Dam Card for “I Love Dam”: Miho Dam 三保ダム

Dam. It’s damned controversial creature. It can be humongous. When we go near, they can invoke awe among us. They can be an object of hate. It destroys communities and natural bounties that will be submerged, in order to satisfy the other people who often live far away from the site. Many times, the beneficiaries of dams have not thought the existence of dam and rural villages that have to cope with complete uprooting ... so our city rats have been, I guess. In 2019, at the time Emperor Akihito abdicates his throne to his son Naruhito, dams in Japan have started to gain strange popularity. They even have trading cards, like Major League Baseball players, or those for Premier League. Let me tell you this week and next my adventures with 2 different dams in Kanagawa Prefecture: Miho Dam 三保ダム today, and Miyagase Dam 宮ケ瀬ダム later.

Looking down from flood gates of Miho Dam

The access to Miho Dam is as to Dam Hiroba Park about which I posted on April 5th. It locates in a north-western corner of the Prefecture, creating Lake Tanzawa 丹沢湖. Its construction began in 1971. After 7 years and 82.3 billion yen (which is about 123.8 billion yen = USD 1.24 billion in 2015), the dam started its operation in 1978. At that time, the construction was to satisfy expected increase in water consumption in the prefecture ... Whether this objective is effective or not might be debatable in this age of slow economic growth and shrinking population. But certainly, Kanagawa Prefecture rarely has water shortage, unlike Tokyo. Thank you. The dam keeps up water of Kawachi River 河内川 that is a tributary of Sakawa River 酒匂川 whose catchment area is 576.5 km². Sakawa River provides roughly 30% of tap water in Kanagawa Prefecture, and water from Miho Dam is about 30% of Sakawa River. It may sounds strange for that amount of money invested in only 10% of water at best? Why did they do such investment? One possible explanation is, the main water sources for Sakawa River are in Shizuoka Prefecture 静岡県 via Ayusawa River 鮎沢川. Damming up neighbor’s water would not be desirable. Another reason could be geographical. To construct a dam to collect water from Sakawa River, that was the max we could expect, and that construction point was the only site for new dam. In any case, the design of the dam shows constraint the engineers faced when they had to build a dam in western Tanzawa. It is a rockfill dam.

On dam property, there are many exhibition panels
 explaining each location for the dam.
 This is to show rockfill structure.

In terms of construction cost, unit price for building concrete dam is definitely cheaper than that for a rockfill. Yet, they had to choose it here as the bedrock for the location was too fragile to sustain a mass of concrete and subsequent water pressure from Lake Tanzawa. This is in Tanzawa Mountains 丹沢 that was created some 6 million years ago by crashes of Eurasian and Philippines Plates. Pushed up sea beds of undersea volcanos are very porous. When we read the blueprint of the dam, beneath the Promenade running from the parking space is the core of the dam with tightly tamped down clay. This part is stabilized from the sides by a bulk of rocks and soils. It creates that 80m tall man-made hill we admired from Dam Hiroba Park. According to the people working for Miho Dam, the place where 5 flood ways now stands was a remnant of a slope of Mt. Furoyama (ASL 928m) 不老山 on the border between Kanagawa and Shizuoka Prefectures. Management of the dam is done by Kanagawa Agency for Public Utility, and Kanagawa Prefectural Office 神奈川県企業庁酒匂水系ダム管理事務所・三保ダム管理事務所. They control the amount of water to be supplied via dam outlets, including flood gates, and mitigate flood damages by storms for downstream.

The former control panel inside the Office.
 Now it’s just a wall decoration,
 and actual job is done with newer displays.

Could you figure out a blue roof at the far end of this photo?
 They are the flood gates.
 Their location subtly depicts the former slope from Mt. Furoyama.

The flood gates of Miho Dam will be opened mechanically
 by these huge machineries.

Water ways from flood gates.
 Hmmmm.
 The slope of Mt. Furoyama must have been relatively sturdy
 so that the engineers chose this point of the dam
 for huge concrete structure and gates.

Seeing the flood gates up close from below.

As this is a manufactured place, people do daily maintenance works inside the mount. The dam has two work tunnels for personnel to check condition of the interior. Recently I had a chance to enter there with the management people, and found the place looks like a scene of Hollywood’s action or sci-fi movies. A narrow and straight tunnel runs deep, and numerous instruments are located at regular intervals. Not much sound could be heard except our excited conversation. In addition to the horizontal tunnels, the inside has ways of trollies going deep down of the dam, where daily maintenance work is performed as well. Hmmmmmm. It’s unsung, but extremely important job … If some structural problem obstructs smooth supply of water from Miho Dam, we live in a city of Kanagawa will have water scarcity before long. In case a collapse of the structure, that’s an enormous disaster, possibly to the downtown of Odawara City 小田原市. Yeah, many, 223 households of 1026 people, were forced to emigrate because of the construction. About 85 ha of private forests were submerged under the Lake. Their record is displayed in Memorial Hall of Lake Tanzawa 丹沢湖記念館 … Yet, the dam is now there, and we have a huge benefit from it. Can we just say “No Dam! It’s evil!”? I think it’s better to say “Not that fast, please.” And it seems to me I’m not alone to feel like that.

An entrance to a tunnel

Hollywood!

A trolley way

A part of the tunnel was home for bats.
 They sidled along when we went near to them.
 Cute.

Is this baby stalagmite on the wall of tunnel
 showing something wrong …?

Memorial Hall of Lake Tanzawa has an old house
 that was moved before the flood.
 It’s a museum now to show the old way of life
 around the Lake Tanzawa.

According to this article, since around the turn of the century, so-called Otaku people started to see dams in deep mountains like scenery we find in virtual interactive games. First it was a sort of counter-counter culture against actions of baby-boomers who started hugging trees to stop dam constructions. Then, actually visiting massive structures that secretly sustain our very urbane life of the 21^st century, the young voice becomes louder to recognize the importance of dams. Yeah, not all dams may be now necessary. Decommissioning dams that ended their function could be a good idea. Look at the removal of Arase Dam 荒瀬ダム, and recovering ecosystem along Kuma River 球磨川 of Kumamoto Prefecture 熊本県. But there is a reason to remove a dam. As of 2018 population of Kumamoto is steadily declining and hence demand for the function of Arase Dam is almost nill. In contrast, we in Kanagawa are still gaining numbers. What is the point to destroy a thing we definitely need? Isn’t it hypocritical to criticize people who are working 24/7 to maintain dams for us, while enjoying a cup of coffee in Starbucks and arguing environmental problems of dams? Number of people visiting dams gradually increased. People exchanged their “I Love Dam” in internet. Then in 2007, a public relations office for Ministry of Land, Infrastructure, and Transport picked up such voices and started to hand out cards of dams, aka Dam Cards.

The office for Miho Dam installed wire mesh fence
 over the locked entrance to the operation rooms of flood gates.
 “There are many people these days try to enter that area
 by climbing the original fence,
 despite of 80m below of the point is rock solid concrete.
 We simply don’t understand
 why they risk their lives,
 and set up the higher fence, just in case.”
 Wow.

To “get” one, you first have to visit the dam of your choice, and ask dam personnel, normally in a management office, for the card. It’s free. The front of a card is a photo of dam you are visiting, and the back describes data and characteristics of the dam. It is now a cultic hit. For example, last year was its 40^th birth year for Miho Dam. So, the dam distributed commemorative dam cards for Miho, for free. Now they are auctioned in internet for about 1000 yen (USD10)! Heck, I’ve been there after the stock of the card has gone completely. “sigh” The entire episode about “dam tourism” is now closely watched and studied among policy makers to promote tourism industry in Japan. Oh, yeah.

This is the front of Dam Card for Miho.

This is the back.
 It depicts the spec of the structure,
 and the attractions of Lake Tanzawa.

Next week, I post my adventure of visiting Miyagase Dam. This is the dam that was an initiator of dam tourism in Japan. Yap, going there was thrilling, and April to November is the season to visit there. I tell you why next week. 😉

Dam Management Office for Sakawa River System / Miho Dam Management Office

神奈川県企業庁酒匂水系ダム管理事務所・三保ダム管理事務所

734 Kamioda, Yamakita Town, Ashigara-kami-gun, 258-0203

〒258-0203 足柄上郡山北町神尾田734

Phone: 0465-78-3711, FAX: 0465-78-3371

http://www.pref.kanagawa.jp/cnt/f8018/

Secret Garden for Cherry Blossoms: Dam Hiroba Park of Miho Dam

Spring! And so we are busy checking which part of our town has fully-bloomed cherry blossoms for spring party. Er, well, having a merrymaking with friends beneath a cherry tree in a packed park, like Ueno Park 上野公園, is one kind of fun. Though, you may prefer a calm cup of tea from your thermo and cherry blossoms. Finding a place for that could be a tall order, especially in metropolitan Tokyo area. Then, recently, I had a sort of sales pitch from people who work for Miho Dam 三保ダム of Lake Tanzawa 丹沢湖. “You see, during cherry-blossoms’ season, the scenery in our place is so gorgeous, but very few would come for picnic. Sometimes, the entire place could be a private garden for just one small family to enjoy cherry blossoms … We don’t know why people fail to check our place. *sigh*” OK, so, in this post, I tell you how to go there for your private cherry-blossoms’ festivity. As Miho Dam is in a very deep mountains of Tanzawa 丹沢, the time their trees are in full-bloom is roughly 2 weeks later than in downtown Tokyo. The expected best days to go there are around the weekend of the next week. We still have time to plan!

Actually, the place for cherry blossoms in Miho Dam is not at the dam. It is in a park spreading in the bottom of the dam, called Dam Hiroba Park ダム広場. Miho is a rockfill dam so that what dams up the stream, in this case Kawachi River 河内川, is a man-made gigantic mound. (The structural plan of the dam can be checked here.) The foot of the “hill” which is the other side of Lake Tanzawa is Dam Hiroba Park. I guess a reason why not many people visit the place is the structure of the dam. The altitude of crown of the levee is ASL 325m. Dan Hiroba Park is at ASL 245m. 325-245=80m for difference of elevation. Sure, the wall of Miho Dam appears gentler compared with concrete dams. But when we look down to the direction of the Park, it’s like Karasawa Cirque 涸沢カール we observe from Mt. Hotaka Cottage 穂高岳山荘 (er… yeah, that’s an exaggeration). The slope of the dam rapidly goes down to the bottom, which gives intimidating impression for visitors. Of course, it is not allowed to drive down the slope by car, bike, motorbike …anything. The rise must be treated with care in order to avoid collapse, you know. But the road zig-zagging over the slope of the dam is perfectly paved, and the steps are well-manicured. Walking there is a good way to “experience” physically the scale of this man-made structure in mountainous forests. And, the Park at the base is really pleasant spot to have your lunch, I tell you.

Looking down Dam Hiroba Park
 from the top of the Miho Dam.

The slope of Miho Dam …
 I realized in the end it was an artificial construction.

We can also use steps to go down/up.

To visit Dam Hiroba Park, the standard way would be going to “Miho Dam,” which is the name of the crown of the dam. By car, please set your navigation system to “Miho Dam.” At the entrance of the crest of the dam, there is really an ample parking space. Or you can take a commuter bus of about an hour ride from Odakyu Shin-Matsuda Station 小田急新松田駅 to Tanzawako Bus Stop 丹沢湖. (Time table is here.) The bus stop is in front of the car lot. From the bus stop, there is a wide “promenade” that is the crown of the dam. On your right is man-made Lake Tanzawa, and to the left is that huge slope of artificial hill going down to the Dam Hiroba Park. From the boardwalk, please just walk down and we reach to the Park. Actually, we can go to the Dam Hiroba Park directly by car, making a left to “Hidamarinosato Auto Camping Ground ひだまりの里オートキャンプ場” via Prefectural Road #76 to Lake Tanzawa. After turning, we first observe the Camping Ground along Kawachi River on the left. Simply proceed further to the Park. The parking lots are large and often vacant (closed on Wednesdays). By bus, please get off the bus at Kaminawa Bus Stop 神縄, and go to the direction of Camping Groud as for cars. I think this route might be more interesting to see the detail of the dam. As we advance, the entire body of the dam comes near to us, and we view its 5 flood ways and the mouths of outlets from the bed of the Lake. It’s the route to look a huge dam from the bottom, which is thrilling in itself.

Tanzawako Bus Stop

To the top of the Dam from car park.

Winter of 2018-19 did not provide much rain for Lake Tanzawa.
 The peninsula in this photo is normally an island
 … drought this summer?

The well-paved road on the slope of Miho Dam

Kaminawa Bus Stop

Either by car or bus, please turn left here.

The sign for Camping Ground. Adelante, por favor.

The Dam is approaching to us.
 Could you figure out a tunnel in the left of this photo?
 It’s a mouth of the left outlet of the dam.
 It’s used to control the tonnage of water discharge.

The gate for parking lots on one Wednesday. “Closed.”

Dam Hiroba Park is a prefectural park of Kanagawa spreading over the foot of Miho Dam. It has wide roads for pedestrians to stroll. The flowering trees are chosen for this place which is in the end man-made. The center of the Park is a large lawn yard where we can bring our blanket and relax in a fine day. The point near Kawachi River, or aqueduct from the dam, there is a miniature of Miho Dam and Lake Tanzawa, a diorama model made of pond and garden bushes. In the east of the Park, they have a hydroelectric power plant using regular outlets from the bottom of the dam. The electricity generated here is sold to TEPCO, and becomes a part of power distributed in Kanagawa Prefecture. Looking north, we see an enormous synthetic hill of Miho Dam. And yet, the rock slope covered by grasses does not give us imposing feeling of concrete dam. Hmmmmm. Yeah, this is a good place to have a peaceful party for admiring cherry blossoms with your family ... Oh, by the way, near the parking space, there is a knoll of wood chips that is created from the debris accumulated at the flood ways of the dam. You can take it as much as you like. Locals come here in pick-up and use it for their garden. They are also applied liberally to maintain the roads in Dam Hiroba Park soft and pleasant. Why is it free? Becaaaaause, selling it from this deep mountain costs more than the profit ... a familiar story of Japanese forests …

Dam Hiroba Park of Miho Dam, early March.
 That was the time for plum flowers …

The place also has gazebos and toilets.

Power plant

The water from the dam to the plant
 generates electricity

Let’s have a nap here …

In the park they display some mechanical parts
 of power generator used before.
 It is a water wheel.

It’s a georama of Lake Tanzawa with …

mini flood ways.

They will be in full bloom within 2 weeks from now …

Next week, I tell you about Miho Dam itself, and Miyagawse Dam 宮ケ瀬ダム. They are a kind of contrasting dams, but forming a tag team for tap water in Kanagawa Prefecture. Meanwhile, enjoy your cherry blossom parties in Japan!

Dam Management Office for Sakawa River System / Miho Dam Management Office

神奈川県企業庁酒匂水系ダム管理事務所・三保ダム管理事務所

734 Kamioda, Yamakita Town, Ashigara-kami-gun, 258-0203

〒258-0203 足柄上郡山北町神尾田734

Phone: 0465-78-3711, FAX: 0465-78-3371

http://www.pref.kanagawa.jp/cnt/f8018/

Water, water, everywhere … in Kanagawa Prefecture

Before visiting water source forests of Kanagawa Prefecture, let me tell you how the supply coordination goes for our community’s potable water. Very roughly speaking, we have 2 kinds of water utility corporations. One is Kanagawa Water Supply Authority 神奈川県内広域水道企業団 who supplies water for 93% of us in Kanagawa. Another is smaller water authorities that provide water mainly from local underground water and springs to the mountainous west of the prefecture, and the city of Odawara. These two entities cover 99.9% of the population. Historically speaking, the area for Kanagawa Water Supply Authority includes the City of Yokohama where the oldest modern water supply network was established in Japan. (More to Yokohama’s system in my later post.) Yokohama has the second largest population in Japan, and composes the megalopolis Tokyo area together with the cities of Kawasaki and Sagamihara.  All the 3 cities are covered by the Authority.

The municipalities and water supply in Kanagawa Prefecture

When Japan had a go-go economic growth, the population growth in those cities and the rest of the eastern Kanagawa was very fast. It was a serious problem for the prefecture 50 years ago how to secure large enough water supply for rapidly growing cities. Between 1961 and 1966, the prefectural government of Kanagawa, cities of Yokohama, Kawasaki, and Yokosuka built Shiroyama Dam 城山ダム in the north of Shiroyama 城山 (that’s the place we visited in my post on October 20^th). It created Tsukui Lake 津久井湖 providing water and electricity to the east of the prefecture. Though, it was not enough. In 1969, the local offices decided to have one entity for permanently pooling the public fund to build and maintain larger water supply system covering 2/3 of Kanagawa. The Kanagawa Water Supply Authority was born.  With this money, in 1978 they completed the construction of Miho Dam 三保ダム surrounded by deep West Tanzawa Mountains 西丹沢, and in 2000 Miyagase Dam 宮ケ瀬ダム in the north of Mt. Oyama 大山. Kanagawa has 2416 km² occupying only 0.64% of Japanese land, where 74.9% of us live in a megalopolis Tokyo. Nonetheless, regarding water sources, we have 4 large dams surrounded by deep mountain forests (; that is, the aforementioned 3 dams and Sagami Dam 相模ダム to which I return in my later post). In contrast, Tokyo of 2191 km² has only 1 dam, Ogouchi Dam 小河内ダム, as water sources within their domain. We in Kanagawa seldom have water shortage. Tokyo had drought alert this summer, an annual event. Projecting decreasing population for decades to come, water management of Kanagawa is sitting pretty these days.

Shiroyama Dam.
We can visit this structure in 5 minutes’ walk
from Tsukuiko Shiroyama Park 神奈川県立津久井城山公園we visited 2 weeks ago.

Tsukui Lake created by Shiroyama Dam.
It’s one of the water reservoirs for Kanagawa Prefecture.
Could you see a peak with a tower?
It’s on the border between Kanagawa and Tokyo.
Mt. Takao 高尾山 is beyond that point.

Miyagase Lake created by Miyagase Dam

On the north shore of Miyagase Lake,
there is a picnic park.
The view of the lake from the park’s rambling promenade
is refreshing for sure.
Driving or biking is a popular option to go there,
but there also is a commuter bus service, Hashi-07 橋07,
by Kanachu Bus from the north exit of JR/Keio Hashimoto Station.
The destination is the terminal stop for the service
at Toriihara-Fureai-no-Ie 鳥居原ふれあいの館.
(Time table, here.)

The park has a farmers’ market where we can find fresh produce
daily harvested in the mountainous northern Kanagawa.
Lunch and craft souvenirs are available as well.

According to Dr. Keiko Izumi 泉圭子 of Iwate Prefectural University, Tokyo and Yokohama have a similar modern history for the development of water source. Even though, as early as 1926, Tokyo started to request sharing water with Kanagawa. No attempt by Tokyo has succeeded so far. Granted, Tokyo has a larger population in a smaller domain than we. Though, at least we have not had a governor as Mr. Ishihara who ordered to “annihilate all the coniferous trees in Tokyo to reduce hay fever problem.” I think we are paying at least the minimum dues in taxes and water tariffs to build and maintain dams and water source forests. It’s essential nurturing forests that can store rain water and release it naturally to rivers. Dams are a sort of the final step to maintain water reservoir, not the beginning. The other day, we Kanagawa forest instructor trainees had a seminar with Mr. Masashi Chokki 一寸木将資 of West Sagami Forestry Ltd. （有）西さがみ森林. His company undertakes works from the prefectural government for the forests in Odawara and Hakone area. He said “It’s a kind of occupational habit … whenever we have TV footage of floods, I cannot stop checking the form of trees floating in muddy streams. Are they processed logs probably stored in a lumberyard deep in the mountain? If so, it could be a sign they cut trees rather too much. Or, are they large trees uprooted? It would suggest the upstream mountain has been neglected for a long time … not sufficient undergrowth was there to prevent the massive landslides. In contrast, don’t you think we in Kanagawa so far have been spared from the disaster recently? I think we are doing our best for protecting our forest for water.” I agree.

The main watershed and water facilities in Kanagawa Prefecture

At Samukawa Water Intake Facility,
there is a small museum explaining
water distribution system of Kanagawa Prefecture.
They have a very interesting chronological table
listing requests from Tokyo for water to Kanagawa.
Hmmmmmmmmm …

Samukawa Water Intake Facility on Sagami River.
The water collected here is distributed
to the east of the prefecture, including Yokohama.
We can see water-source mountains of Tanzawa over there.

A Forest of Growing of Kanagawa Prefecture
where no-pollen cedars were planted 5 years ago.
This summer, we completed a final mowing
for baby coniferous trees.
Now they are tall enough and
have no threat of shadows cast by undergrowth.
They should be able to have lots of sunshine
to get bigger by themselves.
To reach to this stage,
forest volunteers of Kanagawa
have invested lots of man-power, and money
(; could you see at the bottom a protection mesh against deer?).
Here, the prefecture is planning
to create a “Forest of Centuries.”
In 400 years’ time this place may have
gigantic cedars with diversified lower trees
and underbrush
where lots of water is reserved for Sakawa River.

Er, well, I am not deserved for this self-congratulation at all, actually. Telling you the truth, before starting the forest instructor training, I did not recognize how deeply water supply of my home prefecture interconnects many forests. I was like, “Well, Yokohama hasn’t received any water from Western Tanzawa, have we? Then, taking care of forests near Miho Dam does not have much everyday meaning for our life!” WRONG. The water of Miho Dam is certainly used for Odawara, but thirsty Yokohama is daily receiving water from there too. The Authority pumps up water using lots of fossil fuel at Iizumi Water Intake Facility (ASL12m; we can see the facility from windows of Shinkansen bullet train just before Odawara Station) and sends it to Kosuzume Water Treatment Plant (ASL 58m) in the south of Yokohama, some 43km north. The prefecture has a huge aqueduct running from Odawara to Sagamihara with a diversion to the east, i.e. Yokohama, starting near Mt. Oyama. Maintaining good forests now in Hakone will pay dividends for Yokohama’s water bill in future. By the same token, it is not at all useless remembering the water levels of all 4 dams far from the downtown Yokohama. (We can check real-time water levels of all 4 dams here.) Each municipality in Kanagawa Prefecture has a complicated system of water pipes where computerized systems watches and predicts water flows 24/7. If a community would have a surge of water demand, the system adjusts the entire distribution, including the discharge from dams, in order to halt water outage as much as possible. (That’s why water outage occurs here when we have electricity outage. No-power means no-computer working.) So, taking care of the condition of all the dams and water source forests in Kanagawa has a very practical sense for people living in Yokohama.

This summer,
Lake Miyagase has experienced very low water level
due to erratic patterns of rain.
Even though, the prefecture did not have water problem.
When Miyagase has shortage,
2 underground aqueducts from another tributary of Sagami River,
i.e. Doshi River 道志川 (more to this very important river in my later post),
divert the water directly to Miyagase.

These days, I do not care much whether water stored underground in a particular forest could end up at my faucet. Even man-made water system can have such a complicated connection. No one knows how natural water moves beneath the thick leaf-litter of rich forest. Besides, for water of Kanagawa Prefecture, the ultimate source is Mt. Fuji. Sagami River originates from Oshino-Hakkai 忍野八海. Sakawa River starts from the east of Mt. Fuji. Between there and my bathroom, there are lots of forests. In deep mountains, I really felt it nonsense to identify the water source for particular me, this tiny creature. It’s much more fun to thank God for pure water from beautiful Mt. Fuji 24/7. It would be a privilege on earth where many people face serious disputes for scarce water … Any way, let’s visit water source forests in Kanagawa from next week!

Kanagawa Water Source Authority

1194 Yasashi-cho, Asahi-ku, Yokohama, 241-8525

Phone: 045-363-1111