Contents

1                      Introduction                                                                          

1.1                   Project Background                                                        

1.2                   Project Overview                                                                

1.3                   Objectives of the Modelling Exercise                     

1.4                   Model Selection                                                                   

1.5                   River Network Generalisation                                     

1.6                   River Terrain Data                                                               

1.7                   Hydrological Conditions                                                

1.8                   Uncertainty Analysis in Assessment                         

2                      Identification of Water Quality Sensitive Receivers        

3                      Working ConditionS for modelling scenario of Construction Phase        

4                      Working ConditionS for the modelling scenarios for construction and operational Phase                                                              

5                      Cumulative Impacts                                                             

6                      Model Input Paramters                                                    

6.1                   Model Input Parameters for Different Working Conditions During construction Phase                                                           

6.2                   Model Input Parameters For Different Working Conditions During Operation Phase                                                                   

6.3                   Input Parameters for Water Quality Modelling under Different Working Conditions During Operation Phase                           

6.4                   Hydrology, Sediment and Water Quality Data at Different

                        Boundaries in Typical Years                                           

6.5                   Model Parameter Values                                                

 

Appendixes

Appendix A One-Dimensional Mathematical Mode

Appendix B Hourly Tidal Level recorded in the Dry and Wet Season of a Typical Year

 

1                                            Introduction

1.1                                      Project Background

In association with the development of the proposed Liantang / Heung Yuen Wai (LT/HYW) Boundary Control Point (BCP), it is proposed to train the relevant section of Shenzhen River in order to meet the required flood protection standard for the BCP.  The proposed Stage 4 of the regulation program will continue the works of Stage 3 regulation program starting from the Ping Yuen River to about 250m upstream of the proposed LT/HYW BCP (a total of about 4.5 km of Shenzhen River will be regulated) (hereafter refers to as “the Project”).  In addition, associated with the river training works about 4.5 km of the existing border patrol road and boundary fence running alongside the concerned river section are required to be realigned.  The location and alignment of the Project site is shown on Figure 1.1.

Changjiang Water Resources Protection Institute (CWRPI 長江水資源保護科學研究所) in association with ERM-Hong Kong Ltd was jointly commissioned by the Shenzhen River Regulation Office of the Shenzhen Municipal Government (深圳市治理深圳河办公室) and the Drainage Services Department of the Hong Kong Special Administrative Region (HKSAR) Government to undertake the Regulation of Shenzhen River Stage IV EIA Study in accordance with the requirements of the EIA Study Brief No. ESB-200/2009 and the Technical Memorandum on EIA Process (EIAO-TM).  In accordance with Clause 3.4.5.4 (xiii) of the EIA Study Brief, detailed methodology for water quality impact assessment shall be agreed with the Environmental Protection Department (EPD).  This Method Statement presents information on the approach for the water quality assessment and modelling works for the EIA Study.

1.2                                      Project Overview

Shenzhen River is the boundary river between the HKSAR and the Shenzhen Special Economic Zone.  In order to prevent serious flooding in the vicinity and improve the livelihood of residents on both sides, the government of the HKSAR and the Shenzhen Municipal Government have jointly completed the Shenzhen River Regulation Program Stages 1, 2 & 3 between 1997 and 2006.  About 13.67 km of Shenzhen River, starting from the confluence with Ping Yuen River to the river mouth, has been regulated under the first three stages of regulation program. 

The section of the Shenzhen River to be regulated under this Project is relatively flat, wide and winding.  The width of the river is uneven and erosion can be found along the river bed and river banks.  Some sections of the river embankment have collapsed.  The current flood prevention performance cannot meet the drainage requirements for 1 in 20 to 50 years storm of the PRC National Standard or 1 in 50 storm of the Hong Kong Standard.  Hence, there is a need to carry out the Project to rectify the flood prevention performance of this section of the Shenzhen River and to safeguard the livelihood of settlements along the river.  In addition, the regulation program will also tie in with the development of the proposed LT/HYW BCP development.

The section of the Shenzhen River to be regulated under this Project starts from Pak Fu Shan down to the confluence of Ping Yuen River.  The main works of this Project include river training, sewage interception works along the river on Shenzhen side, embankment afforestation and reconstruction of border patrol roads and boundary fences.   

1.3                                      Objectives of the Modelling Exercise

The main objective of the modelling work is to provide quantitative predictions of potential impacts of the regulation works to hydrodynamics and water quality of the Shenzhen River that will inform the impact assessment.  The specific objectives of the modelling exercise are to assess:

·           Changes in hydrodynamics: to assess the changes in hydrodynamics of the Shenzhen River such as water level and flow features caused by the Project (deepening/widening and river straightening) which may affect the water quality of the Shenzhen River during the construction and operation phases;

·           Impacts on sediment transportation: siltation of the Shenzhen River both with and without the Project;

·           Impacts on water quality during construction: to analyse the potential impacts of foundation pit drainage during construction and the water quality impacts due to re-suspension of dredged sediment; to simulate the concentration distribution of water quality indicators during the construction of the Project.

·           Impacts on water quality during operation: to simulate the concentration distribution of water quality indicators.

Figure 1.1      Project Site

1.4                                      Model Selection

An one-dimensional mathematic model of flow and sediment transportation will be used for the hydro-dynamic assessment and the sediment modelling will use unsteady flow and uniform suspended sediment transport model (see Appendix A).  This model has been used for the hydrodynamic assessment of the approved Regulation of Shenzhen River Stage III EIA (EIA-039/2000).  For water quality simulation, the AD module of MIKE II Model developed by the Danish Hydraulics Laboratory will be used, which has been applied and verified in emergency response plan study for the Three Gorges Project.

The scope of the model simulation is shown in Figure 1.2 by red line.  The main tributaries are treated as sink flows, such as the Kong Yiu Drainage Channel, Ping Yuen River, River Indus, Buji River, Futian River and Huanggang River.

1.5                                      River Network Generalisation

River network generalization will focus on the main stem of the river channel (i.e. Shenzhen River) and make the volume of river channel after generalization as essentially same as volume of actual river channel.  The tributaries along the Shenzhen River are treated as sewage outfalls.

Figure 1.2      Map Showing the Extent of One-Dimensional Model Simulation

1.6                                      River Terrain Data

The length of the simulated river segment is 18.229 km divided into 178 sections before the Project site, and 17.881 km divided into 175 sections after the Project site.  The river terrain data before implementation of the Project were measured before the wet season of 2008 and further data were obtained in 2009 (hereafter is referred to as the “existing terrain”).  After the implementation of the Project, the river terrain of the Liantang segment will use the engineering design sections and those downstream of Ping Yuen River will be based on the river terrain measured before the wet season of 2008 (hereafter is referred to as the “design terrain”).  The Yellow Sea datum ([1]) is used for all terrain and tidal elevation.  The existing terrain has 178 sections with spacing ranging from 39m to 233m.  Since some of the river sections will be straightened after the river training work, the design terrain will only have 173 sections, with spacing ranging from 52m to 185m.  The sections for predicting the water quality impact we shown in Figure 1.3.

Figure 1.3      Computational Sections for Predicting Water Quality Impact

1.7                                      Hydrological Conditions

For simulating the changes in hydrological regime, the hydrological conditions entered in the model include:

·           design peak flows at open boundaries under different frequencies; and

·           design highest tide levels at Shenzhen estuary under different frequencies.

For simulating the changes in river channel erosion and deposition, the hydrological conditions entered in the model include:

·           flow regime and siltation processes in typical years at upstream endpoint of this Project,

·           tidal processes and siltation processes in typical years at downstream Shenzhen estuary; and

·           flow regime and siltation processes in typical years of main tributaries.  

Simulation of changes in water quality differs from dry season and wet season.  The conditions entered into the model include:

·           monthly average flow regime and concentrations of pollutants of corresponding seasons for upstream;

·           monthly average lowest tide levels and concentrations of pollutants of corresponding seasons for lower boundary; and

·           monthly average flow regime and concentrations of pollutants of tributaries. 

Figure 1.4 presents the locations of the water quality monitoring stations.  

For simulating the potential impacts of sediment re-suspension during construction, hourly series of hydrology and sediment in dry season (January) and wet season (August) at each boundaries are applied.  

It is expected that maintenance dredging will be undertaken infrequently and in small scale during the operation phase of the Project.  Therefore, water quality impacts caused by maintenance dredging will not be considered in the model and will only be assessed qualitatively.

Figure 1.4       Locations of Water Quality Monitoring Stations

1.8                                      Uncertainty Analysis in Assessment

In order to study the worst case environmental impacts during construction and operation of the Project, it is conservatively assumed that all sediment re-suspended will be used in this EIA.  The total sediment leaked would be treated as intensively discharging into the water body at the same time.  In reality, this would not happen and thus will represent a worst case scenario.

2                                            Identification of Water Quality Sensitive Receivers

The water sensitive receivers (WSRs) have been identified in accordance with Annex 14 of the Technical Memorandum on EIA Process and the EIA Study Brief.  These WSRs are illustrated in Figure 2.1 and include:

·           Shenzhen River;

·           Wetland Conservation Area at Shenzhen River estuary;

·           Mai Po and Inner Deep Bay Ramsar Site;

·           Kong Yiu Drainage Channel; and

·           Ping Yuen River.

As Kong Yiu Drainage Channel and Ping Yuen River will not be affected by tidal influence, water from Shenzhen River will not intrude into these river/channel.  Hence, the water quality impact to Kong Yiu Drainage Channel and Ping Yuen River will only be assessed qualitatively.

Figure 2.1    Water Quality Sensitive Receivers  

  

3                                            Working ConditionS for modelling scenario of Construction Phase

Water will be diverted before the commencement of the soil excavation and construction works.  Both sides of the central line of the designed river course will be excavated first and the river course along the central line will be kept as “diversion dyke” which will be constructed to meet the design criterion for 1 in 5-year design period.  When the excavation works and placement of embankment foundation are carried out on one side, the river course on the other side will be used as diversion channel.  

A longitudinal cofferdam will be built at the centre of the designed river course to meet the design criterion for 1 in 5 years storm period.  The cofferdam will be made of hessian bags with clay with a width of 1m at the top and a slope in 1:1 ratio.  The surface will be laid with impermeable membrane.  Additional cofferdams will be built across the river in 200 to 300m intervals in designed river course.  

The cofferdams will be demolished after completion of the excavation works on both sides of the river and the embankment construction works.  Excavation to the designed depth will then be carried out along the central line of the designed river course during cofferdam demolition works.  Thus, the wet excavation works have the potential to increase the suspended solids (SS) concentration of the river water in the vicinity of the works area.  At present, there is no quantitative study on the amount of SS to be released during demolition of the cofferdam, which can be used as a reference.  According to the Stage 3 EIA Study, for every 1m3 of sediment/soil excavated about 25kg and 20kg of sediment will be released from an open grab and closed grab, respectively.  These sediment release rates will be adopted for the modelling exercise.  A total of 100,000 m3 of sediment/soil will be excavated along the river of which about 25,000 m3 will be excavated from each of the four Works Areas during the period of excavation (please refer to Figure 3.1 for the location of the Work Areas).  Excavation works will be carried out concurrently among Works Areas I and II and among Work Areas III and IV, respectively.  The sediment release rates from an open grab and a closed grab are calculated based on an estimated total monthly excavation volume of 10,800 m3 and 24,900 m3 from each of the four Work Areas for the wet and dry season periods, respectively.  Assuming there are 25 working days per month and 12 hours per day, the sediment release rate from an open grab and a closed grab would be 0.250 kg s-1 and 0.200 kg s-1 in the wet season and 0.576 kg s-1 and 0.461 kg s-1 in the dry season at each of the Work Areas (the corresponding daily excavation rate is 996 m3 day-1 for dry season and 432 m3 day-1 for wet season).  In the calculation it is assumed that the total excavation volume is equivalent to the total wet excavation volume and this assumption would lead to a higher sediment release rate than that would be expected from the actual works condition which involves both dry and wet excavation works.  This project will use backhoe (1m3) and long boom backhoes (0.55m3) and the sediment release rate of these backhoes will make reference to that of an open grab.  For comparison purpose, the use of closed grab will also be modelled. 

Foundation pits will be excavated for the construction of the new dykes on both sides of the Shenzhen River within the Project site.  Before the foundation pits are being filled, it is required to discharge wastewater from the pits regularly.  The foundation pit drainage, which contains certain amount of river sediment, will have the potential to increase the SS concentration of the river water in the vicinity of the works area during the construction phase.  According to the Guangdong Province Discharge Limits for Water Quality Pollutants (DB44/26-201), SS concentration in the foundation pit drainage shall not be higher than 100 mg L-1.  The recommended flow rate of the foundation pit drainage is 0.17 m3 S-1.  With the adoption of the maximum allowable value of 100 mg L-1 , the SS release rate from the foundation pit drainage is 0.017 kg s-1. (see Table 3.1).

According to the WQO for inland waters of the Deep Bay WCZ (including Ganges Subzone, Indus Subzone and other inland waters with the Study area), effluent discharge from the Project Site shall not cause the annual median of SS to exceed 20 mg L-1.  However, results of the water quality modelling show that baseline SS concentration within the Study area is well above 20 mgL-1 which limits the practicality to adopt such standard.  As effluent from the Project Site will eventually flow into Deep Bay through the Shenzhen River, the WQO for marine waters which states that effluent discharge shall not cause a 30% increase in SS level in the natural environment is used for the assessment.  This criterion can be used to determine whether the increase of SS concentration in the river water at 500 m upstream and 1000 m downstream of the Project site would cause unacceptable water quality impact.

There are no major tributaries along the section of Shenzhen River within the Project Site.  The river flow and sediment conditions are mainly influenced by Liantang River (ie the section of Shenzhen River within and upstream of the Project Site).  The sediment concentration in Liantang River water is quite high during wet season.  According to the water and sediment data of the wet season (August 2007), the average flow rate can reach 6.28 m3 s-1 with a sediment concentration of 2,418 mg L-1.  According to the statistics of the water and sediment data of the dry season (taken from January 2007), the average daily river flow of the Liantang River is about 1.57m3 s-1 and the average SS concentration is 20 mg L-1.  The SS concentrations of the water discharge from the waste sites of foundation pits and demolition of the cofferdam are significantly higher than the background SS concentration of the river.  Impact on river water quality is expected if unmitigated.  

In this EIA study, the SS concentration distribution along the river will be simulated and predicted using the 1-D flow and sediment mathematical model.  In the model, the existing river terrain will be used and flow and sediment data measured in January and August 2007 will be used as model boundary conditions.  The SS release points are generalised into four areas at Changling Village, the proposed LT/HYW BCP, Luofang Village and Ping Yuen River, respectively (see Figure 3.1).  All the data will be input into the sediment model for simulation and calculation.  Finally, the average monthly SS concentration at each defined computational section will be calculated.  The working conditions and SS release assumptions are summarised in Table 3.1.

Table 3.1 Generalised Sources of SS Release During Construction

Working condition

 

Work Site

 

SS release rate using backhoe (closed grab) – cofferdam demolition

SS release rate using backhoe (open grab) – cofferdam demolition

SS concentration-foundation pit drainage

 

Wet Season

Dry Season

Wet Season

Dry Season

1

Near Changling village

0.200 kg s-1

0.461 kg s-1

0.250 kg s-1

0.576 kg s-1

0.017 kg s-1

2

Near the proposed LT/HYW BCP

0.200 kg s-1

0.461 kg s-1

0.250 kg s-1

0.576 kg s-1

0.017 kg s-1

3

Near Luofang village

0.200 kg s-1

0.461 kg s-1

0.250 kg s-1

0.576 kg s-1

0.017 kg s-1

4

Near Ping Yuen River confluence

0.200 kg s-1

0.461 kg s-1

0.250 kg s-1

0.576 kg s-1

0.017 kg s-1

During wet excavation works for the cofferdam demolition, heavy metals (including arsenic, cadmium, chromium, copper, lead, nickel, silver and zinc), nutrients (including unionised ammoniacal nitrogen, total nitrogen and total phosphorus) and micro-organic pollutants (including PAHs, PCBs and chlorinated pesticides) may potentially be released from the disturbed/agitated river sediment.  Elutriate tests (sediment to water ratio of 1:4) were carried out on sediment samples collected from five locations (SR1, SR3, SR5, SR6 and SR8) under the EIA study to assess the potential for the release of heavy metals, micro-organic pollutants and nutrients from the river sediments as they are disturbed/agitated through wet excavation during cofferdam demolition (see Figure 3.2).  Results of the elutriate tests show that levels of all heavy metals and micro-organic pollutants are below the reporting limits.  This indicates that the release of these pollutants at detectable levels is unlikely to occur and the associated water quality impacts are thus considered negligible.  Levels of total nitrogen, unionised ammoniacal nitrogen and total phosphorus were recorded above the reporting limits, consequently, the water quality impacts associated with the release of these nutrients from the disturbed river sediments are further evaluated.

Table 3.2        Results of Elutriate Test Conducted for River Sediment

Sampling Location

Total Nitrogen

(mg L-1)

Total Phosphorus (mg L-1)

Ammoniacal Nitrogen (mg L-1)

SR1

5.8

1.6

4.63

SR3

23.2

0.4

18.8

SR5

53.8

1

12.5

SR6

12

1.5

11.9

SR8

9

0.8

6.11

River Water Concentration

7

0.6

6.98

The sewage from the work sites during the construction period will either be discharged to the foul sewer or be collected for disposal at the sewage treatment works.  Hence, sewage discharge into Shenzhen River during the construction of the Project will not be taken into consideration.

In summary, the following working conditions are set to assess the impacts on sediment and water quality during the construction phase:

·       Condition 1: The SS concentrations with cofferdam demolition and foundation pit drainage near Changling Village (Work Area I) and the proposed LT/HYW BCP (Work Area II).

·       Condition 2: The SS concentrations with cofferdam demolition and foundation pit drainage near Luofang Village (Work Area III) and Ping Yuen River confluence (Work Area IV).

The model input parameters for each working condition are summarised in Table 6.1.

 

Figure 3.1       Work Areas

Figure 3.2       Locations of Sediment Sampling Stations for the Elutriate Test. 

 

4                                            Working ConditionS for the modelling scenarios for construction and operational Phase

The changes in hydrodynamic conditions after implementation of the Project will be assessed, especially the changes in water surface profile of the river before and after the implementation of the Project.

In the hydraulic model calculations, the hydraulic elements of Shenzhen River under different design conditions (ie before and during the implementation of the Project and one to three years after operation) will be simulated.  The flood control standard before implementation of the Project is 1 in 10 to 20 years, and after implementation of the Project, it will achieve the 1 in 50 year standard.  The working conditions for the modelling are formulated as follows:

·           Condition 1: Before and during the implementation of the Project, the flood surface profile when 1 in 50 years flood encounters 1 in 50 years tidal level;

·           Condition 2: Before and during the implementation of the Project, the flood surface profile when 1 in 50 years flood encounters 1 in 10 years tidal level;

·           Condition 3: Before and after the implementation of the Project, the flood surface profile when 1 in 10 years flood encounters 1 in 50 years tidal level;

·           Condition 4: Before and after the implementation of the Project, the flood surface profile when 1 in 10 years flood encounters 1 in 10 years tidal level;

·           Condition 5: One year after the implementation of the Project, the flood surface profile when 1 in 50 years flood encounters 1 in 50 years tidal level;

·           Condition 6: One year after the implementation of the Project, the flood surface profile when 1 in 50 years flood encounters 1 in 10 years tidal level;

·           Condition 7: One year after the implementation of the project, the flood surface profile when 1 in 10 years flood encounters 1 in 50 years tidal level;

·           Condition 8: One year after the implementation of the project, the flood surface profile when 1 in 10 years flood encounters 1 in 10 years tidal level.

The model input parameters for each working condition are summarised in Table 6.2.

The variation of channel erosion and deposition after the implementation of the Project will be assessed.  The working conditions for the modelling are formulated as follows:

·       Condition 1: Before implementation of the Project, erosion and deposition of riverbed experiencing one year’s flow and sediment;

·       Condition 2: After implementation of the Project, erosion and deposition of riverbed experiencing one year’s flow and sediment;

·       Condition 3: After implementation of the Project, erosion and deposition of riverbed experiencing two consecutive typical water and sediment years;

·       Condition 4: After implementation of the Project, erosion and deposition of riverbed experiencing three consecutive typical water and sediment years.

The existing river terrain refers to the river bed just before the implementation of the Project; design river terrain refers to the river bed after the implementation of the Project; typical water and sediment year is chosen by hydrographs of flow, tide and sediment content in 2007.

As part of the Project scope, dry weather flow interception works will be carried out on the Shenzhen side in which sewage discharge to the Liantang River will be diverted to the Luofang Sewage Treatment Plant for treatment in order to meet the PRC’s Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002) before being discharged into Shenzhen River.  The potential impacts of the Project implementation on Shenzhen River water quality will be predicted.  The major pollutants along Shenzhen River include Chemical Oxygen Demand (COD), 5-day Biochemical Oxygen Demand (BOD5), Unionised Ammoniacal Nitrogen (NH3-N), Total Nitrogen (TN) and Total phosphorus (TP).  In this EIA study, BOD5, COD, NH3-N, TN, TP and dissolved oxygen (DO) are chosen as the parameters for simulation.  The working conditions formulated for the modelling are as follows:

·       Before the implementation of the Project, the concentrations of concerned pollutants in river channel during the dry and wet seasons;

·       After completion of the Project, the concentrations of concerned pollutants in river channel during the dry and wet seasons.

The model input parameters for the water quality prediction are summarised in Tables 6.3 to 6.12.

5                                            Cumulative Impacts

Sewage and wastewater effluents generated from the staff, food and beverage outlets and passengers of the proposed LT/HYW BCP will be directed to a high level wastewater treatment plant using Membrane Bioreactor treatment (MBR) technology, which will be designed with a treatment capacity of 387.56 m3 d-1.  Up to 111.25 m3 d-1 of the treated effluent will be reused on site for irrigation and flushing and the remaining effluent will be discharge at the Shenzhen River, within the Project Site.  The effluent discharge characteristics are summarised below:

·            Flow (m3/day): 216.31

·            SS (kg/day): 0.43

·            BOD (kg/day): 2.16

·            TN (kg/day): 1.73

·            NH3N (kg/day): 0.22

·            E.Coli (no./day): 2.16 x 107

The above information have been input into the water quality model for assessing cumulative impact during the operation phase.

6                                            Model Input Paramters

6.1                                      Model Input Parameters for Different Working Conditions During construction Phase

Table 6.1        Sediment and Water Quality Model Input Conditions for Different Working Conditions during Construction Phase

Working condition

Input conditions

1(b)

2(b)

Pollution Parameters

SS

SS

Upper boundary flow（m3 s-1）

2007.1 (a)

2007.1 (a)

Upper boundary conc.（mg L-1）

2007.1 (a)

2007.1 (a)

Lower boundary tidal level（m）

2007.1 (a)

2007.1 (a)

Lower boundary conc.（mg L-1）

2007.1 (a)

2007.1 (a)

Kong Yiu Drainage Channel

0.5/20 (c)

0.5/20 (c)

Ping Yuen River

1.2/20 (c)

1.2/20 (c)

Indus River

1.68/77 (c)

1.68/77 (c)

Buji River

2.48/162 (c)

2.48/162 (c)

Futian River

-

-

Huanggang River

-

-

Location of sources

Near Changling Village and the proposed LT/HYW BCP

Near Luofang Village and Ping Yuen River confluence

Release rate (kg s-1)

0.154/0.193/0.017(d)

0.154/0.193/0.017(d)

Notes:

(a)        Please refer to Tables 6.09 to 6.12

(b)        Please refer to Section 3.

(c)        Discharge volume (m3s-1) / discharge concentrations (mgL-1)

(d)        Release rate: closed grab backhoe for cofferdam demolition/ open grab backhoe for cofferdam demolition/ foundation pit drainage.

6.2                                      Model Input Parameters For Different Working Conditions During Operation Phase

Table 6.2       Model Input Conditions of Hydraulic Simulation for Different Working Conditions during Operation

Working

condition

Terrain

Design peak flow（m3 s-1）

Design tide

level（m）

End of

StageⅣ

Ping Yuen River

 

River Indus

 

Buji

River

Futian

River

Shenzhen river

estuary

1

existing terrain

125.8

166.7

118.5

683.0

288.8

2.896

design terrain

2

existing terrain

125.8

166.7

118.5

683.0

288.8

2.496

design terrain

3

existing terrain

83.6

116.6

107.6

496.4

199.8

2.896

design terrain

4

existing terrain

83.6

116.6

107.6

496.4

199.8

2.496

design terrain

5

After 1 yr scouring

 & silting

125.8

166.7

118.5

683.0

288.8

2.896

6

After 1 yr scouring

 & silting

125.8

166.7

118.5

683.0

288.8

2.496

7

After 1 yr scouring

 & silting

83.6

116.6

107.6

496.4

199.8

2.896

8

After 1 yr scouring

 & silting

83.6

116.6

107.6

496.4

199.8

2.496

6.3                                      Input Parameters for Water Quality Modelling under Different Working Conditions During Operation Phase

Table 6.3       Input Conditions of COD Simulation under Different Working Conditions

Working Condition

1

2

Season

Wet Season

Dry Season

Wet Season

Dry Season

Terrain

Existing Terrain

Design Terrain

 

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

End of Stage Ⅳ

0.9

300.0

0.9

300.0

0.9

100.0

0.9

100.0

Kong Yiu Drainage Channel

0.1

8.7

0.05

19.3

0.1

8.7

0.05

19.3

Luofang sewage treatment plant

2.8

40.0

2.8

40.0

2.8

40.0

2.8

40.0

Ping Yuen River

0.2

30.5

0.2

21.1

0.2

30.5

0.2

21.1

Shawan River

0.4

8.8

0.3

29.9

0.4

8.8

0.3

29.9

Ng Tung River

4.3

9.4

3.4

19.3

4.3

9.4

3.4

19.3

Buji River

3.7

90.1

2.9

102.0

3.7

90.1

2.9

102.0

Binhe sewage treatment plant

2.5

22.0

2.5

22.0

2.5

22.0

2.5

22.0

Futian River

1.2

112.0

0.4

61.1

1.2

112.0

0.4

61.1

Huanggang River

0.4

61.0

0.3

43.8

0.4

61.0

0.3

43.8

Table 6.4       COD Model Calibration Data for Working Condition 1 (unit: mg L-1)

Computational Section

Quarry

Luohu Bridge

Ludan Village

Brick Pier

Wet season

15.7

23.7

38.3

26.3

Dry season

19.0

24.9

56.5

45.5

Note: See Figure 1.4 for section location

Table 6.5       Input Data of TN Simulation under Different Working Conditions

Working condition

1

2

Water season

Wet season

Dry season

Wet Season

Dry season

Terrain

Existing Terrain

Design Terrain

 

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

End of Stage Ⅳ

0.9

35.0

0.9

35.0

0.9

30.0

0.9

30.0

Kong Yiu Drainage Channel

0.1

1.3

0.05

2.5

0.1

1.3

0.05

2.5

Luofang sewage treatment plant

2.8

8.8

2.8

8.8

2.8

8.8

2.8

8.8

Ping Yuen River

0.2

4.9

0.2

22.8

0.2

4.9

0.2

22.8

Shawan River

0.4

9.6

0.3

16.3

0.4

9.6

0.3

16.3

Ng Tung River

4.3

3.7

3.4

13.7

4.3

3.7

3.4

13.7

Buji River

3.7

35.3

2.9

47.3

3.7

35.3

2.9

47.3

Binhe sewage treatment plant

2.5

0.3

2.5

0.3

2.5

0.3

2.5

0.3

Futian River

1.2

19.7

0.4

35.0

1.2

19.7

0.4

35.0

Huanggang River

0.4

17.3

0.3

22.3

0.4

17.3

0.3

22.3

Table 6.6       TN Model Calibration Data for Working Condition 1(unit: mg L-1)

Computational Section

Quarry

Luohu Bridge

Ludan Village

Brick Pier

Wet season

11.1

15.92

18.52

16.26

Dry season

13.79

14.44

25.34

21.62

Note: See Figure 1.4 for section location

Table 6.7       Input Data of TP Simulation under Different Working Condition

Working condition

1

2

Water season

Wet season

Dry season

Wet Season

Dry season

Terrain

Existing terrain

Design Terrain

 

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

Flow

m3s-1

Conc

mgL-1

End of Stage Ⅳ

0.9

4.5

0.9

4.5

0.9

3.0

0.9

3.0

Kong Yiu Drainage Channel

0.1

0.3

0.05

0.1

0.1

0.3

0.05

0.1

Luofang sewage treatment plant

2.8

0.5

2.8

0.5

2.8

0.5

2.8

0.5

Ping Yuen River

0.2

0.3

0.2

2.6

0.2

0.3

0.2

2.6

Shawan River

0.4

0.2

0.3

0.5

0.4

0.2

0.3

0.5

Ng Tung River

4.3

0.3

3.4

0.5

4.3

0.3

3.4

0.5

Buji River

3.7

0.9

2.9

1.1

3.7

0.9

2.9

1.1

Binhe sewage treatment plant

2.5

0.4

2.5

0.4

2.5

0.4

2.5

0.4

Futian River

1.2

1.5

0.4

2.0

1.2

1.5

0.4

18.5

Huanggang River

0.4

0.9

0.3

0.6

0.4

0.9

0.3

0.6

Table 6.8       TP Model Calibration Data for Working Condition 1(unit: mg/L)

Computational Section

Quarry

Luohu Bridge

Ludan Village

Brick Pier

Wet season

0.396

0.884

1.152

0.975

Dry season

0.338

1.059

1.975

1.543

Note: See Figure 1.4 for section location

6.4                                   Hydrology, Sediment and Water Quality Data at Different Boundaries in Typical Years

Monitoring of hydrological and sediment condition and water quality at the tributaries and main river of the Shenzhen River commenced in 2004.  To date, four complete years of data is available.  For choosing a typical year, the average sediment concentration and average sediment transport rate data were referenced.  The Shenzhen River, Shenzhen Bay River Channel Sedimentation and Flow Characteristics Report (深圳河、深圳湾河道冲淤及水沙特性分析报告)([2]) concluded that the sediment along the upstream of Shenzhen river mainly come from tributaries upstream of the confluence of Ping Yuen River and Buji River, contributing 33% and 62% of the sediment concentration, respectively.  Tables 6.9 and 6.10 summarized the sediment concentration and sediment transport rate at the confluence of Ping Yuen River and Buji River.  These results were used to establish the typical flow/sedimentation year. 

Table 6.9        Daily Average Sediment Concentration from 1999 to 2008 (unit：kg m-3）

Monitoring Station

1999

2000

2001

2002

2003

2004-2005

2006

2007

2008

Confluence of Ping Yuen River

Max

0.750

0.470

1.790

0.710

1.170

3.770

5.560

12.100

2.810

Average

0.269

0.148

0.119

0.052

0.104

0.402

0.538

0.839

0.455

Buji River

Max

-

-

-

-

-

12.500

9.160

5.660

6.550

Average

-

-

-

-

-

0.265

0.670

0.394

0.646

Table 6.10      Daily Average Sediment Transport Rate from 1999 to 2008（unit：kg s-1）

Monitoring Station

1999

2000

2001

2002

2003

2004-2005

2006

2007

2008

Confluence of Ping Yuen River

Max

50.200

16.700

133.000

22.100

47.400

136.000

184.000

195.000

81.700

Average

0.792

0.482

1.201

0.308

0.933

3.054

2.460

3.640

2.310

Buji River

Max

-

-

-

-

-

103.000

17.300

86.400

148.000

Average

-

-

-

-

-

0.777

3.170

1.680

3.650

As shown from Tables 6.9 and 6.10, 2007 was the year with highest sedimentation concentration and transport rate.  Hence, the flow and sediment process in 2007 was selected as the typical year to represent the worst case scenario and to set the boundary conditions for the sediment erosion and deposition model.  For the construction period, the hydrological conditions for the forecast simulation and prediction of sediment re-suspension in the dry and the wet seasons would take the hydrological processes in January and August 2007, respectively (see Tables 6.11 and 6.12).  The tide levels at Shenzhen River Estuary, which are obtained from the Shenzhen River Mouth monitoring station (Figure 1.4), are adopted as the lower boundary conditions in the model. 

Table 6.11      Typical Year (2007) Dry Season Model Boundary Hydrodynamic Conditions

Date

Flowrate

(m3 s-1)

SS Concentration

(kg m-3)

Shenzhen River Estuary Tide Level

(m)

Shenzhen River Estuary SS Concentration (kg m-3)

Buji River Tributary Flow rate

 (m3s-1)

Buji river Tributary SS Concentration

(kg m-3)

2007-1-1

2.84

0.017

0.5

0.019

2.91

0.096

2007-1-2

2.77

0.017

0.48

0.022

2.59

0.093

2007-1-3

2.78

0.018

0.47

0.024

2.42

0.09

2007-1-4

2.76

0.019

0.43

0.028

2.44

0.087

2007-1-5

2.73

0.02

0.41

0.023

2.44

0.084

2007-1-6

2.69

0.02

0.24

0.031

2.43

0.081

2007-1-7

2.69

0.021

0.38

0.034

2.44

0.079

2007-1-8

2.71

0.022

0.43

0.030

2.45

0.076

2007-1-9

2.67

0.023

0.34

0.030

2.51

0.073

2007-1-10

2.66

0.024

0.34

0.026

2.56

0.07

2007-1-11

2.67

0.024

0.43

0.033

2.52

0.067

2007-1-12

2.64

0.025

0.34

0.033

2.67

0.064

2007-1-13

2.68

0.026

0.41

0.031

2.33

0.061

2007-1-14

2.74

0.027

0.47

0.032

2.33

0.058

2007-1-15

2.73

0.027

0.46

0.032

2.34

0.056

2007-1-16

2.69

0.028

0.37

0.032

2.34

0.053

2007-1-17

2.72

0.029

0.27

0.038

3.22

0.05

2007-1-18

2.67

0.03

0.35

0.037

2.38

0.05

2007-1-19

2.67

0.028

0.38

0.042

2.38

0.05

2007-1-20

2.63

0.026

0.35

0.044

2.35

0.05

2007-1-21

2.65

0.023

0.31

0.043

2.56

0.05

2007-1-22

2.65

0.021

0.51

0.042

2.58

0.05

2007-1-23

2.61

0.019

0.51

0.038

2.46

0.05

2007-1-24

2.57

0.017

0.45

0.034

2.29

0.05

2007-1-25

2.6

0.014

0.53

0.037

2.18

0.05

2007-1-26

2.73

0.012

0.23

0.039

2.19

0.049

2007-1-27

2.82

0.01

0.25

0.033

2.39

0.049

2007-1-28

2.84

0.007

0.33

0.034

2.54

0.048

2007-1-29

2.75

0.008

0.28

0.033

2.59

0.047

2007-1-30

2.63

0.01

0.2

0.032

2.66

0.046

2007-1-31

2.62

0.012

0.14

0.036

2.69

0.045

Table 6.12      Typical Year (2007) Wet Season Model Boundary Hydrodynamic Conditions

Date

Flowrate

(m3 s-1)

SS Concentration

(kg m-3)

Shenzhen River Estuary Tide Level

(m)

Shenzhen River Estuary SS Concentration (kg m-3)

Buji River Tributary Flow rate

 (m3s-1)

Buji river Tributary SS Concentration

(kg m-3)

2007-8-1

2.72

0.11

0.53

0.030

3.74

0.184

2007-8-2

2.71

0.178

0.51

0.030

3.97

0.218

2007-8-3

2.74

0.246

0.48

0.039

4.37

0.249

2007-8-4

2.76

0.313

0.42

0.031

3.71

0.254

2007-8-5

12.3

0.371

0.42

0.026

3.94

0.251

2007-8-6

13.9

0.436

0.46

0.023

6.31

0.242

2007-8-7

2.78

0.518

0.5

0.020

3.89

0.204

2007-8-8

5.04

0.597

0.58

0.019

4.82

0.163

2007-8-9

23.9

0.649

0.64

0.023

5.35

0.127

2007-8-10

28

0.854

0.69

0.024

7.12

0.087

2007-8-11

29.2

1.32

0.62

0.034

9.51

0.089

2007-8-12

21.6

2.64

0.44

0.037

6.83

0.099

2007-8-13

16.4

3.85

0.36

0.036

4.41

0.102

2007-8-14

27.3

5.05

0.48

0.040

11.6

0.104

2007-8-15

7.38

5.98

0.38

0.039

5.22

0.099

2007-8-16

21.6

7.69

0.43

0.037

9.78

0.093

2007-8-17

21

8.52

0.47

0.040

6.35

0.09

2007-8-18

2.86

9.86

0.45

0.030

5.29

0.084

2007-8-19

3.05

11.1

0.43

0.026

4.77

0.079

2007-8-20

23.8

8.19

0.39

0.025

6.56

0.074

2007-8-21

11.3

3.37

0.34

0.038

5.2

0.07

2007-8-22

16.8

2.05

0.33

0.027

7.49

0.067

2007-8-23

10.9

0.868

0.28

0.030

4.99

0.082

2007-8-24

2.81

0.025

0.29

0.030

4.9

0.097

2007-8-25

2.83

0.025

0.37

0.022

7.01

0.111

2007-8-26

2.75

0.025

0.4

0.029

4.82

0.109

2007-8-27

5.59

0.025

0.4

0.029

7.38

0.106

2007-8-28

5.5

0.025

0.42

0.036

5.02

0.104

2007-8-29

2.73

0.025

0.4

0.040

4.5

0.101

2007-8-30

2.73

0.025

0.38

0.040

4.8

0.098

2007-8-31

2.75

0.025

0.4

0.039

4.38

0.095

6.5                                   Model Parameter Values

1. Representative diameter of sediment , d=0.017 mm

2. Sediment-carrying capacity coefficient index to be determined according to the following formula:

      ebb tide（）                   （1）

    flood tide（）

Where:

 - mean sediment concentration for the early ebb, obtained from the model calculation;

、 are used to describe the high flow, normal and dry periods of the Shenzhen River, generally taking the average of three cases.

Namely: ，

3. Sediment restoring saturation coefficient, calculated according to equation (2)

                                （2）

where ,。

4. Roughness coefficient, from confluence of Ping Yuen River to Changling village, n=0.035; from confluence of Ping Yuen River to Shenzhen River estuary, n=0.0225.

 


([1])           Yellow Sea datum is a common height referencing system in Mainland and it is 0.854m less than mPD level system used in Hong Kong.

 

([2])           治理深圳河办公室委托长江水利勘测设计研究院于2007年编制