Iwaki River system
Aseishi River
History of Aseishigawa Dam
June 1971:
Implementation plan survey begins
April 1973:
Construction begins
December 1975:
Conclusion reached on compensation standards andagreement signed (201 properties submerged)
September 1979: Construction of main dam structure begins
August 1986:
Concrete casting of main dam structure is completed
November 1987: Trial flooding begins
October 1988: Construction is completedApril 1989: Transition made to management and operations
April 2017:
Renamed Aseishigawa Dam Management Branch
October 2018:
30th anniversary of operations

Aseishigawa Dam MascotsAtchan and Papa

Aomori prefecture
Iwaki River

Aseishigawa
Dam

Akita prefecture

Iwate
prefecture

The Aseishigawa Dam is a concrete gravity dam constructed to stabilize water demand and to upgrade floodcontrol functions as a replacement to the Okiura Dam completed in 1945.
The Aseishigawa Dam is a “multipurpose dam” that has four different roles: flood control, river ecosystemconservation, municipal water supply, and power generation.

Aseishigawa Dam’s functions
Mitigating flood disasters

Planned flood discharge at dam site:
Adjusted from 2,000m3/sec to 500m3/sec

Generating power

Maximum generation output: 17,100 kW

Maintaining proper waterflow functions

Providing consistent replenishment for existingwater supplies, and conserving the river’secosystem.

Supplying municipal water

Water supply to the 9 municipalities of Kuroishi,
Hirosaki, Goshogawara, Hirakawa, Aomori, Fujisaki,
Itayanagi, Tsuruta, and Inakadate
Up to 132,800 m3/day

Aseishigawa Dam and Reservoir Specifications
Dam and Reservoir Specifications
RiverDam crown: EL.201.00 mReservoir<Outside of flood season>(Oct 1 thru Jun 30 next)
Surcharge capacity: 4,200,000 m 3

Water holding level for flood
readiness: EL184.50 m

Water utilization capacity outside offlood season: 38,900,000 m 3● Maintaining proper
waterflow functions● Municipal water

Water utilization capacity during
flood season: 19,100,000 m3● Maintaining proper waterflow
functions● Municipal water

Minimum water level: EL164.00 m

Sedimentation capacity:
10,000,000 m3
View of Tsugaru Dam fromdownstream

Water releasing facilities
schematic

Effective storage capacity

Maximum stored water level at
normal times: EL. 196.00 m

Total storage capacity

Flood control capacity:
24,000,000 m3Aseishigawa River, Iwaki River system, Class-A River

Watershed area

225.5 km2

Flooded area

2.2 km2

Total storage
capacity

53,100,000 m3

TypeConcrete gravity dam

Dam head elevation

EL: 201.0m

Dam height91.0 mDam head length

330.0 mDam head width
Dam<Flood season> (Jul 1 thru Sept 30)
Maximum water level during floods: EL. 198.00 m

8.0 m

Dam volume

Approx. 700,000 m3

Water intake facilities

Shared intake facility: 5-stage cylinder gate
Agricultural water intake facility: 4-stage cylinder gate
Municipal water intake facility: 4-stage cylinder gate

Water releasing
facilities

Crest gates: Width 7.0 m x Height 10.8 m x 4 gates
Orifice gate: Width 4.0 m x Height 5.3 m x 1 gate
Conduit gates: Width 2.8 m x Height 3.6 m x 2 gates

Total project cost

Approx. 90.5 billion yen

Intake towers

These facilities are used for taking water in from the dam lake. They open theirgates to take in water from the dam lake. From these intake towers, the water
passes through the dam to different facilities, finally flowing out into Iwaki River.

Crest gates (emergency flood spillway)
These gates are used during major flooding.
There are four gates at a height of 189.5 meters.

Orifice gate (principal spillway)
This is used to release water to maintain the water level
when there is an inflow from snowmelt or minor flooding.
There is one gate at a height of 177.0 meters.

Conduit gates

Elevation EL: 189.5 m
Crest gates
Agricultural water intake
facility
Maximum water level during
floods EL: 198.0 m

Shared intake facility
Municipal water
intake facility
Dam crown: 201 m

Maximum stored water level at
normal times EL: 196.0 m

Water holding level for flood
readiness EL: 184.5 m
Orifice gate
Elevation EL: 177.0 m

Minimum water level EL: 164.0 m

These gates are central to the dam’s flood regulating
functions.
There are two gates at a height of 147.2 meters.
Conduit gates
Elevation EL: 147.2 m

Water quality preservation measures

Unusual odor and taste (moldy odor) in the water from Aseishigawa Dam was reported in September 2012. To address thisissue, we now operate three lake water circulators as part of our water quality preservation efforts.
What causes the moldy odor?

Surface strata temperature:
20ºC or more
Water temperature gradient:
0.5ºC/m or more

Algae that produces moldy odor begin to appear when the surface strata of the waterreaches a temperature of 15ºC or higher, and begin to actively proliferate at 20ºC or higher.
Circulation between the surface and lower strata is suppressed when the surface strata
has a water temperature gradient of 0.5ºC/m or more. This causes algae to accumulate in
the euphotic (light-reaching) layer of the surface strata where they actively proliferate.

Effects of lake water circulators (aerators)

Lake water circulators

With lake water circulators

Without lake water circulators

Water temperature

Vertical temperature profile

Lake water circulators(aerators) are is use inother dams as a measure
to curb moldy odors andhave been verified to beeffective in significantly
reducing watertemperatures.
Calculations indicate that bycirculating and mixing thewater with lake water
circulators (aerators), thetemperature of the water’ssurface strata can be
reduced from 23ºC to 18ºC.

Air bubbles
Entrainment

Diffusion

DiffusionFloatingEntrainment

Aeration tube2.

Dam management<Gate operating room>

Flood response
Whenever flooding is expected, we prepare forecasts on potential inflow volumes into
the dam, and conduct reviews on flood control and projected release volumes basedon weather information, as well as data on rainfall amounts, water levels, and otherdata from different observatories. Before we perform a release, we alert river users
and residents downstream who live near the river through public loudspeakers andsirens, conduct patrols on alert cars, and notify all relevant organizations.

<Patrolling by drone>

Response during normal times
We monitor flow rates on a daily basis, and adjust the volumes we release from thedam to ensure that water flowing in rivers downstream of the dam maintain theirproper functions, as well as for supplying municipal water.
Managing our surroundings
We keep an eye out for any anomalies or changes to the dam lake and its bankslopes, as well as for any illegal waste disposal.
We perform monitoring studies of water quality, and flora and fauna to understand theimpact the completed dam has on the environment, and the effectiveness of thedifferent environmental conservation actions being taken.

Dam Light-Up Events<Repairing a release valve>

We hold regular light-up events as part of our effort to help vitalize our neighboring
communities.

Okiura Dam: Japan’s first multipurpose dam
Name: Okiura Dam
Purposes: Flood control, irrigation, and power generation
Type: Linear overflow concrete gravity dam◆ This was the first construction project for a multipurpose dam to belaunched in Japan.
◆ Construction began in December, 1933, and concrete casting for its mainstructure began in November 1936.
The dam was completed on March 31, 1945.
◆ 75 years since its completion, the dam remains a valuable heritage sitethat gives us a glimpse into the civil engineering technologies of the time.
At a time when supplies and materials were in short supply, engineers
applied their engineering expertise to cast the dam’s internal and externalconcrete.
◆ Now that the Aseishigawa Dam has been constructed, this dam is now
submerged in the former’s dam lake.

Okiura Dam in operation (photo taken in 1964)

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Roadside station,
Michinoko

Free resting area andadministration building

Nijinoko LakePeony garden

Nijinoko Lake
Rock Festival▲ Relax and enjoy the meals youpurchase at the food stall village in theresting area. Thank you for your kindconsideration for other guests.

▶ Furusato Shop
▶ Nijinoko Rest House▶ Food stall village▶ Free resting area and administration building▶ Kaiju no Izumi▶ BBQ area
▶ Peony garden ▶ Large playground equipment▶ Putting golf
▶ Stage tents

Food stall village(Best time to visit: mid to late June)(Scheduled for early August)Oyama noOmoshie School▲ Crowd-favorite mochimochi-doughnuts▲ Kuroishi’s B-grade
gourmet dish, yakisoba insoup

Come and enjoy Kuroishi’s
B-grade gourmet dish—yakisoba in soup—as wellas crowd favorite mochimochi (chewy-soft)
doughnuts, and crispy curry
bread. These are perfect forlunch or when you just needa little bite to eat.

Japanese erythronium
walking trail

To Mt. Hakkoda
Okawara hot springs
Josenji Temple ●Nakano Momijiyama
Nakano Shrine

Bask innature’s beauty

394

Yasuragi parking zone
●Nakano Shrine
Nakano Momijiyama(Best time to visit: late April
to early May)

Aseishigawa Dam Museum
Iwaki River Dam Central Management Office
Itadome hot
Aseishigawa Dam Management Branchsprings
Aseishigawa
Dam
Ochiai hot springs
Aoni hot102
springs

Kuroishi special support school ●(Best time to visit: mid-October to early November)

To AomoriNuruyu hot springs

102

Nijinoko Lake Park

268
To Kuroishi
town center

Aseishigawa Dam
Mt. Raizan
Kuroishi
Tourist apple farm

To Hirosaki

Kuroishiexit

Tsugaru Kokeshi Doll
CenterTo Owani exit

Nijinoko
Lake Park

Tsugaru Traditional
Craft Center

Kuroishi tourist
apple farm

Koarashiyama Kuroishi Hot Springs
Snow Festival
Snow Village Festival

Nijinoko Lake canoes

Open early September to mid-November

Tohoku Regional Development Bureau, Ministryof Land, Infrastructure, Transport and Tourism

Iwaki River Dam Central Management Office
Aseishigawa Dam Management Branch

Tsugaru Traditional Craft Center(special events area)
From early February to mid-February)

2 Aza Suginosawa, Oaza Itadome, Kuroishi city,
Aomori Prefecture 036-0404
Tel: 0172-54-8782 Fax: 0172-54-8785

URL: http://www.thr.mlit.go.jp/iwakito/
Twitter @mlit_iwakito〈Twitter〉

Other tourist destinations

Legend〈Web site〉Nature-oriented tourist destinations
Facility-based tourist destinations

Restrooms

Souvenirs

Meals

Hot spring(day trip visitorswelcome)

ParkingDam Light-Up
Aseishigawa Dam

Nakano Momijiyama

Kuroishi hot springs

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