Tochigi Prefecture Dam

0568-Fukayama Dam (Miyama Dam)

0568-Fukayama Dam (Miyama Dam) Tochigi Prefecture Dam
This article can be read in about 9 minutes to read.

Date of interview: Wednesday, November 19, 2014

We came here via Shiobara Dam (glimpse only) and Itamuro Dam (entrance only). It was one of the main dishes of the day. The Fukayama Dam was constructed at the uppermost reaches of the Naka River as part of the state-run Nasunohara Development and Construction Project. In addition to agricultural water and water supply, water taken from the Fukayama Dam is used for hydroelectric power generation at the prefectural Itamuro Power Station. It also serves as the lower reservoir for pumped storage power generation at the Jensen Kaihatsu Numahara Power Station. The upper reservoir is the Numahara Dam.

View of the top edge and wooden sign from the right bank

At Shiobara Dam, the autumn leaves were in full bloom, but the area looks a bit closer to winter, perhaps because it is further north and at a higher elevation.

View of the top edge and wooden sign from the right bank
View of the top edge and wooden sign from the right bank

administration office

It is a large management center for a prefectural government-run facility.

administration office
administration office

View of the flood discharge from the right bank

When I first saw the downstream face of the Miyama Dam, my impression was that it was rough. Although it is an asphalt-faced fill dam, the downstream face is thickly wooded. In addition, the sprayed concrete around the flood discharge may have made it look even rougher than it was.

View of the flood discharge from the right bank
View of the flood discharge from the right bank

Toilets on the right bank

There is a public toilet on the downstream side of the right bank. However, it is said to be closed in winter, so please be careful in case of emergency 😁.

The right bank of the river is so wide that it looks like it could be used for a small festival. It is so wide that it looks like it could be used for a small festival. Also, I noticed from Google Maps that there is an observatory on the right bank called "Fukayama Dam Park" where you can see the embankment from a bird's eye view. I didn't know it existed at the time, but now I have an excuse to visit it again.

Toilets on the right bank
Toilets on the right bank

Looking downstream from the right bank

Another factor in the roughness of the area. The ski jump flood discharge is almost left in its natural state, with only concrete blocks laid under it. The fact that there is no water flowing in the river below the flood discharge may also contribute to the sense of roughness.

Across the valley, one can see Nasunogahara stretching out.

Looking downstream from the right bank
Looking downstream from the right bank

Water taken from the Fukayama Dam as agricultural water and tap water flows through a conduit to the Itamuro Power Plant. After being used for power generation, the water is back-conditioned at the Itamuro Dam, taken into the upper trunk canal as agricultural water and tap water, and the rest is discharged into the Naka River. The rest of the water is discharged into the Naka River. Because water is used without excess in this way, no water flows directly under the dam.

When we contacted the Tochigi Prefecture Nasu Agricultural Promotion Office and the Nasu Regional Dam Management Branch, we were given materials, which we have also included here. Tochimaru-kun is very cute. (We also received permission to post this information.)

Itamuro power generation (data provided by Nasu Regional Dam Management Branch Office)
Itamuro power generation (data provided by Nasu Regional Dam Management Branch Office)

However, it is not as if it is not always flowing. There is a branch in the middle of the water pipeline from the intake tower, and there is actually a Howell Bunger valve on the left bank side. When the Itamuro Power Plant is closed for inspection or construction, alternative discharge may be made from this valve. The valve was covered with trees and we did not notice its existence on the day we visited, but we were told that "after the leaves fall, you can see the alternative discharge from the top edge of the valve.

Itamuro power generation and alternative discharge (Source: Nasu Regional Dam Management Branch Office)
Itamuro power generation and alternative discharge (Source: Nasu Regional Dam Management Branch Office)

Incidentally, the Fukayama Dam actually has another discharge structure that is not normally visible, but you can guess that by looking at the GSI map. I hope this will not be used.

Water Use Signs

The water use signage is a single, easy-to-understand sign for irrigation by MAFF, power generation and water supply by Tochigi Prefecture, and power generation by Power Development Corporation.

Water Use Signs
Water Use Signs

Tourist map of the area around the Miyama Dam

There are hiking and climbing routes around the Fukayama Dam, and the Fukayama Dam is also a tourist attraction. On this day, there was always someone visiting the site.

Tourist map of the area around the Miyama Dam
Tourist map of the area around the Miyama Dam

Nanasenzan Water Source Forest

The Nanasenzan Water Source Forest is recognized as one of the 100 best water source forests in Japan.

Nanasenzan Water Source Forest
Nanasenzan Water Source Forest

View of the crest gate from the right bank

The Fukayama Dam is equipped with three radial gates on the crest.

View of the crest gate from the right bank
View of the crest gate from the right bank

Looking downstream from above the flood discharge

It is the downstream direction that is still full of wildness.

Looking downstream from above the flood discharge
Looking downstream from above the flood discharge

View of the crest gate from another angle

The right bank dam site and part of the top edge protrude in the downstream direction, allowing the crest gate to be viewed from the downstream side.

View of the crest gate from another angle
View of the crest gate from another angle

Commemorating the completion of the Fukayama Dam

A monument is placed on a landslide on the right bank.

Commemorating the completion of the Fukayama Dam
Commemorating the completion of the Fukayama Dam

View of the downstream face of the dike from the right bank landslide

The slope looks more like gravel than rock. The grass also grows on the slope, making it look like a rougher version of the Miho Dam.

View of the downstream face of the dike from the right bank landslide
View of the downstream face of the dike from the right bank landslide

dog run entrance

Unlike the Miho Dam, Inunashiri is unfortunately off-limits.

dog run entrance
dog run entrance

Looking downstream from the left bank

It looks wild from every angle. Perhaps it looks that way because it is late fall.

Looking downstream from the left bank
Looking downstream from the left bank

View of the top edge from the left bank

The top end of the road is open to automobile traffic and the road continues toward Fukushima Prefecture on the right side of the photo. However, because the road is blocked on the way, it is not possible to go to Fukushima Prefecture, but only to the Fukayama Power Station of the Tochigi Prefectural Enterprise Bureau, passing through the Numahara Power Station and the Forest Power Generation Ohanashi Kan.

View of the top edge from the left bank
View of the top edge from the left bank

Looking upstream from the left bank

This is the part that most indicates that it is an asphalt-faced fill dam. It is interesting that the asphalt-faced area looks like a horizontal line drawn by the water level.

Looking upstream from the left bank
Looking upstream from the left bank

View of the intake tower from the top

This is the intake tower for delivering water to the Itamuro Power Plant. The tower has no control bridge and is independent.

View of the intake tower from the top
View of the intake tower from the top

Workers working on the downstream face

There was a worker doing some kind of work on the downstream face of the dike. Is it an inspection?

Workers working on the downstream face
Workers working on the downstream face

Downstream view of the levee and reservoir from the right bank

The water level was quite low on that day. I think the water level was low because water was sent to Numahara Dam during the night, but the situation at that time is not certain.

Downstream view of the levee and reservoir from the right bank
Downstream view of the levee and reservoir from the right bank

Deep mountain dam CCTV system

After a quick look at the embankment, it was time to assemble, so we moved to the control center and received various explanations from the staff. The photo below shows the CCTV monitors installed at various locations of the Fukayama Dam so that visitors can check the images.

Deep mountain dam CCTV system
Deep mountain dam CCTV system

Basin hydrography

This system indicates water levels and rainfall in the watershed of the Fukayama Dam.

Basin hydrography
Basin hydrography

Diagram of dam discharge

This is a discharge status chart with a diagram that imitates the flood discharge of the Fukayama Dam. The color of the crest gate and the position of the Howell Banger valve are different, but the CG makes it easy to understand.

Diagram of dam discharge
Diagram of dam discharge

Detailed drawing of asphalt pavement

This figure shows a cross-section of the asphalt facing section of the Fukayama Dam. It can be seen that it is divided into several layers and is thick.

Detailed drawing of asphalt pavement
Detailed drawing of asphalt pavement

Water intake tower model

A 1/100 scale model of the intake tower was placed inside the control center. The cross-sectional view makes it easy to understand the structure.

Water intake tower model
Water intake tower model

Yurukyara!

Tochimaru-kun" from Tochigi Prefecture, "Ruri-chan" also from Tochigi Prefecture, "Cottonberry" from Moka City... and mascot characters were posted on the partitions. They are cute ☺.

Yurukyara!
Yurukyara!

Looking upstream from the side of the control center

Once you have been briefed at the control center, you will move on to your next destination.

Looking upstream from the side of the control center
Looking upstream from the side of the control center

Forest Power Generation Story House

The next stop was the Mori no Denryoku Ohanashi Kan, an exhibition facility operated by Denpatsu Co. From here, we were to tour the Numahara Power Plant and other facilities.

Forest Power Generation Story House
Forest Power Generation Story House

Inside the Mori no Denryoku Ohanashi Kan

We will take a tour of the Forest Power Generation Museum. I remember that we were given a briefing by a person from Power Development...but it was 8 years ago, so my memory has faded considerably. I guess I should write about this kind of thing right away.

Inside the Mori no Denryoku Ohanashi Kan
Inside the Mori no Denryoku Ohanashi Kan

Inside Numahara Power Plant

Next, we will visit the Numahara Power Plant. Pumped storage power plants are underground, but I am always surprised every time I visit any power plant that such a large space is spread out underground.

Inside Numahara Power Plant
Inside Numahara Power Plant

Emperor Showa and Empress Kajun visit

It seems that Emperor Showa and Empress Kajun visited Numahara Power Plant on August 8, 1974.

Emperor Showa and Empress Kajun visit
Emperor Showa and Empress Kajun visit

Generator Explanation Panel

A Power Supply Developer explains about the generator. It is amazing that this is buried underground.

Generator Explanation Panel
Generator Explanation Panel

Numahara Pond under excavation

There were other valuable photos displayed in this room where we were briefed. It must have been soon after the construction of Numahara Dam started.

Numahara Pond under excavation
Numahara Pond under excavation

Numahara Pond before the start of waterlogging

The caption reads "Numahara Pond" rather than "Numahara Dam," perhaps out of pride in having rewritten the map by creating an artificial pond. If you look closely, you can also see the Fukayama Dam under construction in the upper right corner of this photo.

Numahara Pond before the start of waterlogging
Numahara Pond before the start of waterlogging

Asphalt paving of Numahara Pond

Like the Fukayama Dam, the Numahara Dam is also an asphalt-facing fill dam, and this is a rare photo of the asphalt paving in progress.

Asphalt paving of Numahara Pond
Asphalt paving of Numahara Pond

Completed Numahara Pond

New Numahara Dam. It is very beautiful.

Completed Numahara Pond
Completed Numahara Pond

Underground power plant under excavation

Another precious photo.

Underground power plant under excavation
Underground power plant under excavation

Installation of generator rotor and waterwheel runner

This is a view of the rotor and runner, the key components of the power plant, during installation.

Installation of generator rotor and waterwheel runner
Installation of generator rotor and waterwheel runner

underground power plant

Next, we enter the power plant. As I have said many times, it is always amazing to see such a large space spread out underground.

underground power plant
underground power plant

Generator No. 3

Generator manufactured by Hitachi, Ltd.

Generator No. 3
Generator No. 3

main shaft

The thick vertical silver bar is the main axis. This spins around when electricity is being generated. The waterwheel is housed under this rod.

main shaft
main shaft

The group then left the Fukayama Dam and the Numahara Power Plant behind, and after lunch moved on to their next destination, the Numahara Dam.

Miyama Dam Specifications

LocationFukayama area, Hyakumura, Nasushiobara City, Tochigi Prefecture
River NameNaka River System Naka River
ObjectiveA (irrigation water)
W(Water for water supply)
P(Power generation)
ModelFA (Asphalt Facing Fill Dam)
Bank height75.5m
Bank length333.8m
Dam volume1,967,000 m3
Watershed Area65.9 km2 (direct: 52.9 km2, indirect: 13 km2)
Reservoir area97 ha
Total storage capacity25,800,000 m3
Effective water storage capacity20,900,000 m3
Dam operatorKanto Agricultural Administration Bureau, Ministry of Agriculture -> Tochigi Prefecture
Main body constructorTaisei Corporation
Year of launch1968.
Year Completed1973
Name of Dam LakeMiyama Lake

Other facilities/observations

Fishing is not allowed at Lake Miyama, but you can go mountain stream fishing in the Okawa River upstream. (There is a closed season for fishing.)

Parking lot
Toilet○○ (closed in winter)
Park×
PR Exhibition Hall○○ (Forest Power Generation Ohanashi Kan)
Fishing×
Viewing platform

Map of the area around the Miyama Dam

Weather around Fukayama Dam

Accommodations that may be close to the Miyama Dam

Hotels and inns in Itamuro - Accommodation Reservations (Tochigi Prefecture) [Rakuten Travel] (in Japanese only)
If you are looking for hotels and inns in Itamuro, Rakuten Travel is the best place to go! You can use and earn Rakuten points, and it is a very economical accommodation reservation site. You can also use discount coupons! Domestic tours, airline tickets, car rentals, and bus reservations!
47 hotels in Nasu-cho, Japan.
Save big on hotels in Nasu-cho, Japan when you book online. We offer a wide variety of rooms with competitive room rates. You can choose the best hotel deals based on actual guest ratings.
This article was written by.
Shin Jinma

Dam enthusiast who loves Momosuke Fukuzawa / Dampedia and Dam News administrator / Certified Dammeister (01-018) by the Japan Dam Foundation / Started selling discharge caution goods.https://shop.dampedia.com

Follow Damapedia
Dampedia

Comment

タイトルとURLをコピーしました