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Technical seminar on Impacts of Technical seminar on Impacts of Infrastructure Development on Infrastructure Development on

Hydrodynamics and Water Quality Hydrodynamics and Water Quality of Deep Bayof Deep Bay

23 April 2005

Challenges for the Protection of Water QualityChallenges for the Protection of Water Qualityin Deep Bayin Deep Bay

K. L. PunDepartment of Civil Engineering, Chu Hai Post Secondary College

Deep Bay

2

~5 km

~17 km

3

4

Mangroves and Mudflat at Futian

Sha Chau and Lung Kwu Chau

Marine Park

Chinese White Dolphin Feeding

Ground

Seagrass Bed/Horseshoe Crab Area

Pak Nai SSSI

Tsim Bei Tsui SSSI

Ramsar Site

Mai Po

Seagrass Bed/Horseshoe Crab Area

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The Importance of Deep BayThe Importance of Deep Bay

• A wetland to support many different species of flora and fauna. It comprises:

inter-tidal mudflatsbrackish or freshwater marshesfish and shrimp ponds (“gei wai”)mangrove areasreedbedsseagrass beds oyster bedsstreamsbreeding habitats for birds,horseshoe crabs, dragonflies,amphibians and reptiles

• Deep Bay is a haven for migratory birds Photo courtesy of Ecosystems

Over 60,000 waterbirds in and around the Mai Po and Inner Deep Bay Ramsar Site during winter (WWF)

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• Commercial fishing

trawling

Fishing area (ha)~ 13,350 ha~ 7.3% of total fishing

area in HK

Annual catch of adult fish~ 0.5% of the total catch in HK

(AFD 1998)

• Oyster farming

oyster rafts (HK)

Oyster production (tonnes/year)

•Late 1950’s: 1,200•…•1992: 120•1993: 100•1994: 100•1995: 90•1996: 70•1997: 60•…•2000: 76•…•2004: 210 (?)

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oyster beds (HK)

The Changing Coastline of Deep BayThe Changing Coastline of Deep Bay

The total sea area in Deep Bay is reducing!

1988

1992

1995

20002001Source: Hong Kong Outdoors

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River InflowRiver InflowRivers, streams and nullahs in Deep Bay Water Control Zone:1. River Ganges (GR1)2. River Indus (IN1) 3. River Beas (RB1)4. Fairview Park Nullah

(FVR1)5. Kam Tin River (KT1)6. Yuen Long Creek (YL1)7. Ting Shui Wai Nullan

(TSR1)8. Ha Pak Nai Stream (DB1)9. Tai Shui Hans Stream

(DB2)10.Pak Nai Stream (DB3)11.Sheung Pak Nai Stream

(DB5)12.Ngau Hom Sha Stream

(DB6) 13.Tsang Kok Stream (DB8)

Source: EPD

River Indus• Affected by livestock activities and

unsewered villages• High E. coli: 78,000 count/100mL (2003)• 1990 – 2003: 88% BOD load reduction

River Ganges• Affected by livestock activities and

unsewered villages• High E. coli: 59,000 count/100mL (2003)• 1990 – 2003: 96% BOD load reduction

River Ganges at GR1

0

50

100

150

200

250

300

350

September-97

July-98

May-99

March-00

January-01

November-01

September-02

June-03

April-04

Date

Con

cent

ratio

n (m

g/L)

BOD5TKNTP

River Indus at IN1

0

5

10

15

20

25

30

35

40

45

September-97

July-98

May-99

March-00

January-01

November-01

September-02

June-03

April-04

Date

Con

cent

ratio

n (m

g/L)

BOD5TKNTP

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Yuen Long Creek• Affected by livestock activities and

unsewered villages• High E. coli: 1,400,000 count/100mL

(2003)• 1990 – 2003: 92% BOD load reduction

Yuen Long Creek at YL4

0

100

200

300

400

500

600

December-96

September-97

July-98

May-99

March-00

January-01

November-01

September-02

June-03

April-04

Date

Con

cent

ratio

n (m

g/L)

BOD5TKNTP

Kin Tin River• Affected by livestock activities and

unsewered villages, factories• High E. coli: 190,000 count/100mL (2003)• 1990 – 2003: 92% BOD load reduction

Kan Tin River at KT1

0

20

40

60

80

100

120

140

September-97

July-98

May-99

March-00

January-01

November-01

September-02

June-03

April-04

Date

Con

cent

ratio

n (m

g/L)

BOD5TKNTP

Chi Wan

Shekou

Nan Shan

Da Sha JinxiuZhonghua

Xin Zhou River

Shenzhen River

YuenLongTin Shui Wai

South West Catchment

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Discharge Location BOD kg/d

SS kg/d

Org-N kg/d

NH3-N kg/d

E.coli no./d

TP kg/d

Ortho-P kg/d

TON kg/d

Shenzhen River 97938 77817 6164 6844 2.80E+16 3062 2176 15582 Dasha River 9085 12634 625 645 5.31E+15 197 103 241 Xin Zhou River 22495 27275 1664 2064 1.75E+16 583 328 657 Shekou 9085 12634 625 645 5.31E+15 197 103 241 Jinxiu Zhonghua 60221 61684 4233 5188 3.69E+16 1707 1075 4803 Nanshan 9085 12634 625 645 5.31E+15 197 103 241 Chiwan 31950 23418 2021 2336 8.29E+15 1080 787 5594 Tin Shui Wai 3339 5519 236 156 2.22E+15 75 23 35 Yuen Long 5009 8137 346 226 2.97E+15 104 35 53 Southwest Catchment 651 1071 45 31 4.20E+14 15 5 7

TOTAL 248860 242823 16585 18779 1.12E+17 7216 4738 27455

Pollution loading in Deep Bay (HK + Mainland) – Wet Season

Source: Highways Department, SWC EIA, 2002

Marine Water QualityMarine Water Quality

DM1DM2

DM3

DM4

DM5

Total Nitrogen

0.0

2.0

4.0

6.0

8.0

10.0

12.0

Sep-97 Feb-99 Jun-00 Nov-01 M ar-03 Aug-04

Date

Concentration (mg

DM 5 DM 3 DM 1

Total Phosphorus

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Sep-97 Feb-99 Jun-00 Nov-01 M ar-03 Aug-04

Date

Concentration (mg

DM 5 DM 3 DM 1

Dissolved Oxygen

0

1

2

3

4

5

6

7

8

9

10

Sep-97 Feb-99 Jun-00 Nov-01 M ar-03 Aug-04

Date

Concentration (mg

DM 5 DM 3 DM 1

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Marine Water Quality Monitoring Results in Deep Bay WCZ – 2003

Source: EPD

Inner Deep Bay Outer Deep Bay Parameter DM1 DM2 DM3 DM4 DM5

Salinity (ppt)

16.4 18.2 21 23.4 27.1

SS (mg/L)

59.8 42.8 26.1 21.2 11

DO (mg/L)

2.9 3.6 5.3 5.5 5.3

5-day BOD (mg/L)

4.7 4 1.8 1.3 1.1

Unionised Ammonia (mg/L)

0.095 0.105 0.035 0.017 0.009

TIN (mg/L)

5.29 4.23 1.79 1.08 0.7

Total Nitrogen (mg/L)

6.32 5.01 2.07 1.28 0.85

Ortho-phosphate (mg/L)

0.443 0.373 0.139 0.064 0.04

Total Phosphorus (mg/L)

0.61 0.48 0.18 0.1 0.06

E.coli (cfu/100ml)

3800 2200 100 260 540

Sediment QualitySediment Quality

42110270UCEL1265200LCEL

13 - 5546 - 93200 - 300Measured

Arsenic(mg/kg)

Copper(mg/kg)

Zinc(mg/kg)

Parameter /Criteria

Source: Highways Department, SWC EIA, 2002LCEL: Lower Chemical Exceedance LevelUCEL: Upper Chemical Exceedance Level

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Sedimentation in Deep BaySedimentation in Deep Bay• High sediment deposition rate in the region near Shenzhen River

outlet• Sedimentation rate near Mai Po: ~ 25-30mm/year

De-silting the water channel of gei wai 17 at Mai Po in 2003

A Cooling Water Discharge Point in Deep BayA Cooling Water Discharge Point in Deep Bay

CLP Power Plant at Black Point

Pollutants:• Heated water

~6oC or higher• Residual chlorine• Biocides

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Major Infrastructure DevelopmentsMajor Infrastructure Developments

• Shenzhen Western Corridor

• Shenzhen River Regulation project

• Reclamation projects on the Shenzhen side

• A proposed project to pump the seawater from Mirs Bay to flush into the Shenzhen River through a 13 km long pipe with a pumping station at Sha Tau Kok

SWC

Shenzhen RiverReclamation

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Mirs Bay Deep Bay

Salinity

05

10152025

303540

4550

Jun-97Apr-98

Feb-99Dec-99

Oct-00Jul-01

May-02

Mar-03

Jan-04Nov-04

Date

Salin

ity (p

pt

Deep Bay Salinity (DM1)Mirs Bay Salinity (MM1)

pH

4

5

6

7

8

9

10

11

12

Jun-97Apr-98

Feb-99

Dec-99Oct-00

Jul-01May-02

Mar-03

Jan-04Nov-04

Date

pH

Deep Bay pH (DM1)Mirs Bay pH (MM1)

• Deep Bay is a semi-enclosed water body• tidal flushing is limited• exchange of water is also limited• current speeds in shallow water region are low

• High pollution loads entering Deep Bay• Increase in population in the catchment areas (HK + PRC)• High sediment load from rivers• Polluted sediments in inner bay, e.g. high heavy metal content• High sedimentation rates in inner bay• More infrastructure developments, e.g. reclamation• Two systems implemented in the waters of Deep

Bay/Shenzhen Bay – cross-border water quality issue• +

ChallengesChallenges

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Thank you!Thank you!