Horikawa Sen-nin Chosatai 2010 （HSC)

Summary meeting for the 27th stage

Place：
WILL AICHIBig Conference room

The secretariat of Horikawa Sen-nin Chosatai 2010
Oct. 10th. 2020

1

1. Horikawa Sen-nin Chosatai 2010
〜Transmission of Raw Water from
Kiso Riveｒ (TRWKR)〜

The formation of HSC (April.22nd.2007)
With a viewpoint and a sence of citizens, the survey of theclarification effect of TRWKR started

1.Purpose
To verify the clarification effects of TRWKR with citizens(1)Develop to new clarifying measures(2)Asses the influence on an ecosystem(3)Sustain and enhance citizens activities(4)Develop citizens awareness in the entire
Horikawa River basin

2.Water source and Volume oftransmission of raw water(1)Water Source : Kiso River(2)Volume of transmission of raw water : Maximum 0.4 m3/s

■ The survey from a viewpoint and a sence of citizens＊Clearness ＊Transparency ＊Color ＊Bubble ＊Smell＊Garbage ＊Living things, etc

3.Pilot project period(1)Evaluation and Survey term : About 5 years（from Apr.2007 to Mar.2012）(Including the term of follow-up survey and evaluation after
the stop of TRWKR)(2)TRWKR period : about 3 years(from Apr.22nd.2007 to Mar.22nd.2010)■Increase of Transmisson Volume from the Shonai River(additional pilot project）
1.Water source and Volume of transmission of raw water(1)Water Source : Shonai River(2)Transmission Usual 0.4m3/sec (maxium 0.7m3/sec)

2.Period of Increase(1)Experiment Period ： Oct.1st - Dec.31st.2010(2)Period of Increased Transmision Volume : Oct.5th - Nov.2nd.2010

The first Nagoya City
Environmental Practice Prize,
Feb.2012
Branch of contribution for
Regional Environment
Development Award
for Excellence

Water Resource Contributor
Awards
Minister of Land,
infrastructure andTransportation) Aug.20162

Transmission of Raw Water from Kiso River (TRWKR)
3 years from April.22nd.2007（Stopped on March.22nd.2010）
Surveys during TRWKR period :April.2007 〜 March.2010
Surveys after the stop of TRWKR period :April.2010 〜 March.2012

Horikawa Sen-nin Chosatai
April.2007 〜 March.2012■ Fixed Point Observation Groups
Surveying effects of TRWKR■ Free Survey Groups Researching
Horikawa River by free themes■ Horikawa Support Groups Supporting
clarification of Horikawa

The survey froma viewpoint andsense of citizens

Results of pilot project (Clarification effects of TRWKR)■ It was confirmed that the water quality tended to improve
during TRWKR between Sanage Bridge and Matsushige
Bridge.
■ Network of citizens who wish for clarification andrestoration of Horikawa River expanded.
■ Citizens awareness of cleaning of the river wasdeveloped.

■ Role of Horikawa Sen-nin Chosatai(Conclusions of Summary Meeting for the 10th Stage)① More surveys should be implemented.
・Continuity of investigation, clarification of thesituation of the river, identification of cause ofpollution in the river, are needed.
・We improve our plan and take action against
the pollution.
・After that, citizens and public administration
do what is possible to clean the river.

②There are many things that citizens
can do.
・We expand our partners who love
Horikawa River and hope TRWKR again.
・We deepen exchanges with people
living in the basin of Kiso, Nagara, and Ibi
River.
・We check the effects of pollution
removal from domestic wastewater andimplement it in each residence.

3

Won the21st Japan Water Award Minister of Land,
Infrastructure and Transport Award June 2019
Public-private academic
collaboration step-up partnership

Ａ

Ｐ

Plan
ActionCitizen's viewpoint
and sense

Do

Ｃ

Check

Ｄ

Horikawa Sen-nin Chosatai Executive Committee
visited Mayor Kawamura to report getting a prize on theJapan Water Award and Minister of Land, Infrastructure,
Transport and Tourism award.

On June 25, 2019, the award ceremony for the 21st Japan Water Awards
was held in the presence of Crown Prince Akishino. Horikawa Sen-nin
Chosatai Executive Committee received the Minister of Land, Infrastructure,
Transport and Tourism Award.

National Museum of Emerging Science and Innovation(Ome, Koto-ku, Tokyo)

4

Water Environment of Horikawa River
Area of basin: 51.9km2
Length: 16.2km

Change in temperature, precipitationand hours of sunshine
Cause of breedingof phytoplankton,
nitrogen andPhosphorus areincluded inwastewater fromhouses, factories
and stores.

Kiso River is our water source.

The primary cause of water pollution is wastewater from houses, factories, and stores.
Wastewater is discharged after treatment in wastewater treatment plant.
●●●

After heavy rain, wastewater isdischarged without treatment.

●●●

Red Tide●●●

Shonai River
Privisional raw watertransmission: 0.3m3/s

●●●

●●●

●●●

Wastewater
Treatment Plant

Tide Gate
It has looked like redtide or blue tide.
In Nagoya Port anddownstream ofHorikawa, it is said
that phytoplankton
does over breedingand extinction, so
water basin is polluted●●● ●●●Sanage Bridge

Motoiri Sluiceway▼High Tide Horikawa River
Difference of water level is more than 2m between
high tide and ebb tide.
Water level, direction of current and velocity are changed, by tide.

▼Ebb Tide

Nagoya Port

Shimizu wakuwaku-sui

Groundwater, etc

RisingIse Bay
Blue Tide

Sludge rises and floats.

Floating Sludge

Raised Sludge52. Number of Participants ofHorikawa Sen-nin Chosatai(Horikawa Sen-nin Chosatai started
accepting participation on 26th Mar.2007)

Investigation spots

Network of citizens who wish for clarification
and restoration of Horikawa River is growing.

More than 50 thousand citizens network
Horikawa, the Mother River of Nagoya, waspolluted in rapid economic growth.
The citizens have rised to get the past back.

Nagoya Station駅

Start

Now

22nd Apr.2007

10th Oct.2020

Fixed Point
Observation
Groups55 groups
497 persons

10７ groups
1,043persons

Free Survey
Groups

22 groups
234 persons

40 groups
650 persons

Horikawa
SupportGroups

88 groups
1,531 persons

2,605 groups
52,022persons

Total

165 groups
2,262 persons

2,752 groups
53,715persons

6

Number of Participants
Horikawa Sen-nin Chosatai was established to clean Horikawa River and tocheck the effective of experiment for it by city citizen s viewpoint.
This activities are not only to surveys, but also spread to the clarification,cleanup, enlightenment activities and exchanges between regions.

Total 53,715
Fixed Point Survey Group(FPOG) 1,043
Free theme Survey Group(FSG) 650
Horikawa Support Group(HSG) 52,022

Activity in three categories◆ Fixed Point Survey Group (FPOG)
Investigate by city citizen’s viewpoint and sense◆ Free theme Survey Group (FSG)
Survey on free themes◆ Horikawa Support Group (HSG)
Support clarification of Horikawa

10ｔｈ.Oct.2020

7

3．Survey Periods and Number of Reports
Content

Fiscal year

Survey Period
1st stage

Horikawa River Purification Social Experiment

2007

With
TRWKR
0.4
m3/s

2nd stage
3rd stage

2008

2009

2010

2011

2012

Publicprivate
academiccollaboration
step-uppartnership

Autumn - Early winter9/20 - 12/16

Interval

12/17 - 3/31

104

9/8 - 12/16

Interval

12/17 - 3/31

Spring - Early summer

4/1 - 6/30
7/1 - 9/27
9/28 - 12/16

Interval

12/17 - 3/31

5th stage

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/26

6th stage

Autumn - Early winter9/27 - 12/16

Interval

12/17 - 3/31

7th stage

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/11

8th stage

Autumn - Early winter9/12 - 12/17

Interval

12/18 - 3/31

9th stage

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/10

10th stage

Autumn - Early winter9/11 - 12/16

Interval

12/17 - 3/31

11th stage

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/21

12th stage

14th stage

16th stage

18th stage
19th stage

2016

Autumn - Early winterAutumn - Early winter17th stage

2015

7/1 - 9/7

4th stage

15th stage

2014

4/22 - 6/30

IntervalInterval

13th stage

2013

258
134
383
103
245
64
152
100
145
54
120
81
111
44
104
72
112
42
133
77
148
60
139
92
145
70
113
79
133
91
99
107
113
81
126
91
127
62
130

Spring - Early summer

20th stage

Autumn - Early winter9/22 - 12/16

Interval

12/17 - 3/31

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/28

Autumn - Early winter9/29 - 12/17

Interval

12/18 - 3/31

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/28

Autumn - Early winter9/29 - 12/16

Interval

12/17 - 3/31

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/19

Autumn - Early winter9/20 - 12/16

Interval

12/17 - 3/31

Spring - Early summer

4/1 - 6/30

Interval

7/1 - 9/19

Reports
Reports
Horika ShinHorika
ShinContent
Fiscal year
Survey Period
wa Horikawa
wa Horikawa
River
River
River
River
21st stage
Spring - Early summer
4/1 - 6/30
258
129 100
29
7/1 - 9/18
Interval
134
58
48
10
2017
22nd stage
Autumn - Early winter9/19 - 12/20 121
383
93
28
12/21 - 3/31
Interval
103
80
67
13
23rd stage
Spring - Early summer
4/1 - 6/30
245
180 10773
7/1 - 9/19
Interval
64
76
44
32
Public2018
24th stage
Autumn - Early winter9/20 - 12/16 184
152
106
78
private12/17 - 3/31 108
Interval
100
67
41
academiccollaboration
25th stage
Spring - Early summer
4/1 - 6/30
145
193 127
66
step-up
Interval
7/1 - 9/19
54
101
43
58
2019
partnership
26th stage
Autumn - Early winter9/20 - 12/16 214
120
105
109
Interval
81
123
67
56
27th stage
Spring - Early summer
4/1 - 6/30
111
333 168
165
Interval
44
2020
28th stage
Autumn - Early winter9/20 - 12/16(plan)
104
Interval
72
112
Total
6,544 5,539 1,005
42
133
77
To date, 6,544 reports have been148
reported. Of these, the number of reports
Background about COVID-19
59
1
for Shin-Horikawa River was 1,005.
2020
135
4
In the 27th stage, there were 333
1/16 It was confirmed infected person in78
14
reports. Of these, 168 were reported forJapan.
129
16
Horikawa River and 165 were reported for
2/27 Prime Minister requested temporary
55
15
Shin-Horikawa River.
99
14
closure of school.
On average, more than 400 surveys are
68
11
4/7 A state of emergency was announced conducted every year in Horikawa River117
16
in 7 prefectures.
and Shin-Horikawa River.
78
13
4/10 A state of emergency was announced
Many citizens are continuously examining
90
9
in Aichi Prefectures.
the actual water environment of Horikawa
89
18
4/16 A state of emergency was announced River and Shin-Horikawa River on a daily
100
13nationwide.
basis from the perspective and sense of69
12
13 prefectures were determinedthe citizens.
109
17
under special precautions.
In the 27th stage, a state of emergency
79
12
5/31 A state of emergency was lifted.
was announced for prevention of spread
116
11
6/19 Self-restraint of move acrossof COVID-19.So survey groups stopped
54
8
prefectures was relaxed.
or worked avoid 3Cs (※), their active
107
23
8/16 Prefectural emergency was84

20

was restricted.

announced in Aichi Pref.
8/24 Prefectural emergency was lifted.

※ 3Cs ： Close space, crowded places, closecontact8

Total Number of Reports
6,544 reports at theend of 27th stage
Include 1,005 reportsof Shin-Horikawa River

More than 400
reports are issued
every year

Over 50,000 people joined in Chosatai.
The total number of reports reached more than 6,500.

9

４．State of the weather
Overview
In the 27th stage, the temperature was high in May and June,especially the temperature in June was the highest on record since
they started record in 1891. The rainfall was as same level as typicalyear. The rainy season started on June 10th, as same as typical year.

Nagoya Local Meteorological Observatory
http://www.jma.go.jp/jma/menu/report.html■temperature
The average is 19.5℃, which was a little higher than typical year (18.7℃).
It was low in March and high in May and June. Especially in June it was
1.9 ℃ higher than typical year, and it was the highest on record since they
started record in 1891.
■rainfall
The Average rainfall was 159mm, as same level as typical year(160.8mm).
It was lower than typical year in April and May but higher in June. The rainyseason started on June 10th.
■daylight hours
The average daylight hours was 211 hours, which was about 30 hours
longer than typical year(181.3 hours). It was longer than typical year in
every month in the 27th stage.

ave18.7℃
The average in 27 stage is 19.5℃, which
was a little higher than typical year.
In 27th stage it was lower in March and higher in May
and June than typical year. Especially in June it was
1.9 ℃ higher than typical year, and it was the highest on
record since they started record in 1891.

average temperature in April, May and June from 1981 to 2010average 18.7℃

10Weather conditions

Changes in periodic average precipitation （Spring-Early summer）(April to June)

230

65

98

128
155

111
135

158
133

21st.
May

118
146
172

200
145
219

19st.

72

15st.

April

149
196

64

13st.

131
149

144
200
56

11st.

214
254
194

331
171

259
112

184
167

210

199
212
229

9st.

27st.

25st.

23st.

0
17st.

27st.

25st.

23st.

21st.

19st.

17st.

15st.

13st.

11st.

9st.

7st.

5st.

3st.

0

100

7st.

100

200

188
240

145 159

119

126

148

5st.

114 118

300

3st.

133

400

128

Average 160.8mm 188

123

June

During the 27st., it was less than Climate
Normal(CN) in April and May.
In June, it was higher than CN.

30

185

220

203 204

Precipitation(mm/month)

213

200

500

During the 27st., the average of monthly Precipitation
was 159 mm. It was about the same as CN.

1st.

Precipitation(mm/month)

300

May

600

April-June Climate Normal(CN) (1971-2010)
Average 160.8mm

500

April

Changes in monthly precipitation （Spring-Early summer）

1st.

600

400

Meteorological Agency ̲ Meteorological Statistics, Nagoya Local Meteorological Observatory
http://www.jma.go.jp/jma/menu/report.html

Precipitation

April-June climate normal(CN)(1971-2010)
Average 181.3 hours

255

268

164

214

219
179

214
176
128

154

181
145

129

121

198
225
223
221
211
190

251

274
220

282

214

220

214

135 170
178

163

235

253

195
173
162

219
184

241

50
27st.

25st.

23st.

21st.

19st.

17st.

15st.

13st.

0
11st.

27st.

25st.

23st.

21st.

19st.

17st.

15st.

13st.

11st.

9st.

7st.

5st.

3st.

0

June

100

9st.

50

150

7st.

100

200

5st.

Average 181.3 hours

122

175 181173 173

250

3st.

150

187

175

215 207 222 211

225

180

200

208

207

206

209

300

1st.

250

During the 27st., the average of monthly sunlight hours was 211
hours. It was about 30 hours longer than climate normal(CN).

Sunlight hours (mm/month)

Changes in average sunlight hours during
the period̲Spring-early summer (April-June)

300 during the period̲Spring-early summer (April-June)

1st.

Sunlight hours (hours / month)

Changes in average sunlight hours

During the 27st., it was longer than Climate Normal(CN) in all

of April, May and June. It was 58 hours longer than CN
Sunlight hours months
especially in April.

11

(Reference) Daily temperature and precipitation
Rainy season: Around June 7Note)Arrangement of the characteristic ofweather in the target period■ Average temperature (℃)
Average temperature-Climate Normal(CN)Over 0.5 ° C→ high temperature
Under -0.5 ° C → low temperature■ Average precipitation (mm / month)
Average precipitation-Climate Normal(CN)Over 20 mm / day→ heavy rain
Under -20 mm / day → light rain

21st stage

Characteristic: Many sunny days,
high temperature and light rain

Rainy season: Around June 7

Characteristic: The weather changes every few days
Record high temperature(cap), heavy rain(cap)23rd stage
12

５．Main Water Quality Improvement Measures
Measures

2007

2008

2009

2010

2011

2012

2013

2014

1st.

3st.

5st.

7st.

9st.

11st.

13st.

15st.

2st.

4st.

6st.

8st.

10st.

14st.

12st.

16st.

New Water Quality Improvement Measures

TRWKR(0.4m3/s)
Making shallow and deep(Improvement of self-

Kurokawa No.1 Bridge〜Meoto Bridge

downstream
Kurokawa No.2 Bridge

upstream
Kurokawa No.2 Bridge

purification function and water enviroment)

Increase of Raw Water transmission from Shounai
River (＋0.4m3/s)
New water resource(from shallow ground water)(0.0805m3/s)*provisional raw water transmission from Shonai River 2001.Jul〜

Max0.3m3/s

upstream Tsujie Bridge 0.01m 3/s(2004)
upstream Kizune Bridge 0.01m 3/s(2005)

upstream
Seko Bridge

upstream
Sanage Bridge

0.01 m3/s

0.01 m3/s

Shimizu wakuwaku water 0.0005m3/s(2008)

Experiment of sand covering for water purification
Habashita Bridge〜Sakura Bridge(water's edge along both banks)

Gojo Bridge〜Naka Bridge

Remove bad smell at Shin-Horikawa River（dredging,sand cover）
Reclaimed wastewaterat the Moriyama Water Treatment
Center(0.046m3/s)
Advanced water treatment
at the Meijo Water Treatment Center
Horikawa Ugan

Rain-water Reservoir for pollution control
Facility for advanced primary treatment

Last year 9th well was dug
atupstream of Kurokawa
17st.
19st.
21st.
23st.
25st.
27st.
No.1
Bridge for using
20st.
18st.
22st.
24st.
26st.
28st.
shallow
grand water to
New Water Quality Improvement Measures
Horikawa
River (0.01m3/s).
upstream
downstream
upstream
downstream
Rurikou Bridge
Shinbori Bridge
Meoto Bridge
Kizune Bridge
Horikawa Sagan Rain-water(donated by Johoku Lions Club)
Reservoir for pollution
control and Facility for
upstream
upstream
upstream
upstream
Kurokawa No.1 Bridge advanced primary treatment
Kinjo Bridge
Shiga Bridge
Nakatsuchido Bridge
0.01 m3/s
0.01 m3/s
at Meijo Water Treatment
0.01 m3/s
0.01 m3/s
Center was put into service
Gojo Bridge〜Naka Bridge
Habashita Bridge〜Gojo Bridge Naka bridge〜Sakura Bridge
for improvement of combined
sewer system.
2015

Measures
TRWKR(0.4m3/s)
Making shallow and deep(Improvement of selfpurification function and water enviroment)

Increase of Raw Water transmission from Shounai
River (＋0.4m3/s)
New water resource(from shallow ground water)(0.0805m3/s)
Experiment of sand covering for water purification
Habashita Bridge〜Sakura Bridge(water's edge along both banks)
Remove bad smell at Shin-Horikawa River（dredging,sand cover）
Reclaimed wastewaterat the Moriyama Water Treatment
Center(0.046m3/s)
Advanced water treatment
at the Meijo Water Treatment Center
Rain-water Reservoir for pollution control
Facility for advanced primary treatment

2016

2017

downstream area

2018

2019

2020

upstream area

Horikawa Sagan※Advanced water treatment
at the Tsuyuhashi Water Treatment Center

Meijo Water Treatment Center
Horidome Water Treatment Center13

■ Shaping of Rapids and Pool
Kingfishers, egrets, tortoises, etc.
Fishes such as
carps, gibels,
hemibarbus barbus

Small fishes suchas pale chubs, Fries of palechubs etc.
rhinogobius
Stacks of stones

Shrimps, crabs, aquatic insects, etc.

It was identified that variousorganisms breed and grow when
rapids and pools were shaped.
This place has been a habitat oforganisms that like cobble
stones.
In winter, some ducks are
waiting for spring here.

*denizen

Waterside
Kingfishers,
egrets, etc.

Dirt of water (organic substance, nitrogen, phosphorus)

Prawns and Japanesemitten crabs areorganisms that
migrate between
rivers and the sea.

Algaes and microbes stick on stones with the dirt as nutrition.

Big fishes and birds prey the small fishes and aquatic insects.

Mauremys
reevesii,
trachemys
scripta*

Carps, hemibarbus barbus
catfishes, black basses*,
bluegills*, northern snakeheads*■ Rise of self-purification by food chain

Small fishes, shrimps, aquatic insects feed the algaes and the microbes.

Water

Kingfisher
January,2020

Gibels, pale chubs, goby minnows,
rhinogobius, mosquitofishes*, etc.

Palaemon paucidens, prawns,
Japanese mitten crabs, aquatic insects, etc.

The components of dirt in water are
taken up by living things in the foodchain and consumed for growth andreproduction.
As the riffles and pools is formed anda diverse and affluent ecosystem isbuilt, more dirt components are
consumed in a chain and removed
from the water, cleaning the water.
The purifying effect of the river will
increase.（＝Increased self-cleaning
effect）

Gray wagtail
April,2020

Photo：Secretariat Aprill,2020
Kurokawa No.2 Bridge downstream

The riffles and pools, which
was formed in the past,maintains its diversity whiletransitioning according to theenvironment.

Photo：Secretariat May,2020
Meoto Bridge downstream

14

Coverd sand construction
Btwn.SakuraBrdg. and HabashitaBrdg.
Jan.-Feb.2015,Dec.2017-Jan.2018

Measure against foul odors
Secured water sourcein the Shin-Horikawa ｒiver(Use of shallow ground water)(Sludge dredged・Coverd sand)
Upstream well in Kurokawa No.1 Brdg.
Section:Downstream
Mar.2020 operation

KeiunnBrdg.

Period:Nov.2017ーMay.2018

ＧｏｊｏBrdg.
KoshioBrdg.

Clean well water
0.01m3/s
ＨａｂａｓｈｉｔａBrdg.

State of middle stream moving on seawall construction（Including sludge dredged)

Photo：secretariat Ｍａｙ.2020

TennmaBrdg. area

FuruwatariBrdg. area

TennnouBrdg. area

ShinsuzakiBrdg. area

15

Countermeasures against bad odorof Shin-Hori River : Sludge Dredging
Section : Tateishi Bridge - Upstream End
Period : Sep 2018 - Feb 2019
Removed sludge
looked like thispicture.

Installed Devices after TRWKR■Improvement of Treatedwater Quality
Meijo Wastewater Treatment Plant installed filtration devices andimproved quality of treated water.
Meijo Wastewater
Treatment Plant
・Installed Device: Mechanical Filter
・Operated since: May 2010

■Preventing the outflow of debris into rivers

Upstream ofKinen Bridge
Oct 2018

Before設置前

overflow intorivers

Debris in sewage overflow
into rivers when heavy rain.

Rainwater without debris
overflows into rivers.

■Installation of
Narrower Slit Screens

Summary of the HSC's survey : 18th meeting

・Shirotoribashi Punp Station
・Nakajima Pump Station
・Chitose Wastewater
Treatment Plant◆Interval of Slits
40mm → 25mm

Debris Guide Device

Afterwastewater
treatment
plants

Debris in sewage are led totreatment plants andremoved.

16

Facilities which started operation after the stop of TRWKR■Control of combined sewer overflow
Reduce volume and frequency of overflow from sewer outlets inrainy weather condition by temporarily store first flush of which
pollution load is highHorikawa-River right bank Rainwater Reservoir
for pollution control
3
Volume 13,000m
Started operation in Sep. 2010

Horikawa-River right bankRainwater Reservoir
for pollution control
Horikawa-River left bankRainwater Reservoir
for pollution control

Subject area of Rainwater Reservoir
for pollution control

Horikawa-River left bank Rainwater Reservoir
for pollution control
Volume 14,000m3
Started operation in Nov. 2019

Horikawa-River right bank reservoir
Horikawa-River left bank reservoir

17

Advanced Facility for simple treatment in Horidome Water Treatment Center

Examination of using ground waterfor Shin-Horikawa River

Started in Mar. 2019

Combined Sewer System in rainy day■Summarize information ofgroundwater capable to use forShin-Horikawa■Review model cases of using groundwater for river clarification

Less than certain amount of rainwater istreated with wastewater in water treatment
center, but more amount is directly
discharged into the river.

Rain-water Reservoir for pollution
control is the facility temporally storing
the initial rainwater (= first flush whichis particularly dirty).
Accumulated rainwater in the reservoir isdelivered to the water treatment centerfor treatment after rain stops.
Raw water

Filtered
water
Upper
screenFiltrationmaterial

Waste cleaningwater tank

There are many water springs in basement floor of
Tsuruma Library. One of springs is abundant (more than
100 litters/min. (fluctuated) ) and water quality is good.

Source:25th HSC Conference(Report by Nagoya City)
Advanced Facility of simple
treatment * can remove morecontaminants from rainwater(excess of normal treatment).

treatment flow
Garbage removal device
set in sewer outlet
Sewer outlet(reference)Well Water of Tsuruma Library

Water Treatment Center

Rain-water Reservoir forpollution control

Advanced Facility ofsimple treatment

Shrinkage of rainwater
screen slit in pumping station
Pumping Station(Source)Website of Nagoya City Waterworks and Sewerage Bureau
https://www.water.city.nagoya.jp/category/mizukankyoukoujou/2096.html*By replacing
sedimentation tank tofiltration facility, water
quality improves
substantially comparedwith conventional simple
treatment.

(Source)Website of Nagoya City Environment Bureau
http://www.city.nagoya.jp/kankyo/page/0000089008.html

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5. 26th stage survey report〜Column〜 For the clean-up and regeneration of Horikawa River
Horikawa Sen-nin Chosatai (HSC)was established on April 22nd, 2007 for clean-up and regeneration of Horikawa River, as aplace for citizens activities (Fixed Point Observation Group, Free Survey Group and Support group).
Fixed Point Observation Group examines Horikawa River to confirm the clean-up effect by the water quality improvement
measure and to make clear the condition of water quality and cause of pollution, from a viewpoint and a sense of citizen.
Free Survey Group studies Horikawa River from various view points.
Support Group supports clean-up and regeneration of Horikawa River in various-free ways. These three groups wish for cleanup and regeneration of Horikawa River, and work together in a large network.
Currently(as of Oct.10.2020), there are 2,752 groups and 53,715 people in HSC.
(107 groups in Fixed Point Observation Groups, 40 groups in Free Survey Group and 2,605 groups in Support Group) At thetime of launch of HSC, there were 165 groups and 2,262 people.
We can see that the network of citizens who wish to purify and regenerate Horikawa-River has expanded significantly.
（Reference. Survey group registration status p.7〜8）
We will explain the status of activities of Fixed Point Observation Groups. The Fixed Point Observation Groups carried out
6,544 observations. It has become clear from the surveys so far that the state of the water area changes from moment tomoment due to the ebb and flow of the tide at the downstream section ( tidal section )from the Sanage Bridge in Horikawa
River. Since Fixed Point Observation Groups made many observations from the perspective and sense of thecitizens(Observation in various places, tide conditions, and time zones), we are able to grasp the average condition of thewater quality of the Horikawa, and trends in that change become clear. (Reference: 3. Survey period / number of reports ofsurvey results̲p.9-10)-Pilot project of Horikawa River clean-up from Apr. 2007 to Mar. 2012 confirmed the effect of TRWKR In 5 years pilot project of Horikawa River clean-up, it was confirmed that the range of improved water quality due to TRWKR
0.4 /sec was about between Sanage Bridge and Matsushige Bridge. And in this period, it was confirmed that the amount ofwaste artificial waste : plastic waste was reduced. This is probably because the public awareness has changed due toincreased cleaning activities.
【Summary of 5 years pilot project】■Confirmed the effect of clean-up between Sanage Bridge and Matsushige Bridge due to TRWKR■The network of citizens who wish to clean and revives the Horikawa River has been expanded■Citizens awareness of clean-up improved as cleaning activities became active

19

The weather of the 27th Stage(2020: in April(Apr.)〜 June(Jun.)) ⇒ In order to prevent the spread of the new coronavirus,
Aichi Prefecture issued its own "Aichi Prefecture Declaration of state of emergency" on April 10, and then the national government
declared official "state of emergency " between April 16 and May 31. The activities of the HSC team were forced to cancelled, or
carried out with prevention of confined space, dense state, close contact. So its activities were limited.
In addition, we think that evaluation of this survey is not enough at this time, for example such as study of impact for decline insocial and economic activities due to new coronavirus. According to further investigations, we think that it is necessary to
reorganize as necessary.
(１) State of the weather (Ref: 4. Weather condition etc.̲p.11-16)
In the 27th stage (from April to June), the temperature was high in May and especially June, the highest temperature since thestart of statistics in 1891 was recorded in June. Precipitation amount was almost usual. And rainy season was started on June
10th. It is also same as normal.
(Feature of the 27th stage weather, etc.) ・ The average temperature is slightly higher than normal.
・ Highest temperature was recorded from start of statistics
・ Precipitation amount was almost usual.

(2) Implementation of new water quality improvement measures(Ref: 5. Implementation status of main water quality improvement measures̲p.15-20)
After the TRWKR was stopped Mar. 2010 , new measures were implemented to improve the water quality.
Last year (Reiwa 1, 2019), ninth well (0.01 m3 / s) was dug upstream of Kurokawa No. 1 Bridge of Horikawa River to use
shallow groundwater, and water conveyance to Horikawa River started.
In addition, left side bank rainwater retention pond and the simple treatment advanced facility of the Meijo Water Treatment
Center have started operation to improve the combined sewerage system.
Regarding to the Shinhorikawa River, dredging and sand covering of the river channel were carried out near the confluence in2017 as a countermeasure against bad odors, and similarly, dredging of the river channel was carried out as countermeasureagainst bad odors in the upstream section in 2018.
And then, In March 2019, the Horidome Water Treatment Center started the operation of simple treatment advanced facility.

(3) Change in water quality of Horikawa River
The water quality of the Horikawa deteriorated after the suspension of TRWKR. However, there is a general gradualimprovement trend from the upstream, except temporal deterioration due to weather conditions, etc.
At 27 stages, there was a marked improvement tendency especially in "impression of water stains", "smell" and "bubbles fromthe river bed". Regarding to improvement of "impression of water stains", between Asahi Bridge and Oseko Bridge wasremarkable. Especially between Matsushige Bridge and Oseko Bridge, the ratio of "good" or "neither" was totally 73%.
Also, between Sanage Bridge and Oseko Bridge, odors and sludge odors decreased, along with the decrease of "bubbles fromthe riverbed and the ratio of odorlessness increased to 84%.
As we mentioned above, in the 27th stage, some clauses checked by human senses such as "smell",were improved along with
the improvement of the condition of the riverbed in the middle and lower stream of Horikawa River.
We believe that this is effect of changes in public awareness aimed at clean-up and regeneration of Horikawa River, and theimplementation of new water quality improvement measures after the suspension of TRWKR.

20Impression of Water Clearness
The ratio of Clean , Slightly clean
and Ordinary
Improvement
Less than 50%(=bad)LittleRain

Hot
LittleRain

In Heavy Hot
Hot
Heavy Hot
Rain Little Heavy Year Rain
Rain Rain Average

Heavy
Rain

In
Little Heavy Hot
Hot
Hot Little In
Heavy Rain Year Rain Rain Little Year
AverageRain Average
Rain

Hot

Hot Cold Hot
Hot
Hot
Hot
Heavy Heavy Little Heavy Heavy
Rain Rain Rain Rain Rain

Hot

Hot

Hot

The ratio of Clean , Slightly clean and Ordinary
Improvement
Improvement

21

Bubble
TRWKR

Ratio of bubble generated from bottom

The effects of sludge on the riverbed
and record high temperatures

TRWKR

Improvement
Improvement

Ratio of Ditch, Sludge,Ditch & Sludge,Smell lessditchsludgeDitch & sludge

Smell lessComposition ratio of kind of smell

Between Sanage Brdg. ‒Oseko Brdg.

22

(4)About the longitudinal change in water quality of Horikawa River（Reference：6.2.10. 4 About the longitudinal change in water quality of Horikawa River̲p.71〜76）
We sorted out the longitudinal change in Horikawa River, the place where the impression of water stains is remarkably bad, and the points
of interest for future research.
As a result, it was found that the areas around Kitashimizu Bridge, Tennozaki Bridge-Nakatsuchido Bridge, Oto Bridge-Shinsuzaki Bridge,
and Goryo Bridge are bad.
■Near Kitashimizu Bridge…Focus on river width
Nakagawa Canal drainage
widens (flow velocity slows down and suspends(Matsushige Lock opened)
things settle down), the environment of dirt easily
From Nakagawa Canal drainage■ Impression is
accumulates on the riverbed.
to Horikawa River
remarkably bad place
Matsushige Lock opened■Near Tennozaki Bridge-Nakatsuchido Bridge…
130000 /day
■ For future research
Focus on the tip of the tide and the riverbed thepoints of interest
environment where dirt is easily accumulated.
(Agglomerates and precipitates of pollutants)
Tide■Near Oto Bridge-Shinsuzaki Bridge…Focus on
impact of drainage from the Nakagawa Canal.
Downstream side
Upstream side
From the Kiso River■Near Goryo Bridge…Focus on the influence of theafter the water conveyance
Shin-Horikawa River.
is stopped

11years

Dirty 〜 A little dirty

Can t say either 〜 Clean(Spring〜early summer：average value)

Meoto

・
Meijo Water Treatment Center
Release

Shiga

Kitashimizu

JohokuNakatsuchido

Koshio

Gojyo

Tenma

NishikiNakagawa Canal drainage(Matsushige Lock gate opened)

Tennonzaki・Main points

Shinsuzaki

Hioki

Sanno

Oto

・
Confluence ofShin-Horikawa river

KameyaAtsutaMemorial

Number ofsurveyGoryo

80％ ormore badOseko

7,9,11,13,15,17,19,21,
23,25,27stage(From the Kiso Riverafter the water
conveyance is stopped,Spring〜early summer：
April〜June) The day
before fall with andwithout rain.
Number of survey：1066

・・

Shonai river
Tide boundary23

(5) The effect of drainage from the Nakagawa Canal(Data) The stop of Tsuyuhashi C 17,19,21 stage
The operation of Tsuyuhashi advanced water treatment facility
23,25,27 stage* Spring〜early summer：April〜July,
We focused on theWith and without rainfall（Ref. : 6.2.11. the effect of drainage from the Nakagawa Canal̲p.77〜82）
We compared the three years before and after the operation of the Tsuyuhashi
water treatment center(The advanced water treatment facility: H29.10〜)
As a result, it was found that the impression of clearness" in Horikawa river improved after the operation of Tsuyuhashi
water treatment center.We need to continue to investigate to clarify the mechanism by which the impression of clearness
in Horikawa river has improved.

effect of drainage
from the Nakagawa
Canal from Oto
Bridge to
Shinsuzaki Bridge.

Impression of clearness

Smell
Color

24

(6)Changes two years after sludge dredging of Shin-Horikawa River(Data)
Horagai Bridge - Maizuru Bridge
before dredging 23th stage
after dredging 25th&27th stage
both rain and no rain

Sludge dredging was carried out as a measure against bad odors for
Shin-Horikawa River in 2017 and 2018. We compared the result of
before and after dredging in the upstream.

2 years after dredging(27th stage)

Comparison before and after dredging■No significant changes in theimpression of clearness wereobserved

Shin
Horikawa -Hrorikawa
Makizuru
Kinen
MukaidaHoragai
Tateishi■"slightly smell" and "no smell"increased at Mukaida Bridge that is in
the middle section. We believe thatsludge dredging improved "Odor" and"Colour".

Confirmation of the effect of sludge
dredging requires continuous investigation
and arrangement until the riverbed becomesstable.

image diagram

ＥＣＯドコ応援隊
fixed point observation at Mukaida Bridge

Mukaida Bridge

Color

Odor

sludgedredging2018 Sep- 2019 Feb(Bridge)

Mukaida Bridge

no smellslightly smell increased.

クラゲの仲間：2014 Oct -2020 Jun
http://www.eco-doco.jp/meiko̲line/html/01.html

Milky decreased.

It has improved.

It has improved.

after dredging

after dredging

Color■The proportion of Bubbles from riverbed, "terrible smell" and "smell" wasincreased at Maizuru Bridge andKinen Bridge. We think that river bed
remains unstable after sludge
dredging.

Sludge dredging improved"Odor" and "Color" aroundMukaida Bridge.

We found the flock of mullets, eels, andjellyfish in the upstream section in the27th stage. We believe that the dredging
of sludge on the riverbed has improved
oxygen in the water.

25

(7) Compare Horikawa River and Shin-Horikawa River

Floating material (sludge scum)

We have organized the issues regarding the differences and characteristics of the impression of water(Data)13,15,17,19,21,23,25,27stage,
stains on the Horikawa River and Shin-Horikawa River.
No rainfall on the day before or on the day

Organize the impression of water stains (citizen's sense) and their characteristics■Impression of water stains
Shin-Horikawa River is
not better than Horikawa River ★
（Characteristic）
・Horikawa River Ａ(Habashita Brdg.〜Tennozaki Brdg.)…The existence of sludge and the hoisting of sludge
・Horikawa River B(Shinsuzaki Brdg.〜Oseko Brdg.)…Phenomenon derived from the existence of seawater・Shin-Horikawa River …Presence of sludge (sludge scum) and generation of sulfide

Comparison of main items (Composition ratio)
Horikawa River
Ａ
Ｂ
Shin-

Habashita Shinsuzaki Horikawa
Brdg.〜
Brdg.〜River
Tennozaki
Oseko
Brdg.
Brdg.

Dirty〜
A little dirty

★

87%

74%

61%

Color

66%

57%

Smell

8%

5%

63%
13%

Bubbles

Bubbles from the bottom of the
river

37%

3%

37%

Floating material(Sludge Scum)

Existence rate

5%

1%

54%

Cloudy

34%

26%

58%

Color

Red tide-like

5%

13%

6%

Sludge-like
Bad smell〜smell

24%

17%

8%

29%

17%

43%

30%
20%

16%

31%

13%

6%

Impression
Evaluation

Color

The number of data

Issues■Horikawa River
The impression of water pollution in Horikawa River may
worsen depending on the weather conditions, but it isgradually improving with the implementation of new water
quality improvement measures.
Horikawa River's issue is to improve the presence ofsludge-like sludge that tends to accumulate on the riverbed
near the tip of the tide and the situation in which it rolls up.
It is awaited to implement measures to reduce sludge
redemption, such as removal of sludge due to revetment
maintenance and improvement of combined seweragesystems.

Smell

The number of data

■Shin-Horikawa River

Gutter odor

Smell
Types

Sludge odor
Rotten egg odor

3%

1%

28%

Odorless

44%

64%

31%

The impression of water stains on the Shin-Horikawa River
is not as good as that on the Horikawa River. The daily
deterioration of "color" and "smell" derived from sulfide
generated at the bottom of the river seems to further
worsen the impression of water stains. Further investigation
data accumulation and organization is an issue in order tounderstand the mechanism of pollution of the ShinHorikawa River and take effective measures. Then, forexample, measures such as reducing the load in rainy
weather, improving the water cycle, and operating regular
vessels (stirring the water area) are awaited.
The number of data26

from secretariat■ Every data you offer to us is valuable
Information about subtle change you find when you survey Horikawa river can bevaluable data to understand the present situation of the river. We re looking forward
to your data from now on.
■ Let us introduce your activity
Your activity, such as survey, think and cheer up Horikawa, is the motivation toincrease the number of those who love Horikawa, Nagoya City and the Earth.
■ Let s hand down the past appearance of Horikawa as record
To know about the past Horikawa is very important to design the future Horikawa.
We refer Horikawa s pictyures taken in Taisho and Showa era to know forgotten
past Horikawa. Do you keep photos which Horikawa was photographed in in youralbum? For example, photo of your family with Horikawa in the background of thepicture is Okay.
(contact)secretariat
e-mail:2010@horikawa1000nin.jp
Please send comments and pictures (with date and place) from mobile phone orPC.
＊We think image quality of picture taken by mobile phone camera is enough.

27