Date of interview: Sunday, 08/17/2014
We came here after visiting Kurobe Dam and Utsukushi-ga-hara Highland Museum of Art in Toyama on a two-day and one-night family trip. The white limestone riprap looks like a chalk castle, and it is more beautiful than it sounds. The Namiaoki Dam is the upper pond of the Kannryugawa Power Plant, where pumped-storage hydroelectricity is generated (the lower pond is located in Gunma Prefecture). (Incidentally, the Lower Pond is the Ueno Dam on the Gunma Prefecture side.)
Unit 1 (maximum output: 470,000 kW) of the Kannagawa Power Plant started operation in 2005, Unit 2 (470,000 kW) in 2012, and Units 3 to 6 (1,880,000 kW) are scheduled to start operation in 2022 or later. When all units are in operation, they will be 2.82 million kW, one of the largest pumped storage power plants in the world.
View of the flood discharge and levee from downstream
The Minamisaki Dam is truly deep in the mountains, but the embankment you see when you arrive is impressive itself. Jizan on the ground in the foreground.Flood dischargeThe white embankment in the back of the dam is the only one like this in all of Japan. The Naramata Dam, another rock-fill dam, has a flood discharge right next to the embankment, but it has a different look.
And to my surprise, they were releasing the fish that day! (I'll spoil the story later.)
Sub-dam and conduit wall
Even a single flood discharge seems to have been designed not only for its function but also to be seen. The design may have been refined as a result of pursuing functionality, but the deliberate slenderness of the end of the flow guide wall shows the designer's intention to make it look beautiful.
Beautifully rounded conduit
Even the curvature of this conduit section is beautiful. I wonder if it is designed to produce a beautiful flow pattern.
Minamiasagigawa Bypass Tunnel Exit
Although the river at the Minamiasagi Dam is supposed to be the Minamiasagi River, in reality, due to water rights and other issues, the river does not flow directly into the dam lake, but is discharged downstream through a bypass tunnel. In other words, the Kannagawa Power Plant is a pure pumped storage power plant. (Exceptionally, the water flows into the reservoir when the water level rises.)
The photo below shows the exit of the bypass tunnel. There is a curtain hanging down at the exit, but what is that?
Flood discharge and downstream face of the embankment from downstream
It is possible to enter downstream, but a view like this is hard to find at any other dam.
Downstream park "Uzumaku Square"
On the downstream side of the embankment, a plaza named Uzumaku Square is spread out as landscape art. Like the design of the flood discharge, it is a plaza completely designed for visitors to see. While most dams designed exclusively for power generation are rugged in their pursuit of functionality alone, the fact that this dam specializes in art and design is very unusual.
The concrete structure on the far right is a conduit wall, and the one next to it is a combined toilet and observation deck called a "lassen.
The Uzumaku Plaza won the Good Design Award in the Architecture and Environmental Design category in 2006. The director is Isao Komiya of Isao Komiya Architects, and the designers are Isao Komiya, contemporary artist Kazushi Sasaguchi, and landscape architect Tokiko Furuuchi.
Lacen (restrooms and observation deck)
I have never seen a toilet designed like this in any other dam. In addition, it is an environmentally friendly bio-toilet.
View of the downstream face of the dike
The neatly laid limestone riprap is so beautiful to behold. The lawn is also beautifully landscaped.
slab with a haiku cut on it
Because the Minamiami Dam itself is so beautiful, it is easy to miss these stone monuments, but they are scattered around the dam, not only in design, but also in literature.
The stone that has passed through the ages of time The fill dam Shining with the souls of those who built it Dedicated to all those who worked on the Minamiami Dam Dedicated to all the people involved in the Namisaki Dam Fumiko Tanji
Mysterious tunnel entrance
There was a mysterious tunnel entrance directly below the flood discharge. It is surrounded by limestone and has a sense of unity in design with the surrounding area. Is it an inspection tunnel? Or is it connected to an audit corridor?
Speaking of tunnels, there is a nearby tunnel called "Osutakayama Tunnel," which is closed to the general public, including the surge tanks, and has become a favorite target of conspiracy theorists who talk about human experimentation and the crash of the Japan Airlines jumbo jet. The only difference is that the tunnel is not shared.
Incidentally, a running event starting from Ueno Dam and finishing at Minamiasagi Dam is sometimes held, and this Osutakayama Tunnel is said to be the course for the event.
Still, it would be very convenient to go to and from the Ueno Dam if this tunnel were shared, but I wonder if it would be difficult due to administrative problems.
Right bank dam site (Stone Plaza in the Sky)
After enjoying the downstream Usumaku plaza at its best, we moved up to the top level. The name "Tenku" comes from the fact that it is the highest dam in Japan, with a top elevation of 1,532 meters.
View of the top edge from the right bank
The top end is closed to motor vehicle traffic but can be explored on foot. The dam lake can also be circled.
Looking downstream from the top of the right bank
The riprap is really beautiful. I described it as "orderly" in the previous paragraph, but I think it is literally true. And it's white.
View of the dam lake from the top
The water in the dam lake is also very beautiful.
View of the flood discharge on the lake side of the dam from the top
It is a side channel type flood discharge of the Minamisaki Dam.
Flood discharge on the lake side of the dam
Huh? I thought I was overflowing from downstream, but I didn't!
Reasons for not overflowing
The reason water was not overflowing from the overflow bank of the flood discharge and was flowing as seen downstream was that the water was coming from a pipe drawn from a rim tunnel or stream by the side of the control bridge and it only appeared as if it was overflowing 😓.
Left bank rim tunnel
This portal was not surrounded by limestone like the mysterious tunnel we saw downstream, but only had decorative panels? The slope is made of limestone. The slope is made of limestone.
Tire Monument
Tire monuments like this are often installed in rockfill dams, but in the case of the Minamiasagi Dam, they are installed on the left bank, not on the right bank where many people are likely to be. The tires are said to be those of a 90-ton dump truck.
Looking upstream from the left bank
The upstream bank is also white. Also, the sky seems closer, perhaps because of the higher elevation.
View of the flood discharge downstream from the top
There are two places where the flood discharge is sloped, perhaps for the convenience of the ground, which makes the structure a little interesting.
Looking downstream from the left bank
The huge white chalk castle is beautiful from every angle.
View of the top edge from the left bank
The top edge is also clean and may be maintained on a daily basis.
View of Uzumak Square downstream from the top
The plaza really looks like a whirlpool when viewed from the top edge.
swallow at the edge of the sky
For some reason, there were an unusually large number of swallows flying that day, and some of the limestone rocks at the top edge looked black.
Swallows on the downstream face of the dike
Most of the black dots are swallows. Is this a good feeding ground for them?
To the right bank plaza again.
The monument is also built of limestone. It is nice to have a sense of unity.
Looking upstream from the right bank
The sigh-inducingly beautiful embankment and beautiful dam lake. And the sky is so close that it seems to reach the heavens. Is this heaven?
Overview panel and upstream face of the embankment
The design of the panel explaining the outline of the Minamiami Dam also gave me the impression that a lot of thought had gone into its design. The reason why the panels are low and not huge is probably because the levee is the main structure of the dam. Audio guidance in Japanese and English is also available. The deck also shows how the dam is designed for visitors to see.
Toilets and Administration Office
An unmanned control center and restrooms are located on the right bank. Parking is of course available.
Right bank dam site
It is no exaggeration to say that it is a "dam in the sky," and everything about it is substandard and beautiful. Please visit.
Minamisaki Dam Specifications
| Location | Minamiasagi Village, Minamisaku-gun, Nagano Prefecture |
| River Name | Shinano River System Minamiaoki River |
| Objective | P(Power generation) |
| Model | R (Rock-fill dam) |
| Bank height | 136m |
| Bank length | 444m |
| Dam volume | 7,300,000 m3 |
| Watershed Area | 6.2 km2 |
| Reservoir area | 59 ha |
| Total storage capacity | 19,170,000 m3 |
| Effective water storage capacity | 12,670,000 m3 |
| Dam operator | Tokyo Electric Power Company Renewable Power Co. |
| Main body constructor | Maeda Corporation, Taisei Corporation, Obayashi Corporation, Aoki Corporation |
| Year of launch | 1995 |
| Year Completed | 2005 |
| Name of Dam Lake | Okumikawa Lake |
Other facilities/observations
| Parking lot | ○ |
| Toilet | ○ |
| Park | ○ |
| PR Exhibition Hall | × |
| Fishing | × |
| Viewing platform | × |
Map of the area around Minamisaki Dam
Weather around Minamisaki Dam
Accommodations that may be close to Minamiami Dam
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