What the Koniwadani River Aqueduct Is
The Odai Irrigation Canal Koniwadani River Aqueduct (小田井灌漑用水路小庭谷川渡井, Odai Kangai Yōsuiro Koniwadanigawa Toi) is a single-arch brick aqueduct built in 1909 to carry the Odai Irrigation Canal over a stream at Kasedahigashi, Katsuragi Town, Ito District, Wakayama Prefecture, and it was registered as a Registered Tangible Cultural Property of Japan on March 2, 2006. The Agency for Cultural Affairs gives it a length of 9.3 meters and a width of 7.4 meters; it belongs to the Odai Land Improvement District.
Its registration number is 30-0087, and it was registered for contributing to the country's historic scenery. It is the second of the four registered structures counting from upstream and stands near Kaseda Station on the JR Wakayama Line.
One of the First Finished in the Canal's Rebuilding
The Agency's description places the Odai Irrigation Canal Koniwadani River Aqueduct among the very first structures completed in the canal improvement works begun in the late Meiji era. Its 1909 date is the earliest of the four; the Nakatani River Water Gate followed in 1912, the Kozumi River Aqueduct in 1914 and the Tatsunotoi Aqueduct in 1919.
MAFF, Japan's agriculture ministry, says the aqueduct built when the canal was dug in the Edo period was wooden and was often damaged by heavy rain. This one shows an early stage of the program that replaced timber flumes with brick arches, and the ministry notes it keeps nearly its original form.
A "Koniwadani" Aqueduct over the Dodengawa
The registered name refers to the Koniwadani River, yet both the Agency and MAFF say the Odai Irrigation Canal Koniwadani River Aqueduct crosses the Dodengawa (堂田川), a right-bank tributary of the Kinokawa. Wakayama Prefecture's 2014 river plan for the Kisen area lists the Dodengawa as a stream of about 2.0 kilometers rising in the Izumi Mountains and flowing through Katsuragi, and its plan of the stream also marks the Odai canal.
None of the sources consulted explain how the name Koniwadani relates to the Dodengawa. This article keeps the registered name for the aqueduct and follows the sources in naming the stream it crosses.
How the Koniwadani River Aqueduct Is Built
According to the Agency, the Odai Irrigation Canal Koniwadani River Aqueduct springs a brick arch four bricks thick from a stone base, and its spandrel walls are laid in Flemish bond (French bond, フランス積, in Japanese usage). Stone below and brick above: the material changes partway up.
MAFF describes it as a filled-spandrel arch bridge, solid from the arch up to the channel, 9.3 meters long and 7.35 meters wide, carrying a channel 3.6 meters across. It is broad for its length, and the Agency's width of 7.4 meters is the greatest of the four registered structures.
Seeing the Koniwadani River Aqueduct
Water still runs across the Odai Irrigation Canal Koniwadani River Aqueduct today. Nobody takes tickets; you simply look at it from the road. Do not climb down to the streambed or into the channel.
Look for the line where the stone base gives way to the brick arch, the ring of the arch four bricks deep, and the alternating long and short brick faces of the spandrels.
MAFF gives a 10-minute walk from Kaseda Station on the JR Wakayama Line; in a straight line the aqueduct is about 420 meters from the station. Getting around all four structures is covered on the Odai Irrigation Canal page.
Q&A
- When was the Odai Irrigation Canal Koniwadani River Aqueduct built?
- In 1909, replacing an Edo-period wooden aqueduct. It was registered as a Registered Tangible Cultural Property on March 2, 2006.
- Why is the Odai Irrigation Canal Koniwadani River Aqueduct registered?
- It was registered for contributing to the country's historic scenery. The Agency for Cultural Affairs counts it among the very first structures finished in the canal improvement works begun in the late Meiji era.
- Which stream does the Odai Irrigation Canal Koniwadani River Aqueduct cross?
- Both the Agency and MAFF name the Dodengawa (堂田川), a right-bank tributary of the Kinokawa. No source consulted explains how this relates to the name Koniwadani.
- How big is the Odai Irrigation Canal Koniwadani River Aqueduct?
- The Agency lists it as 9.3 meters long and 7.4 meters wide. MAFF gives a width of 7.35 meters and a channel 3.6 meters across.
- How do I get to the Odai Irrigation Canal Koniwadani River Aqueduct?
- MAFF gives a 10-minute walk from Kaseda Station on the JR Wakayama Line. There is no fee or reception, and it is viewed from the surrounding roads.
Basic Information
| Name | Odai Irrigation Canal Koniwadani River Aqueduct (小田井灌漑用水路小庭谷川渡井) |
|---|---|
| Location | Kasedahigashi, Katsuragi Town, Ito District, Wakayama Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | 2006 (registered) |
| Quantity | 1 |
| Dimensions | Length 9.3 meters, width 7.4 meters (single-arch brick bridge) |
| Owner | Odai Land Improvement District |
| Public Access | Working aqueduct; exterior can be viewed from nearby (no fee) |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: Odai Irrigation Canal Koniwadani River Aqueduct
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00005353
- MAFF, Cultural Heritage of Rural Infrastructure: Odai Irrigation Canal Koniwadani River Aqueduct (Japanese)
- https://www.maff.go.jp/j/nousin/sekkei/museum/m_bunka/yuukei9/index.html
- Wakayama Prefecture, River Improvement Plan for the Kisen Area of the Kinokawa System (Japanese, PDF)
- https://www.pref.wakayama.lg.jp/prefg/080400/keikaku/seibikeikaku_d/fil/kisenkeniki_keikaku.pdf
Last verified: 2026.10.07
