Wuhan University, China 21-22 November, 2008

Research on
Deterioration ofWater Quality and Its Improvement
Caused by Dam Construction in Japan〜Case Study of ISAHAYA Bay
Reclamation Project〜
Teiichi AOYAMA(青山貞一) Professor,Faculty of Environment and Information Studies
Musashi Institute of Technology(Specialty: Environmental Science and Policy

我是青山貞一
感謝邀请我来武汉大学
遇到武汉大学的大家能很高兴The Purpose of the Research
The main purpose of this research isto evaluate and examine the possibility ofanalyzing the impact of water pollution
and also the improvement of water quality
caused by the dam construction here in Japan,
by applying Spline interpolation method and3 dimensional multi layer tidal simulation method
developed by the authors.

Keyword:Environmental
Advocacy

■GEOGRAPHICAL LOCATION of the PROJECT site
is in a part of ARIAKE Sea, the dead end part of
ISAHAYA Bay in the west Kyushu Island.

Location of ISAHAYA Bay

Location of Kyusyu

LOCATION of the RECLAMATION PROJECT
in ARIAKE Sea

Location ofISAHAYA Bay

Source: Office of ISAHAYA Bay Reclamation

ARIAKE Sea

The collection
watersArea in
ARIAKE SEA
有明海の集水域

出典：九州農政局

■ISAHAYA Bay
Before constrution of Reclamation Project

Source:Environmental Research Institute, Tokyo■ISAHAYA Bay Reclamation Project Plan

Its Phisical Features

North Gate
ISAHAYA BAY
Tidal Bank
Control Pond
South GateISAHAYA of Reclamation Project(Compleation)

Source: Google Earth■ISAHAYA Bay Reclamation Project Plan
is one of the huge development projects taking
almost 40 years from the planning to completion,
totally spending about 300 billion yen.
1986
Formaly approved as a name of Isahaya Bay Disaster
Prevension Comprehensive Project・Total Project Expense: 1,35 billion yen
・Shut Down Area:
3,550ha・Reclamation land Area: 1,635ha
・Control Pond Area:
1,710ha・The completion in fiscal year 1999 is decided.
1999・Total Project Expense was doubled as 249billion yen

HISTORY of the ISAHAYA Reclamation Project
1956 The reclamation project was planned for thefirst time after WW2 for food supply difficulities
1970

South Nagasaki Region Comprehensive Plan

1982 Comprehensive Plan discontinued
1986

Name change to Isahaya Bay Disaster Prevension 40years
Comprehensive Project

1988 Name change again to ISAHAYA Reclamation
Project
1990 Starting Tidal Bank Construction
1997 Shutting the Tidal Bank

■The INITIAL PURPOSE of this projectis to develop agricultural land by shutting this back end
part of ISAHAYA Bay by constructing tidal bank(a kind of dam that separate sea water).
However,■the INITIAL PURPOSE has been changed
several times by the developers (Ministry of Agriculture,Forestry and Fisheries) and finally settled down
as disaster prevention of urban areas of Isahaya City.

ENVIRONMENTAL and FISHERY VＡLUE
Originally, ISAHAYA Bay was one of theimportant fishing area in Kyushu having nutritious
tideland with big tidal difference of ebb and flowwhich effectively purified the sea water quality
to grow and cultivate various forms of life.

Source:Environmental Research Institute, Tokyo

Environmental Educaiton in
Wetland Observation of ISAHAYA Bay

Source:Environmental Research Institute, Tokyo

The MAIN MARINE PRODUTS〜MUTSUGORO〜MIGRANTin ARIAKE Sea

TidoriSnipe

有明海の渡り鳥Migrant（Bird） Flight Routs
from Russia to Australia and New Zealand
シギ・チドリ類とよばれるものの中には、シベリアからオーストラリア・ニュージーランドまでその距離12,000ｋｍを旅するものがいる。
ISAHAYA BayMIGRANTin ARIAKE Sea
有明海の渡り鳥

Snipe and Tidori

Shut Down

the ISAHAYA Bay
Separating the Bay back end
by the huge bank
In 1997ギロチンによる諫早湾の閉め切り
１９９７年

Shutting of ISAHAYA Bay
by the Tidal Bank Construction

Source: BBC Tokyo News Report
14 April 1997

Shutting of ISAHAYA Bay
by the Tidal Bank Construction

Source: KBS Kyusu Asahi Broadcasting
30 May 2004

Pictures before and After Sutting of
ISAHAYA Bay by Sattelite of ＡＤＥＯＳ

After Sutting the Bay
27 May 1997

Before Sutting the Bay
14 December 1996

ISAHAYA of Reclamation Project

Source: Google EarthHuge Tidal Bank of ISAHAYA Project

Inland Sea Side

Pond Side

Sourece: Mr. Kozo Oshima

North Water Gate ofISAHAYA
Reclamation ProjectLocation of ISAHAYA Bay
Before constrution of Reclamation Project

Source:MoAFF

諫早湾干拓事業事業後の干潟First ENVIRONENMTALADVOCACY
AFTER Shut Down

the ISAHAYA Bay
Change of Water quality
for the 3 Pollutants(COD, Nitrogen, Photrus)

After shut dwon, it was seriously concerned about thewater quality of the newly constructed lake(water control pond) which might be heavily
affected by separating the Bay end by the huge bank.

Separating the Bay end by the huge bank

■EUTROPHICATION OCCURENCE
Actually, the eutrophication of the artificial
dam lake was estimated from the very beginningof the dam construction caused by the inflow oforganic compounds from the rivers likeHonmyo-River of Isahaya City.
However, the Ministry of Agriculture(MoA), theDeveloper, forecasted and evaluated in theEnvironmental Impact Statement(EIS) that thewater quality of the lake could satisfy the Water
Environmental Quality Standard.

In this research, the annual trend monitoring dataof the water quality of 5 monitoring points
concerning①COD②Total-Nitrogen and③Total-Phosphorus
were analyzed and evaluated in detail before andafter the dam (tidal bank) construction, which
separated the ISAHAYA Bay into sea water andartificial fresh water pond (inner bank lake).
We have applied the spline interpolation method
which configurate the point data into plane
dimensional data.

諫早湾潮受堤防内の水質観測地点

5 monitoring points for Water Quality Monitoring
Honmyou River

高来町

本 明川

Water control pond
P1

ブロックⅠ 排水門

B1
潮受堤防

ブロックⅡ

S11

諫早市

B2

森山町

P2

ブロックⅢ

川排水門

Ｎ有明

5 Monitoring
PointsTidal Bank

吾妻町

瑞穂町

Result of Water Quality(COD) Survey
in ISAHAYA Bay Pond
by SPLINE Interpolation Method(1997)
Unit：mg/L

Result of Water Quality(COD) Survey
in ISAHAYA Bay Pond
by SPLINE Interpolation Method(1998)
Unit：mg/L

Result of Water Quality(COD) Survey
in ISAHAYA Bay Pond
by SPLINE Interpolation Method(1999)
Unit：mg/L

Annual Trend of COD Concentration and its
Distribution in Control Pond from 1997 to 1999

Annual Trend of Total-N Concentration and its
Distribution in Control Pond from 1997 to 1999

Annual Trend of Total-Phosporus Concentration andits Distribution in Control Pond from 1997 to 1999

mg/L

10.0
8.0
6.0
4.0
2.0
0.0

Shutting Down 14 April 1997
ＣＯＤ
Standard 3.0

1987

1988

1997閉切前 1997閉切後

1998

1999

2000

1998

1999

2000

1998

1999

2000

mg/L

2.00
1.50

Total−Nitrogen

1.00

Standard 0.40.50
0.00

mg/L

1987
0.30
0.25
0.20
0.15
0.10
0.05
0.00

1988

1997閉切前 1997閉切後

Total−Phoshorus
Standard 0.03
1987

1988

1997閉切前 1997閉切後

Trend and Change of Water quality forthe 3 Pollutants after the shutting ofISAHAYA Bay by the tidal bank construction

Article of Tokyo Shimbun (Tokyo Press)東京新聞 2000年4月14日

www version

Eutrophication andTrend of Decresingof Fishery in
ISAHAYA Bayand ARIAKE Sea

■DRAMATIC DECREASE OF ofthe FISHERY(Fish Harvest)
It was revealed that not only the inner fresh water pondof the shut down ISAHAYA Bay, but the sea water
quality of the whole ISAHAYA Bay and ARIAKE
Sea had been gradually degraded after the constructionof the tidal bank.
This severe water quality damage caused the sudden
decrease of the fishery in ISAHAYA Bay Area.

Eco-System Damage Mechanism by Eutrophicaion
干拓事業工事による富栄養化と海洋生態系への影響

■ SHORTAGE of OXYGEN)(oxygen-deficient water)of ISAHAYA BAY
In addition to that the sand and gravel digging
caused the shortage of oxygen (oxygen-deficient water)
at the bottom of the ISAHAYA Bay. 貧酸素化

Trend of Fishery in ISAHAYA Bay
from 1985 to 1999ムツゴロウ

Construction Start!

Trend of Fishery in ISAHAYA Bay
Before and Afterof Construction and Shutting Down

Construction
Start
Shutting Down
Start

Trend of Fishery in ISAHAYA Bay
from 1985 to 1999

Question in Diet
On Fishery Decrease
Construction Start!

Trend of Shell（Tairagi) in ISAHAYA Bay
from 1988 to 1999
Red Tide
Gravel Digging

Calm Fishery

Construction Start!

Calm(Tairagi)
タイラギ

■DAMEGE OF the LAVER(SEAWEED)
of ARIAKE Sea
Further, the cause and effect concerning the damageof the laver(seaweed) cultivation had also been a big
controversy in the northern part of ARIAKE Sea.
All of these damage were caused by the constant
outflow of various pollutants from the fresh water
pond (artificial lake) into ISAHAYA Bay, whichbrought about eurtrophication and caused the damage
on ecosystem of the whole bay.

ARIAKE Sea in Kyusyu Island

Sourece: Nagasaki Bunka Hosou

有明海の海産物への影響

有明海の海苔への影響

Blue-green algae(Water-bloom)
アオコの顕微鏡写真
Anabaena and Microcystis

Agricultural Chemicals, Herbicide, and Insecticide
Scatter in ISAHAYA Reclamation Land

Fishermen
Strongly Protest
AgainstMinistry of AgricultureAfter those serious situation, the fishermen of theISAHAYA Bay and north of ARIAKE Sea area
insisted that the damage was mainly causedby the dam (tidal bank) construction and strongly
requested and protested against Ministry of Agriculture
to keep 2 water gates of the tidal bank open permanently.
The fishermen's protests had escalated to filean administrative lawsuit against the National Ministry.

Fishermen’s Protest Against Ministry (Developer) in ISAHAYA area

■ISAHAYA Bay Reclamation Project Plan

Its Phisical Features

North Gate
ISAHAYA BAYTidal BankControl Pond

South Gate

Fishermen’s Protest
Against Ministry(Developer)in ARIAKE SEA

Fishermen’s Protest
Escalated toAdministrative Lawsuit
AgainstMinistry of AgricultureNotice ofAdministrative Lawsuit
Against Ministry of AgricultureSecond ENVIRONENMTALADVOCACY
How can Improve
the quality of Waterby keeping
the Water Gates Open？

First, we have started the preparatory researchon how can improve the quality of waterby keeping the water gates open since
the tidal bank construction.
Actually, we have applied the 3 dimensional
multi-layer tidal simulation model developed
by Environmental Research Institute Inc.
(Director Teiichi AOYAMA), and simulated
the change of tidal current by the opening of
the water gates.
Because, the tidal current is one of the major control
element of the water quality in the whole bay.

■Purpose of the GATE OPEN SIMULATION
That is, we were focusing on the facts thatthe tidal current and its speed was changed
tremendously and caused the water quality
deterioration by the shut down of
ISAHAYA Bay by the tidal bank construction,
we have forecasted and evaluated theimprovement of water quality in case of
opening of the water gates.

Here, we evaluated whether it is possible
to recover the tidal speed from the zerosituation caused by the dam (tidal bank)construction, based on the principle of
C = a・Q/S.
This is the physical dispersion phenomenon
that the pollution concentration of the same
monitoring point (C) is inverse proportion
to the tidal speed (S) under the conditionof the same inflow emission quantity (Q).

Tidal Current Simulation

Phase 1:
Pre-Conditions SettingTarget Sea Area of
the Tidal Simulation
有明海
シミュレーション調査
対象範囲

Oceanic GeographicalFeatures ofthe Tidal Simulation
有明海
海洋地形平面図

3 Dimensional Oceanic GeographicalFeatures of the Tidal Simulation 有明海海洋地形立体図

Oceanic Geographical Cross Section features ofthe Tidal Simulation 有明海海洋地形断面図

Wind Rose on ARIAKE Sea(Omuta City) in 1998
大牟田市（有明海側）１９９８年度年間風配図% N
NNW 15
NNENW
NE
105
WNW
ENE
0W

EWSWESE
SW

SE
SSW

SSSE

■30 SIMULATION CASE SETTING
We have done the following cases ofthe tidal current simulation;
The difference between
before and after the construction of the dam(tidal bank shut down)(2) The difference between shutting andopening of the water gates of the tidal bank.
(3) The difference between high tide andlow tide(ebb tide)(4) The difference between the spring tideand the neap tide.
Table-1 shows the matrix of the different
simulation cases.

30 Simulation Cases Setting
大潮
中潮
小潮
干潮 満潮 干潮 満潮 干潮 満潮
ケース 1 諫早湾干拓工事前
○
○
○
○
○
○
ケース 2 諫早湾潮受け堤防工事後（閉 ○○
○
○
○
○
め切り後）
ケース 3 諌早湾潮受け堤防水門開放
3-1①北水門のみ開放
○
○
○
○
○
○
3-2
②北水門及び南水門の両方を ○
○
○
○
○
○
開放
3-3
③両門の中間にさらにひとつ ○○○○○○の水門を空けた場合

■We have done all the simulation cases
shown in previous Table-1 not only for
ISAHAYA Bay, but for whole ARIAKE Sea.
Since ARIAKE Sea is shallow and semi-closed
water area, the tides (the difference ofthe rise and fall of the sea level) of ISAHAYA Bay
is so high.
] Therefore, it is necessary to simulate for targeting
whole ARIAKE Sea in order to forecast
the tidal change of the ISAHAYA Bay.

Grid Modeling of the Simulation
格子モデル（左：潮受堤防工事前、右閉切後）

Evaluation Point of Tidal Speed and Direction
諫早湾における潮流流速の評価ポイント

潮受堤防

諫早干拓事業（西工区）

Tidal Current Simulation

Phase 2:
Reproduction Analysis

Reproduction analysis before 30 case
Simulation現況再現：流速の実測値と計算値の比較（工事前後：大潮期、上げ潮・下げ潮最強時）
cm/秒
90

工事前上げ潮工事前下げ潮閉め切り後上げ潮
閉め切り後下げ潮

8070
大潮期流速 計算値

60504030
201000

10 20 30 40 50 60 70 80 90
大潮期流速 実測平均(1998〜2000,各1月)
cm/秒Survey Data of Tide in the Isanaya bay
工事前

流況実測図（大潮時）

閉め切り後

上げ潮最強時：平成元年１月

上げ潮最強時：平成１２年１月

下げ潮最強時：平成元年１月

下げ潮最強時：平成１２年１月

Image of Tidal Current Simulation
潮流シミュレーションイメージ
Initial StageEntrance
Open Sea of the Bay湾口
外洋

Back Endof the Bay
湾奥

初期状態

水深海底地形Image of Tidal Current Simulation
潮流シミュレーションイメージ
外洋部分に潮汐による変化を与える

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
物理法則に従って水が移動し水位が変化

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
Rising Tide
上げ潮

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
Rising Tide
上げ潮

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
Rising Tide
上げ潮

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
湾奥まで水位が上がり、外洋では潮が下がり始める

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
Lowering Tide
下げ潮

海底地形

Image of Tidal Current Simulation
潮流シミュレーションイメージ
Lowering Tide
下げ潮海底地形Image of Tidal Current Simulation
潮流シミュレーションイメージ
風による影響も考慮（有明海では潮汐の影響が大きい）

海底地形

現況再現シミュレーション流況図（大潮時）
工事前

閉め切り後

上げ潮最強時上げ潮最強時下げ潮最強時下げ潮最強時潮位変化の現況再現シミュレーション
cm
250
200
150
100
50
0
-50-100
-150
-200
-250
0.0

諫早湾外の潮位

1.0

2.1

3.1

4.1

5.2

6.2

7.2

8.3

9.3

10.3

11.4

10.3

11.4

時間
柳ノ瀬戸
三角cm
250
200
150
100
50
0
-50
-100
-150
-200
-250
0.0

富岡
口之津

島原
竹崎島

三池
大浦

住ノ江

諫早湾内の潮位

1.0

2.1

3.1

4.1

5.2

6.2

7.2

8.3

9.3

時間
湾口

湾口と堤防の中間

調整池外堤防寄り調整池内Tidal Current Simulation

Phase 3:
Simulation Results

Whole Simulation of Ariake Sea After Shut Down
完全閉め切り後（中潮）（満潮）（干潮）CASE１：
諌早干拓工事前（中潮満潮）
BeforeShut Downケース１：
諌早干拓工事前（中潮干潮）

Case２：
完全閉め切り後（中潮満潮）
Afer Shut Down

ケース２：
完全閉め切り後（中潮干潮）

Case ３−１：
水門１つ開放（中潮満潮）
North GateOpen

ケース３−１：
水門１つ開放（中潮干潮）

Case ３−２：
水門２つ開放（中潮満潮）
2Gates Open

ケース３−２：
水門２つ開放（中潮干潮）

Case３−３：
水門３つ開放（中潮満潮）
3Gates Open

ケース３−３：
水門３つ開放（中潮干潮）

Tidal Current Simulation

Phase 4:
Evaluation of the Results

Conclusion
By summing up, as a results of our simulation,

it became clear that the tidal current recovered
to the status of before constructing the tidal bank(shut down of the Bay)by opening the 2 water gates.
This means there were some possibility ofwater quality improvement from physical pointof view as well as improving the eutrophicationof the Bay area.

However, it is quite difficult to recover the healthy
and nutritious ecosystem of the mud flat (tideland)
once lost by the dam construction by just opening
the water gates.
Further, it is also uncertain that the fisherywill be recovered fully by the opening of thewater gates, because the condition of oxygen-deficientat the bottom of the Bay will not be physically improved.

mg/L

ＣＯＤ

Total−Nitrogen

mg/L

2.00
1.50
1.00
0.50
0.00

0.30
0.20
0.10
0.00

Total−Phoshorus

mg/LOpenning Gate 2008 (Simulation Results)

10.0
8.0
6.0
4.0
2.00.0

2007

2000

1999

1998

1997閉切後1997閉切
前

1988

1987

Standard 3.0

1997閉切
後

1998

1999

2000

2007

1997閉切
後

1998

1999

2000

2007

1997閉切
前

1988

1987

Standard 0.4

1997閉切
前

1988

1987

Standard 0.03

Trend and Change of Water quality forthe 3 Pollutants after the opnning gates of
ISAHAYA Bay tidal bank

Article ofAsahi Shimbun(Asahi Press)
朝日新聞 西部本社
2001年3月13日

■Finally the Local Court Direct
2 Gates Open Immediately on the Judegment
It is obvious that the further counter measuresfor environmental quality improvement
should be taken by the Ministry.
Under these circumstances,

the SAGA Local Court gave a rulingthat the water gates of the tidal bankshould be opened immediatelyon the judgement of 28 June 2008

謝辞
Many Thank for listning my Presentaion!
<References>
1) Teiichi AOYAMA, Yukio ONISHI, Atsushi TAKATORI
and Komichi IKEDA,
Tentative Evaluation of the Water Quality Monitoring
Survey for the Control Pond of ISAHAYA Bay, 9, Jan.
2001
2) Teiichi AOYAMA, Atsushi TAKATORI,
Research on Forecasting and Evaluation ofTidal Current in ISAHAYA Bay under Condition ofOpening of Water Gate, 2, April 2001