Friday, January 5, 2018

Treasure Tree: Lake Tanzawa and its surrounding forests 丹沢湖



Kanagawa Prefecture has 4 (main) water reservoirs: Lake Sagami 相模湖, Lake Tsukui 津久井湖, Lake Miyagase 宮ケ瀬湖, and Lake Tanzawa 丹沢湖. Created by Miho Dam 三保ダム in the mountains of West Tanzawa, Lake Tanzawa is the origin of Sakawa River 酒匂川. It is located near the border for Kanagawa 神奈川, Yamanashi 山梨 and Shizuoka 静岡 Prefectures, in Tanzawa-Oyama Quasi-national Park 丹沢大山国定公園. When you visit Lake Tanzawa by public transportation, please take commuter bus services from the bus terminal in front of Odakyu Shin-Matsuda Station 小田急新松田駅 by Fujikyu-Shonan Bus 富士急湘南バス. It’s the service to Nishi Tanzawa Visitor Center (西丹沢ビジターセンター West Tanzawa Visitor Center; time tables are here). There is only one route to reach to Lake Tanzawa. We have to take the same road anyway as the commuter service to go there by car. For automobiles, we get off Tomei Express Way 東名高速 at Ohi-Matsuda 大井松田IC to enter National Route 246. Please drive west along Tomei Express Way until observing Tsuburano Tunnel 都夫良野トンネル above, and turn right at Shimizubashi traffic light 清水橋交差点 after passing JR Yaga Station of Gotemba Line 御殿場線谷峨駅. That’s the way to enter prefectural route #76 heading north to Lake Tanzawa. About 10k drive from the traffic light and before entering Kaminawa Tunnel 神縄トンネル, we can glance at Miho Dam on the left. When we exit to the other side of the tunnel, Lake Tanzawa is spreading before us. There at a T-crossing, if we turn right, the route is now prefectural road #710 that ends at the entrance of West Tanzawa Citizen Forest of Kanagawa Prefecture 神奈川県西丹沢県民の森. If we turn left at the T-crossing, route #76 soon brings us to Kamioda community 神尾田 with the admin office of Miho Dam and tourism information center, named Lake Tanzawa Memorial Hall 丹沢湖記念館. We keep on going to cross Eisaibashi Bridge 永歳橋 and meet with another T-crossing. To the left, we enter prefectural route #729 via Ochiai Tunnel 落合トンネル. After driving for about 4K, #729 becomes for permit-holding construction cars only, which will end in the middle of forest. If you continue driving route #76, we go through Nakagawa Hot Spring Spa 中川温泉郷 and reach to the dead-end at Nishi Tanzawa Visitor Center. With all three driving roads, we run along the shore of Lake Tanzawa for a while, and will be terminated at the middle of mountain streams pouring to the lake. In short, Lake Tanzawa is in deep mountains almost at the end of place where automobiles can reach. And, that’s the reason why the place is so charming.


Sakawa River with Miho Dam over there
along prefectural road #76.
Lake Tanzawa seen from the mouth of Kaminawa Tunnel
Miho Dam.
It’s created by the same methodology
as Aswan High Dam of Nile River.
The other side of the dam is a calm mountain lake.


It seems to me, as always for a country side in the 21st century Japan, the community around Lake Tanzawa faces the problem of aging and shrinking population. At each bus stop for the services from Shin-Matsuda Station to Lake Tanzawa, especially after JR Yamakita Station 山北駅, we are greeted by a large notice board saying “This commuter service was reviewed jointly by the operator and the prefecture who concluded the continuation of the operation for citizens disadvantaged in transportation. The business is subsidized by the prefectural government and Fujikyu Shonan Bus Co. asks the customers to support our services to sustain the system.” Hmmmmm … Actually, Lake Tanzawa is popular among outdoor lovers in metropolitan Tokyo. Yamakita Town 山北町 which is the address for Lake Tanzawa has an agreement with Shinagawa Ward 品川区 of Tokyo by which the residents of Shinagawa can have preferential access to the fun facilities around Lake Tanzawa, such as tennis courts and allotments for Sunday farming. The lake community also hosts an annual half-marathon event every November, called Lake Tanzawa Half Marathon 丹沢湖ハーフマラソン. The area has a good infrastructure. Although the utility roads for automobiles do not go further from the Lake, there is a forestry road completely circling around the lake shore that is damned-well paved with good guardrails. For cars it is a forestry road accessible for permit-holders only; for walkers and bikers, it is a relaxing way around the lake. As Lake Tanzawa is a water-reservoir in deep mountains, the slope around the lake is inevitably covered by water source forests. So if you ramble in the circling road of Lake Tanzawa, you can experience water source forests of Kanagawa without venturing into the mountain itself. It is possible for wheelchairs to enjoy the water source forests. That’s really something.


“Thank you for your cooperation.
Fujikyu-Shonan Bus Co.”
One of the gates
entering into the forestry road surrounding the Lake


One fine winter day, I’ve been there and walked the forestry road around the lake. It was a very quiet strolling with a wide view of Lake Tanzawa. Around the lake is, I would say, 20% of afforested coniferous forests and 80% of natural trees. Steep slopes along the forestry road on the shore are treated with rockfall prevention works. Otherwise, natural soil goes up from the paved way. We can find footsteps of wild animals … deer, bear, boar, … just along the smooth car road. Well, even for wild animals, paved way could be easier to maneuver, couldn’t it? From the forestry road, I could spot pheasants having wormy lunch under trees over there. According to the exhibitions shown in the Tanzawa Memorial Hall 丹沢湖記念館, the area has more than two millennia history of human settlement. During Tokugawa Shogunate period 江戸時代, the forests in the west Tanzawa were owned by the lord of Odawara 小田原藩 who was a loyal follower of Shogun in Edo (Tokyo). The trees in entire Tanzawa were important resource for construction works and fuels in Edo. In the east Tanzawa which the Shogun directly owned, 6 kinds of trees 丹沢六木, Tsuga sieboldii, Torreya nucifera, Castanea crenata, Zelkova serrata, Abies firma, and Cryptomeria japonica, were closely protected as the property of Edo government. The lord of Odawara followed his master’s land management, and ordered the villagers in the west Tanzawa taking care of the trees as in the east Tanzawa. The present day beauty of natural forest around Lake Tanzawa is the product of this 400 years’ tradition. The construction of Miho Dam for 1969-1978 submerged several villages as a result, but the remoteness of the place spared it from the rampant development.


Lake Tanzawa Memorial Hall preserves a 200 years old house
that was once stood in the western part of Lake Tanzawa.
The place has lots of information about the history of the community.
It’s Seuret with infinite variation of pale green, grey, and brown
delicately dotted on a space canvas …
The circling “forestry road” for Lake Tanzawa
I think it’s Ursus thibetanus’.
The forestry road has lots of bridges
over the end of mountain stream pouring to the lake.
The forest surrounding the lake.
Hmmmm …
those grasses should have been “mowed” by deer.
Could you figure out
the remnants of the community road over there?
The below must have remains of the village.


For feeling what was like the area before Miho Dam, we can try walking prefectural road #76 north for a while. Lake Tanzawa eventually becomes Kouchigawa River 河内川. About 2K walk from the lake, we’ll be greeted by Nakagawa Hot Spring Spa 中川温泉郷 which has a legend of the 16th century warlord of Yamanashi Prefecture, Takeda Shingen 武田信玄, who used the place secretly as a sanatorium for wounded soldiers. Walking further to the West Tanzawa Visitor Center, we enter more and more into a deep mountain, with very few houses along the route #76. The very transparent Kouchigawa River flows rapidly, which is assuring as a water source for us in Yokohama. About an hour walk for 3K from the spa, we can find a small community with a gigantic Cryptomeria japonica on the left. It is Hohki Sugi (箒杉 Hohki cedar) in Hohki community . The cedar is estimated to be around 2000 years old, and in 1934 registered as one of the natural treasures of Japan. It is said that the villagers of Hohki has been taking care of the forest of the area for centuries, in accordance with the regulation set by the lord of Odawara. Their mountain was famous for its rich forest, and had the name Hohki 宝木 that is a homonym of Hohki  but whose Chinese character means “Treasure Trees.” During the period of the lord of Odawara, Hohki Sugi had its twin next to it. After Meiji Restoration 明治維新 of 1868, the lord of Odawara was replaced by rotating mandarins by the new government. Eventually the zeal of industrialization reached to this place and in 1908 Hohki sugi’s brother was cut down. The name of the community was changed to Hohki whose Chinese Character means “Broom.” Then in 1972, when a ferocious typhoon hit the area, Hohki Sugi and surrounding forests stopped the landslides along Kouchigawa River and protected the Hohki community. They did a perfect job as water source forests. Dependable 2000 years old …


Nakagawa Hot Spring Spa over there.
The entrance to spa.
We can stay there for days,
or just drop by to have an hour spa experience.
The Route #76 after spa.
During industrial revolution of Japan,
the road was upgraded for forestry use.
Now, it’s a very quiet commuter bus route
to West Tanzawa Visitor Center.
Kouchigawa River has really transparent flow.
Hohki Sugi over there


And I really have to tell you this: the area around Lake Tanzawa is the entrance to one of the main mountaineering routes to the peaks of Tanzawa Mountains. From Kurokura Bus Stop 玄倉バス停 to West Tanzawa Citizen Forest, we can start climbing to Mt. Nabewari (鍋割山 ASL 1272.4m) and Mt. Tonodake (塔ノ岳 ASL 1490.9m) via beautiful Yushin Valley ユーシン渓谷. From West Tanzawa Citizen Forest or West Tanzawa Visitor Center, we visit Mt. Azegamaru (畦ヶ丸 ASL1292.3m), Mt. Kanyudo (加入道山 ASL 1418.1m), Mt. Omuro (大室山 ASL1587.4m), Mt. Hinokiboramaru (檜洞丸 ASL 1601m), Mt. Hirugatake (蛭ヶ岳 ASL 1672.6m), and Mt. Tanzawasan (丹沢山 ASL 1567m). If you plan to climb these peaks, you should

(1) consider your mountaineering level first: the area is a daily training ground for Japanese mountaineers preparing for Mt. Everest;

(2) make an itinerary for at least 2 day hike from Tokyo with camping in refuge huts or staying mountain cottages near the peaks; and

(3) prepare yourself with enough water, food, and appropriate gears: during winter, equipment for snow could be MUST in Tanzawa’s main ridges.


Having said that, these are the peaks uber-popular in the metropolitan Tokyo area. It could be difficult to make a reservation at mountain cottages for weekends. It’s very interesting … such major destinations are important water source forests for us in Kanagawa. That would be why we have to play balancing act around Lake Tanzawa always. As in 400 years ago, these are the treasure trees near us.


I think the left one is Mt. Omuro.


If you find something unusual during your adventure around Lake Tanzawa, please make a contact with West Tanzawa Visitor Center. They also have a drop-box for your climbing registration that is very important especially here … in case you may need emergency-copter service from Yokohama. Their contact address is

Tanzawa-Oyama Quasi-national Park 丹沢大山国定公園・県立丹沢大山自然公園

West Tanzawa Visitor Center of Kanagawa Prefecture 神奈川県立 西丹沢ビジターセンター

867 Nakagawa, Yamakita-cho, Ashigarakami-gun, Kanagawa, 258-0201 神奈川県足柄上郡山北町中川867

Phone: 0465-78-3940





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