Estimation of Water Environmental Capacity Considering Hydraulic Project Operation in the Xiangyang Reach of the Han River, Central China

doi:10.4236/jwarp.2012.48073

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Journal of Water Resource and Protection, 2012, 4, 634-637

http://dx.doi.org/10.4236/jwarp.2012.48073 Published Online August 2012 (http://www.SciRP.org/journal/jwarp)

Estimation of Water Environmental Capacity Considering

Hydraulic Project Operation in the Xiangyan g Reach of

the Han River, Central China

Chen Sun, Hongjuan Wu

School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, China

Email: sccool1983@gmail.com, [email protected]

Received May 28, 2012; revised June 30, 2012; accepted July 8, 2012

ABSTRACT

Using the Xiangyang Reach of the Han River as an example, this paper evaluates the changes of water environmental

capacity after the implementation of Cuijiaying Hydro-junction project. The allowable pollutant loads entering the

Xiangyang Reach were estimated using two-dimensional steady state water quality model with different data sets. The

water environmental capacity has declined in the reservoir area of the Cuijiaying Hydro-junction project during the

low-flow period; it is appearing to increase slightly in the upper and lower stream of this reservoir. However, the state

of flow may turn into the state of reservoirs flow in the reservoir area, and the changes of hydrological regime may

cause the water flow and the nutrient contents suitable for the occurrence of ecological environment problems.

Keywords: Han River; Water Environmental Capacity; Cascade Development; Pollutant Loading

1. Introduction

The Han River is the longest tributary of the Yangtze

River, with a watercourse length of 1577 km and a total

drainage area of 159,000 km2. The Han River Basin is

one of the major agricultural production bases in China,

and plays a significant role in regional economic devel-

opment. Due to its plentiful water resources [1], the Ba-

sin cascade development is being implemented [2].

Meanwhile, changes of hydrological regime may inevi-

tably impact the aquatic environment of the Han River,

especially to the water environmental capacity. Moreover,

the rapid urbanization and industrialization are beginning

to affect water quality in this area. From 1992 to 2005,

large-scale algal blooms had taken place five times in the

middle and lower reaches of the Han River because of

the ecological environment degradation [3].

Total amount control for water pollutants is one of the

main methods to resolve water environmental problems

in China [4,5]. Comprehensively understanding the water

environmental capacity, namely the maximum allowable

pollutant loads discharging into the water body, is a pre-

requisite to effective pollution control. With the aim of

providing a valuable aid to the strategies of water pollu-

tion control, the influence of water conservancy projects

on water environmental capacity is increasingly draw

more attention in China [6-8].

The current study aims to estimate the water environ-

mental capacity through a case study of the Xiangyang

Reach of the Han River in Central China. Using two-

dimensional steady state water quality model, we evalu-

ated the variation of water environmental capacity con-

sidering the dam operation in this area.

2. Study Area

Xiangyang city is located in the middle reach of the Han

River (Figure 1). With a total area of 19,727.68 km2, it

has a population of around 5,888,786 in 2009. The Han

River runs through the city from north to south with a

length of 195,000 m. There are five tributaries in the

Xiangyang Reach: South River, North River, Xiaoqing

River, Tangbai River, and Man River. The Cuijiaying

Hydro-junction project, located in downstream of the

Xiangyang urban area, is the third step of cascade devel-

opment in the middle and lower reaches of the Han River

[9]. Normal storage level of the project is 62.73 m. The

project, which is mainly used for shipping and electricity

generation, has been completed in July, 2010.

3. Methods

According to the actuality of total amount control for

water pollutants in China [10], chemical oxygen demand

(COD) and ammonia nitrogen (NH3-N) were selected as

the calculation factors in this study. We divided the

Xiangyang Reach of the Hn River into six computa- a

C. SUN, H. J. WU 635

Figure 1. Study area.

tional units based on the water environmental function

zone of Hubei Province [11], as shown in Table 1. The

point source pollution data in 2007 for this study was

obtained from the Xiangyang Environmental Monitoring

Station.

As the river width of the Han River is usually in ex-

cess of 200 meters, it is necessary to consider the varia-

tion of pollutants in longitudinal dispersion and horizon-

tal diffusion [10]. Two-dimensional water quality model,

therefore, is suitable for calculation of water environ-

mental capacity under given the unique hydrological

conditions within the Xiangyang Reach.

Under steady flow conditions, fundamental equation of

two-dimensional water quality model is written as:

xyxy

CCCC

EEuukC

xyxy









(1)

where ux is the longitudinal velocity (m/s); uy is the hori-

zontal velocity (m/s); Ex is the longitudinal dispersion

coefficient (m2/s); Ey is the horizontal diffusion coeffi-

cient (m2/s); C is the contaminant concentration (mg/L);

K is the decay coefficient (1/d); x is the longitudinal co-

ordinates (m); y is the horizontal coordinates (m).

Supposing uy and Ex are approximate to zero under

conditions of little changes in water depth, Equation (1)

is converted to the following expression:



,expexp

4π

exp

uy x

Cxy k

Ex u

huE























(2)

where M is the pollutant emission rate (g/s); C0 is the

background pollutant concentration of the river (mg/L);

C is the pollutant concentration (mg/L); K is the decay

coefficient (1/d); x is the longitudinal coordinates (m); y

is the horizontal coordinates (m); h is the average water

depth (m); u is the average longitudinal velocity (m/s).

Assuming the degradation of background pollutant

concentration is negligible, the model which can be ap-

plied to estimate water environmental capacity in the

Xiangyang Reach gives the following formula:



,πexp 4

yu x

WCxyCHuxE k

Ex u



 





(3)

where W is the water environmental capacity (t/a).

30Q10 is selected as the design flow (314 m3/s) in the

light of data from the Xiangyang hydrometric station,

and the designed flow velocity is 0.31 m/s. The river

depth and width are derived from our investigation (Ta-

ble 2).

The horizontal diffusion coefficient (Ey) is usually de-

termined by the empirical correlation or field survey

method. In this study, we adopted the following empiri-

cal correlations [12]:

Table 1. Computational units in the Xiangyang Reach of the

Han River.

Computational unit Environmental

functional category Length (m)

Shenwan-Xianrendu Ⅱ 38.5

Xianrendu-Baijiawan Ⅱ 47.2

Baijiawan-Zhakou Ⅲ 14

Zhakou-Qianying Ⅲ 12

Qianying-Yujiahu Ⅲ 7.6

Yujiahu-Guo’an Ⅱ 53.2

C. SUN, H. J. WU

636

Table 2. Average river width and depth of each com-

putational unit in the Xiangyang Reach.

Computational unit Sewage outlet

and tributary

Width

(m)

Depth

(m)

Jiangshan 180 2.8

Shenwan-Xianrendu

Damingqu 180 2.8

Xianrendu-Baijiawan Jinhuan 235 2.7

Xiaoqing River 323 2.42

Tianjiu 160 3.3

Nanqu 323 4.52

Yuliangzhou 160 3.3

Zhakou-Qianying

Xiangyang

power plant 390 3.35

Yujiahu-Guoan Yakou 390 3.35

EaHU (4)

UgHI (5)

where ay is non-dimensional coefficient; H is average

river depth (m); U* is frictional velocity (m/s); g is grav-

ity acceleration (m/s2); I is gradient of the river (‰).

According to the Surface water environmental capac-

ity of Hubei Province Technical Report, decay coeffi-

cient (K) is assigned values as follows: KCOD = 0.18d –

1，

NH-N = 0.08d – 1. The upper limit value of water

quality standard is selected as the background pollutant

concentration of the Xiangyang Reach.

4. Results and Discussion

4.1. Pollution in the Xiangyang Reach of the Han

River

In 2007, the quantity of waste water entering the Xian-

gyang Reach was 130,414,000 t. The amount of COD

was 38,741 t, and NH3-N was 4418.43 t. Table 3 shows

the amount of pollutants entering the Xiangyang Reach

from various pollution sources. Municipal domestic

sewage was the primary point source pollution, account-

ing for nearly 64% of COD and 62% of NH3-N, respect-

tively. Table 4 shows the quantity of pollutants from

point source pollution in each computational unit. The

pollutant loading mainly originates from Xiangyang ur-

ban area with the highest population densities. The

chemical fiber industry, textile industry, pharmaceutical

industry, and chemical industry are four major industrial

pollution sources, whose COD accounted for nearly 76%

of industrial pollution.

4.2. Changes of the Hydrological Regime

The Cuijiaying Hydro-junction project has mainly exerted

Table 3. The quantity of pollutants from various pollution

sources entering the Xiangyang Reach in 2007.

Pollution source COD (t) NH3-N (t)

Municipal domestic sewage 21905.2 2267.7

Industrial sewage 12388.5 1418.2

Animal breeding 1758.2 353.6

Rural area sewage 1735.2 188.2

Farmland runoff 951.1 190.3

Urban runoff 2.7 0.3

Table 4. The amount of pollutants from point source pol-

lution in each computational uint in 2007.

Computational unit COD (t) NH3-N (t)

Shenwan-Xianrendu 6802.6 553.4

Xianrendu-Baijiawan 11640.6 1256.7

Zhakou-Qianying 10608.1 949

Qianying-Yujiahu 785.4 653.1

Yujiahu-Guo’an 4401 814.4

effects on the hydrological regime of the following two

areas: the reservoir area and downstream of this project.

The flow of reservoir area (backwater area) is mainly in-

fluenced by the upstream flow and runoff, and the de-

signed flow of this area is 554 m3/s. The water level

increased from 2.66 m to 62.73 m, and the designed flow

velocity is 0.138 m/s. The state of flow may turn into the

state of reservoirs flow in the reservoir region, and the

hydrological regime changes cause the water flow and

the nutrient contents suitable for the occurrence of eco-

logical environment problems.

Meanwhile, the minimum discharging downstream

flow (490 m3/s) is used for designed flow of downstream

of the dam. The designed flow velocity is 0.57 m/s, and

the water level has increased by 0.15 m.

4.3. Water Environmental Capacity in the

Xiangyang Reach of the Han River

Based on the specified water quality and hydrological

patterns, the water environmental capacity in the Xiang-

yang Reach of the Han River was estimated. The results

are shown in Table 5, which are the maximum allowable

pollutants loading entering the river (there is no outfall in

the unit of Baijiawan-Zhakou, so this unit does not need

to calculate). The water environmental capacity after the

implementation of the cascade project is shown in Table

6. The water environmental capacity has declined in the

reservoir area (Zhakou-Qianying) during the low-flow

C. SUN, H. J. WU

637

Table 5. Water environmental capacity in the Xiangyang

Reach of the Han River.

Computational unit COD (t/a) NH3-N (t/a)

Shenwan-Xianrendu 3614.1 576.34

Xianrendu-Baijiawan 1904.4 177.11

Zhakou-Qianying 44986.2 2278.76

Qianying-Yujiahu 3570.1 224.13

Yujiahu-Guo’an 9852.23 197.46

Table 6. Water environmental capacity in the Xiangyang

Reach after the implementation of the Cuijiaying project.

Computational unit COD (t/a) NH3-N (t/a)

Shenwan-Xianrendu 3728.3 592.51

Xianrendu-Baijiawan 1905.5 177.6

Zhakou-Qianying 42661.3 2112.2

Qianying-Yujiahu 3612.3 235.1

Yujiahu-Guo’an 10007.6 203.78

period, and it is appearing to increase slightly in the up-

per and lower stream (Shenwan-Baijiawan, Qianying-

Guo’an) of this project.

5. Conclusion

Applying two-dimensional steady state water quality

model, we estimated the water environmental capacity of

the Xiangyang Reach. Owing to the influence of cascade

development, there is a decline of water environmental

capacity in the reservoir region, also a growth in the up-

per and lower stream of the dam. However, the flow rate

has declined in the reservoir area, and what should be

done is to look for the influence of the cascade develop-

ment on the aquatic eco-environment. The reservoir area

should be a priority region for pollution control. The case

study of the Xiangyang Reach shows that municipal do-

mestic sewage was one of the major point source pollu-

tion, which contributed the most COD load entering the

Han River in 2007. Improvement of sewage treatment

facilities should be considered by policy makers in this

area.

6. Acknowledgements

This study was supported by the Environmental Protec-

tion S&T Program of Hubei Province. The authors thank

the Hubei Provincial Environmental Protection Depart-

ment and Xiangyang Environmental Protection Agency

for providing necessary data.

REFERENCES

[1] F. Yuan, Z. H. Xie, Q. Liu, H. W. Yang, F. G. Su, X.

Liang and L. R. Li, “An Application of the VIC-3L Land

Surface Model and Remote Sensing Data in Simulating

Streamflow for the Han River Basin,” Canadian Journal

of Remote Sensing, Vol. 30, No. 5, 2004, pp.680-690.

doi:10.5589/m04-032

[2] G. M. Guan, S. J. Chen and G. H. Rao, “Han River Basin

Planning,” Hubei Water Power, No. 65, 2006, pp. 9-12.

[3] W. H. Luo, S. J. Zhang and H. Y. Liu, “Water Quality

Trend Analysis and the Pollution Control Measures in the

Middle and Lower Reaches of the Han River,” Express

Water Resources & Hydropower Information, Vol. 27, No.

20, 2006, pp. 6-8.

[4] W. Meng, Y. Zhang and B. H. Zheng, “The Quality Cri-

teria, Standards of Water Environment and the Water

Pollutant Control Strategy on Watershed,” Researc h of En-

vironmental Sciences, Vol. 19, No. 3, 2006, pp. 1-6.

[5] W. Meng, “Technique of Total Amount Control for Water

Pollutants in Watershed and Its Application,” China En-

vironmental Science Press, Beijing, 2008.

[6] G. T. Wu and Y. Z. Liang, “The Effect of Dam on River

Ecosystems and Management of Lijiang River,” Journal

of Nanning Teachers College, Vol. 20, No. 4, 2003, pp.

76-80.

[7] Z. L. Dang, B. Wu, M. Q. Feng and F. Hu, “Forecast

Research on Water Environmental Capacity for the Water

Source Area in Shaanxi of Middle Line of Transferring

Water from South to North,” Journal of Northwest Uni-

versity, Vol. 39, No. 4, 2009, pp. 660-666.

[8] L. Ouyang, Y. S. Zhuge and D. F. Liu, “Study on Water

Environment Capacity of the Xiangxi River in TGP Res-

ervoir,” Yangtze River, Vol. 39, No. 20, 2008, pp. 12-14.

[9] G. Z. Jiang and X. B. Han, “The Analysis of Environ-

mental Impact of Cascade Development in the Middle

and Lower Reaches of the Han River,” Environmental

Science and Technology, No. 4, 1998, pp. 9-16.

[10] Chinese Academy on Environmental Planning, “Techni-

cal Guide of National Water Environmental Capacity

Evaluation,” 2003.

http://www.caep.org.cn/ReadNews.asp?NewsID=96

[11] Y. L. Zhang and P. Z. Zhang, “Handbook of the Calcula-

tion of Water Environmental Capacity,” Tsinghua Uni-

versity Press, Beijing, 1991.

[12] T. R. Long, J. S. Guo, Y. Z. Feng and G. Y. Huo, “Artifi-

cial Neural Network Imitation of the Horizontal Diffusion

Coefficient in Two-Dimensional Water Quality Model,”

Chongqing Environmental Science, Vol. 24, 2002, pp. 25-

28.