Hikiyu at Dake Onsen

The hot springs at Dake Onsen are fed by hikiyu—water piped in from off-site rather than drawn from the ground directly below. The ultimate source is 1,500 meters above sea level on nearby Mt. Tetsu. The system of pipes and conduits that delivers this hikiyu extends more than 8 kilometers, making it one of the longest in Japan.

Bringing the Mountain Springs to Town

The source of Dake Onsen is a group of open-air hot springs on Mt. Tetsu with a combined flow of 1,290 liters per minute. A series of conduits combines the waters from the springs into a single flow that is then piped down the mountain. No pumps are required, as gravity does all the work. When the flow reaches the town, it is divided among multiple smaller pipes that lead to individual onsen bath facilities.

At their source, the hot springs range in temperature from 40°C to 90°C. The temperature of the combined flow is 52°C, and with today’s pipes keeping the water at that temperature all the way to Dake Onsen, no reheating is required.

History and Engineering

In earlier centuries, inns prospered at the source of the hot springs, which was then known as Yui Onsen. After Yui Onsen was destroyed by a landslide in 1824, Nihonmatsu domain ordered a new onsen town built lower down the mountain, with hot water piped in from the original source. As Nihonmatsu Castle already had a similar system that delivered fresh water from mountain rivers 14 kilometers away, domain engineers knew how to build and maintain the necessary infrastructure. This was the beginning of the hikiyu system that now supplies Dake Onsen.

The original hikiyu system used conduits made of red pine with removable lids, but these were poorly insulated and deteriorated quickly in outdoor conditions. In the early twentieth century these were abandoned in favor of wooden pipes known as mokkan. Each mokkan was a single massive pine log hollowed out using a drill obtained for this purpose from overseas. That solved the heat retention problem, but deterioration of the wood remained an issue. Starting in the 1950s, mokkan were gradually replaced with the more durable PVC pipes in use today.

Kneaded Water and Milky Days at Dake Onsen

The waters at Dake Onsen are acidic, with a pH of 2.5. This is rare in Japan, where most hot springs are alkaline. The antibacterial effect of the low pH combined with the water’s sulfur content means that soaking in the springs may offer relief from psoriasis, eczema, and skin inflammation.

Onsen connoisseurs believe that the water’s long journey from Mt. Tetsu mixes its mineral content more evenly, making it feel “smoother” on the skin. This kind of mixing is referred to as yumomi, or “kneading the water,” and is also practiced at other hot-spring resorts in Japan.

Milky Days

The pipes that deliver the waters of Dake Onsen from their source on Mt. Tetsu gradually become encrusted with deposits of sulfur and other minerals in the spring water. These deposits are known as yu no hana or “hot-spring flowers.” To ensure that the flow of water remains unimpeded, the pipes are regularly cleaned by scraping off these deposits, allowing the flakes to flow down the pipes all at once. When the accumulated yu no hana of a week or more arrives at Dake Onsen, it turns the baths milky white for the day. Dake Onsen now promotes these events as “Milky Days.”

Milky Days occur weekly in summer and about half as often in winter. The specific dates depend on when the weather permits cleaning, but they are announced online in advance. Many visitors make a point of visiting Dake Onsen on Milky Days to enjoy the distinct texture and rich scent of the yu no hana. Some feel that the additional mineral content enhances the water’s soothing properties.

The Yumori of Dake Onsen

To keep the waters of Dake Onsen flowing from Mt. Tetsu, the 8 kilometers of conduits and pipes must be regularly inspected and repaired. This is the job of the yumori, or “guardians of the springs”: local residents who perform these duties in addition to their regular work.

A Year-Round Job

In winter, the yumori climb into the mountains weekly. The trek to the hot springs’ source in the snow can take several hours. This is followed by around three hours of digging through a few meters of snow to access the pipes and cleaning them, before heading back down to town.

When the weather warms and the snow melts, the yumori begin visiting the mountains more frequently. By summer they are there daily, except when the weather is bad. At this time of year, the work includes clearing vegetation and debris from the access trail and checking for leaks in the pipes along the way.

Unsung Heroes of Dake Onsen

In September 2011, after torrential rain on the mountain, the flow of hot-spring water to Dake Onsen stopped. A landslide on the mountain had damaged the pipes. The yumori led an emergency repair effort, with much of the town pitching in to help. After several days of work, the flow was restored, but the yumori had to monitor and maintain the affected areas for years thereafter as the debris from the landslide settled.

There is no manual for any of this work. Younger yumori learn from more experienced colleagues on the job, then teach new recruits in turn. Yumori culture, passed on from generation to generation, has played an invisible but vital role at Dake Onsen since the town’s founding.

The History of Dake Onsen

Dake Onsen traces its origins to a group of hot-spring inns high up on Mt. Tetsu named Yui Onsen. Hot springs with similar names appear in historical records as early as the ninth century. By the seventeenth century, Yui Onsen was a thriving entertainment district catering to travelers and locals alike.

Moving Down the Mountain

In 1824, however, Yui Onsen was buried in a deadly landslide and the site was abandoned. Two years later, the daimyo of Nihonmatsu domain ordered a new onsen town built in an area called Jumonji Dake at the foot of Mt. Tetsu. As there were no natural hot springs at  Jumonji Dake, a system of wooden conduits and pipes was built to carry the waters of the original springs from 6 kilometers above. Today, Dake Onsen’s water is piped in exactly the same way.

In 1868, Jumonji Dake burned down during the Boshin War, when an alliance led by powerful domains in western Japan overthrew the Tokugawa shogunate. In 1870, it was replaced by a new onsen town in nearby Fukabori, but in 1903 a fire that spread from one of the inns burned Fukabori Onsen to the ground. Finally, in 1906, the town was rebuilt at its present location under the name Dake Onsen. Its waters still come from the same springs on Mt. Tetsu, 8 kilometers away.

The Republic of NikoNiko

The next dramatic move for Dake Onsen was rhetorical: in 1982, the town declared itself an independent country, “The Republic of NikoNiko.” (Nikoniko is a Japanese word for cheerful smiles.) This came as part of a wave of tongue-in-cheek micronation declarations in Japan inspired by Inoue Hisashi’s 1981 satirical novel The People of Kirikiri, about a breakaway village in Iwate Prefecture.

For Dake Onsen, the declaration was driven by concern about the new Tohoku Shinkansen line. With no Shinkansen bullet train station planned for Nihonmatsu and many express trains to be replaced by Shinkansen services, Dake Onsen’s visitor numbers seemed likely to drop. The declaration of independence was meant to keep Dake Onsen in the public eye—and it worked. The Republic of NikoNiko made national news, so the town leaders kept the joke going.

The tourist association’s headquarters were renamed the “National Assembly Hall” and the head of the association was appointed President. The town issued passports and even a currency, the Cosmo (after Dake Onsen’s town flower, the cosmos), which respectively functioned as stamped discount cards and shopping vouchers. It was not until 2006 that the reigning President finally announced that NikoNiko was re-merging with Japan, ending more than two decades of “independence.”

Throughout Dake Onsen’s circuitous history, the determination of the people of Nihonmatsu to preserve the hot springs is a constant. In the face of every challenge, from natural hazards to economic pressure, they have found a way to keep the onsen alive for future generations.

Walking Dake Onsen

Dake Onsen’s recommended walking course covers the town’s most picturesque and historic sites. It is a comfortable stroll along 2.3 kilometers of paved paths and takes about an hour to complete.

Print Your Own Postcards

The walking course starts at the tourist information center at the southeast end of the town’s main strip, which is called “Himalaya Street.” The first point of interest is the postcard-size carved printing block of a tiger outside the center. There are 12 of these blocks dotted around the town, each with a picture of a different animal in the East Asian calendar cycle. The tourist information center can provide printing kits with paper and returnable ink pads for making postcards at each of the 12 printing blocks. The animal images are by Oyama Chusaku, an artist who grew up in Nihonmatsu, and the blocks were carved by sculptor Hashimoto Kentaro.

Kagamigaike and Midorigaike Ponds

From the tourist information center, the walking course leads southeast down Sakura Slope. There is a public foot spa along the way. The slope ends at a small park with a strolling path around Kagamigaike Pond. Atop a small hill nearby is the Yuhigaoka Second Lookout Point, which has the town’s best views of the Adatara massif.

South of Kagamigaike Park lies Midorigaike Pond, which is notable for its brilliant green color. This comes from the used onsen water that is collected here from all the inns in Dake Onsen for dilution and discharge. The round intake tower on the banks of the pond adds a picturesque touch.

Along the Natsunashi River

After the ponds, the walking course leads south along the old road to the nearby town of Motomiya. The blooming cherry trees here are now tended by volunteers from Namie, a town on the eastern coast of Fukushima. Dake Onsen hosted the people of Namie for many months when evacuation orders were issued following the 2011 Great East Japan Earthquake and nuclear accident.

The walking course turns northwest up a tree-lined road following the Natsunashi River, before taking a long, gently curving road that connects to the northwest end of Himalaya Street. Along the way is a small cemetery and memorial site preserving the original grave markers of the guests and employees who died in the 1824 landslide at Yui Onsen.

Onsen Jinja Shrine

At the top of Himalaya Street stands Onsen Jinja shrine. The shrine is a proudly syncretic institution, hosting Shinto rituals in summer and winter and a Buddhist ceremony for the hot springs in spring. It also has a statue of Daikokuten, a deity of prosperity that has been worshiped at the onsen town since the days when it was located on the slopes of Mt. Tetsu.

From the shrine, the walking course returns southeast down Himalaya Street, past onsen inns, restaurants, and confectioners, to the tourist information center where it began.