Watergate Scandal: a tale of two watergates for Lake Ashinoko of Hakone 箱根芦ノ湖

 

John 4:15 The woman said to him, “Sir, give me this water so that I won’t get thirsty and have to keep coming here to draw water.”


Lake Ashinoko 芦ノ湖 is the largest and the only natural lake in Kanagawa Prefecture. By the way, Kanagawa Prefecture is proud of ourselves for self-sufficiency in procuring tap water, which is very different from, say, Tokyo. Surely, the water of Lake Ashinoko is a part of our water supply system, isn’t it? Nay. Water rights of Lake Ashinoko are held by our western neighbor, Shizuoka Prefecture 静岡県. Even Hakone municipality cannot use the water of the Lake, except for tourism ships and small fisheries. The water out of taps in the hotels for this world-famous resort is from 20 underground aquifers in the town. Actually, we’ve visited one of the sources on September 22, 2017. That was Itari Forest イタリ水源林 that maintains the environment for Itari Pond in the Hakone Country Club. The water system Itari Pond belongs to is the water network for Sengokuhara Wetland 箱根仙石原 we’ve visited several times, the most recent ones are for 5th and 12th last months. Yeah, the system surely connects to Lake Ashinoko deep underground, but at least legally these water-supplies DO NOT come directly from the Lake. The HP of Hakone Town neatly describes the situation. “Hakone is blessed by rich forests and rain. They provide us delicious water from our underground.” Er, well. It is so, certainly. But when people first know the fact the water of Lake Ashinoko is the property of Shizuoka Prefecture, many say “What!? Is there any conspiracy? It sounds very unnatural and unfair!” Hmmmmmmmmm … the argument is half true. Let me explain.

The allowed usage of Lake Ashinoko now for Kanagawa

Itari Watersource Forest

The water plant for Hakone Township in Itari Water Source Forest

Inside of the water plant.
They process harvested water from the aquifer of Itari.

Another water pumping plant for Hakone town which is
on Kuzuryu-no-mori Therapy Road we’ve visited last week.
The town has 20 such stations for procuring potable water.

First, I explain to you the current situation of the water of Lake Ashinoko that could pour down to Hayakawa River 早川 reaching to Odawara City 小田原市. Until 1672, it naturally came out to Hayakawa River from the point of Kojiri Watergate 湖尻水門 we’ve visited on June 9th. Now Kojiri Watergate is practically closed. It opens only when storms bring tons of rain over the Lake up to the flood limit of 2.6m at the lakeshore observation point. Pitifully, even such organized arrangement did not exist until 2019 when monster typhoons destroyed infrastructure of Hakone Town. Before global warming, Kanagawa and Shizuoka Prefectures could make do to overcome emergencies by ad-hoc phone conversations. Global warming let the mandarins realize their leisurely approach could not respond to the rapid escalation of crisis anymore. They’ve changed their ways. Early this month, June 2023, when a storm made the water of the Lake cross the threshold, the town issued evacuation order for the affected communities and opened the Gate automatically. Once the crisis was over, it was closed again and the “remnants” of Hayakawa River returned dry near the lake. Come to think of it, even with such arrangement Hayakawa soon has enough water reaching down to Sagami Bay 相模湾. Hakone is really a place of abundant water source forests and underground aquifers … That’s that. Before Japanese industrialization people used water from Hayakawa with closed Kojiri Watergate. Now in the 21st Century Hakone Town and Odawara City do not use Hayakawa River for their water sources, but build complicated water supply system from underground wells, and Sakawa 酒匂川 and Sagami Rivers 相模川 with artificial dam lakes. Not using Lake Ashinoko looks strange for sure.

Kojiri Watergate for Lake Ashinoko. Closed.

Outside the Watergate,
the remnants of Hayakawa River is like this …

but the flow becomes this much
some 6km down near Sengokubara Wetland.
In a sense, it’s amazing.

Iizumi Water Intake Weir 飯泉取水堰 over Sakawa River.
The water harvested here comes from
artificial Lake Tanzawa 丹沢湖 and
the other water sources
including Yadoriki Water Source Forest やどりき水源林.
This water is distributed all over Kanagawa Prefecture
including Yokohama and Kawasaki
where the water plants are on higher ground than the Weir.
Meaning?
For doing so,
Japanese use tons of fossil fuels
to pump up and send long distance H2O to the cities!

So, understanding the strangeness here requires knowing the history and geography. During Ashinoko Walk (my post for June 9th), we also passed Fukara Watergate 深良水門 beyond Kojiri Watergate. It is a historical place, designated as a “World Heritage Irrigation Structures” of ICID. The watergate is the beginning of Fukara (or Hakone) Irrigation 深良（箱根）用水 that was constructed from 1666 to 1671 and opened in 1672. The project was funded by the merchants of Edo (Tokyo). The aim of ancient and large civil engineering was to provide stable water supply to the communities on the slope of Mt. Fuji. Mt. Fuji surely has lots of snow, but its surface layer is made of fragile scoria where water penetrates deep down. That’s the reason why the mountain is so beautiful, but for those people who live there obtaining water for survival was always a serious problem. Then, at the beginning of the 17th century Tokugawa Shogunate (1603-1863) was established. Tokugawa Family originated from the present-day Aichi Prefecture 愛知県, but the first Tokugawa Shogun, Tokugawa Ieyasu, spent his early years in Suruga 駿河, contemporary Shizuoka City 静岡市, due to medieval politics of warlords (i.e., his papa and rivals). It made the area of Shizuoka Prefecture including the slope of Mt. Fuji sentimental hometown for the Shogunate Government. They kept the area under their direct control. Simultaneously for the security of Edo (Tokyo) the Shogunate allocated Hakone area under the control of one of their faithful subordinates who could watch in/out of Kanto Plain from/to the Western region. This person who was in charge of Hakone was allowed to have a fortress-like castle in Odawara, a luxury at that time, and kept special status in Shogunate government until 1863. For the warlord of Odawara, there was a good reason to make things easier for the western side of Hakone caldera. The exit for Fukara Irrigation was still in the territory for Odawara Warlord next to Shogun’s property. You see? Let’s start a large project in my garden whose exit immediately connected to the garden of my boss who needed some help from my land!

Fukara Watergate

The water of the Lake comes in the Watergate, then,

Gushes down to Shizuoka Prefecture, 24/7.

The Tunnel of the Irrigation,
piercing the Hakone Caldera to the west.

The Fukara Irrigation started from Fukara Watergate indeed helped the communities from starvation in the slope of Mt. Fuji, which is in the present-day Susono City 裾野市. Helping villagers was a great achievement of ancient civil engineering. But villagers on the eastern side of the Caldera was not completely happy with the arrangement. During Shogunate, they had a special status in the government for the security of Edo, and received several bonuses from Shogun. They could shut their mouths. After the Shogunate gone, villagers in Hakone lost their brownies from observing water of the Lake going to somewhere. Besides, Sengoku Area was not good for rice cultivation et al. The community there was also poor as their western neighbor. In 1895 Hakone people tried to end the exclusive water right for the villages in Shizuoka Prefecture. They voluntarily started another construction that could divert water flow from Fukara Watergate. A lawsuit followed. The villagers of both sides of the Caldera fought. It ended in the highest court of Japan at that time. The Court ordered to build a compromise structure that could lower the amount of water going to Shizuoka side. The arrangement had never materialized. I guess they did not have enough money … Hakone Town suffered many times lake floods due to their awkward status for the management of Kojiri and Fukara Watergates. As of June 2023, the cheerily PR pages for Fukara Irrigation system comes only from municipalities of Shizuoka side (like here or here). The matter is still a tricky concern.

The sign says “KEEP OUT! DANGER!”
at Fukara Watergate …

OK, well, but there might be happening a change. For one thing, the opening Kojiri Gate early this month was executed quietly under the thunderous storm rain. Global warming does not give leeway for human feeling or else to avoid a catastrophe. Anyway, Hakone is now a world famous + luxurious resort town. So far scarcity of water, including hot spring water for tourists, is not a problem in the area. Adding one more tourist attraction like World Heritage site is not a bad thing for the business. Else, say, if the water going to Shizuoka now came to Kanagawa side, what would happen for the environment, including national treasure Sengokubara Wetland, that has evolved for these 350 years and reached the current condition? It might be about time to settle the feeling in a peaceful way.

Next week, let’s walk the slope where Fukara Irrigation penetrates beneath. It’s a quiet hike. I enjoyed it a lot.

The condition of the Hakone National Park is watched by Hakone Visitor Center of the Ministry of Environment. Their contact info is

Hakone Visitor Center of the Ministry of Environment 環境省箱根ビジターセンター

164 Motohakone, Hakonemachi, Ashigarashimo-gun, Kanagawa, 250-0522
〒250-0522 神奈川県足柄下郡箱根町元箱根164
TEL：0460-84-9981
FAX：0460-84-5721
http://hakonevc.sunnyday.jp/english-info/