Assessing and modeling impacts of different inter-basin water transfer routes on Lake Taihu and the...

Ecological Engineering 60 (2013) 399 413

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Ecological Engineering

journa l h om epage: www.elsev ier .com

Assessing and modeling impacts of different intetransfe Riv

Yiping Li , Chunyan Tang , Chao Wang , Wei Tianc, Baozhu Pan , Lei Hua ,Janet Lauf, Zhongbo Yug, Kumud Acharyah

a Key Laboratory of Integrated Regulation and Resources Development of Shallow Lakes of Ministry of Education, Hohai University, Nanjing 210098, Chinab College of Environment, Hohai University, Nanjing 210098, Chinac Hydrology and Changjiang Re Zhejiang Instif Chemical andg Department oh Desert Resear

a r t i c l

Article history:Received 27 JuReceived in reAccepted 20 SAvailable onlin

Keywords:EFDCInter-basin waMulti-objectivLagrangian paWater age

CorresponResources DevNanjing 21009 CorresponResources DevNanjing 21009

E-mail add

0925-8574/$ http://dx.doi.od Water Resources Investigation Bureau of Jiangsu Province, Nanjing 210029, Chinaiver Scientic Research Institute, Wuhan 430010, Chinatute of Hydraulics & Estuary, Zhejiang 310020, China

Process Engineering, University of Western Australia, Perth 6009, Australiaf Geoscience, University of Nevada, Las Vegas, NV 89119, USAch Institute, Las Vegas, NV 89119, USA

e i n f o

ne 2013vised form 14 August 2013eptember 2013e 16 October 2013

ter transfere optimization methodrticle tracking

a b s t r a c t

To enhance water exchange and alleviate eutrophication in Lake Taihu, the third largest freshwaterlake in China, four different inter-basin water diversion named Route One to Four, have been imple-mented or planned to ush pollutants out of Lake Taihu by transporting freshwater from Yangtze River.Due to the shallowness and large size of Lake Taihu, it is quite complex to set the optimal transferredinow rate for each route or the combination of routes to maximize the benets for improving the lakeswater exchange with minimum economical cost and environmental impact. In this study, the appropriatetransferred inow rates and environmental impacts of the different water transfer routes on both LakeTaihu (receiver) and the Yangtze River (supplier) were assessed using the concept of water age andLagrangian particle tracking based on a three-dimensional Environmental Fluid Dynamic Code (EFDC)model. The results showed that the appropriate ow rates were quite different from the single routediversion to the combination of routes, depending on priorities such as lowest economical cost and high-est water quality improvement for specic lake regions or the entire lake. Two optimal combinations ofroutes to achieve specic results in different seasons were determined to improve the water exchange ofthe lake. During the algal bloom seasons, the objective of the combination focused on enhancing waterexchange in the specied lake regions such as Meiliang Bay and Zhushan Bay. The optimal ow ratesfor Route One to Route Four were 80, 70 ( means outow), 100 and 20 m3/s, respectively. In thenon-algal bloom seasons, the combination concentrated on lowering water ages in the entire lake. Theoptimal ow rates for Route One to Route Four were 90, 40, 70 and 20 m3/s, respectively. The resultssuggested that the Yangtze River Diversion, as an emergency stopgap measure, played important roleson enhancing water exchange in the lake, but had minimal impact on the Yangtze River. The ndings ofthis study provide useful information for the local government and decision-makers to better understandthe physical and hydrological processes of water transfer projects and to assist in managing the watertransfer projects.

2013 Elsevier B.V. All rights reserved.

ding author at: Key Laboratory of Integrated Regulation andelopment of Shallow Lakes of Ministry of Education, Hohai University,8, China. Tel.: +86 25 83787330.ding author at: Key Laboratory of Integrated Regulation andelopment of Shallow Lakes of Ministry of Education, Hohai University,8, China. Tel.: +86 13951787286.resses: [email protected] (C. Wang), [email protected] (Y. Li).

1. Introduction

Eutrophication has become ubiquitous in many lakes, reservoirsand other freshwater bodies affected by anthropogenic nutrientinputs over the past few decades (Paerl and Huisman, 2008; Qinet al., 2010; Schindler and Vallentyne, 2008; Smith and Schindler,2009). Water transfer engineering, an important method for lakerestoration, has been successfully used in many water bodies foraccelerating water exchange, diluting polluted water, improvingwater quality and mitigating eutrophication issues by transferring

see front matter 2013 Elsevier B.V. All rights reserved.rg/10.1016/j.ecoleng.2013.09.067r routes on Lake Taihu and the Yangtzea,b, a,b a,b,/ locate /eco leng

r-basin waterer, China

d b,e

400 Y. Li et al. / Ecological Engineering 60 (2013) 399 413

large volumes of water from a relatively clean source to a severelypolluted water body. There are currently over 160 large-scale inter-basin water transfer projects in 24 countries (Ghassemi and White,2007; Wangin Canada (United StatDiversion i1985) and China, majomade GreatSouth-to-Nsouthern Ch(Liu and ZhYangtze Riv

The Yanthe Yangtzewater transfreshwater problems, t(Hu et al., 2phication bRiver Watenow, four dor planned 2002, transvia the WanPrevious litsure, could bloom in soLake Taihu west ZonesRoute Two the water eby adding tgou aroundshowed thain enhancinow rate fr120 m3/s, anMeiliang puon the multOne and Roin the northof Lake Taidesigned toRoute ThreRiver to theplanned to west lake reclean sourcush the pdiversions whydrodynam

AlthougOne and Twobtained th2011a, 201Three and Three or Fouto set the opbination of with a minitransfer divand donatassessed th

Li et al., 2011a, 2013; Zhai et al., 2010), ignoring the donating sys-tems.

Thus, the hydrodynamic and hydrological impacts on both Lakend tasin er agnmentaileof sinic prsed

optiihu i

especynam

the tandynam

dy ar

e Tawer 12

(Figys du90s (ic prs wime

he avs divologiorthwnd Dlakerthwuenf Lakone arious

sectr proiverate

o 200 m3/sang

to it.te Onws oino40 msted e Rivgoute fo

was ng Rio Rived mour angx

rate , 2004), including the famous Snowy Mountain SchemePigram, 2000), the California State Water Project in thees (Davies et al., 1992), the Northern Siberian Riversn the former Soviet Union (Voropaev and Velikanov,the Ganges Water Diversion in India (Mirza, 2004). Inr inter-basin water transfer projects include the man-

Canal from Beijing to Hangzhou city (Yao, 1998), theorth Water Diversion Project transferring water fromina to northern China by three different transfer routeseng, 2002) and the water transfer project from theer to Chaohu Lake (Xie et al., 2009).gtze River Water Diversion, transporting water from

River to Lake Taihu, is another example of inter-basinfer engineering in China. Lake Taihu, the third largestlake in China, is suffering from severe eutrophicationhreatening the water supply for the surrounding cities008; Yang and Wang, 2003). In order to relieve eutro-y enhancing water exchange in Lake Taihu, the Yangtzer Diversions have been built (Qin et al., 2010). Up toifferent routes of this project have been implemented(Fig. 1). Route One (the original route), implemented infers freshwater from the Yangtze River into Lake Taihugyu River and discharges water through the Taipu River.erature showed that Route One, as an emergency mea-temporarily improve water quality and mitigate algalme lake regions excluding the most polluted area in

(i.e., Meiliang Bay, Zhushan Bay, Northwest and South-) (Hu et al., 2008, 2010; Li et al., 2011a; Zhai et al., 2010).(the improved route) was applied in 2004 to improvexchange in Meiliang Bay in the northern lake regionwo additional pump stations named Meiliang and Xin-

Meiliang Bay (Fig. 1) (JWRA, 2006). Li et al. (2013)t Route Two played a supplementary role for Route Oneg water exchange directly in Meiliang Bay. The optimalom the Wangyu River (Route One) was predicted to bed the corresponding appropriate outow rate from themp station (Route Two) was about 1520 m3/s basedi-objective optimization method. However, both Routeute Two did not signicantly enhance water exchangewest and western regions, the heavily polluted areas

hu. Hence, Routes Three and Four have been recently enhance water exchange in those polluted lake regions.e is planned to bring fresh water from the Yangtze

northwest region via the Xinmeng River. Route Four istake fresh water via the Changxing River to the south-gion. The design concept is to transfer water from thee into the specied hyper-eutrophic areas directly andollutants out of Lake Taihu. However, whether theseill work or not is difcult to predict due to the complexics of Lake Taihu.

h previous papers have evaluated the effect of Routeso on accelerating water exchange in Lake Taihu ande optimal transferred ow rates for them (Li et al.,3), it still remains unclear about the effects of RoutesFour. For example, how will the new-planned Routesr work for enhancing water exchange in the lake? Howtimal transferred ow rate for the single route or com-the four routes to improve the lakes water exchangemal economical cost? Additionally, the impact of waterersions should focus on both the receiver (Lake Taihu)or (Yangtze River). However, previous research onlye impacts on the receiving system (Hu et al., 2008, 2010;

Taihu ainter-bof watEnviroThe deeffect dynamrate batify theLake Tasons, rhydrodto helpundershydrod

2. Stu

Lakthe lo11953of 1.9 m181 dathe 19dynamchangethe sumwhile tTaihu iand ecBay, NZone aof the the noand efparts owest Zand se

Thetransfeujing Rin the w1950 t28,700to the Ywater

Rouand oactual 20 to 2rst teYangtzand Xinow raThree XinmeCaoqiadesignRoute Fthe Chinowhe Yangtze River and appropriate ow rates of differentwater transfer routes will be assessed using the concepte and particle tracking based on a three-dimensionaltal Fluid Dynamic Code (EFDC) model in this paper.

d objectives of this study were to: (1) understand thegle route of inter-basin water transfer on the hydro-ocess of Lake Taihu and its appropriate transferred owon a multi-objective optimization program; (2) iden-mal combinations and the corresponding ow rates forn the algal bloom seasons and the non-algal bloom sea-tively; (3) assess the impact of water diversions on theic processes of the Yangtze River. This study aimed

local government and other decision-makers to better the effect of water transfer projects on the physical andic processes in Lake Taihu and the Yangtze River.

ea

ihu, a well-known large shallow lake, is located inYangtze River delta between 30563133 N and036 E, with an area of 2338 km2 and a mean depth. 1, Qin et al., 2010). The lake retention time was aboutring the period from 1951 to 1988 and 309 days afterQin, 2008). Wind is a key driving force in the hydro-ocesses of Lake Taihu. Wind direction around the laketh the seasons, with southeasterly winds prevailing inr and northwesterly winds prevailing during the winter,erage wind speeds are 3.55 m/s (Hu et al., 2006). Lakeided into eight sub-areas according to its hydrologicalcal characteristics: Zhushan Bay, Meiliang Bay, Gonghuest Zone, Southwest Zone, Central Zone, East Epigeal

ongtaihu Bay (Fig. 1, Hu et al., 2008). The southeast part has a signicantly better water quality compared toest section due to the special locations of the inuentt rivers (Hu et al., 2010; Li et al., 2011b). The northweste Taihu, including Meiliang Bay, Zhushan Bay, North-nd Southwest Zone, suffer from frequent algal blooms

eutrophication problems.ion of the lower Yangtze River related to this waterject extends from the Wufeng Mountain to the Xuli-

(Fig. 1). The length of the main stem is about 221 kmr transfer study area. The averaged ow discharge from5 of the Yangtze River in Jiangsu Province was about

(Chen et al., 2001). All water transfer routes are relatedtze River, either withdrawing water from it or returning

e takes water to Gonghu Bay through the Wangyu Riverut via the Taipu River in Dongtaihu Bay (Fig. 1). The

w rate in operation from the Wangyu River ranges from3/s (Jia et al., 2008). Route Two, built in March 2004 andin 2006, takes polluted water out of Meiliang Bay to theer by using two new pump stations named Meiliang

around Meiliang Bay. The designed maximal operationr each pump station is 50 m3/s (JWRA, 2006). Route

planned to bring water from the Yangtze River to thever, and go though Lake Gehu, the Taige River and theer, and eventually ow into Zhushan Bay (Fig. 1). Theaximal inow rate of Route Three is about 100 m3/s.was designed to transfer water into Lake Taihu throughing River near the Southwest Zone, with a predictedin the range of 050 m3/s.

Y. Li et al. / Ecological Engineering 60 (2013) 399 413 401

Fig. 1. The locThe eight suba(8) Central Zonthe Yangtze Ri

3. Method

3.1. Numer

EFDC, a tby the Unitwas used tothe Yangtzeand Lagrangapplied to aculation, thquality andlakes, reser2011a, 201Hamrick (1

3.2. Water

WA wasenvironmenfer process time that haregion in w1999; ShenTaihu can b

A particlmotion traiation of Lake Taihu, Yangtze River watershed and the main tributaries. The bold lines anreas of Lake Taihu are: (1) Gonghu Bay, (2) Meiliang Bay, (3) Zhushan Bay, (4) Northweste. (I) The details about the topography around Route Three in the Yangtze River; Z1Z3 ver, respectively. (II) The details about the river networks around Routes Two and Three

s

ical model description

hree dimensional numerical model, initially developeded States Environmental Protection Agency (USEPA),

simulate the impact of water transfer on Lake Taihu and River including water level, current, water age (WA)ian particle tracking (LPT). EFDC has been successfully

wide range of environmental studies simulating cir-ermal stratication, sediment transport, tracers, water

eutrophication process in coastal regions, estuaries,voirs, rivers, and wetlands (Gong et al., 2009; Li et al.,3). The details of the EFDC model are documented by992) and Craig (2011).

age and Lagrangian particle tracking

a suitable parameter for describing spatiotemporaltal benet in assessing the impact of the water trans-

in this study (Li et al., 2011a, 2013). It is dened as thes elapsed since the particle under consideration left thehich its age is prescribed as being zero (Delhez et al.,

and Wang, 2007). The details of water ages used in Lakee found in Li et al. (2011a, 2013).e-tracking model was used to understand the real-timel of water parcels. Currently, it has been widely used

for simulatclides, oil sand coastalGillibrand, 2been appliethe Yangtzedocumente

3.3. Multi-ooptimal ow

The multhe optimaldecrease thet al., 2013)

Minimize y

Subject toQ

where y(Qiminimum vreach the ovalue and asmall valuetransferredrespectivelytransferredd digitals ( , , and ) represent different water transfer routes. Zone, (5) Southwest Zone, (6) Dongtaihu Bay; (7) East Epigeal Zone,and D1D5 represent sections in the main and branching channel ofin Lake Taihu.

ing the dispersion of passive tracers, larvae, radionu-pills and even contaminated milk in estuaries, lakes

waters (Gong et al., 2008; Liu et al., 2011; Murray and006; Wang et al., 2005). However, the method has notd to understand the real-time new water dispersion in

River Diversion yet. The details of LPT calculations ared by Craig (2011).

bjective optimization method for quantifying the rates of water transfer

ti-objective optimization method was used to obtain ow rates from the different water transfer routes toe WA in Lake Taihu and reduce the economic cost (Li. The function is shown as below (Eq. (1)):

(Qi) =WA(Qi) WA

SWA+ M(Qi) M

SM

i [q1, q2](1)

) is the objective function. When y(Qi) reaches thealue, the corresponding inow or outow rate (Q)

ptimal values. It means that the WA gets its minimumt the mean time the economic cost takes a relative. WA(Qi), WA and SWA are water age changing with

ow, the mean and standard deviation of water age,. Similarly, M(Qi), M and SM are the economic cost of

ow, the mean and standard deviation of economic


Fig. 2. Time s ifferenGate, (b) Qiwe

cost, respecstandardizevariances oobjective minow or outo the mode

3.4. Model

3.4.1. Lake The Lake

based on thconsisting othe x and y vertical direThe model and inow/lake with wtemperaturon the resuboundary cshowed thabe ignored.eight monitThe daily wLaboratory ences situatstep was usbility. Specand verica

3.4.2. YangFor the

nates wererepresentatputational clengths varused in the

h-retion rent eleva

Xulimed ay frarysischaed fro

(JPHc surThe initia

ran xederies of simulated water levels (solid lines) and observed data (cross symbol) at di Ferry, (c) Jiangyin Station, and (d) Tiansheng Harbor.

tively. (WA(Qi) WA)/SWA and (M(Qi) M)/SM are thed dimensionless objectives with means of zero andf one. A smaller value of the standardized dimensionlesseans a smaller water age and less economic cost. Thetow rate is in the feasible range of q1 to q2 accordingl simulated scenarios.

setup, calibration and verication

Taihu model Taihu model was developed by Li et al. (2011a, 2013)e EFDC. This model used rectangular horizontal gridsf 4465 active cells with a uniform cell size 750 m in bothdirections. Three evenly distributed sigma layers in thection were applied to better t the bottom topography.

The higsimula

Curby an namedary nafar awboundow dobtainSystemgraphiRiver. of the usuallythan awas driven by atmospheric forcing, surface wind eldoutow tributaries. Since the lake is a typical shallowind-driven currents and a lack of thermal stratication,e could be considered as constant due to its slight effectlts. The details of the inow/outow tributaries as theonditions are found in Li et al. (2011a), and the resultst the impacts of other tributaries around the lake could

The daily precipitation data were averaged data fromoring stations in the vicinity of the lake (TBA, 2009a).ind data were sourced from the weather station of Taihufor Lake Ecosystem Research, Chinese Academy of Sci-ed near Meiliang Bay. For this model, a 100-second timeed in the simulations with no signs of numerical insta-ic details regarding the Lake Taihu model calibrationtion can be found in Li et al. (2011a).

tze River modelYangtze River model, orthogonal curvilinear coordi-

used in the horizontal direction, allowing for a betterion of the complex shorelines. There were 4037 com-ells in the horizontal plane of the model grid with cellying from 400 to 3000 m. The sigma coordinates were

vertical direction with ve evenly distributed layers.

els, a movinassigning a wetting/dry

Model con Februaryinto two da2009 were March 2Mthe calibratheight (z0) downstream2003). The sof 2009 at Ferry, Jiangpared. The absolute rel0.079 m anStation, and(Fig. 2). Thof water levon the dataJiangyin Stavelocities at monitoring stations in the Yangtze River, China. (a) Shengli Sluice

solution bathymetry was collected to ensure accurateof the tidal circulation and water level.and water level within the model domain were drivention specied condition at the open boundary nodesujing River and ow discharge at the upstream bound-Zhenjiang Station. The open boundary was extendedom the inlets of water transfer projects to avoid the

impact on the accuracy of model simulations. Therge at the upstream boundary (Zhenjiang Station) wasm the Jiangsu Province Hydrology Information InquiryIIS). The wind data was obtained from the whole hydro-vey synchronously at Zhenjiang Station and Xuliujinginitial surface elevation was set as the average valuel time of the simulation period. A stepping time step,ging from 1.0 to 15.0 s, was used in this study rather

time step. To adapt to the uctuation of water lev-

g water surface boundary was applied in the model bycritical dry water depth (0.05 m) and implementing theing procedure proposed by Hamrick (1994).alibration and verication were conducted from 08:00

26 to 8:00 on March 5, 2009. The data were dividedta sets. Data for the period of February 26March 1 ofused for model calibration, while data for the period ofarch 5 of 2009 were applied for model verication. Fromion process (gure not shown), the bottom roughnesswas set at a range of 0.0220.011 m from upstream to

and 0.080.04 m near the central island (Zhao et al.,imulated and observed water elevations on March 25four monitoring stations (Shengli Sluice Gate, Qiweiyin Station and Tiansheng Harbor, Fig. 1) were com-results showed that the mean absolute error and meanative error were 0.101 m and 8.5% at Shengli Sluice Gate,d 3.46% at Qiwei Ferry, 0.094 m and 6.5% at Jiangyin

0.061 m and 4.1% at Tiansheng Harbor, respectivelye calibrated model provided satisfactory descriptionsel variations. The results of current verication, based

from available measurements (Shengli Sluice Gate andtion, March 45 of 2009), suggested that the modeledlmost agreed with the observations of the monitoring


Fig. 3. Verication results of water current in the Yangtze River, China (cross symbol represents measurements, solid line signies model results) (a) Shengli Sluice Gate,and (b) Jiangyin Station.

stations (Fig. 3). The mean absolute error and mean absolute rel-ative error between the model results and observations were asfollows: 0.13 m/s and 18% at Shengli Sluice Gate, and 0.12 m/s and14.7% at Jiangyin Station section, respectively. Overall, the modelreproduced the main features of water level and ow velocity inthe Yangtze River quite well.

3.5. Model application

The impof both Lakeestimated bFive groupsdischarge sconducted (Table 1). Awater transwater transYangtze Rivratio by the

The purRoute Threemost econousing differan incremewith a winwind). The oFour via the50 m3/s. Th

the two main inow transfer routes (Route One and Route Three)on water exchange in Lake Taihu. In Group Three, the inuent dis-charge from the Wangyu or Xinmeng River was set to 100 m3/sand the outow from Meiliang/Xingou River pump station was setas 20 m3/s, which was the optimal pumping rate according to theresults of Li et al. (2013). Meanwhile, the sum of outows from theTaipu River and Meiliang pump station were always equal to theinow from the Wangyu or Xinmeng River to keep the water bal-ance consistent. Group Four investigated the optimal combinationof Routes One, Two and Three based on the previous results with the

/s inoutee copre

Taihom , 20tandf wattranswerep Fivall of

the tiontion)to beT win thact of the Yangtze River Diversions on water exchanges Taihu (receiver) and Yangtze River (donator) werey the validated Lake Taihu and Yangtze River models.

of scenarios including a series of various wind and owcenarios from four different water transfer routes wereto assess the effects of water transfer on Lake Taihudditionally, one group of scenarios including differentfer routes were simulated to understand the impact offer engineering on the hydrodynamic processes of theer, including water elevation, local current and split

central island (Fig. 1).pose of Group One aimed to determine the effect of

on water exchange in Lake Taihu and to determine themically efcient inuent ow via the Xinmeng River byent ow discharges ranging from 10 to 100 m3/s withnt of 5 m3/s and three typical wind forcing conditionsd speed of 5 m/s (wind directions of SE, NW, and nobjective of Group Two was to assess the effect of Route

Changxing River with inow rates ranging from 0 toe objective of Group Three was to compare the effect of

120 m3

from Reffectivthe comin Lakerates fr50200underscases owater routes of Grou

For exceptas mensimulawater lake. LPparcel Fig. 4. Water age on Julian day 365 in eight lake zones under three different wind sow rate from Route One and the 20 m3/s outow rate Two. Group Five was conducted to determine the mostmbination of the water transfer routes and to estimatehensive effects of the four water transfer routes on WAu. In Group Five, the various ranges of inow or outowthe four water transfer routes were accordingly about50, 0100, and 050 m3/s. Group Six was conducted to

the effect of water transfer on the Yangtze River. Twoer transfer were taken into account (i.e., with or withoutfer projects). The ow discharges of the water transfer

based on the optimal ow rates from the combinatione.

the groups, the model congurations and parameters,driving factors shown in Table 1, were kept the sameed in Section 3.4. The WA on Julian 365 (the last day of

was selected to reect the time elapsed for transferred transported from the inlet to any given location in theas used to understand the motion trail of a new watere water exchange process in Groups One and Three. Acenarios with 100 m3/s inow from Route Three.


Table

1M

odel

sim

ula

tion

scen

ario

s.

Mod

el

scen

ario

s

Win

ds

Flow

disch

arge

(unit:

m3/s

)

Wan

gyu

Riv

er

(Rou

teOne,

inow

)M

eilian

g/Xin

gou

pum

pst

atio

n

(Rou

te

Two,

out

ow)

Xin

men

g

Riv

er

(Rou

teTh

ree,

inow

)Chan

gxin

g

Riv

er

(Rou

teFo

ur,

inow

)Ta

ipu

rive

r

(out

ow)

Lake

Taih

u

mod

elGro

up

One

No

win

d, d

omin

ant

win

d

spee

d

5

m/s

, win

ddirec

tion

s

are

SE

and

NW

From

10

to

100

incr

ease

d

by

5

Kee

p

wat

er

bala

nce

:ou

tow

from

Taip

uRiv

er

= in

ow

from

Wan

gyu

+

inow

from

Xin

men

g

Riv

er

+

inow

from

Chan

gxin

g

Riv

er

ou

tow

from

Mei

lian

g/Xin

gou

pum

pst

atio

n

Gro

up

Two

No

win

d

From

0

to

50

incr

ease

dby

10Gro

up

Thre

eNo

win

d10

0

10

0

20

100

20

100

Gro

up

Four

No

win

d

Optim

al

inow

(120

)ob

tain

ed

from

Li

et

al.

(201

3)

Optim

al

out

ow

(20)

obta

ined

from

Li

et

al.

(201

3)

From

10

to

100

incr

ease

d

by

10

Gro

up

Five

No

win

dM

onte

Car

lo

sam

pling:

the

range

s

of

inow

rate

from

the

Xin

men

g

Riv

er, t

he

Wan

gyu

Riv

er

and

the

Chan

gxin

g

Riv

er

are

010

0,

502

00

and

205

0,re

spec

tive

ly. T

he

range

of

out

ow

rate

from

the

Mei

lian

g/Xin

gou

pum

p

stat

ion

is

050

.

Yan

gtze

Riv

er

mod

elGro

up

Six

Win

d

spee

d

5

m/s

,w

ind

direc

tion

is

SE.

Withou

t

wat

er

tran

sfer

engi

nee

ring

With

wat

er

tran

sfer

engi

nee

ring.

Outlet

and

inle

t

ow

disch

arge

are

acco

rdin

g

to

the

optim

al

com

binat

ion

of

Gro

up

Five

(in

the

alga

l blo

om

seas

on

conditio

n)

Not

e:

mea

ns

no

ow

disch

arge

.

multi-objective optimization method was required to obtain theoptimal ow rates for water transfer engineering in Groups One,Two and Five.

4. Results

4.1. Effect o

4.1.1. Effectof Lake Taih

The effeassessed byresults for tvariability. lake regionbution of WThree as andays) was y(262 days).mer and nowater exchRoute ThreeRoute Threeation of WA18 days. Wcent to Zhuthe changinthat in the days in the days in thetively. WA iother heaviwater exch268364 daeasily exchaEpigeal Zonwere aboutconditions

In genering water exZone and tinlet, Howelake regioninant windlake region

4.1.2. LagraLPT was

by Route Twere releaarea of Meparcel pathregion (Memarked withat the mBay, Northwparticles inthere was nluted waterhelp enhaniang Bay, wThree withBay.f Route Three on water exchange in Lake Taihu

of Route Three on water age in different lake regionsuctiveness of Route Three on WA in Lake Taihu was

the simulation scenarios of Group One (Table 1). Thehese scenarios showed that WA exhibited great spatialRoute Three mainly helped decrease WA in the westerns, and winds had strong impacts on the spatial distri-A (Fig. 4). Taking a 100 m3/s of inow rate from Route

example, for the entire lake, WA with no wind (235ounger than that with the dominate wind directions

The dominant wind directions (i.e., southeast in sum-rthwest in winter) did not provide good conditions forange associated with this water transfer processes via. Zhushan Bay, directly connected with the entrance of, had the youngest WA (less than 25 days). The uctu-

caused by the different winds in this bay was less thanithin the Northwest Zone and the Central Zone adja-shan Bay, WA was greatly dependent on winds, andg trends of WA in these two zones were similar withentire lake. WA in the Northwest Zone was about 96conditions of no winds, while it was about 260 and 325

conditions of southeast and northwest winds, respec-n the Central Zone varied from 185 to 231 days. As forly polluted zones, Meiliang Bay and the Southwest Zone,ange had little improvement with WA of 305354 andys, respectively, suggesting that water parcels were notnged in those areas using Route Three. WA in the Easte, Dongtaihu Bay and Gonghu Bay, far from Route Three,

185, 215 and 288 days, respectively, in suitable wind(i.e. southeast winds).al, Route Three could have a positive impact by enhanc-change and decreasing WA in Zhushan Bay, the Central

he Northwest Zone relatively near the water transferver, there was only a slight WA reduction for others, such as Dongtaihu Bay and Gonghu Bay. The dom-s had few improvements for water exchange in mosts.

ngian particle tracking in Route Three water transfer used to study the pathways of water parcels impactedhree. The virtual particles marked with red trianglessed in the inlet in Zhushan Bay and in the middleiliang Bay, which could be used to show the waterway from the Yangtze River and in the polluted lakeiliang Bay), while the end positions of particles wereth blue circles shown in Fig. 5. The results showedain possible paths of particles covered the Zhushanest Zone and part of the Central Zone (Fig. 5). The

Meiliang Bay were trapped in this bay which meanto exchange between the new clean water and the pol-

in this bay (Fig. 5). Thus, Route Three could effectivelyce water exchange in the polluted area excluding Meil-hich showed that it was essential to coordinate Route

Route Two to improve water exchange in Meiliang


Fig. 5. The paangle and blueinterpretationto the web ver

4.1.3. OptimWA was

sive with aThree. WA dynamic anrespectivelyimizing thethe multi-ooperate thistransferredwere quanttion.

A seriesThree (Grouships betwewestern lakaddressed bting markedthrough Roto 235 days100 m3/s. Hin the differ

Specicagreatly enhdecreasing in the earlyreached 30days and thincreased fr30 m3/s, Wtrend of Wto be a goodFor the Norinow increimproveme

days when transferred inow increased from 10 to 100 m3/s. As forMeiliang Bay, there were no changes to WA caused by Route Three.

e the results suggested that the inow rate of Route Threefferencessasettin) andhe wing tferenake rt wei

pollake rin La

= ww1, n Baone l Zonor thnwh

enerchan

give

126Q

ordin)), thriate

ize

t tothways of water parcels from Route Three (100 m3/s) (the red tri- circles represents the released and end position, respectively). (For

of the references to color in this gure legend, the reader is referredsion of the article.)

al transferred inow rate for Route Three younger and the energy power cost was more expen-n increase in the transferred inow rate from Routeand energy power cost were considered as hydro-d economic factors during the water transfer process,. It is necessary to optimize the inow rate for max-

effect of water transfer at a minimal cost based on

Sinchad diit is newhen rate (Qcess. Taccordthe difcial lhighesheavilyother l(days)

WA(Q )

where Zhushawest ZEpigeastand f

Meaby thewater, ship is

M = 0.Acc

(Eq. (3approp

Minim

Subjec

bjective optimization method in order to manage and

transfer route effectively. Specic relationships among inow rate (Q), averaged WA, and cost of water transferied as the rst step of the multi-objective optimiza-

of ow discharges from the Yangtze River via Routep One in Table 1) were conducted to assess the relation-en Q and WA in Lake Taihu, especially in the pollutede regions where water quality problems could not bey Route One. The results showed that WA was get-ly younger with an increase of transferred inow rates

ute Three (Fig. 6). WA substantially decreased from 352 in the entire lake as the inow increased from 10 toowever, the changing trends between Q and WA variedent polluted western lake regions (Fig. 6).lly, the water exchanges in Zhushan Bay could beanced with a younger WA by Route Three. The

rates of WA in Zhushan Bay were particularly obvious stages with increased inow rates until the ow rate

m3/s. More specically, WA decreased from 62 to 22e change rate of WA was about 65% when the inow rateom 10 to 30 m3/s. When increasing the ow rate aboveA remained approximately 15 days. From the changeA, an inow rate of 30 m3/s for Route Three appeared

choice for enhancing water exchange in Zhushan Bay.thwest Zone, WA decreased from 321 to 96 days as theased from 10 to 100 m3/s. For the Southwest Zone, thent of WA was very limited, and WA decreased by 60

The resuabout 85 m3

objective fuof 0.31 (pbest solutiobenets anthis optimaand Zhushathe cost of (about 1.7 m

4.2. Effect o

The effeassessed byresults showproblem inalways be ithe envelopnew water were aboutsponding 50 m3/s, resdischarges ever, the amt effects on water exchange in different lake regions,ry to assign the weights (w) of WA in each lake regiong up the relationship between the transferred inow

averaged WA in the multi-objective optimization pro-eights (w) of WA in each lake region were assignedo the benets from Route Three discussed above andt functions of the lake region itself. The most bene-egion (i.e. Zhushan Bay) was assigned the relativelyghts. The lake regions with drinking water sources oruted areas had relatively high weights compared withegions. Then the relationship between the weighted WAke Taihu and ow rate (Q, m3/s) was as follows:

1 WA1(Q ) + w2 WA2(Q ) + + w8 WA8(Q ) (2)w2, . . ., w8 were the weights of the eight sub-areas:y (0.2), Meiliang Bay (0.15), Gonghu Bay (0.05), North-(0.2), Southwest Zone (0.15), Central Zone (0.15), Easte (0.05) and Dongtaihu Bay (0.05). WA1, WA2, . . ., WA8e average WA in the eight sub-areas.ile, the economic cost of transferred water, quantiedgy power cost (M, million RMB/year) for transportingged with transferred inow rate (Q, m3/s). The relation-n below (Li et al., 2013):

(3)

g to the function between Q, WA (Eq. (2)), and Me multi-objective optimization method determines the

inow rate from Route Three (Eq. (4)):

y(Qi) =WA(Qi) WA

SWA+ M(Qi) M

SM

WA(Q ) = w1 WA1(Q ) + w2 WA2(Q ) + + w8 WA8(Q )

M = 0.126QQi [0, 100]

(4)

lts showed that the optimal transferred inow was/s from Route Three and the corresponding value of thenction (the solid black line, Fig. 7) reached the minimumoint A). The transferred inow rate of 85 m3/s was then for tradeoff between the environmental and economicd gained the maximum efciency of water transfer. Inl water transfer scenario, the averaged WA in Lake Taihun Bay were about 253 days and 9 days, respectively, andenergy power was approximately 10.71 million RMBillion dollars).

f Route Four on water exchange in Lake Taihu

ct of the fourth water transfer route (Route Four) was the simulation scenarios of Group Two (Table 1). Theed that Route Four mainly solved the water exchange

the Southwest Zone where water exchange could notnduced by Route One and Route Three (Fig. 8). Frome line of water areas having been exchanged by thefrom Route Four, the percentage of exchanged areas

11.6%, 19.4%, 26.9%, 33.0% and 36.8% for the corre-ow discharges from Route Four of 10, 20, 30, 40, andpectively (Fig. 8). This showed that increases in owcorresponded to better exchanges as expected. How-ount of change in exchange area decreased with the


Fig. 6. The impact of transferred inow rate (Q, unit: m3/s) via Route Three on water age (WA, unit: day) in the entire lake, Zhushan Bay, Northwest Zone and SouthwestZone.

increasing ow rate. The increments of exchanged areas percent-age were 7.8% (1020 m3/s), 7.5% (2030 m3/s), 6.2% (3040 m3/s)and 3.9% (4of water traaveraged Wthe obviouswere few im

4.3. Overallwater excha

4.3.1. CompSince Ro

ing water frto comparethe conven(Group thresince Routethe relativeoptimal inrate from R

(1) Com

The results showed that Routes One and Three had similar con-tributions on reducing WA (235 days) in Lake Taihu (Fig. 9a and b).

er, dution.cicantakhile

one, ). Onor wg Ba

lakehan stan

eutroter ee lakroupcreasig. 9ao w8% c

Fig. 7. The relthe multi-objeobjective func050 m3/s). This suggests that the maximum efciencynsfer occurs at a ow rate of 20 m3/s. In this case, theA in the Southwest Zone was about 220 days. However,

deciency of this water transfer route was that thereprovements of water exchange in other lake regions.

effect of the combination of water transfer routes onnge in Lake Taihu

arison of Route One and Route Threeute One and Route Three were the major inlets for bring-om the Yangtze River into Lake Taihu, it was important

the effects and contributions from both of them. Forience of comparison, the same inow rate of 100 m3/se, Table 1) was selected for both routes. Additionally,

Three was being planned, it was necessary to calculately efcient inow rate from Route Three based on theow rate from Route One (120 m3/s) and the pumpingoute Two (20 m3/s) we gained before (Li et al., 2013).parison of the two water transfer routes

Howevdistriband b)

Spewater idays), wwest Z(Fig. 9ament fMeilianeasternlarger tnot subhyper

Wainto thTwo (GBay deTwo (Fand Twby 44.7ationship for transferred inow rate (Q) from Route Three and standardized water age (ctive programming for water transfer in Lake Taihu. (Notes: standardized water age andtion curve (black line) using vice coordinates).ue to the different locations of inow inlets, the spatials of WA across Lake Taihu were very different (Fig. 9a

lly, for Route One, Gonghu Bay with several drinkinges was the biggest beneciary with the youngest WA (18

all the heavily polluted areas (i.e., Zhushan Bay, North-Southwest Zone and Meiliang Bay) beneted the least

the contrary, for Route Three, there was great improve-ater exchange in the polluted lake zones excludingy and parts of the Southwest Zone (Fig. 9b), while the

regions had poor water exchange where the WA was300 days. However, the two water transfer routes couldtially enhance water exchange in Meiliang Bay wherephic areas and drinking water intakes were located.xchange would be improved if routes bringing watere (e.g. Routes One, Three and Four) operated with Route

Three, Table 1). The results showed that WA in Meilianged from 286 to 133 days by combining Route One and

and c). Similarly, the effect of combining Routes Threeas signicant on WA in Meiliang Bay, which decreasedompared to use of Route Three only (Fig. 9b and d).WA) in Lake Taihu, and standardized cost of water transfer (M); and standardized cost of water transfer using principal coordinate, the


Fig. 8. The different envelope line of water areas having been exchanged by thevarious inow rates (1050 m3/s) from the fourth water transfer route.

However, Route Two had little impact on other lake regions. RouteTwo played a supplementary role to both Route One and RouteThree by solving the water exchange issue in Meiliang Bay.

(2) Efcient inow rate from Route Three based on the optimalow rates of Route One and Two

The inow rate from Route Three was tested using values from10 to 100 m3/s to determine its relatively efcient inow rate basedon the best operation of Route One (120 m3/s) and Route Two(20 m3/s) (Group four, Table 1). The results showed that the lowerWA areas spread from Gonghu Bay (


Fig. 10. The spthe Route Two

The partparcels frommal water tas an examptriangles wroutes (i.e.,Meiliang Bablue circleswater transresults shoered ZhushZone and scles from Renhance wDongtaihu iang Bay wethe water e

4.3.2. OveraFifty num

sampling intively and aFive, Table

The bestroutes were(Eqs. (5)(8atial distribution of water age in Lake Taihu under different inow rates via the Route T. (a) 10 m3/s; (b) 30 m3/s; (c) 40 m3/s; (d) 100 m3/s.

icle tracking was used to determine the path of water the different water transfer routes. Taking the opti-

ransfer case of Route One, Route Two and Route Threele (Group Four, Table 1), the particles marked with redere released in the inlets of two main water transfer

Zhushan Bay and Gonghu Bay) and the middle area ofy, and the end positions of particles were marked with

to show the water parcel pathways from the differentfer routes and in the polluted lake region (Fig. 11). Thewed that the particles from Route Three mainly cov-an Bay, the Northwest Zone, parts of the Southwestmall portions of the Central Zone. The paths of parti-oute One illustrated that this route was benecial toater exchanges in Gonghu Bay, the East Epigeal Zone,Bay and the major Central Zone. The particles in Meil-re taken out by the Meiliang pump station, which aidedxchange in Meiliang Bay.

ll effect of all the water transfer routeserical simulations were conducted based on random

order to combine all the water transfer routes effec-ssess the comprehensive effect on Lake Taihu (Group1).

solutions to the combinations of all the water transfer provided based on four specic constraint conditions)). The rst one was to enhance water exchange in

every lake rout water efor the heaBay, Southwexchange aeutrophicatter hydrody(i.e., Gonghwas about ebinations oconditions, weights of circumstanand non-algsons, moreregions andin those areWhile in theexchange in

Minimum

Minimum hree, 120 m3/s inow from the Route One and 20 m3/s outow from

egion and minimize the percentage of lake area with-xchange as far as possible (Eq. (5)). The second one wasvily polluted lake regions (i.e., Meiliang Bay, Zhushanest and Northwest Zone) to reduce WA, enhance waternd decrease the possibility of algal blooms in thoseion areas (Eq. (6)). The third was for enhancing bet-namic conditions at the drinking water source areasu Bay and the East Epigeal Zone) (Eq. (7)). The fourthconomic efciency (Eq. (8)). When the different com-f water transfer routes had similar water exchangethe more economical solution would be chosen. Thethe four constraint conditions were determined by theces, which were divided into the algal bloom seasonsal bloom seasons. Namely, during the algal bloom sea-

considerations need to be put in the polluted lake the main target was to accelerate water exchangeas. It was essential to lower the risk of algal blooms.

other seasons, the main goal was to enhance the water the entire lake.

Area without water exchangeTotal water area

100% (5)

WA = 1n

ni=1

WAi(heavily polluted area) (6)


Fig. 11. The p(20 m3/s) and the released ancolor in this g

Minimum

Minimum

Accordinthe best soluseasons waof 90, 70 awould owsituation, Warea had be

was about 118, 10, 112 and 212 days in the polluted Meiliang Bay,Zhushan Bay, Northwest Zone and Southwest Zone, respectively(Fig. 12a).

However, in the algal bloom seasons, the optimal combination ofwater transfer routes was to have the inow rates for Routes One,Three and Four of 80, 100 and 20 m3/s, while the outow rate ofRoute Two (two pump stations in Meiliang Bay) was 70 m3/s. In thissituation, WA in Meiliang Bay, Zhushan Bay, Northwest Zone andSouthwest Zone were about 99, 7, 96 and 200 days, respectively.WA in this situation were 1020 days younger than in the previoussituation, especially in the heavily polluted lake regions (Fig. 12b).Additionally, it should be mentioned that the water transfer processshould be put into practice in the early spring to dilute the pollutedwater and to prevent the potential for algal blooms in summer.

4.4. Impact of water transfer on hydrodynamic processes in theYangtze River

The impact of water transfer engineering on the Yangtze Riverwas investigated by the numerical simulation cases of Group Six(Table 1). The result did not show remarkable changes in the hydro-dynamic process of the Yangtze River caused by the water transferdiversions.

rder to analyze the effect of water transfer on the hydro-ic prlevelf owof Rohreeow rhe tocated

in thf lessut thhe o

Fig. 12. The spseasons (b), reathway of water parcel from the Route One (120 m3/s), Route TwoRoute Three (40 m3/s) (the red triangle and blue circles representsd end position, respectively). (For interpretation of the references toure legend, the reader is referred to the web version of the article.)

WA = 1n

ni=1

WAi(drinking water source) (7)

M = M(Q ) (8)

g to the constraint conditions, the results showed that

In odynamwater rates ointake Route Tmain since tcomplichangerates o

Abonear ttion for all water transfer routes in the non-algal blooms to have inow rates from Routes One, Three and Fournd 20 m3/s, respectively, while the transferred water

out through Route Two at 40 m3/s, respectively. In thisA in Lake Taihu was about 160 days and 98.4% of theen exchanged with relatively low economic input. WA

the local vedifferences Route One would increFor the maxdue to the w

atial distribution of water age in Lake Taihu under the optimal combinations of water trspectively.ocess in the Yangtze River, ow rates, local velocity and were selected to describe the phenomena. The change

rates in the main channel of the Yangtze River near theutes One and Two were all less than 1%. The impact of

on the ow rate in Yangtze River was divided into theate (Z1Z3) and branching channel ow rate (D1D5),pography around Route Three (Xinmeng River) was

(Fig. 1). The results showed that there was no obviouse main river and branching channel with ow change

than 0.5% and 3%, respectively.e local ow eld, changes occurred in the small scaleutlet and inlet of water transfer routes. Comparinglocity before and after water transfer, the maximumof velocities were 0.07, 0.12 and 0.1 m/s due to theto Three (Fig. 13). Generally, water transfer diversionsase the local velocity in near the inlet/outlet (Fig. 13).imum change of water level, there was less than 0.1 mater transfer diversions. Thus, the impact of the water

ansfer routes in the non-algal bloom seasons (a) and the algal bloom


Fig. 13. Veloci entati(a) Route One,

transfer divin the Yang

5. Discussi

5.1. Effect o

Water trpolluted walevel whenatively bett1981; Welcto Lake Taihshort-term polluted wacertain regiroutes had vital to opeoptimal comlakes wateronmental WA on the

5.1.1. EffectThe resu

in different using the coregions (Tabinow ratecorrelationscorrelation routes work

The owcoefcient (was great imimplementhad a positregions. Getaihu Bay h0.8) with

eilian Ba

withLi et trackt rivard o

Taihe mainto

(Zhte Twd a slmeasubstn coeliangThusl effeg Baeilia

in Mt al.,

tranient eas wnueely he Noom iontrge inhree

u Bayf lessad a

Table 2Correlation co

Route One Route Two Route ThreeRoute Four ty changes before (solid line with circles) and after (solid line with cross) the implem (b) Route Two, and (c) Route Three.

ersions was not obvious on the hydrodynamic processtze River.

on

f water transfer routes on Lake Taihu

ansfer could enhance hydrodynamic processes, diluteter, improve water quality, and lower the lake trophic

the water quality of inow from the supplier is rel-er than that in the receiver (Oglesby, 1969; Welch,h et al., 1992). The water transfer from the Yangtze Riveru with various routes could play an important role as a(emergency) measure to temporarily dilute the heavilyter, enhance water exchange and ease water crisis inons of Lake Taihu. The different single water transfervarious effects on WA in different lake regions. It israte each water transfer route effectively and to set thebination of the four transferred routes to improve the

r exchange with a minimum economical cost and envi-impact. Nutrient loads and impact of the reduction inalgal bloom were discussed below.

of the single water transfer route on Lake Taihults showed that each water transfer route decreased WAlake regions. The effect could be quantitatively analyzedrrelations between ow rates and WA values in the lakele 2). Overall WA in the lake decreased with increasing

from the transfer project, thus there was a negativehip between WA and inow rate. The stronger negativecoefcients mean the more effective the water transfer

on the lake. rate from Route One had a large negative correlation0.74) with WA in the entire lake, suggesting that thereprovement of water exchange in Lake Taihu due to the

ation of Route One. Additionally, as expected, Route One

then MZhushasistentroute (parcel inuenwestwof Lakeally, thwater quickly

RouBay, hawhich It had relatioin MeiThree. mentaMeiliandata. Mwater (Zhai e

Thecoefctive armain irelativand thents frgreat cexchanRoute TGonghcient oThree hive effect leading to decreased WA in most of the lakenerally, Gonghu Bay, the East Epigeal Zone and Dong-ad the most sensitive correlation coefcient (less thanRoute One, followed by the Central Zone (0.59) and

in Lake TaihRoute Fo

effect on thlation coef

efcients between water age (WA) in Lake Taihu and water transfer routes based on Mon

Entire lake CentralZone

East EpigealZone

DongtaihuBay

GonghuBay

0.74 0.59 0.85 0.83 0.90 0.10 0.15 0.19 0.19 0.04

0.56 0.33 0.32 0.35 0.01 0.33 0.21 0.04 0.10 0.05 on of water transfer routes in the Yangtze River near the inlets/outlets.

ng Bay, the Northwest Zone, the Southwest Zone andy having the least (larger than 0.5), which was con-

the result of the evaluation of the rst water transferal., 2011a). The results were consistent with the watering pathway by the LPT method. The water from theer (Wangyu River) pushed the water in Gonghu Bayr southward to the Central Zone and the eastern partu (i.e., Dongtaihu Bay and East Epigeal Zone). Addition-in out ow, Taipu River, could help discharge pollutedDongtaihu Bay and exchange water with other zonesai et al., 2010).o, the improved water transfer engineering in Meiliangight positive coefcient (0.1) with WA in the entire lake,nt it could not enhance the average WA in Lake Taihu.antial impact only on WA in Meiliang Bay with a cor-fcient of 0.74. This route enhanced water exchange

Bay, which was a blind zone for Route One and Route, Route Two was the best choice for minimizing detri-cts such as eutrophication and harmful algal blooms iny. This result has been demonstrated by the observedng Bay had a better water exchange in 2007, since theeiliang Bay was pumped out at a ow rate of 40 m3/s2010).sferred inow rate from Route Three had a correlationof 0.56 with WA in Lake Taihu. The most two sensi-ere Zhushan Bay and the Northwest Zone where thent rivers were located. The eutrophication levels areigh and algal blooms occur frequently in Zhushan Bayrthwest Zone due to the high concentration of nutri-nuent rivers and human activities. Route Three hadibutions on solving this problem and enhanced water

Zhushan Bay and the Northwest Zone. Additionally, had hardly any contributions to the water exchange in

and Meiliang Bay with an absolute correlation coef- than 0.1. Additionally, compared with Route One, Route

relatively weak effect on the average water exchange

u.ur, an aided route of water transfer, had an obviouse water exchange in the Southwest Zone and a corre-cient of 0.78. It had few additional effects on other

te Carlo sampling.

MeiliangBay

NorthwestZone

SouthwestZone

ZhushanBay

0.48 0.29 0.11 0.030.74 0.05 0.13 0.060.05 0.85 0.76 0.880.01 0.18 0.78 0.04


lake regions. This planned route may offer some aid to overcomethe deciency of Routes One and Three to solve the eutrophica-tion problem in the Southwest Zone, a seriously polluted and poorwater exch

5.1.2. EffectAs each

Taihu, it watively especseasons, rebeen taken in water exextent. Sincseasons, it wios rather throutes. It wcombinatioabout 80, 1was about water exchalgal bloomfrom RouterespectivelyRoute Two ato enhance

These diwere considtransfer in Lroutes in thlakes such uniform anHilt et al., 2

5.1.3. ImpaGenerall

inow fromaged TN anheavily poll(Hu et al., 2for the Yangent (N & P)that in Laketwo main wthe monitorResources,

The tranOne (the Wperiod of 20the amountTN loading occurred in2005 and a there were ing the watfrom 30 trito the lake)water transrespectively

The inuand Taige Rtrations witet al., 2011about 5.97 heavily pollpollution pr

Route Three could run more frequently, both Lake Taihu and thesurrounding river networks would be improved through dilutionand diversion of pollutants out during the water transfer period.

he lot wop to

Effectept fage orcomstionreaseiver aihu f wataterergeerathe dactioot reitions in tdes aThes

pactes of

watic pre ining ted out 2transet al.

watnsferely sm/L) a

Yangd qulf-puynamrowtitione Rivpactto-Nbitiohina

tonsorth

200r roun roue low

he wThe Sce th

a dn rivesonaange capacity lake region.

of the combined water transfer routes on Lake Taihuwater transfer route had various effects on WA in Lakes essential to combine all water transfer routes effec-ially in the algal bloom seasons and non-algal bloomspectively. In this study, different weight factors hadinto consideration, so that there would be an increasechange capacity with relatively less cost to the greateste we focused on different lake regions in the differentas essential to provide different water transfer scenar-an using a constant xed combination of water transferas found that in the algal bloom seasons, the optimaln for inow rates from Routes One, Three and Four were00 and 20 m3/s, while the outow rate for Route Two70 m3/s. This combination would focus on enhancingange in the heavily polluted lake regions. In the non-

season, the optimal solution was that the inow ratess One, Three and Four were about 90, 70 and 20 m3/s,, while the transferred water would ow out throught 40 m3/s. This combination could cover all lake regionswater exchange rates.fferent priorities for four specic constraint conditionsered due to the heterogeneous impacts caused by waterake Taihu. The combinations of different water transfere large shallow lake are more complex than other smallas Moses and Green Lakes in Washington with mored good exchange rates in the entire lake (Welch, 1981;011).

ct of water transfer on the nutrient loads in Lake Taihuy, the concentrations of TN and TP in the transferred

the Yangtze River were slightly higher than the aver-d TP concentrations in the lake, but lower than mostuted lake regions (e.g., Meiliang Bay, west lake zones)010). This overloading of nutrient is controversial onetze River Diversion project, especially since the nutri-

concentrations in the Yangtze River are higher than Taihu. Here we discuss the nutrient load due to theater transfer routes (Routes One and Three) based oning data from Taihu Basin Authority, Ministry of WaterChina.sferred inow and nutrient loads (TN & TP) from Routeangyu River) to Lake Taihu were calculated during the03 to 2008. Results indicated that nutrients varied with

of transferred water (Figure not shown). The minimumwas 664 tons in 2005 while the maximum (4110 tons)

2007. The TP input loads had a minimum (34 tons) inmaximum (170 tons) in 2007. The results showed thatadditional nutrient loads entering into Lake Taihu dur-er transfer. However, compared with the nutrient loadsbutaries (approximately 85% of the total runoff input

(Qin et al., 2007), the additional nutrient loads fromfer projects were for less than 5% and 7% for TN and TP,.ent rivers connected with Lake Taihu (i.e., Caoqiao Riveriver) around Route Three had higher nutrient concen-h major contributions to Lake Taihu for each season (Lib). The TN and TP concentrations in those rivers wereand 0.57 mg/L, which were in the same range as theuted Zhushan Bay (TBA, 2009b). Thus, those rivers boostessures on Lake Taihu in non-water transfer periods. If

In tnutriennot hel

5.1.4. Exc

water to ovein queto decJohn RLake Tinlet othat wand emagglomThus, tterm rewere n

AddsourcepesticiTaihu.

5.2. Improcess

Thedynamnear thAccordaveragwas abwater (Chen

Thethe trarelativ(7.2 mgin the diffusehigh sehydrodalgal g

AddYangtzthe imSouth-and amnorth Cbillionto the nZheng,transfewesterfrom thfrom tstudy. inuenduringweakethe seang-term perspective of the water transfer process, theuld likely accumulate gradually in the lake which maysolve the eutrophication problems.

of the reduction of water age on algal bloomor the most radical ushing options for the bays, thef major sections of the lake are not reduced enoughe the growth rates of the problematic cyanobacteria. Estimated WA would have to be less than 80 days

Chl-a concentration based on the results from St.(Lowe et al., 2012). However, WA in most subzones ofis greater than 80 days excluding some areas near theer transfer (e.g. Gonghu Bay). Thus, it is recommended

transfer projects should be regarded as a stopgapncy method to drive the accumulated cyanobacteriales along with currents away from the water intakes.ecrease in Chl-a concentration would only be a short-n if the nutrient concentration in the transferred waterduced to a reasonable level.ally, it is possible and inevitable that some existinghe Yangtze River (e.g. some industrial organic waste,nd herbicides, and heavy metals) could ush into Lakee process need to be further studied.

of water transfer diversions on the hydrodynamic the Yangtze River

er transfer engineering had little impact on hydro-ocesses in the Yangtze River, such as the split ratioow/outow rivers, local current eld and water level.o the statistical information from 1950 to 2005, theow discharge of the Yangtze River in Jiangsu Province8,700 m3/s, and the designed maximum ow rates offer occupied a very small proportion of its ow rate, 2001).er quality in the area of the Yangtze River receivingred efuent water from Lake Taihu may deteriorate onall scales. The annual averaged concentrations of TN

nd TP (0.16 mg/L) in Meiliang Bay were larger than thattze River. But the polluted water would be diluted andickly due to the large amount of upstream ow and therication capacity of the Yangtze River. Besides, theic conditions in the Yangtze River does not suit the

h transferred from Lake Taihu either (Zhai et al., 2010).ally, compared with another well-known project in theer named the South-to-North Water Diversion Project,

of this water diversion was obviously limited. Theorth Water Diversion Project is regarded as a strategicus approach to resolving water shortage problems in

with three transfer routes delivering water (about 48) seasonally from a different reach of the Yangtze River

of China facing water shortages (Berkoff, 2003; Liu and2). This project is implemented through three watertes named the eastern route, the middle route and thete. Among them, the eastern route would carry waterer reaches of the Yangtze River, which is not far away

ater transfer engineering routes to Lake Taihu in thisouth-to-North Water Diversion Project would in turne middle and lower Yangtze River hydrology especiallyry season. The rapid increase in water removal willr hydrology further in the coming decades, sharpeningl contrast in water discharge to the sea (Chen et al.,


2001). The South-to-North Water Diversion Project also causedsome ecological and environment problems disturbing the fragileecological balance of North China, such as seasonal drying ofriver coursgroundwateand Zheng,of water trawork is nedealing wit

6. Conclus

The impLake Taihu model by uresults showquite differdepending nomical colake regiontions includexchange obloom seastion was thaabout 80, 1was about water exchZhushan Ba7, 96 and 20tion was thwere aboutwater woulcombinatioexchange rafer only haprocesses obefore and for variableinlets/outlewater transmeanwhileFrom a longa temporarcrisis. The rand decisiodynamic prthe single o

Acknowled

The res2010CB95151009049 ation (BK201for ExcellenInnovation (CXZZ13 022012ZX075thank the TAcademy of

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earch was supported by Grant # 2010CB429003,101, Chinese National Science Foundation (51379061,nd 51179053), and Jiangsu Province Science Founda-31370). The research was also supported by Programt Talents in Hohai University, Qing Lan Project, theProgram of Graduate Students in Jiangsu Province70), China Scholarship Council, Grant # 40911130507,06-002, IRT0717, 1069-50986312. We would like toaihu Laboratory for Lake Ecosystem Research, Chinese

Sciences, for providing monitoring data.

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Assessing and modeling impacts of different inter-basin water transfer routes on Lake Taihu and the Yangtze River, China1 Introduction2 Study area3 Methods3.1 Numerical model description3.2 Water age and Lagrangian particle tracking3.3 Multi-objective optimization method for quantifying the optimal flow rates of water transfer3.4 Model setup, calibration and verification3.4.1 Lake Taihu model3.4.2 Yangtze River model

3.5 Model application

4 Results4.1 Effect of Route Three on water exchange in Lake Taihu4.1.1 Effect of Route Three on water age in different lake regions of Lake Taihu4.1.2 Lagrangian particle tracking in Route Three water transfer4.1.3 Optimal transferred inflow rate for Route Three

4.2 Effect of Route Four on water exchange in Lake Taihu4.3 Overall effect of the combination of water transfer routes on water exchange in Lake Taihu4.3.1 Comparison of Route One and Route Three4.3.2 Overall effect of all the water transfer routes

4.4 Impact of water transfer on hydrodynamic processes in the Yangtze River

5 Discussion5.1 Effect of water transfer routes on Lake Taihu5.1.1 Effect of the single water transfer route on Lake Taihu5.1.2 Effect of the combined water transfer routes on Lake Taihu5.1.3 Impact of water transfer on the nutrient loads in Lake Taihu5.1.4 Effect of the reduction of water age on algal bloom

5.2 Impact of water transfer diversions on the hydrodynamic processes of the Yangtze River

6 ConclusionAcknowledgmentsReferences

Assessing and modeling impacts of different inter-basin water transfer routes on Lake Taihu and the...

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