Imbe Water Purification Plant

A Taishō-Era Waterworks Still Supplying Matsue

Imbe Water Purification Plant (忌部浄水場, Inbe Jōsuijō) is a waterworks at Higashi-Imbe-cho in Matsue City, Shimane Prefecture, completed in 1919, whose nine historic concrete structures were entered on the national register as Registered Tangible Cultural Properties on 18 April 2008. It was built for Matsue's first public water supply and has been treating water ever since.

The site lies a little over 5 kilometres south of the city centre, where the valley narrows and the road starts into the hills. Raw water arrives by pipe from the Senbon reservoir upstream. It is received at the western edge of the plant, runs east along a channel, is shared out among six filtration ponds set side by side, sinks through beds of sand, gathers in a collecting well and leaves for the distribution reservoirs. The nine registered structures sit along that single path, in order.

They are the former valve chamber and receiving well, the water conduit and discharge well, filtration ponds No. 1 to No. 6, and the collecting well. None of them is a building in the usual sense. What gives the Imbe Water Purification Plant its character is the finish: granite coping stones along the rims of the ponds, and small roofed housings over each pond's regulating well, every one of them decorated differently.

From Burton's Survey to the First Expansion

The story of the Imbe Water Purification Plant begins with a survey in July 1895. W. K. Burton, a British engineer employed by Japan's Home Ministry, came to Matsue to look for a water source and laid the groundwork for a scheme based on the Imbe valley. Nakajima Eiji, a professor at Tokyo Imperial University, directed the design. The project received approval in October 1913, planned for 50,000 people and a peak daily supply of 6,300 cubic metres.

Work started in November 1914. The Senbon dam was finished in March 1918, and water reached the city on 1 June that year. The plant itself was completed in March 1919. Records from the founding period give each filter bed an effective area of 597 square metres; three were run at a time, passing water at 3.03 metres a day, for a capacity of 5,430 cubic metres daily.

Within a decade that was not enough. Matsue was courting a silk mill, building schools and offices, and growing. The city won approval for its first expansion in November 1927. In August 1929 a drought forced supply restrictions, and by mid-November of the same year two new filtration ponds were complete. Four of the nine registered structures date from this expansion: the former valve chamber and receiving well, ponds No. 1 and No. 2, and the collecting well. The water conduit and discharge well carry both dates, 1918 and 1929.

Expansion never really stopped. From 1935 sedimentation basins were added because rain was washing fine clay into the reservoir, and Matsue's water system has now been enlarged eleven times. Today the plant combines chemical settling with slow sand filtration and can treat 25,600 cubic metres a day. When the founding waterworks were registered in 2008, fourteen structures were listed on the same day: the nine here, plus the Senbon reservoir dam, its management bridge, and three parts of the former Shōgiyama distributing reservoir.

Reading the Layout

The easiest way to understand the Imbe Water Purification Plant is to follow the water.

At the western end, about 500 metres northeast of the Senbon dam, stands the former valve chamber and receiving well. From there a straight channel 60 metres long runs east, with a round discharge well along its course, dividing the raw water among the ponds. The ponds are numbered from west to east, No. 1 through No. 6. The numbers record position, not age: the two western ponds were added in 1929, while No. 3 to No. 6 belong to the original works.

Each pond is a rectangle of roughly 22 by 31 metres with a regulating well at the centre of its north side. Filtered water runs along a groove in the floor to that well, then on to the collecting well north of pond No. 4, and from there toward the clear-water and distribution reservoirs.

The six well housings are the detail most visitors remember. One is half-cylindrical, another round, one bristles with pilaster strips, another has a cornice of linked hexagons. Each structure's own page covers its measurements and design.

Visiting and Getting There

The Imbe Water Purification Plant is a working utility, and the grounds are not open to the public. The Matsue City Water and Sewerage Bureau has in the past run weekday tours for groups, lasting about two hours and booked by telephone with the plant. When we checked in September 2026, however, the bureau's website no longer showed a tour page. If you hope to visit, contact the bureau's main office (0852-55-4888) to ask whether tours are running and how to apply. Photography on site is at the discretion of staff during a visit.

By public transport, take the Unnan City Bus Daitō-Matsue-Nogi line from JR Nogi Station on the San'in Main Line and get off at Suigenchi, meaning "water source". The ride takes around 10 minutes and costs 200 yen. The 2026 timetable has seven runs each way per day, with no service from 31 December to 3 January. The stop is close to the plant entrance. Nogi is one stop by train from Matsue Station.

The Senbon dam lies southwest of the plant, surrounded by a park. Even without access to the plant, you can see the reservoir and dam that feed it from there.