Horikawa Sen-nin Chosatai 2010 （HSC) Place：
Nagoya Urban Institute
Summary meeting for the 24th stage
Conference room (11 floor)th

The secretariat of Horikawa Sen-nin Chosatai 2010
Feb.23rd.2019

1

1. Horikawa Sen-nin Chosatai 2010
～Transmission of Raw Water from
Kiso Riveｒ～

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

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

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

Transmission of Raw Water from Kiso River
3 years from April.22nd.2007（Stopped on March.22nd.2010）
To verify the clarification effects of TRWKR
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 Cheering Groups Cheering
clarification of Horikawa

The survey froma viewpoint and asence 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 house.

3

Water Environment of Horikawa River
Area of basin: 51.9km2
Length: 16.2km(Tidal effect section 13.6km)

Change in temperature, precipitationand hours of sunshine
Cause of breedingofpphytoplankton,
nitorogen andphosphorus areincluded inwastewater fromhouses, factories
andstores.

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.

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
Red Tide

Kiso River is our water source.

●●●●●● ●●●●●●

Shonai River
Privisional raw watertransmission: 0.3m3/s

●●●

●●●

●●●

Wastewater
Treatment Plant

Tide Gate

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 Sludge

4Observation method at fixed-point
Measurement of Transparency
Transparency
Meter
100cm
Photo: Shinko Survey Group

Measurement of COD
COD: Chemical Oxygen DemandThis is an index of water contamination
used for sea, lakes, and marshes.
It is an oxygen consumption required foroxidation of organic matters dissolved inample water.
The higher COD, the more it iscontaminated.

COD Pack Test
What is yourimpression of…
Clearness?
Transparency?
Color? Bubbles?
Smell? Garbage?
Living things?

ゆりの会調査隊

5

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, was polluted in rapid economic growth..
The citizens have rised to get the past back.
名古屋駅

Start

Now

22nd Apr.2007

23rd Feb.2019

Fixed Point
Observation
Groups55 groups
497 persons

101 groups
1,010persons

Free Survey
Groups

22 groups
234 persons

40 groups
650 persons

Horikawa
Cheering
Groups

88 groups
1,531 persons

2,598 groups
51,920 persons

Total

165 groups
2,262 persons

2,739 groups
53,580 persons

6

Number of Participants◆ Fixed Point Survey Group (FPOG) ・・・・・・・1,010
surveying on the fixed points◆ Free theme Survey Group (FSG) ・・・・・・・・・・650
surveying on free themes◆ Horikawa Cheering Group (HCG) ・・・・・・・51,920
supporting clarification of Horikawa
total 53,580

As of Feb. 23rd, 20197

3. Survey Periods and Number of Reports
Survey Period
Utilization ofshallow
groundwater
At upstream fo
Kitashimizu bridge

With TRWKR

Introduction of advanced
water treatment
at the Meijo Water Treatment Center
Increase of Transmission
Volume fromthe Shonai River

In-service of Horikawa
Ugan Rain-Water
Reservoir for pollution control
Utilization ofreclamed wastwaterfrom Moriyama
Water Treatment
Center from Apr. to
Oct.
At upstream of
Seko Bridge

At upstream of
Sanage Bridge
Covered sandAt upstream of
Shiga Bridge
At upstream of
Nakatodo Bridge

1st stageinterval
2nd stageinterval
3rd stageinterval
4th stageinterval
5th stageinterval
6th stageinterval
7th stageinterval
8th stageinterval
9th stageinterval
10th stage
interval
11th stage
interval
12th stage
interval
13th stage
interval
14th stage
interval
15th stage
interval
16th stage
interval
17th stage
interval
18th stage
interval
19th stage
interval
20th stage

23rd stage

Spring～Early summer/Apr.22nd～Jun.30th.2007
Jul.1st～Sep.7th.2007
Autumn～Early Winter/Sep.8th～Dec.16th.2007
Dec.17th.2007～Mar.31st.2008
Spring～Early summer/Apr.1st～Jun.30th.2008
Jul.1st～Sep.27th.2008
Autumn～Early Winter/Sep.28th～Dec.16th.2008
Dec.17th.2008～Mar.31st.2009
Spring～Early summer/Apr.1st～Jun.30th.2009
Jul.1st～Sep.26th.2009
Autumn～Early Winter/Sep.27th～Dec.16th.2009
Dec.17th.2009～Mar.31st.2010
Spring～Early summer/Apr.1st～Jun.30th.2010
Jul.1st～Sep.11th.2010
Autumn～Early Winter/Sep.12th～Dec.17th.2010
Dec.18th.2010～Mar.31st.2011
Spring～Early summer/Apr.1st～Jun.30th.2011
Jul.1st～Sep.10th.2011
Autumn～Early Winter/Sep.11th～Dec.16th.2011
Dec.17th.2011～Mar.31st.2012
Spring～Early summer/Apr.1st～Jun.30th.2012
Jul.1st～Sep.21th.2012
Autumn～Early Winter/Sep.22th～Dec.16th.2012
Dec.17th.2012～Mar.31st.2013
Spring～Early summer/Apr.1st～Jun.30th.2013
Jul.1st～Sep.28th.2013
Autumn～Early Winter/Sep.29th～Dec.17th.2013
Dec.18th.2013～Mar.31st.2014
Spring～Early summer/Apr.1st～Jun.30th.2014
Jul.1st～Sep.28th.2014
Autumn～Early Winter/Sep.29th～Dec.16th.2014
Dec.17th.2014～Mar.31st.2015
Spring～Early summer/Apr.1st～Jun.30th.2015
Jul.1st～Sep.19th.2015
Autumn～Early Winter/Sep.20th～Dec.16th.2015
Dec.17th.2015～Mar.31st.2016
Spring～Early summer/Apr.1st～Jun.30th.2016
Jul.1st～Sep.19th.2016
Autumn～Early Winter/Sep.20th～Dec.16th.2016
Dec.17th.2016～Mar.31st.2017
Spring～Early summer/Apr.1st～Jun.30th.2017
Jul.1st～Sep.18th.2017
Autumn～Early Winter/Sep.19th～Dec.20th.2017
Dec.21st.2017～Mar.31st.2018
Spring～Early summer/Apr.1st～Jun.30th.2018

interval

Jul.1st.2018～Sep.19th.2018

24th stage

Autumn～Early winter/Sep.20th～Dec.16th.2018

interval
Odor control
at Shin-Horikawa
River
At upstream of
Kinjo Bridge

total

21st stage

interval
22nd stage

intervalreports

Horikawa
River

Shin-Horikawa
River

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

258
134
383
103
245
64
152
100
145
54
120
81
111
44
104
72
112
42
133
77
148
59
135
78
129
55
99
68
117
78
90
89
100
69
109
79
116
54
107

1
4
14
16
15
14
11
16
13
9
18
13
12
17
12
11
8
23

104
129
58

20
29
10
28
13

80

84
100
48
93
67

180

107

73

76

44

32

121

184

106

78

5,472

4,962

510

8

Number of Reports
5500
5000

at the end５，４７２件
of 24th stage

4000
3500
3000
Average of 200
reportsin every stage

2500
2000
1500
1000
500
0

Over 50,000 people joined in Chosatai.
Number of reports is above 5,000 in total.
第1st.
第2st.
第3st.
第4st.
第5st.
第6st.
第7st.
第8st.
第9st.
第10st.
第11st.
第12st.
第13st.
第14st.
第15st.
第16st.
第17st.
第18st.
第19st.
第20st.
第21st.
第22st.
第23st.
第24st.

report
調査報告数（件）4500

第２３ステージ終了時
5,472
reportsstage
ステージ
We got 5,472 reports in total by when 24th stage finished.
The number of reports by Shin-Horikawa River were 510 out of 5,472.
Lots of people research the water environment of Horikawa River
continually from a viewpoint and sense of citizens.

9Nagoya Local Meteorological Observatory

4. State of the weather(Overview)
From mid to late September, the autumn rain front andTyphoon No. 24 brought a lot of rain and little sunshine.
From October to early December, the temperature wasquite high, with the maximum temperature exceeding 20
C in early December.

区分

降水量
(mm)
合計

統計期間

1981
～2010

30
124.8
156.5
201.0
160.8
234.4
128.3
79.7
45.0
121.9

資料年数
4月
5月
6月

平均
9月
10月
11月
12月

in the 24th Stage(September-December)■Precipitation
Although it became more than normal in September
under the influence of the autumn rain front and thetyphoon No. 24, stable weather continued in Octoberand November. Especially October was around 20% of
the average year.
■Sunshine Hours
It became shorter than normal in September when
there was a lot of rain. In October and November there
were more sunny days, longer than normal.

最低

日照時間
(時間)
合計

1981
～2010

1981
～2010

1981
～2010

1981
～2010

30
14.4
18.9
22.7
18.7
24.1
18.1
12.2
7.0
15.4

30
19.9
24.1
27.2
23.7
28.6
22.8
17.0
11.6
20.0

30
9.6
14.5
19.0
14.4
20.7
14.1
8.1
3.1
11.5

30
196.6
197.5
149.9
181.3
151.0
169.0
162.7
172.2
163.7

Source: Meteorological Agency _ Meteorological Statistics
http://www.jma.go.jp/jma/menu/report.html
2016 20th Stage2017 22nd Stage
Average temperature(℃)■Temperature
It fell below normal in September, but has risen
above October since October. The averagetemperature of the period (September to December)was 16.1 ° C, higher than the average value (15.4 °
C).

平均

平均

気温
(℃)
最高

2018 24th Stage

Quite hightemperature
Higher temperature
continued even after
the early winter.

10

Nagoya Local Meteorological Observatory average daily temperature and precipitation

Normal value 15.4 (C)Monthly mean precipitation 151mm/monthDay with precipitation 44days
Average daily temperature 16.4℃

Temperature(C)(2017)

Temperature ave.(C)Rainy in Oct.

Temperature high(C)Low temperature
Abundant rain fall

Normal value 15.4 (C)Monthly mean precipitation 178mm/monthDay with precipitation 41days
Average daily temperature 14.7℃

24th stage(2018)

Temperature(C)Precipitation (mm)Temperature ave.(C)Dry in Oct. and Nov.

Temperature high(C)High temperature
Precipitation is average

Normal value 15.4 (C)Precipitation (mm)High temperature
Abundant rain fall

Precipitation (mm)22nd stage

Temperature high(C)Precipitation (mm)(2016)

Temperature ave.(C)Over 20℃ in Dec.

Rainy in Sep.

Precipitation (mm)20th stage

Temperature(C)Precipitation (mm)Average temperature from
October to December is highcompared to the average year.
Precipitation is high in
September. Precipitation is low
in October and November.

Monthly mean precipitation 123mm/monthDay with precipitation 51days
Average daily temperature 16.1℃

Statistical information: Meteorological bureau Meteorological information Nagoya Local Meteorological Observatory
http://www.jma.go.jp/jma/menu/report.html

Note )days with precipitation :over 0.5mm/day from Sep to Dec

11■ 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

shrimps, crabs, aquatic insects, etc.

stacks ofstones■ Rise of self-purification by food chain
dirt of water (organic substance, nitrogen, phosphorus)
Algaes and microbes stick on stones with the dirt as nutrition.
Small fishes, shrimps, aquatic insects feed the algaes andthe microbes.
Big fishes and birds prey the small fishes and aquatic insects.

It was identified that variousorganisms breed and growwhen rapids and pools wereshaped.
It was a place of inhabiting
and growing of creatures that
prefer the environment, suchas Oikawa, which has stones
and moss. When wintercomes, some ducks are
waiting for spring here.
Prawns and Japanesemitten crabs areorganisms that
migrate between
rivers and the sea.

*denizen

Waterside
kingfishers,
egrets, etc.

Watermauremys
reevesii,
trachemys
scripta*

carps, hemibarbus barbus
catfishes, black basses*,
bluegills*, northern snakeheads*

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

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

Rapids and pools shaped in
the past keep a diversity
with change according toenvironment.

Kurokawa No.1 Bridge

photo by the secretariat January in 2019
Mallard12

Newly sand-cover construction Securement of a water source Measures against smells
at Shin-Horikawa River
Bet. Sakura -Habashita Bridge(Using shallow ground water)
Jan.2015-Feb.2015,Dec.2017-Jan.2018

A well at upstream of Kinjo Bridge
started its operation in Mar 2018

Keiun Bridge(Dredging・Sand covering)
Downstream Dec.2017-May.2018

Gojo Bridge

Koshio Bridge

Habashita Bridge
School of young mullets
at the sand-covered place

Photos by the secretariat
Jan.2019
Photos : May 15, 2018

Photos by the secretariat
May 17, 201813

Countermeasure against bad smell of Shin-Horikawa-Dredging work for sludge removalArea：Upstream Tateishi Bｒｄｇ. ～ Upstream area
Term：
Sep.2018～Feb.2019

Upstream of Kinen Brdg.
Oct.5th .2018

it was the situation ofremoval sludge.

14

5. 24th stage survey report
5.1. Introduction ～Column～～Column～ For the clarification and regeneration of Horikawa River
Horikawa Sen-nin Chosatai (HSC)was established on April 22nd, 2007 for clarification and regenerationof Horikawa River, as a place for citizens’ activities (Fixed Point Observation Group, Free Survey Groupand Cheering group).
Fixed Point Observation Group examines Horikawa River to confirm the clarification effect by the water
quality improvement measure and to make clear the condition of water quality and cause of pollution, froma viewpoint and a sense of citizen. Free Survey Group studies Horikawa River from various view points.
Cheering Group supports clarification and regeneration of Horikawa River in various-free ways. These threegroups wish for clarification and regeneration of Horikawa River, and work together in a large network.
Currently(as of 23rd), there are 2,739 groups and 53,580 people in HSC. (101 groups in Fixed Point
Observation Groups, 40 groups in Free Survey Group and 2,598 groups in Cheering Group)
At the time of launch of HSC, there were 165 groups and 2,262 people. It shows that the network of
citizens wishing for clarification and regeneration of Horikawa River has expended greatly
Fixed Point Observation Group have observed 5,472 times from 1st stage to 24th stage. So far, we foundever-changing state of the water due to the influence of the tides, at the downstream from the Sanage
Bridge. And we found that a lot of observation results from the Fixed Point Observation Group can capture
the average state of water quality of Horikawa River from citizens’ point of view and sense, and understandthe tendency of the change of water quality.

15

5. 24th stage survey report
5.1. Introduction ～Column～～Column～ For the clarification and regeneration of Horikawa River～Pilot project of the clarification of Horikawa River～;we confirmed the clarification effect of TRWKR from April.2007 to March.2012
We confirmed that water quality between Sanage Bridge and Matsushige Bridge had been improved by
TRWKR(0.4m3/sec.) in this five years. And in this period, we confirmed that garbage (artificial garbage:
plastic type garbage etc.)were reduced. It is considered that because the citizen’s awareness changed,
and cleaning activity became active.
【Five years summary】■We confirmed clarification effect of TRWKR.
■Network of citizens wishing for clarification and regeneration of Horikawa River has expanded greatly.
■Citizen’s awareness changed, and the cleaning activity became active.

16

(1)Weather Condition
As the trend of weather conditions in the 24th stage (from September to December 2018), we are able tomention that amount of rainfall is usual level and temperature is high.
From middle to end of September, there was a lot of precipitation and the sunshine time was short, due to autumn
rain front and typhoon No. 24. And then, from October to beginning of December, stable weather continued,
temperature was high and the amount of precipitation was low except for early November. (In early November,heavy rainfall was observed due to the trough line and fronts.)
Especially, maximum temperature in early December exceeded 20 degrees Celsius, temperature tended to behigh. (Feature of weather in the 24th stage: High temperature and average annual amount of rainfall)(2) New Measures for Water Quality Improvement
After the stop of water conduction from the Kiso River in March 2010, new measures for water quality
improvement of Horikawa River have been implemented. Shallow and deep in upstream section of Sanage Bridge
for improvement of self-purification function has been implemented since 2010. Also, advanced water treatment
at Meijo Water Treatment Center was installed, and river rain-water reservoir for pollution control in right bank ofHorikawa River was available in 2010.
Water conduction to Horikawa River (max. 4,000 m³/day, Period: Apr.-Oct) using recycled waste water(advanced treatment/ membrane filtration method) of Moriyama Water Treatment Center) started since 2011.
Experiment of covering sand for water purification between the Naka Bridge and the Gojo Bridge started in Feb.
2015. The 8th well was dug in the upstream section of Kinjo Bridge in March 2017 and utilization of shallow
ground water (0.01m3) started as new water source. (Utilization of shallow ground water has been implemented
in 2004).
Furthermore, in reference to the results of the Horikawa River purification experiment with citizens which started
in February 2015, covering sand was carried out for waterside environment improvement of Habashita Bridge toGojo Bridge and Naka Bridge to Sakura Bridge in 2018.
Also, since deposition and exposure of sludge, air bubbles and cloudiness were confirmed in the Shin Horikawa
River junction through citizen's survey, dredging and converting sand were carried out as measures against odors.
Such a measures were also proceed in the upstream district since September 2018.
And then, new shallow and deep was formed upstream of the Kizune Bridge on the Horikawa River.

17

(3) Change of the water quality of Horikawa River
The impression of the clearness of Horikawa River worsened after stopping water conduction from the Kiso
River. However, after that, generally we can confirm the trend of improvement little by little from upstream
though water quality sometimes deteriorated due to weather conditions, etc... Espeically, it was possible toconfirm remarkable improvement trend regarding to “impression of water pollution”, “transparency” and “scent”
in the 24th stage.
The average transparency between Sanage Bridge and Oseko Bridge was more than 80 cm, and transparency
between Asahi Bridge and Oseko Bridge was around 90 cm in particular.
In addition, “bubble from bottom of river” and “percentage of ditch-smell / mud-smell” decreased, so
percentage of odorless increased to 75% between Sanage Bridge and Oseko Bridge.
As we mentioned above, some improvements were confirmed in the several clauses surveyed by citizen's
viewpoints and senses, such as the condition of the riverbed, transparency (perspective), and scent, in the mid
and downstream sections of Horikawa River in the 24th stage.
We think that reason of such a result is the change of public awareness for "purification & regeneration ofHorikawa River", implementation of new water quality improvement procedure after water conduction, andmaintenance of revetment including removal of sludge on the river channel.

18

Impression of Water Clearness（Section Average）
The ratio of “Clean”, “Slightly clean” and “Ordinary（Note）Except the data between Minatoshin Brdg. and Oseko Brdg. for not enough data

The 1st-6th stage ： With TRWKRNo rain on the day and the previous day
The 7th-24th stage： No TRWKRNo rain on the day and the previous day

New Measures for Water Quality Improvement

With TRWKR

Making shallows and deeps
Making shallows and deeps
Transmission of Raw Water from Shonai River

Covered Sand

Introduction of advanced water treatment at Meijo Water Treatment Center
In-service of Horikawa Ugan Rain-water Reservoir for pollution control
Utilization of reclaimed wastewater at Moriyama Water Treatment Center(Ｅｖａｌｕａｔｉｏｎ)（ upstream ）Influence of transmission of raw water from Shonai River単位：％

Btwn. SakaeBrdg.
and SanageBrdg.
（Not enough data)

39

93

87

50

87

100

60

100

100

100

100

100

75

100

100

100

100

100

100

67

60

100 50100

Btwn. Sanage Brdg.
and Johoku Brdg.

16

57

43

73

53

36

29

62

40

39

23

20

50

30

56

73

58

70

60

69

46

77

63

56

Btwn. Johoku Brdg.
and Asahi Brdg.
(Not enough data)
Btwn.Asahi Brdg.
and Matsushige Brdg.

Improved a little from upstream(Sometimes, the weather condition influences)
8

38

36

50

23

50

39

23

57

21

20

12

42

21

25

14

27

40

67

50

62

0

20

34

50

75

67

37

28

21

12

20

24

31

24

53

27

48

17

10

5

55

After the stop
Of TRWKR→WorsenedWith TRWKR→Improved from upstream
11

0

25

0

28

5

Btwn. Matsushige Brdg.
43
14
6
84
72
50
45
34
3
16
61
18
55
56
27
20
22
12
54
56
62 100 57
20
and Oseko Brdg
4st.
5st.
7st.
2st.
16st.
6st.
8st. 9st. 10st. 11st. 12st. 13st. 14st. 15st.
3st.
1st.
17st. 18st.19st.20st.21st. 22st. 23st. 24st.
（downstream ）Hot Hot Cold Hot Hot
Hot＊“Clean”, “Slightly clean” and “Ordinary” are categorized
as the acceptable range for citizens.

Heavy Heavy Little Heavy Heavyrain rain rain rain
rain％（Dirty）％（Clean）

Impression of water clearness could see the tendency of the improvement from upstream with TRWKR. But it worsened after the stopof TRWKR. After that, overall it improved a little from upstream. (sometimes it deteriorated by the weather condition.) It is thought that
this is the effect by change in citizen consciousness and new measures for water quality improvement after the stop of TRWKR.

19The 1st-6th stage ： With TRWKRNo rain on the day and the previous day
The 7th-24th stage： No TRWKRNo rain on the day and the previous day

Impression of Water Clearness（Section Average）
Note）Except the data between Minatoshin Brdg. and Oseko Brdg. for not enough data

New Measures for Water Quality Improvement

With TRWKR

Making shallows and deeps(Ｅｖａｌｕａｔｉｏｎ)（upstream）
Btwn. SakaeBrdg.
and SanageBrdg.

Organize thetransparency of 70cm
or more as an
acceptable of citizen

Use of shallow ground water
Covered Sand
Transmission of Raw Water from Shonai River
Introduction of advanced water treatment at Meijo Water Treatment Center
In-service of Horikawa Ugan Rain-water Reservoir for pollution control
Utilization of reclaimed wastewater at Moriyama Water Treatment Center

(cm)
57

80

63

59

42

88

55

62

55

64

67

86

71

79

85

100

71

88

52

54

58

80

71

87

68

79

58

77

64

Btwn. Sanage Brdg.
and Johoku Brdg.

（Not enough data)

87

50

41

Satisfied continuously
from 21st to 24st（Not enough data)

Btwn. Johoku Brdg.
and Asahi Brdg.

75

67

63

75

66

75

65

82

68

84

63

65

74

75

76

78

55

43

69

73

Improved a little from upstream(Sometimes, the weather condition influences)
59

74

52

45

61

65

43

50

51

57

54

57

50

56

56

74

51

75

47

40

Worsened

After the stop
With TRWKROf TRWKR→Improved from upstream→Worsened

Satisfied continuously
from 22st to 24st

53

84

61

90

60

92

52

79

65

77

60

78

57

77

60

85

65

86

62

74

67

75

74

89

59

89

56

83

54

95

56

83

57

87

48

81

58

85

56

95

54

81

47

69

53

75

45

88

Btwn.Asahi Brdg.
and Matsushige Brdg.
Btwn. Asahi Brdg.
1st. 2st. 3st. 4st. 5st. 6st. 7st. 8st. 9st. 10st. 11st. 12st. 13st. 14st. 15st. 16st. 17st. 18st. 19st. 20st.21st. 22st. 23st. 24st.
and Matsushige Brdg.
Hot
In
Hot
Hot
Hot
Hot
Hot
Hot
Cold
Hot
Little Year
Heavy Heavy Little Heavy Heavy（downstream）
Rain Average
Rain
rain
Rain
Rain
Rain
cm

cm

The transparency improved from upstream with TRWKR. But transparency worsened after the stop of TRWKR. After that, the transparency improved a little
from upstream(sometimes the weather condition influences). Considered the result of change of public awareness and the new water quality improvement
measure. Btwn. Sanage Brdg. and Johoku Brdg. , Btwn.Asahi Brdg. and Matsushige Brdg. Sutisfied 70cm of acceptable of citizen continuously.

20

The 1st-6th stage ： With TRWKR

Occurrence of bubbles from river bottom(Section Average) No rain on the day and the previous day
The 7th-24th stage： No TRWKRNo rain on the day and the previous dayNote）Except the data between Minatoshin Brdg. and Oseko Brdg. for not enough data

New Measures for Water Quality Improvement

With TRWKR

Making shallows and deeps
Use of shallow ground waterTransmission of Raw Water from Shonai River
Covered Sand
Introduction of advanced water treatment at Meijo Water Treatment Center

In-service of Horikawa Ugan Rain-water Reservoir for pollution control
Utilization of reclaimed wastewater at Moriyama Water Treatment Center(Evaluation)（upstream）
Btwn.Sakae Brdg.
And Sanage Brdg.

％
25

3

33

50

13

0

0

0

0

0

13

Though the bubbles condition got worse
depending on water conditions,
It hada31tendecy
to improve from upstream area
25
6

36

0

21

17

0

12

18

35

40

（Not enough data）

Btwn. Sanage Brdg.
and Johoku Brdg.
Btwn. Johoku Brdg.
and Asahi Brdg.

21

6

19

0

11

6

32

13

20

8

5

0

0

8

0

After the stop
Of TRWKR→Worsened
10
0
0

58

23

56

30

42

0

38

With TRWKR→Improved

0

0

0

0

0

0

0

0

0

0

20

0

0

0

13

17

22

13

27

23

8

0

0

7

0

20

0

40

17

0

0

0

0

0

0

0

31

7

24

19

18

9

21

11

62

8

（Not enough data）

Btwn.Asahi Brdg.
and Matsushige Brdg.

1358

Btwn. Matsushige Brdg. 7 3
0
0
0
14
5
0
3
5
0
7
0
3
13
5
0
0
0
0
13
8
0
5
and Oseko Brdg.
2st.
4st.
7st.
5st.
6st.
8st. 9st. 10st. 11st. 12st. 13st. 14st. 15st. 16st. 17st. 18st. 19st.20st. 21st. 22st. 23st. 24st.
3st.
1st.
In
Hot
Hot
Little Year
Rain Average（downstream）%

Hot

Hot Hot
Hot
Heavy Heavy Little
rain rain
Rain

Hot
Cold
Heavy Heavy
Rain
Rain

Hot

%

It is observed that bubbles from river bottom condition was improved with TRWKR and after TRWKR stopped, it got worse. After that, it had a tendency to improve while
bubbles condition has fluctuated repeatedly although weather conditions sometimes made it worse. It is assumed that the change of public awareness and new measures for
Water Quality Improvement after stop of TRWKR have effects on this. It seems that the condition of river bottom is gradually improved.

21

The change of ratio about “Ditch・Sludge・Smell less”

The ratio of smell type(%)

Between Sanage Bridge.-Oseko Bridge.

Ditch

SludgeThe 1st-6th stage ： With TRWKRNo rain on the day and the previous day
The 7th-24th stage： No TRWKRNo rain on the day and the previous day

Ditch & Sludge

Smell less1st.1stは
No調査なしdate

Sample size 106 210 170

50

109

62

84

67

75

113

108

98

93

82

87

62

74

82

52

65

81

61

46

85

22

(4) Water Quality of Shin-Horikawa River
We got 510 reports of Shin-Horikawa River by when 24th stage finished.(180 reports in 24th stage)
According to the reports, it has turned out that impression of cleanness is bad in upper area, many bubbles
rise from the bottom, and it always smells (the percentage of “Terrible Smell”-“Slight Smell” is 80-95%)
Impression of Cleanness in Shin-Horikawa River Impression of cleanness is especially bad in upper area.

lower area←

Impression of Smell in Shin-Horikawa River

lower area←*few reports→upper area

It smells hard in upper area, always smells from Maizuru Bridge
to Kinen Bridge and at Mukoda Bridge.

→upper area23

No ans.
[4]slightly
0%clean[5]clean5%1%[3]Neither
13%

We found the impression of cleanness of ShinHorikawa is bad in any season. We think one of thecauses is a sulphide produced at an oxygen-poorbottom sediment or bottom water, that gives off thefeatures of Shin-Horikawa; the rotten egg smell andthe white-colored.
We have to know the process of getting dirty to
improve the impression if the water cleanness of
Shin-Horikawa.
At 24th stage, Based on the result of citizen’s survey,
We took a new step to investigate how Shin-Horikawa
gets dirty.

the impression of cleanness of Shin-Horikawa
is bad in any season

The impressionof cleanness
Shin-Horikawa[2]slightly
dirty
43%

This is a feature of the water cleanness of Shin-Horikawa
Comparing Shin-Horikawa and Horikawa

・Shin-Horikawa’s features Shape and water flow)
・How does the sludge accumulate at the confluence of ShinHorikawa and Horikawa and the Upstream of Shin-Horikawa

alldata=521

The impression of cleanness
Clean～Neither

All season

Slightly dirty～dirty

19

No ans.

810Over 90% in Spring and Summer

Spring10900Summer8

92

0Autumn■Organize the features of Shin-Horikawa[1]dirty
38%•The impression of cleanness Shin-Horikawa

Ratio of “slightly dirty and dirty”
・Over 80%
・Over 90% in spring and summer
・60% even in winterＦｒｏｍ Sep.1st 2012
To Dec. 18th 2018

19

81

0

60% in winterWinter

39

0%

20%

60

40%

60%

ratio(％)•The impression of cleanness by season

1

80%

100%

24

Considering mechanism about impression ofclearness of Shin-Horikawa River
Impression of clearness of Shin-Horikawa river
is not good around the year.
The percentage of ‘Dirty’ ‘Slight Dirty’ is :・Over 80%
・Over 90% in spring and summer
・About 60% in winterSurvey results so far show that impressionof clearness of Shin-Horikwa is not goodaroud the year.
According to survey results, we organizedfeatures of the impression of cleaeness ,and considerd the mechanism of this.
Clarificating mechanism of impression ofcleaeness is the first step to consider
improvement measures for impression ofcleaeness.

Impression of clearness of Shin-Horikawa River■Color is:■Smell is:

・Like‘White cloud’ ‘red tide’ ・More terrible than Horikawa River・‘Like ditch’ ‘Rotten‘ more
more frequently than that of
freqnetnly
Horikawa River・ ‘Like ditch' ,about 50% people
・Like 'White cloud' more
answerdfrequently in spring
・ Like 'Red tide' more frequently ・‘Rotten' around the year
・‘Rotten' especially in autumn
in summer■ＣＯＤ is:■Transparency is:

・Over 20mg/L,about twice
the density of Horikwawa
River・Especially high in autumn

・64cm,equal to the value ofHorikawa River・not notable about
seasonable change

Comparing Shin-Horikawa River with Horikawa River:・About both Shin-Horikawa River and Horikawa River, percentage of 'Color' is the largest ,about 50%
・Evaluation of ‘Smell’ is larger than Shin-Horikawa River around the year
・Smell of Shin-Horikawa River is more teribble
・Percentage of ‘Transparency’ ‘Garbage’ is smaller than that of Shin-Horikawa River・COD of Shin-Horikawa River is about twice

Why do these things occur?

25

Features of water clearness mechanism of Shin-Horikawa River
weather condition ・temperature・precipitation・hours of sunshine etc.

water hardly replaces
plankton easily increasesorganic substance

Sea water

hypoxia・salt water(heavier
than fresh waterin specific gravity) sulfide is easily・plankton
generated
2・sulfur(S04 )suspended
substance settles
easily to thebottomsediment
includingorganic
substance iseasily generated■Organizing the features of Shin-Horikawa to
think of water clearness mechanism
・Feature of topography and water flow of ShinHorikawa River・Mechanism of sludge sedimentation near confluencewith Horikawa and that in upstream section・wastewater fromwater treatment center・rain water fromcombined sewer system・fresh water (lighter thansea water in specific gravity)
・warm through a year
・including organic substance,
N, P etc.
We think that water clearness mechanism of
Shin-Horikawa highly is affected by featureof topography and water flow, and feature ofurban tidal area where wastewater, which is
fresh water and water source of ShinHorikawa, and sea water is mixed.
Result of citizens’ survey let us know thewater clearness mechanism of ShinHorikawa..
We organize the feature of Shin-Horikawa
to think of ater clearness mechanism.

26

Shape of Shin-Horikawa River and Features of River water flow
Ohseko Bridge
Horikawa tidewater gate

Water lver(T.P.m)

2
1
0
-1
-2
-3
-4
-5
Sea water-6-7-8 0

Confluence with
Shin-Horikawa River

Naka Bridge.
Matsushige Bridge
Naya Bridge
Sumiyoshi Bridge
Asahi Bridge

Meijo water
treatment center Sanage Bridge.

1.20m

Mean high water level

Change in water level by tide
2.57m

-1.37mMean law water level

Horikawa River
2

1

Water lever(T.P.m)

By comparing two crosssections of Horikawa and ShinHorikawa, three features ofRiver flow of Shin-Horikawa
River can be showed in rightbox.

Sea water

4

UchidaBridgeHinode Bridge
Atsuta water
Horagai Bridge
treatment center

2
1
0
-1
-2
-3
-4
-5
-6
-7
-8 0

5

6

8

3

7

9

Horidome water
treatment center

1.20m-1.37m10

Mean highwater level

Change in water levelby tide2.57m

Mean lawwater level

11

12

13

Distance from
14 river mouth (km)(Main Features)
・River water is hard to be replaced
because the bottom of upstream area
is not high・River water is hard to be replaced
especially when the change of tide is
not often
・Water of bottom layer in upstream area
is especially apt to be stagnant

Note)T.P.…
“T.P.0m” mean sea level of Tokyo Bay（Tokyo Peil：T.P.）

Easy to be stagnant

Ref：River development Plan ofHorikawa River Area
p.43 Cross section of Horikawa River
Distance fromp.44 Cross section of
6 river mouth (km)Shin-Horikawa River

Shin-Horikawa River
1

2

3

4

5

27

HYPOTHESIS : How sludge accumulates around junction and upstream
Junction with
Horikawa River

Temmacho & Atsuta
Wastewater Treatment
Plant

2

Ushimaki
Pump Station

Horidome
Wastewater
Treatment Plant

Takakura Pump
StationEnvy High Tide Level 1.20m
1

2.57m

0

Tide changes water level.
→ River water moves.

-1
Envy Low Tide Level -1.37m-2Depth [m]Two places where
sludge accumulated
heavily werereported in the 23rd
Meeting.
We makehypothesis about it.

→ River water below theebb tide hardly moves.

-3

Sludge accumulates aroundjunction and upstream

-4
-5

Why？

Accumulated Sludge

Accumulate
d Sludge(Around Junction)● The width of the river enlarges, which makes
waterflow slower and more suspended materials to sink.
-7 ● Suspended materials from upstream accumulate.
● Suspended materials from Horikawa Riveraccumulate.

-6

-8 0

500

1000

1500

2000

2500

3000

3500

Distance from junction [m](Upstream)● Suspended materials in theeffluent of wastewater treatment
plants and the overflow fromcombined sewer tend to sinkeasily.
4000

4500

5000

5500

6000

28

of clearness in Shin-Horikawa River is not good all year round. Because
Why is the impression of clearness not Impression
river bottom of Shin-Horikawa River is low to upstream from downstream, it is thoughtthat the bottom water in the lower layer is always stagnant, and it is difficult for thewater to be replaced. For this reason, the upstream area where effluent water from
Good all year round?
water treatment center and suspended substance associated from rain water by（hypothesis）
Mechanism of contamination in the
upstream area of Shin-Horirawa River
Bad smell occurrence（smell of the rotten egg）

Hydrogen sulfide(H2S)

combined sewer system is an environment that tends to settle and accumulate on
bottom river. And it is thought that poor oxygenation of water and mud of bottom isadvanced. In the area, it is considered that a large amount of sulfide is generated,causing milky and bad smell, and it is a factor that deteriorates impression of clearness.

Fresh water(Warm all year round)

Milky＝Blue white

Diffusion

Sulfied（mostly H2S,HS-）
reacts with Ｏ２ &ＣＯ２ tocolloid formation sulfide(including organic
substance)

Suspended
substance(including organic
substance)

2Ｈ2Ｓ+O2→2S+2H2O
2Ｈ2Ｓ+CO2+Sun→CH2O+2S+2H2O

Sea water

Floating mud with manyorganic substances

Sinking

A flow occurs that lifts the bottom
layer sea water to the face
→Sea water and fresh water mix
・Flocculation…suspending
・Oxidation of sulfide…milky

Sea water→Sludge generation
Deposited in the mud and water
Sulfied（Ｈ２Ｓ，ＨＳ－etc）

ＳＯ42(Including
Sulfate ion)・Effluent water fromwater treatment center・Rain water by combined
sewer system

Dissolved
substance

Consumption of oxygen accompanying decomposition of organic
substance, etc. and colloid formation of sulfide.

Poor oxygenation of water and mud of bottom

Sulfate reducing bacteria（mostly in mud）
＊bacteria that like environment without oxygen

Sulfate reducing bacterium produce hydrogensulfide (Ｈ2Ｓ) etc. ,with organic substance(Properties of hydrogen sulfide)
decomposed and sulfate ion(ＳＯ42- ) reduced. ・Heaviar than air ・Specific gravity 1.1905
ＳＯ42-＋Organic Substance→Ｓ2-＋Ｈ2Ｏ＋ＣＯ2
・Colorless, water soluble ・mild acidity
Ｓ2-＋Ｈ+→ＨＳＨＳ-＋Ｈ+→Ｈ2Ｓ

29

（Reference）
Create of Sulfide by sulfate−reducing bacteria
inflow of organic substance→Lack of oxygen of the bottom waterand sludge→Sulfide(H2S, HS-, etc.)

Inflow of organic substance
Water

Blue and white
2Ｓ（colloid）

Ｈ2 O
decomposition oforganic substanceＯ2

Ｏ2
Consuming
Ｏ2 oxygen

Ｏ2

SludgeSulfide(H2S, HS-, etc.)
Ｏ2

Ｏ2

Ｏ2

Ｏ2

decomposition oforganic substance

Sea water

ＳＯ42sulfate−reducing bacterialack of oxygen

30

(5) Change of Horikawa river by the regular ship’s sailing
We think that the impression of the clearness of Horikawa River is improved that if sailing of the ship becomes frequent, water ofHorikawa river is stirred regularly, and environment of the bottom of a river improves because oxygen continues being supplied to thebottom of a river, and bubble, bad smell and muddy white decrease.
We carried out general survey to examination ship’s sailing of Nagoya city（Autumn Cruise; 24th from 23rd and18th from November 17,2018）and investigated the change of Horikawa river by the examination ship’s sailing from a viewpoint and sense of citizens.

The expectation for the effect of the water quality improvement by
the regular ship’s sailing

Boat Asahi Bridge～Gojo Bridge～Nayabashi Bridge
Keun Bridge

伝馬橋方向

Past discovery of citizens■Main viewpoint When a ship moves・・・
Trail

Water Area is stirred. In this way, it is reported that the bottom sludge rolls
up, and the water of Horikawa river becomes gray. In addition, when bubbles
such as the hydrogen sulfide exist in the bottom sludge, bubbles may appear
with sludge raised up on the surface of the water, and the causative agent of
the smell may be released by the atmosphere. Therefore, the impression of
the clearness of Horikawa River may worsen temporarily.

now
Water area

temporarily
stirring

stirring

Photos：Kawasemi survey group

stirring

bubblebubblebubbleBottom sludge

Bottom sludge

Bottom sludge

When a ship is sailed regularly・・・
Water Area is stirred regularly.
When the bottom sludge is rolled up, the bubbles such as hydrogen sulfide of the bottom sludge arereleased in the atmosphere regularly, and it is thought that the quantity of bubbles of the bottom sludge
decreases than the present conditions.
Furthermore, when a ship is sailed regularly in the future, water area is stirred continuously, andsuspended substance (including organic substance) becomes the environment where it is hard to deposit,
and oxygen continues being supplied to the bottom of the river.
In this way, the state of the bottom of the river is improved little by little (the sulfide decreases, andsulfide of the bottom sludge decreases), and we think that the impression of the clearness of Horikawa
River is improved more.

Nishiki Bridge

Photos：River Planning Division survey group

Ship Nayabashi
Bridge～Shiratori～Miyanowatashi
普通船
納屋橋～白鳥～宮の渡し間

Regularly stirring
Water area

Water area

Gojo Bridge

Trail
Trail

Hioki Bridge
Photos：River Planning Division survey group

Atsutakinen Bridge Photos：Chikyu-kurabu survey group

We expected that when the quality of the water was
worsened by decreasing the Transparency orsmelling bad, when a ship was sailed temporarily inHorikawa river, sludge was raised up by the stirringwith the screw. However, it was not confirmed
temporarily that the hoist of remarkable sludge andthe bad smell by the examination ship’s sailing, andthe impression of the clearness of Horikawa River
was not worsened. Our expectation was disappointed
in a good meaning.
On the other hand, it was confirmed that bubbles
were generated to the trail, and those bubbles was
hard to clear away.
Why? This reason researches as a future problem.

31

■ Problems
We believe that we need to continue to check and analyze the state of Horikawa in some conditions suchas a season, a ship, a section and frequency to understand the effect of water quality improvement byregular operation using the results of this general research as a reference.
We also think that measures such as using more biodegradable cleaners properly in daily lives and businessactivities are needed to control the bubbles in the river.

Bubbles produced by a sailing ship

Photos : Nov. 23rd, 2018(6)Creatures
The secretariat found barnacles (at the upper of Horikawa
River from Sannou Bridge) and families of bivalves (at thelower of Horikawa River from Nishiki Bridge) attached to theedge of the water in river walls and abutments using by the
information from a party of Kojo, Horikawa and daily lives
survey group. They can’t move by themselves once they get
their places. Growing of these creatures proves that oxygen
dissolve continuously in the water. We can say from thecondition of these creatures that water quality of Horikawa isimproving. In addition, we found common kingfishers and mullets
in the upper side of Shin-Horikawa where measures for the badsmell such as a removal of sludge has been carried out.

A common kingfisher

Mullets
about 20cm long32

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.

33