Research on the Influence of Different Working Conditions of

Wastewater Treatment Plants on Water Quality of Guanlan River

Main Stream

Tao Zhou

1,2,3

, Xiaoqi Zhang

1,2,3

, Shuai Xie

1,2,3

, and Yongqiang Wang

1,2,3,*

Changjiang River Scientific Research Institute, Changjiang Water Resources Commission of the Ministry of Water

Resources of China, Wuhan 430010, China

Hubei Key Laboratory of Water Resources & Eco-Environmental Sciences, Changjiang River Scientific Research Institute,

Wuhan 430010, China

Research Center on the Yangtze River Economic Belt Protection and Development Strategy, Hubei Wuhan 430010, China

Keywords: Guanlan River, Working conditions of overflow and water supplement, Water quality simulation calculation,

Water pollution control

Abstract: The operation condition of wastewater treatment plants has great influence on river water quality. Different

simulated working conditions of overflow and water supplement in Guanlan River Basin were established in

this study according to the sewage treatment capacity of decentralized sewage treatment facilities in the basin

and water purification capacity of water purification engineering for Guanlan estuary storage pond. A

hydrodynamic and environment mathematical model for Guanlan River mainstream was developed, using

pollution indicators like COD, NH3-N and TP concentrations to quantitatively analyze the water quantity and

quality of the basin under different working conditions overflow and water supplement and to simulate the

water quality changes in the main under the different operating conditions. The calculation results show that:

(1) If there were only one overflow point and the overflow volume does not exceed 30,000 m3/d, the water

quality of Qiping Section can meet the assessment requirements; (2) If overflow occurs at both overflow

points, the water quality of Qiping Section meets the assessment requirements only when the overflow volume

downstream the Guanlan plant does not exceed 20,000 m3/d and the overflow volume upstream the terminal

gate does not exceed 15,000 m3/d; (3) The concentrations of COD, NH3-N and TP along the main stream are

obviously lower under all working conditions of water supplement. This research is expected to provide

scientific basis for water pollution control of Guanlan River Basin.

1 INTRODUCTION

In city regions of China, rivers are exposed to heavy

pollution due to the large proportion of impermeable

areas, complex production activities and diverse

pollution sources. With the continuous improvement

of wastewater collection and interception systems in

city regions and the higher construction standard

raised for wastewater treatment plants over the years,

the pollution sources have been well controlled, and

the influence of different operating conditions of

wastewater treatment system on river water quality

has become increasingly prominent. So, it is urgent to

study the effect of different operating conditions of

urban wastewater treatment plants on river water

quality, so as to provide data support for further

improvement of urban river water quality.

Hydrodynamics is the basis for studying the

evolution of river flow. The two main methods

commonly adopted for researching on hydrodynamics

are mathematical statistics and mathematical model

simulation (Sun et al., 2017; Huang et al., 2015;

Shchepetkin & Mcwilliams, 2005). With the

development of computer technology, mathematical

model methods have gradually been applied to

different disciplines. Numerical simulation software

has also been widely applied, and commonly used

simulation software includes EFDC, ROMS,

FVCOM, MIKE, etc. (Chen et al., 2003; Yuan & Xu,

2006; Zuo & Li, 2013). Numerical model methods

have also been widely used in water quality

simulation of rivers and lakes (Jorgensen et al., 2005;

Huang et al., 2010; Beletsky et al., 2006).

284

Zhou, T., Zhang, X., Xie, S. and Wang, Y.

Research on the Inﬂuence of Different Working Conditions of Wastewater Treatment Plants on Water Quality of Guanlan River Main Stream.

In Proceedings of the 7th International Conference on Water Resource and Environment (WRE 2021), pages 284-295

ISBN: 978-989-758-560-9; ISSN: 1755-1315

However, previous studies mainly focus on the

investigation of point-source and non-point source

pollution in cities (Cheng et al., 2017), based on

which empirical equations were used for some

estimates that later became the input conditions of

hydrodynamic models. Wang et al. (2014) estimated

the loads of NH

-N, COD, TN and TP in the annual

rainfall runoff pollution in Neijiang City by studying

the rainfall event mean concentrations in different

underlying surfaces of Neijiang City; Yang et al.

(2021) and Yang et al. (2015) estimated the loads of

pollutants such as SS and COD of urban non-point

source pollutants in Beijing by the event mean

concentration statistics method. Chen et al. (2020)

selected Shenzhen Guanlan River Basin as the

research object, and built an evaluation model of

urban non-point source pollution in the basin through

field investigation and a study on surface

accumulation samples. According to the pollution

status of Guanlan River, the causes of water pollution

and the local watershed planning, Zhang et al. (2018)

put forward new water pollution control measures and

built a flow and water quality coupling model to

quantitatively analyze the water environment

improvement effect of those measures. With the

continuous improvement of the construction of urban

wastewater treatment system and the increasing

influence of different operating conditions of

wastewater treatment plants on the water quality of

rivers in cities, more and more studies show that

working conditions of wastewater treatment system

have an important impact on river water quality (Jia

et al., 2021; Cho et al., 2020; Xiang et al., 2018;

Xiong et al., 2017). However, the above researches

did not consider the working conditions of wastewater

treatment systems in detail. The lack of consideration

of working conditions of wastewater treatment

systems in previous studies limits the accurate

simulation of urban river water quality, or makes it

hard to provide comprehensive support for

developing urban water pollution control schemes.

Different from the above researches, this paper

focuses on the simulation of different working

conditions of wastewater treatment system so as to

quantitatively analyze the influence of different

working conditions of wastewater treatment system

on river water quality.

In response to the insufficient consideration of

different operating conditions of wastewater

treatment system in previous studies, different

working conditions of overflow and water

supplement in Guanlan River Basin were established

according to the current decentralized wastewater

treatment facilities in the basin and the actual

operating conditions of water purification engineering

for Guanlan estuary storage pond. A hydrodynamic

and hydrographic environment mathematical model

for Guanlan River main stream was built, using

pollution indicators like COD, NH

-N and TP

concentrations to quantitatively analyze the water

quantity and quality of the basin under different

working conditions overflow and water supplement,

and to simulate the water quality changes in Guanlan

River main stream under different operating

conditions. The model is expected to provide

scientific basis for water pollution control of Guanlan

River Basin.

2 OVERVIEW OF STUDY AREA

2.1 Natural Conditions

Figure 1: Geographical location of Guanlan River Basin.

Located in the north-central part of Shenzhen,

Guanlan River Basin is the upstream section of Shima

River in Dongjiang River system (Figure 1). The river

basin originates from Jigongtou region of Niuzui

Reservoir in Danaoke Mountain, Minzhi Sub-district.

Its main stream passes through Longhua New District

from south to north, and then enters Dongguan City

through Qiping Village, Guanlan Sub-district. The

rainwater catchment area above the junction between

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285

Shenzhen and Dongguan is 196.4 km

, and the river

length is 14.2 km (excluding the main source,

Yousong River). Then, the Guanlan River leaves

Shenzhen, merges into other tributaries and forms

Shima River in Tangxia Town, Dongguan City, and

further merges into Dong River at the boundary of

Dongguan and Huizhou. Apart from Guanlan River,

Shima River system contains additionally five

independent tributaries in Shenzhen, i.e., Niuhu River,

Junzibu River, Shanxia River, Egongling River and

Mugu River, all of which join Shima River in

Dongguan City.

Guanlan River Basin involves 31 rivers of

different sizes, serving as drainage channels for floods

from Guanlan River Basin and urban rainwater, and

playing a role of flood control and urban drainage

together with reservoirs, drainage pumping stations

and rainwater drainage culvert systems in the basin.

There are 6 independent rivers, i.e., Guanlan River,

Junzibu River, Niuhu River, Shanxia River,

Egongling River and Mugu River and 14 first-class

tributaries of Guanlan River Basin, of which only

Guanlan River has a catchment area larger than 100

2.2 Current Problems

The recently expanded wastewater treatment plants in

Guanlan River Basin will gradually be put into

operation, and then the source clean-up and rain-

wastewater diversion works will be further promoted

and optimized, which can significantly lower the risk

of wastewater overflow in Guanlan River Basin.

Before the completion of the annual construction

target, however, the following problems may still

exist in the water quality compliance of Guanlan

River Basin:

(1) Insufficient wastewater treatment capacity in

the basin

The daily average water discharge of Guanlan

River is about 10

/d according to the hydrological

monitoring results at Qiping Section in November

2018. The total treatment capacity of the in-service

water purification plants and decentralized

wastewater treatment plants has reached 1.18×10

/d by now. Limited by factors such as changes in

peak of incoming water, sludge disposal and

equipment maintenance, however, the actual daily

treatment capacity of wastewater treatment facilities

in the basin may fluctuate from 8×10

to 10

which means there is a possible risk of wastewater

overflow.

The existing wastewater treatment plants in the

basin are estimated to be standard raised and capacity

expanded by 2019. By that time new plants (e.g.

Minzhi plant) are anticipated to be completed and put

into operation, and expected to raise the designed

wastewater treatment capacity in the basin to

1.33×10

/d, which is higher than the drainage

volume of the basin in November 2018 (dry season),

and basically meets the needs of wastewater treatment

during the dry season. Nevertheless, it is still possible

that a single-day or instantaneous wastewater inflow

exceeds the designed treatment capacity when

considering the social and economic development,

maintenance and shutdown of wastewater plants and

other factors.

(2) Defective interception box culvert system

The existing box culverts of the Guanlan River

main stream were built on a basis of 7 mm initial and

small rainwater. The intercepting pipes along the river

of tributaries are built with the interception ratio was

set 2-5. The initial and small rainwater system,

however, was not separated from the wastewater

system. As a result, the box culvert is prone to

siltation and overflow. In addition, the interception

capacity of the main stream does not match that of

tributaries, making the tributary box culvert easy to

overflow.

(3) Low operation efficiency of storage ponds

Currently there are 2# (Longhua) storage pond

(volume of 25,900m

), 3# (Guanlan) storage pond

(volume of 220,000m

) and 4# (estuary) storage

ponds (volume of 220,000m

) in Guanlan River Basin.

However, the design objectives of each storage pond

are not clear, resulting in low efficiency of initial

rainwater storage. There is a lack of effective system

linkage between the dispatching scheme of storage

ponds, interception box culverts and wastewater

plants.

Figure 2: River system distribution of Guanlan River Basin.

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286

To tackle the above problems and assure the

continuously up-to-standard water quality of Guanlan

River, it is urgent to establish a flow and water quality

model for Guanlan River main stream based on the

current situation of plants, networks, rivers, stations

and ponds in the basin, to calculate and analyze the

water quality changes in the main stream of Guanlan

River, so as to provide a basis for wastewater control

and making dispatching plans for water quantity and

quality in Shenzhen Guanlan River Basin.

3 GUANLAN RIVER MAIN

STREAM FLOW AND WATER

QUALITY MODELING

Guanlan River is considered as a relatively smooth

river as its gradient of the main stream is 1.2‰. The

water bodies are mixed vertically and evenly and are

distributed unevenly in the spatial plane. For this

reason, the depth-averaged two-dimensional

mathematical equation was adopted to describe the

movement characteristics of water flow and quality in

the main stream of Guanlan River in order better to

reveal the overall change characteristics of water flow

and quality in the study area and meet the actual

demand. Through analysis, this study tends to build a

mathematical model for Guanlan River main stream

water environment based on MIKE21.

Figure 3: Underwater topographic map.

3.1 Calculation Area and Underwater

Topography

There are 14 first-class tributaries and 5 independent

tributaries (directly entering Dongguan) in the basin.

The length of the main stream is about 17 km. See

Figure 2 for the river system. Through field

investigation and monitoring data analysis, the

calculation area of Guanlan River main stream model

includes all areas of Guanlan River main stream. The

underwater topography after generalization of the

model is shown in Figure 3. Due to the irregular

boundary shape of Guanlan River, it is suggested to

adopt unstructured grid (triangular grid) for division

and enhance the calculation stability of the

mathematical model. The x represents the east

direction, the y represents the north direction, and the

coordinate value is the length. The model involves

2750 nodes and 3835 computational grids (Figure 4).

Figure 4: Grid division chart.

3.2 Calibration and Verification of

Model Parameters

3.2.1 Hydrodynamic Parameters

1) Calibration of hydrodynamic parameters

According to the field investigation and the study

results in similar areas, the initial roughness of

Guanlan River main stream n is assumed as 0.033 for

calculation, and the eddy viscosity coefficient is

determined according to Smagorinsky equation.

2) Verification of hydrodynamic parameters

The measured daily hydrology and other basic data of

Guanlan River main stream were used as the input of

the constructed model for simulation calculation. The

model was verified by the water level data of Qiping

Section at the exit of Guanlan River main stream. The

comparison between the calculated water level

process (from January 1, 2019 to May 31, 2019) of

Qiping Section at the exit of Guanlan River main

stream and the measured water level change process

is shown in Figure 5.

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287

Figure 5: Comparison between the simulated and measured water levels in Qiping Section

3.2.2 Water Quality Parameters

1) Calibration of water quality parameters

From the monitored water quality data from

January 1, 2019 to May 31, 2019, combined with the

study results in similar areas, it can be concluded that

the comprehensive degradation coefficients of COD,

-N and TP in Guanlan River are 8.0 e

-8

/s, 1.0 e

-8

and 1.0 e

-8

/s, respectively.

2) Verification of water quality parameters

Available data indicates that overflow occurred all the

time except for 4 days in the first 21 days in March,

2019. During the rainfall period, the facilities in

Guanlan River Basin are unable to fully receive the

mixed flow of rain and wastewater at peak, and the

wastewater interception system may overflow to the

river channel, resulting in the deterioration of the

water quality of main streams and tributaries and the

unstable daily water quality monitoring data of each

tributary estuary. This makes it difficult to calibrate

the water quality model. The measured daily

hydrology and other basic data of Guanlan River main

stream were used as the input of the constructed

model for simulation calculation, and the main

monitoring data of Guanlan River were used for

verification. The water quality data of four monitoring

points, i.e., Qinghu Bridge, Meiguan Expressway,

Fangmapu and Qiping Section along Guanlan River

and 11 first-class rivers of Guanlan River from

January 1, 2019 to May 31, 2019 were simulated and

calculated by the model. See Figure 6 for comparison

between the simulated process of main water quality

(COD, NH

-N, TP) and the measured water quality

change process (e.g., Qiping Section of the main

stream). The water quality process of Guanlan River

(COD, NH

-N and TP) simulated by the water quality

model is well consistent with the measured values,

demonstrating the constructed water quality model

well reflects the migration and diffusion law of

pollutants in Guanlan River. Therefore, the model can

be used for water environment simulation and

analysis in lake regions along Guanlan River main

stream.

(a) Comparison between the simulated and measured COD concentrations in Qiping Section of main stream

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(b) Comparison between the simulated and measured values of NH

-N concentration in Qiping Section of main stream

Figure 6: Comparison between the simulated and measured water quality of Qiping Section of main stream.

4 ANALYSIS OF MAIN STREAM

WATER QUALITY CHANGES

UNDER DIFFERENT

OVERFLOW CONDITIONS

4.1 Assumption of Different Overflow

Conditions

According to the analysis of wastewater treatment

capacity of Guanlan River, the daily wastewater

treatment capacity of Guanlan River Basin

wastewater treatment plant varies from 701,500–

1,234,700 tons under the current conditions (January

1–July 31, 2019), while the daily wastewater

treatment capacity of Guanlan River Basin

wastewater treatment plant is 1,075,000 tons under

the current conditions. It can be concluded that the

wastewater treatment facilities basically meet the

needs of basin wastewater treatment under the current

conditions. Field investigation shows that there are

mainly two overflow points in the main stream of

Guanlan River, i.e., the overflow point downstream

the Guanlan water purification plant and the terminal

culvert gate overflow point. When the wastewater

treatment plants in Guanlan River Basin reduce

production or stop production, the wastewater to be

treated will be transferred to the downstream through

the main stream culvert. When it exceeds the box

culvert capacity in the Guanlan estuary storage pond

water purification project, the wastewater to be

treated will continue to fill the box culvert, and the

wastewater in culvert pipes will be forced to the

vicinity of Guanlan water purification plant and

overflow to the main stream of Guanlan River, as

shown in Figure 7.

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289

Table 1: Assumption of overflow conditions in Guanlan River main stream.

Operating conditions Downstream the Guanlan water

urification

lant (×10

/d)

Terminal culvert gate (×10

/d)

Condition 1 3 2

Condition 2 2 1.5

Condition 3 3 3

Condition 4 3 0

Condition 5 10 0

Condition 6 18 0

Condition 7 16 0

Condition 8 14 0

Condition 9 0 15

Condition 10 0 14

Condition 11 0 13

Condition 12 0 19

Condition 13 0 18

Condition 14 0 16

Figure 7: Location of overflow points of Guanlan River

main stream.

4.2 Analysis of Water Quality Changes

in Qiping Section of Guanlan River

under Different Overflow

Quantities

Based on the hydrodynamic and water environment

mathematical model built in Section 3, the flow and

water quality changes in Guanlan River main stream

under those 14 conditions (as shown in Table 1) were

simulated, respectively. The water quality of Guanlan

River main stream and Qiping Section under each

condition was subsequently analyzed according to the

simulation results. Conditions 1, 4 and 9 are used for

specific explanation, while the calculation results of

other conditions are shown in Table 2. Figures 8–10

show the pollutant distribution of Longhua and

Qiping Sections under each condition.

(1) Condition 1 represents all wastewater

treatment plants whose effluent is discharged into the

main stream of Guanlan River operate normally

according to the designed capacity, and indicates the

water quality changes in the section downstream the

Guanlan water purification plant when overflow

occurs, both at the overflow point downstream the

Guanlan water purification plant and at the overflow

point of the terminal culvert gate (Figure 8). Under

Condition 1, COD, NH

-N and TP concentrations in

overflow point downstream the Guanlan water

purification plant are 36.59 mg·L

-1

, 2.18 mg·L

-1

and

0.40 mg·L

-1

, while COD, NH

-N and TP

concentrations in Qiping Section are 37.22 mg·L

-1

2.26 mg·L

-1

and 0.41 mg·L

-1

. The water quality of

Guanlan River main stream is Inferior-to-Class V.

a) COD distribution under Condition 1

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290

NH3-N distribution under Condition 1

c) Figure 8c. TP distribution under Condition 1

Figure 8. Pollutant distribution under Condition 1.

(3) Condition 9 represents all wastewater

treatment plants whose effluent is discharged into the

main stream of Guanlan River operate normally

according to the designed capacity, and indicates the

water quality changes in the section downstream the

Guanlan water purification plant when overflow does

not occur at the overflow point downstream the

Guanlan water purification plant but occurs at the

overflow point of the terminal culvert gate (Figure 10).

Under Condition 9, COD, NH

-N and TP

concentrations at overflow point downstream the

Guanlan water purification plant are 30.57 mg·L

-1

1.53 mg·L

-1

and 0.31 mg·L

-1

. COD, NH

-N and TP

concentrations in Qiping Section are 39.72 mg·L

-1

2.43 mg·L

-1

and 0.45 mg·L

-1

. The water quality of

Guanlan River main stream is Inferior-to-Class V.

a) COD distribution under Condition 4

NH3-N distribution under Condition 4

c) TP distribution under Condition 4

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291

Figure 9: Pollutant distribution under Condition 4.

a) COD distribution under Condition 9

b) NH3-N distribution under Condition 9

c) TP distribution under Condition 9

Figure 10: Pollutant distribution under Condition 9

As shown in the table above, the calculation

results show that: (1) If overflow only occurs at the

overflow point downstream the Guanlan water

purification plant and the overflow volume does not

exceed 30,000 m

/d, the water quality of Qiping

Section can meet the assessment requirements; (2) If

overflow only occurs at the overflow point upstream

the terminal gate and the overflow volume does not

exceed 30,000 m

/d, the water quality of Qiping

Section can meet the assessment requirements; (3) If

overflow occurs at both overflow points, the water

quality of Qiping Section meets the assessment

requirements only when the overflow volume

downstream the Guanlan plant does not exceed

20,000 m

/d and the overflow volume upstream the

terminal gate does not exceed 15,000 m

/d.

5 ANALYSIS ON THE

INFLUENCE OF THE

GUANLAN STORAGE POND

WATER PURIFICATION

PROJECT ON WATER

QUALITY OF THE MAIN

STREAM

5.1 Working Conditions Setting of

Water Supplement at Different

Junction of Main and Tributaries

Referring to the water supplement planning of

Longhua District, five working conditions of water

supplement are assumed to analyze the influence of

water supplement at the main stream/tributaries

confluences in the middle and lower reaches of

Guanlan River on the change of water quality in the

main stream. See Table 3 for details.

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Table 2: Analysis of water quality at the overflow points.

Water

quality

analysis

Overflow point downstream the Guanlan

water

urification

lant

Qiping Section

COD NH

-N TP

Water

standar

COD NH

-N TP

Water

standar

Condition 1

36.59 2.18 0.40

Inferior-to-

Class V

37.22 2.26 0.41

Inferior-to-

Class V

Condition 2

34.62 1.96 0.37 Class V 36.20 2.00 0.39 Class V

Condition 3

36.59 2.18 0.40

Inferior-to-

Class V

39.07 2.47 0.40

Inferior-to-

Class V

Condition 4

40.44 2.72 0.46

Inferior-to-

Class V

44.51 3.13 0.53

Inferior-to-

Class V

Condition 5

50.28 4.30 0.67

Inferior-to-

Class V

41.36 3.13 0.52

Inferior-to-

Class V

Condition 6

46.02 3.69 0.59

Inferior-to-

Class V

38.86 2.75 0.46

Inferior-to-

Class V

Condition 7

42.31 3.05 0.49

Inferior-to-

Class V

36.71 2.36 0.41

Inferior-to-

Class V

Condition 8

38.53 2.39 0.43

Inferior-to-

Class V

34.59 1.98 0.37 Class V

Condition 9

30.57 1.53 0.31 Class V 39.72 2.43 0.45

Inferior-to-

Class V

Condition 10

30.57 1.53 0.31 Class V 37.89 2.23 0.42

Inferior-to-

Class V

Condition 11

30.57 1.53 0.31 Class V 36.02 2.03 0.39

Inferior-to-

Class V

Condition 12

30.57 1.53 0.31 Class V 46.74 3.30 0.56

Inferior-to-

Class V

Condition 13

30.57 1.53 0.31 Class V 45.02 3.11 0.53

Inferior-to-

Class V

Condition 14

30.57 1.53 0.31 Class V 41.50 2.73 0.48

Inferior-to-

Class V

Table 3. Assumption of water supplement conditions at different main stream/tributaries confluences

Condition

Additional point of main stream/tributary estuaries

Additional water volume (×10

/d)

Baihuashui River 5

Zhangkengjing River 6

Dankengshui River 2

Xikengshui River 2

Changkengshui River 4

Qinghushui River 1

5.2 Analysis of Influence of Supplement

Water on Main Stream Water

Quality

The results of numerical simulation analysis on the

middle and lower reaches of Guanlan River show that

the water quality along the main stream of Guanlan

River has been greatly improved in comparison with

the condition without water supplement, as shown in

Figure 11, in which water supplement at the

confluence of main stream/tributaries in the upper

reaches of the basin (Condition 6) has the most

significant effect on reducing COD and TP.

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293



(a) COD changes along the middle and lower reaches of the main stream under each water supplement condition

(b) NH

-N changes along the middle and lower reaches of the main stream under each water supplement condition

Figure 11: Water quality changes along the middle and lower reaches of Guanlan River main stream under each water

supplement condition.

6 CONCLUSIONS

In this study, a depth-averaged 2D mathematical

equation was used to describe the characteristics of

water quality in the main stream of Guanlan River,

and a MIKE21-based mathematical model for water

environment in the main stream of Guanlan River was

built. According to the actual operating conditions of

the decentralized wastewater treatment facilities in

Guanlan River Basin and the Guanlan estuary storage

pond water purification project, different overflow

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and water supplement condition were assumed. By

using the mathematical model of hydrodynamic water

environment, the influence of different working

conditions overflows and water supplement on the

water quality changes of Guanlan River was

simulated and quantitatively analyzed.

When the main stream of Guanlan River

overflows, the simulation results show that: (1) If

overflow only occurs at the overflow point

downstream the Guanlan water purification plant and

the overflow volume does not exceed 30,000 m

/d, the

water quality of Qiping Section can meet the

assessment requirements; (2) If overflow only occurs

at the overflow point upstream the terminal gate and

the overflow volume does not exceed 30,000 m

/d, the

water quality of Qiping Section can meet the

assessment requirements; (3) If overflow occurs at

both overflow points, the water quality of Qiping

Section meets the assessment requirements only when

the overflow volume downstream the Guanlan plant

does not exceed 20,000 m

/d and the overflow volume

upstream the terminal gate does not exceed 15,000

/d. In addition, the calculation results demonstrate

that the concentrations of COD, NH

-N and TP along

the main stream are obviously lower under all

working conditions of water supplement. The above

conclusions are expected to provide a scientific basis

for water pollution control of Guanlan River Basin.

ACKNOWLEDGEMENT

This study is funded by the Water Resource Science

and Technology Innovation Program of Guangdong

Province (2017-03).

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