Measures to make Horikawa River
LimpidImplementation by Nagoya city

Sep.29th .2013
Nagoya City Greenification &Public Works Bureau
River Dep.River Planning Div.
1

■ Reservation ofadditional water source◆ Use of shallow ground waterin the upstream of Horikawa River
Upstream of Seko Bridge

0.01m3/s

Upstream of Tujie Bridge
Sanage Bridge

Upstream of Kizune Bridge

Simizu-wakuwaku-water

0.01m3/s

0.01m3/s

0.0005m3/s

Meijo Park

Nagoya Castle
Koshio Bridge
Naya Bridge

2

■ Reservation of additional water source（fiscal year 2013）◆ At downstream of Chigomiya Bridgetransmitted into Horikawa River (0.01m3/s)

downstream ofChigomiya
Bridge.

Sanage Bride

Meijo Park

Nagoya Castle
Koshio Bridge
Naya Bridge

3■Improvement of water quality◆Improvement in theself-clarification bychanging monotone straightflow to diversionary flow
with wood piles, stones
and vegetation.

Wood piles

monotone flow

Wood piles
Wood piles
Obstaclestonesdiversionary flow
ObstaclestonesImage photo4

■Improvement of water quality

in fiscal year 2012

◆Kizune Bridge – Kurokawa No.2 Bridge
Putting stones in the river to change the flow.
Habitats for the living things and Plants werealso set under the stones.

Children also supported this activity.

Piled stones

U-shaped gutter

PVC pipes

Artificial habitat
Under piled stones

6 months later, September 20135

■ Reserve additional water resource◆ Use of reclaimed wastewaterMoriyama Water
Treatment Center

Conducting reclaimed wastewater thatwas membrane filtered in Moriyama
Water Treatment Center into Horikawa
River up to 4000㎥/day

Membrane units
Shounai
Irriegation

Horikawa River
Reclaimed wastewater was conducted during
irrigation season(Apr.-Oct.)6

■ Removal and inflow reduction of pollutants◆Garbage Catcher（near Johoku Bridge）

FY 2012 collected

1.1t7

■ Removal and inflow reduction of pollutants◆ Advanced water treatment in Meijo Water Treatment Center
Filtering equipment ,Disc Filters, removes
more fine particles remaining in treatedwater.
Averagebeforeintroduction（2007～2009）

Average(2012)

BOD

５．５

４．２

SS

３．３

１8

■ Removal and inflow reduction of pollutants◆ Control of combined sewer overflow
Rain-water reservoirs (RWR) for pollution control are constructed
for storing rainwater temporarily and decreasing pollution load.

Ozone RWR

Completed in 2006
（12,000ｍ3）

Horikawa-Ugan RWR

Completed in 2010
（13,000ｍ3）

Horikawa-Sagan RWR

Under construction（14,000ｍ3）

9

■Water quality survey with operating gate of
Shonai Irrigation Headwork
Mizuwake
BridgeHorikawa River

Shonai Irrigation
Headwork

Motoiri Sluiceway

Kita
ward

Moriyama
ward

investigated the surface
and the bottom layer ofShonai River

Hatta River
ShonaiRiver10

■ Gate Number

Left Bank①②③④Winch Gate⑤⑥１

４

Right Bank

（Right Side) 4 tilting gates（Left Side） 6 winch gates

Tilting Gate11２３

■The difference between Winter and Summer
WinterSummer

Water quality tends to bebetter when a winch gatenear left bank is open.

Water quality does notseem to depend on whichgate is open.

Mizuwake Bridge

The gap of watertemperature could
cause the different
way of mixture.

Horikawa
River
Motoiri Sluiceway

Shonai River
Winter １０℃
Summer ３０℃

Shonai Irrigation
Headwork
Kita Ward

Hatta River
Winter ２５℃
Summer ３０℃
Shonai River12

■ Result of survey
Mizuwake Bridge

Difference between surface and bottom
1 6 転
Winch
gate No.1
water temperature

average

Ligninwintersummerwintersummer

０．９－０．４５

０．２７－０．０３Hatta River
Shonai River13

■ Relation between flow
and concentration of Lignin
Lignin(mg/l)
4.0
3.5

Summer ①
夏①

3.0

夏⑥
Summer ⑥

2.5

Winter ①
冬①

2.0

Winter ⑥
冬⑥

1.5
1.0
0.5
0.0
0.0

10.0

20.0

30.0

40.0

flow(m3/s)

14

■ Relation between COD
and concentration of Lignin（Winter）

Lignin(mg/l)
9.0

9.0

8.0

8.0

7.0

7.0

6.0

6.0

5.0

5.0

4.0

4.0

y = 0.2752x - 0.44
R² = 0.8771

3.0（Summer）

Lignin(mg/l)

y = 0.2856x - 1.5169
R² = 0.7182

3.0

2.0

2.0

1.0

1.0
0.0

0.0
0

51015

20

COD(mg/l)

2530

35051015

20253035

COD(mg/l)

COD and concentration of Lignin relate each otherIn the research of both Winter and Summer.

15

■ Relation between transparency
and concentration of Lignin
Lignin（mg/l)（Winter）

Lignin(mg/l)
12.0

12.0

10.0

10.0

y = -0.1113x + 11.479
R² = 0.6344

8.0（Summer）

8.0

6.0

6.0

4.0

4.0

2.0

2.0

y = 0.0204x + 2.6563
R² = 0.0161

0.00.0020406080
Transparency (cm)

100120020406080
Transparency （ｃｍ）

100120Transparency and concentration of Lignin relate eachother in Winter but not in Summer.

16

■ Conclusion of survey
・Both the concentration of Lignin and water temperature are different
between surface and lower layer at the confluence of the Shonai Riverand the Hatta River. At that point, water from two rivers sometimes
make different layers.
・When the flow volume of the main stream of the Shonai River is morethan some extent, the concentration of Lignin of inflow into theHorikawa River doesn’t probably increase.
・The difference of water quality caused by the operation of gatesappears in winter, but does not in summer.
・Because there’s a correlation between the concentration of Lignin
and COD, the volume of inflow from Hatta River can be estimated bymeasurement of COD.
◎ We keep operating gates from the left side.
17

Removal of Sludge
・mainly around the ebb water route・completed from Shiga Bridge toShin-Horikawa River confluence：現在の断面Removing sludge on
the ebb water route18

Removal of Sludge
・removed near to the river-wall whenriver-bed excavation as flood prevention
works
completed by the place that isclose to Kameya Bridge①building river-wall：現在の断面②removing sludge
when river-bed
excavation

19