What the Ozatogawa Power Plant Water Intake Station is
The Ozatogawa Power Plant Water Intake Station is a 1925 river intake on the Satokawa in Tokudacho, Hitachiota, Ibaraki Prefecture, entered on Japan's list of Registered Tangible Cultural Properties on 8 November 2004. It lies about 3 kilometres upstream of the powerhouse and forms the part of the scheme, planned by the Ozatogawa Electric Power Company, that takes water out of the river. The owner is Tokyo Hatsuden Co., Ltd.
At its centre is a gravity concrete weir 20 metres long and 2.1 metres high, lying low across the full width of the channel. A fish ladder occupies the right bank; a control gate and a sand-flushing gate occupy the left. An intake mouth and 74 metres of dry stone revetment go with them.
Water drawn in here follows a headrace along the hillside to a head tank, then falls through the penstock. That fall gives the head of 102.31 metres which drives the turbine in the powerhouse, and the Ozatogawa Power Plant Water Intake Station is where the sequence begins.
Why it is a Registered Tangible Cultural Property
The Agency for Cultural Affairs describes the Ozatogawa Power Plant Water Intake Station as a small river work that nonetheless carries modern elements throughout. The criterion applied was contribution to the historic landscape of the country, and the powerhouse, the tailrace and the spillway were registered on the same day.
A height of only 2.1 metres tells you what kind of structure this is. It does not dam the Satokawa into a reservoir; it lifts the surface a little and draws off the volume the turbine needs. That approach was normal for small and medium hydro schemes of the period, and the river still runs over the crest and away downstream.
In 2017 the stations along the Satokawa were recognised by the Japan Society of Civil Engineers as a Selected Civil Engineering Heritage.
What to look for
At the Ozatogawa Power Plant Water Intake Station the fish ladder on the right bank is the feature most worth stopping for. A structure built to generate electricity was given a route for migrating fish at this early date, and read together with the low crest it shows an attitude to river use preserved in physical form.
On the left bank the two gates stand side by side. One regulates the volume taken in; the other flushes out sand that collects behind the weir. Their different jobs give them different openings and different positions, and their presence marks this out as more than a simple barrage, a work built to keep functioning in a sediment-laden mountain river.
Dry stone revetment runs above and below the weir. Cut stone laid up by hand feels nothing like the concrete beside it, and the junction between the two shows old and new techniques used within a single contract.
Reaching and seeing the Ozatogawa Power Plant Water Intake Station
The Ozatogawa Power Plant Water Intake Station remains in service. It is an operational structure and is not open to visitors. The area around the weir and gates is managed by Tokyo Hatsuden Co., Ltd. and cannot be entered, though there are points on the riverside road from which the whole weir is visible. Photography from those public roads is fine.
The site is roughly 3 kilometres up the river from the powerhouse. Tokudacho is entered from Route 349; the drive from Hitachiota Station takes about 1 hour, and the intake lies further upstream again. There are no signboards and no parking, so fix the position on a map before setting out.
The water immediately below the weir moves fast and the approach is impassable when the river rises. Avoid the days after heavy rain and the snowmelt season, and do not climb down to the bank. (Access information checked in September 2026.)
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Q&A
- Where is the Ozatogawa Power Plant Water Intake Station?
- It stands on the Satokawa in Tokudacho, Hitachiota, Ibaraki Prefecture, about 3 kilometres upstream of the powerhouse.
- Can I visit the Ozatogawa Power Plant Water Intake Station?
- It is an operational structure and is not open to the public. The managed area cannot be entered, but the weir can be seen from the riverside road.
- How large is the weir at the Ozatogawa Power Plant Water Intake Station?
- It is a gravity concrete weir 20 metres long and 2.1 metres high, with an intake mouth and 74 metres of stone revetment.
- When was the Ozatogawa Power Plant Water Intake Station built?
- It was built in 1925 and became a Registered Tangible Cultural Property on 8 November 2004.
- Does the Ozatogawa Power Plant Water Intake Station have a fish ladder?
- Yes, on the right bank of the weir. A control gate and a sand-flushing gate sit on the left bank.
Basic Information
| Name | Ozatogawa Power Plant Water Intake Station |
|---|---|
| Location | Tokudacho, Hitachiota, Ibaraki Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2004 (Heisei 16) |
| Quantity | 1 facility |
| Dimensions | Gravity concrete weir, 20 metres long, 2.1 metres high, with intake and 74 metres of stone revetment |
| Owner | Tokyo Hatsuden Co., Ltd. |
| Public Access | Exterior only; interior not open |
References
- National Cultural Properties Database, Ozatogawa Power Plant Water Intake Station (Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/heritage/detail/101/00004316
- Cultural Heritage Online, Ozatogawa Power Plant Water Intake Station
- https://online.bunka.go.jp/heritages/detail/180536
- Registered Tangible Cultural Properties, Tokyo Hatsuden Co., Ltd.
- https://tokyohatsuden.co.jp/csr/cultural_property/
- Japan Society of Civil Engineers Kanto Branch, Satokawa River System Hydroelectric Power Stations
- https://www.jsce.or.jp/branch/kanto/04_isan/h29/h29_4.html
Last verified: 2026.09.05