-bridge timbers 1 set, commemorative monument 1 |
| Dimensions | Power station main building: building area 970.6 square metres; Momosuke Bridge: 247.8 metres long, 3.0 metres wide; Kakizore Aqueduct Bridge: 142.5 metres long |
| Owner | Nagiso Town; Kansai Electric Power Co., Inc. |
| Public Access | Momosuke Bridge open year-round as a town road (free). Power station and Kakizore Aqueduct Bridge are operating facilities, closed to the public; exterior view only |
References
- Database of National Cultural Properties: Yomikaki Power Station Facilities, Power Station (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/bsys/maindetails/102/1002
- Database of National Cultural Properties: Yomikaki Power Station Facilities, Momosuke Bridge (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/bsys/maindetails/102/00004055
- Database of National Cultural Properties: Yomikaki Power Station Facilities, Kakizore Aqueduct Bridge (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/bsys/maindetails/102/00004054
- Cultural Heritage Online: Yomikaki Power Station Facilities, Power Station
- https://online.bunka.go.jp/heritages/detail/174242
- Nagiso Town: List of Cultural Properties in Nagiso (Japanese)
- https://www.town.nagiso.nagano.jp/0000000253.html
- Nagiso Town: About Nagiso (Japanese)
- https://www.town.nagiso.nagano.jp/0000000370.html
- Nagiso Tourism Association: Yomikaki Power Station (Japanese)
- https://nagiso.jp/topics/yomikaki-power-station/
- Nagiso Tourism Association: Momosuke Bridge (Japanese)
- https://nagiso.jp/topics/momosuke-bridge/
- Nagiso Tourism Association: Kakizore Aqueduct Bridge (Japanese)
- https://nagiso.jp/topics/kakizore-aqueduct/
- Ministry of Land, Infrastructure, Transport and Tourism: Momosuke Bridge case study (Japanese)
- https://www.mlit.go.jp/sogoseisaku/region/kankosyakaisihon/85/2007.pdf
- Go! NAGANO (Nagano Prefecture official tourism site): Yomikaki Power Station Facilities (Japanese)
- https://www.go-nagano.net/tradition-and-culture/id19246
- Kansai Electric Power: Outline of Yomikaki Power Station, July 25, 2007 (Japanese)
- https://www.kepco.co.jp/corporate/pr/2007/__icsFiles/afieldfile/2007/07/25/0725_1j_01.pdf
Last verified: 2026.10.06
Cultural Treasures in the Same Area
All are within walking distance in the same area, so we recommend visiting them together.
- Yomikaki Power Station Facilities Power Station 0.00 km
- Yomikaki Power Station Facilities Momosuke Bridge 1.96 km
- Yomikaki Power Station Facilities Kakizore Aqueduct Bridge 5.99 km