Nakanotao Tunnel

An Irrigation Tunnel Dug to Save a Village from Drought

The Nakanotao Tunnel (中の峠隧道, Nakanotao Zuido) is an agricultural water tunnel completed in 1930 in Goso, Saijo-cho, Higashihiroshima City, Hiroshima Prefecture, which in 2000 was registered as a Registered Tangible Cultural Property.

The Agency for Cultural Affairs records reinforced concrete arched portals and a total length of 327 metres. It belongs to the Kashiwara Water Users Association and was registered for its contribution to the historic landscape.

According to the Agency, it was built after the drought of 1926 as part of a channel carrying water between the Odayama River and the Fukamichi Pond.

From One Man's Digging to a Village Project

The Ministry of Agriculture, Forestry and Fisheries tells how Okita Kaichi, a resident of drought-stricken Kashiwara, decided the only answer was to bring water from the Odayama River, beyond a rocky ridge, into the meagre Fukamichi Pond. In March 1927 he began digging through the ridge alone. Gradually the whole village joined him, and the tunnel was finished around 1930.

The Agency also credits Okita Kaichi with its design and construction.

Why It Matters: An Early Concrete Portal

The Agency notes that the original south portal is a segmental arch of reinforced concrete about 0.7 metres in span. In 1943 a reinforced concrete box section about 3.8 metres long was added to prevent rockfalls.

The ministry points out that portals were then usually built in stone or brick, and calls the early use of concrete, a technique that spread only after the war, an unusual design.

The Tunnel Today and Visiting

The ministry says the Nakanotao Tunnel still carries water to the Fukamichi Pond and irrigates the district's fields. The Kashiwara Water Users Association cleans the tunnel once a year and cuts the grass on the maintenance path twice a year.

As a working irrigation channel, the tunnel cannot be entered. The ministry gives access as about 30 minutes by car from JR Saijo Station. Visitors should take care not to interfere with the waterworks.