Kami Power Plant Outfall and Spillway

Kami Power Station Tailrace and Spillway: A Century of Hydroelectric Heritage

Nestled in the verdant mountain valley of Kamifukagi, Hitachiota City, Ibaraki Prefecture, the Kami Power Station Tailrace and Spillway (賀美発電所放水路及び余水路) stands as a remarkable testament to Japan's early twentieth-century hydroelectric engineering. Built in 1919 during the Taisho era, this waterway system has been channeling water from the power station to the Sato River for over a century, and was designated as a nationally registered tangible cultural property in 2004.

The Kami Power Station is part of the Satogawa River System Hydroelectric Power Station Group, which was recognized as a JSCE (Japan Society of Civil Engineers) Heritage of Civil Engineering in 2017. For visitors interested in industrial heritage and the story of Japan's modernization, this site offers a rare and atmospheric encounter with the infrastructure that once electrified entire regions of Ibaraki Prefecture.

Historical Background

The story of the Kami Power Station begins with the rapid industrialization of the Meiji and Taisho periods. In the early 1900s, the Ibaraki Electric Company (茨城電気株式会社) was established to bring electric power to Mito and surrounding areas. As demand for electricity surged—growing from just 6,511 electric lights in 1911 to over 21,000 by 1914—the company urgently needed new power sources.

Construction of the Kami Power Station began on July 16, 1917, on the Sato River, a tributary of the Kuji River system. The station was completed in February 1919 and began operations on March 5 of that year. Notably, it was the first power station that Ibaraki Electric planned and built entirely on its own, at a total cost of 293,030 yen. The facility was equipped with a 600-kilowatt AC generator manufactured by Hitachi, Ltd. and a horizontal Francis turbine imported from the Swiss firm Escher Wyss.

Over the decades, ownership of the station passed through several companies—from Ibaraki Electric to Ibaraki Power, Tobu Electric Power, Dai Nippon Electric Power, and Kanto Distribution—before arriving at its current owner, Tokyo Hatsuden Co., Ltd., a subsidiary of TEPCO. Remarkably, the power station continues to operate to this day, generating clean, renewable energy just as it has for over a century.

Why It Was Designated a Cultural Property

The tailrace and spillway of the Kami Power Station were registered as a national tangible cultural property on November 8, 2004, in recognition of their historical and engineering significance. Several key factors contributed to this designation.

The waterway system comprises two main components: the tailrace, which carries water from the segmental arch (also known as a depressed arch) discharge outlet on the east side of the main station building to the Sato River, and the spillway, which channels overflow water from the surge tank to merge with the tailrace. Together, they extend approximately 299 meters in total length.

What makes this structure particularly noteworthy is the exceptional quality of its stone masonry. The side walls of the channel are built with precisely laid rubble stone (谷積石張) at a gradient of approximately one-third, demonstrating a high level of craftsmanship. Near the confluence with the Sato River, a reinforced concrete maintenance bridge spans the channel, featuring ashlar (布積石張) masonry side walls and a segmental arch design. This combination of concrete and stonework reflects the transitional period in Japanese civil engineering when modern materials were being blended with traditional techniques.

As part of the broader Satogawa River System group—which includes five active power stations and one former substation—the Kami facility represents the earliest systematic hydroelectric development in Ibaraki Prefecture and serves as invaluable evidence of how civil engineering contributed to the modernization of regional communities.

Highlights and Points of Interest

The tailrace and spillway offer visitors several compelling features to appreciate.

The Satogawa River System Power Station Group

The Kami Power Station is one of six facilities that make up the Satogawa River System Hydroelectric Power Station Group, recognized by the Japan Society of Civil Engineers in 2017 as a Heritage of Civil Engineering. The group includes the Nakazato, Satogawa, Kami, Kosatagawa, and Tokuda power stations—all still operated by Tokyo Hatsuden—as well as the former Machiya Substation, now owned by Hitachiota City.

These facilities represent the earliest systematic hydroelectric development in Ibaraki Prefecture, spanning from the Meiji era through the Taisho period. Together, they tell the story of how water power transformed rural communities in the mountainous interior of the prefecture, bringing electric light and industrial energy to areas that had previously relied entirely on manual labor and natural daylight.

Surrounding Area and Nearby Attractions

Hitachiota City offers a rich array of cultural and natural attractions that pair well with a visit to the Kami Power Station.

The Former Machiya Substation (旧町屋変電所), located in the Nishikawachi area, is another registered cultural property connected to the same power distribution network. It has been preserved through the efforts of a local citizens' group and is occasionally open for special events.

The Ryujin Great Suspension Bridge (竜神大吊橋), one of Japan's longest pedestrian suspension bridges at 375 meters, spans the spectacular Ryujin Gorge. The bridge offers breathtaking panoramic views of the Yamizo and Abukuma mountain ranges and is famous for bungee jumping from a height of 100 meters above the lake surface.

For those interested in Japanese history, the Seizan-so (西山御殿), the retirement villa of Tokugawa Mitsukuni—the feudal lord famous for compiling the monumental history "Dai Nihonshi"—is located nearby. The beautifully restored thatched-roof complex sits amidst tranquil gardens.

The city is also known for its local soba noodles, made with buckwheat flour from the surrounding highlands. Seasonal events such as cherry blossom viewing in spring, the Carp Streamer Festival at Ryujin Bridge in May, and autumn foliage viewing make any time of year a rewarding period to visit.