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Desalination and Water Treatment
ISSN: 1944-3994 (Print) 1944-3986 (Online) Journal homepage: /loi/tdwt20
Evaluation of nitrogen and phosphorus loads from agricultural nonpoint source in relation to water quality in Three Gorges Rervoir Area, China
Xiao Ma, Ye Li, Bolin Li, Weiyi Han, Dongbin Liu & Xi Liu
To cite this article: Xiao Ma, Ye Li, Bolin Li, Weiyi Han, Dongbin Liu & Xi Liu (2015): Evaluation of nitrogen and phosphorus loads from agricultural nonpoint source in relation to water quality in Three Gorges Rervoir Area, China, Desalination and Water Treatment, DOI:10.1080/19443994.2015.1112307
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Evaluation of nitrogen and phosphorus loads from agricultural nonpoint source in relation to water quality in Three Gorges Rervoir Area,China Xiao Ma a ,b ,*,Ye Li b ,*,Bolin Li b ,Weiyi Han b ,Dongbin Liu b ,Xi Liu b
a
美国诗人College of Urban and Environmental Sciences,Hubei Normal University,Huangshi 435002,P.R.China,Tel.+18271675211;email: b School of Resource and Environmental Engineering,Wuhan University of Technology,Wuhan 430070,P.R.China,emails:ly1218@whut.edu (Y.Li), (B.Li), (W.Han), (D.Liu), (X.Liu)Received 6March 2015;Accepted 15October 2015A B S T R A C T Following the implementation of the Three Gorges Dam Project,water quality deterioration due to an excess of nitrogen (N )and phosphorus (P )from agricultural nonpoint source (ANPS)is of major concern in Three Gorges Rervoir Area (TGRA),People’s Republic of China.An export coefficient model (ECM)was developed to provide reasonable estimates on the influence of ANPS on N and P loads to TGRA bad on field investigation datats from 1996to 2013.Additionally,the potential total nitrogen (TN)and total phosphorus (TP)loads from ANPS originating from a variety of sources were estimated and analyzed.The gave the spatial and temporal distributions of the potential ANPS loads within the rervoir area,and the relationship between TN/TP loads from ANPS and water quality was analyzed after impoundment in TGRA.The TN and TP loadings were calculated as 4.11×104tonnes and 0.31×104tonnes in 2013,respectively,with a ratio of TN/TP of 13.46,and algae blooms occurred 13times in the tributaries of TGR that year.Therefore,there may be a correlation between the eutroph
ication potential in the inlet water and the TN/TP ratio of potential ANPS loads in TGRA.According to field monitoring,incread P loading to the water systems may cau excessive algal and macrophyte growth and conquent environmental degradation.The findings provide uful and valuable information for
decision makers and planners to take sustainable measures for the control of ANPS pollu-
tion in TGRA.It is also demonstrated that the ECM could provide a simple and reliable
approach to evaluate the potential TN and TP loadings to the TGRA,and thus,it is uful
for the aquatic environment management of the local agricultural watersheds.
Keywords:Eutrophication;Agricultural nonpoint source;Export coefficient model;Three
Gorges Rervoir Area;Water quality
*Corresponding authors.
1944-3994/1944-3986Ó2015Balaban Desalination Publications.All rights
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Desalination and Water Treatment
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doi:
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1.Introduction
Three Gorges Dam (TGD)in China is one of the
largest hydroelectric dams ever built in the world,
measuring 2,335m long and 185m high,and the
rervoir created by it had an area of 1,080km 2in
2010[1].The region surrounding the rervoir,with a
total area of approximately 58,000km 2,has now
become known as the Three Gorges Rervoir Area
(TGRA)[2].Since the rervoir was filled to an alti-
tude of 135m above a level after impoundment in
June 2003,the rervoir bays of Three Gorge rervoir
(TGR)was showing symptoms of eutrophication,and
algal blooms often occur in many new formed bays
[3].A common reason for eutrophication in a water
牙龈红肿怎么办
body is the increa in N and P nutrients [4–6].During
the last two decades,the significant improvement in
point source depuration technologies has highlighted
problems regarding N and P pollution from nonpoint
source,especially agricultural nonpoint sources
(ANPS)[7].According to incomplete statistics,52–59%
of TP,TN pollutants in the condary rivers of the
TGR derived from ANPS pollution [8].Agricultural
activities and increasing population have led to
incread pressure on the land and water resources
[9–11];hence,there is an urgent need to determine the
relationship between N /P loads from ANPS and
ecological water quality.
Currently,field studies and modeling techniques
are two uful approaches in evaluating ANPS pollu-
tant loadings.It is very difficult to monitor on site due
to significant spatial variations [12,13].Many rearch-
ers have propod a variety of methods to estimate
ANPS pollution loads,mainly including physically
bad model and empirical method [14–16].Physically
bad models have been regarded as not only the
most reliable and flexible but also as having the great-
est potential for applications [17].There are many
well-rounded functional and mechanistic models for
ANPS pollution estimation in the world,including
Soil and Water Asssment Tool,Agricultural Non-
point Pollution Source,Hydrologic Simulate Program-
FORTRAN,etc.,and many worldwide ca studies
have been conducted [18,19].In general,incread
model complexity implies an improved prediction
涤纶面料好不好becau of accurate reprentations of the process [20].
However,as for ANPS model rearches in China,
due to the enormous number of parameters,require-
ments for a large body of input data,and limited
available information,it is difficult to calibrate and
validate the models,which restricts their u for
large-scale regions [21].
In contrast,empirical models u monitoring data
in typical experimental plots to build empirical relationships between hydrological parameters,such as the agricultural pollution potential index,phospho-rus index,export coefficient method (ECM),etc.[22,23].Actually,the ECM has been recognized as reli-able for modeling nutrient pollution in a wide range of studies [24]since it is simple and logical,the lim-ited input requirements make the approach uful for catchment asssments and management [25,26].In addition,it considers the spatial distribution of data from various nutrient sources and predicts the total annual load of a particular nutrient into a catchment.In fact,the ECM has been ud successfully in veral countries to predict catchment-scale nutrient loading [25].On the other hand,export coefficients usually operate on an an
nual time step [27,28],so they cannot easily be ud to infer asonal patterns of nutrient delivery.It is also important to note that the ECM does not take into account the uneven temporal–spa-tial distribution of precipitation,terrain and soil condi-tions.It us the same export coefficient for the same nutrient in different hydrological years and districts,although precipitation and terrain are believed to be the key factors affecting ANPS pollution [29,30].How-ever,ECM has acceptable precision,especially suitable for areas where few obrved data are available,and can meet the needs of long-term nutrient source pollu-tion load simulation [30].Ding et al.developed and improved ECM by introducing the precipitation impact factor and terrain impact factor,which were defined to characterize the nonuniformities of precipi-tation and terrain,respectively [28].The improved model was tested in the Upper Reach of the Yangtze River and the relative error between simulated dissolved nitrogen and the obrved value was effectively reduced.Since the ECM is known to be a uful empirical model,it is important to address the shortcomings to enable better and broader applications of the model.After the start of the Three Gorges Project,great attention has been paid to environmental problems in the TGRA [31].The increasing of chemical fertilizers applied and the declining moisture in the soil in TGRA lead to rious ANPS pollution.This study herein focus on describing the temporal–spatial scale model of ANPS pollution in TGRA and linking the relationship between tributary algae blooms occur-rence and the TN/TP ratio of ANPS loads after impoundment.
The pollution load emissions from dif-ferent pathways of ANPS in TGRA have been investi-gated and analyzed.In addition,the water quality of mainstream and eight tributaries has been analyzed during different impoundment stage.The data are obtained from national environmental agencies,who 2X.Ma et al./Desalination and Water Treatment
D o w n l o a d e d b y [P e k i n g U n i v e r s i t y ] a t 17:54 18 N o v e m b e r 2015
reported them routinely.Understanding the temporal–spatial pattern of water quality and its relationships with watershed ANPS load is important for watershed and rervoir management.The results will provide uful and valuable information for decision makers and planners to take sustainable land-u management and soil conrvation measures for the control of ANPS pollution in TGRA.It is expected that it will also provide a practical way for developing countries to conduct ANPS pollution loads estimation and sup-port the aquatic environment management in the large-scale watershed or region.
2.Study area and datats
2.1.Study area
TGRA lies between28˚56´–31˚44´N and106˚16´–111˚28´E(Fig.1),covers the lower ction of the upper Changjiang River,including a low-mountain canyon in Hubei Province and a parallel valley of ridged and hilly areas in Chongqing Municipality.It consists of two cities(Chongqing Urban and Yichang Urban)and 19counties or districts(Fig.2).In2012,the TGRA had a population of1.68×107,gross domestic production was 5.11×1011RMB Yuan(8.05×1010U.S.dollar), and the per capita gross domestic production was 3.04×104RMB Yuan(4.79×103U.S.dollar)[32].
Geographically,the TGRA is bordered by the foot-hills of the Daba Mountains in the north and the margin of the Yunnan–Guizhou Plateau in the south.Of the region,about74%is mountainous,4.3%is plain,and 21.7%is hilly[33].Due to the monsoon climate,there is obvious asonality at the TGRA.The annual precipita-tion ranges from1,000to1,400mm(Fig.4),with80%of the rainfall occurring between April and October.The average annual temperature is approximately18˚C.The catchment compris forests,agricultural areas,streams and stretches of steep terrain.The main soil types in this area are purple(47.8%),limestone(34.1%)and yel-low(16.3%)earths.Agriculture and crop farming is the principal economic activity in the region.The propor-tion of cropland in this area is18,and78%of the culti-vated land is on sloped land(>10˚).
The Changjiang River was dammed successfully on8November1997.The TGD is situated upon San
douping Island in Yichang,Hubei province,China. The rervoir associated with the dam occupies a total area of approximately1,084km2.It is a narrow and long rervoir about650km in length and2km in width,with a total volume of nearly390×108m3and a water area of1,100km2.The rervoir includes40 large tributary bays(watershed area>100km2),and the surface area of the bays account for33%of the total surface area of TGR[34].The streamflow in the tributaries is considerably lower than in the main channel.The mean dailyflows for most of the tributaries are generally less than100m3/s,whereas they are high in the main stream(mean dailyflow 6,300m3/s).
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TGD,which begun to be built in1993and com-pleted in2009,had experienced four
impoundment Fig.1.Location and water system of TGRA.
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stages (Fig.3).After rising to 135m by 2003,156m by
2006,and 172m by 2008,the water level of the TGR
fluctuates from 145m in summer to 175m in winter
after it fully functioned in October 2010(Fig.3).After
impoundment,the TGR has been operated in the
mode of “storing clear and releasing muddy,”which
caud a great difference between the water residence
time within a year [35].This hydrologic regime is the
opposite of the Changjiang River’s natural regime
before TGD construction when the peak flows熟悉的一个人
occurred in summer (July–September)and low flows occurred in winter (January–March).During the stor-age period,the water level of TGR is very high and the water velocity is accordingly slowed,also water residence time is prolonged.This kind of dramatic change in the hydrological conditions will cau an influence on the ecosystem of the rervoir (Fig.4).2.2.Data The national surface water-monitoring network is coordinated and maintained by the China
National Fig.2.Counties and districts of
TGRA.
Fig.3.Impoundment stages and water lever of TGR.
4X.Ma et al./Desalination and Water Treatment
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