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The Nasu irrigation canals
provide water to Nasunogahara

How were waterways built underground?

The old water pump for theNasu irrigation canals wasbuilt by tunneling through asteep cliff along the NakaRiver. A newer facility built
nearby is currently being used.

To draw water from the Nasu
irrigation canals to each farm, it wasnecessary to build undergroundwaterways across the Sabi River.
This was done by taking advantageof the dry river. Rather than digging
underground, riverbed rocks weremoved, rocks were arranged in apentagonal shape to create a tunnel,
and then covered with the riverbed
rocks. This created one single long,underground waterway.

Exit

upstreamchannel❶ Stack rocks in a pentagonal shape tocreate a hollow tunnel.

❷ Cover the rock tunnel with sand andgravel from the riverbed.

A waterway passing
under the Sabi River.
The water is delivered by
Entrance
diverting the water
through a U-Shaped
waterway where thelower water emerges in a
vertical direction.
(fusekoshi / siphonwaterway).
❸ Water flows through the completed
underground tunnel.

The Nasu irrigation
canals today
While the location of the water pump haschanged a number of times, the Nasu
irrigation canals are still in use today. Water
carried by the waterways throughout theNasunogahara region are still used for
agriculture, industry, and hydroelectric power.
▲ The water pump for the Nasu

The lack of water was a large obstacle to the development ofNasunogahara. Prominent locals lobbied the government tobuild the Nasu irrigation canals to provide water to the region.

irrigation canals that draws waterfrom the Naka River. The former
pump is on the cliffs on the right,
and the facilities currently in use
on the left were completed in
1976.

Canal map

◀ A siphon exit where water

History of the Nasu
irrigation canals
People gathered from around thecountry to reclaim Nasunogahara
during the Meiji era. But the area lacked
water, and there wasn’t enough drinking
water to support a large population.
Prominent locals such as Jousaku
Innami and Takeshi Yaita lobbied thegovernment, and a canal was built in1882 to draw drinking water from theNaka River that flows to the northeastof Nasunogahara. But an even larger
canal was necessary to bring enoughwater for agriculture. After further
lobbying, the Nasu irrigation canals
were built in 1885.
3emerges after passing through anunderground waterway on the Sabi
River. The water then flows along
an aboveground waterway once
more.

Nishiiwazaki water pump

Kuma River

Naka River

Sabi River

The big three canals of Japan

Jousaku Innami

Takeshi Yaita

Born in 1831 in what is
now the city of Nikko.
Served in various
positions such as village
head, and founded theNasukaikonsha farmand became its firstpresident in 1880.

Born in 1849 in what is
now the city of Yaita.
Served as village headand prefecturallegislator before
becoming the second
president ofNasukaikonsha in 1888
and founding what
would later become
Yaita Farm.

The tunnel inside the old water pump
The east tunnel (above) and west tunnel (below)

A canal is a waterway built to draw water from its source. The Nasu
irrigation canals are known as one of the big three canals of Japan, together
with Asaka Canal in Fukushima Prefecture and the Lake Biwa Canal thatlinks Shiga and Kyoto Prefectures.

Nasu irrigation canals
main channel

Houki River
1st branchchannel

4th branchchannel

3rd branchchannel
2nd branchchannelAsaka Canal

Nasu Irrigation Canal

Lake Biwa Canal

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