Cost-effectiveness analysis of water-saving irrigation technologies based on climate change response: A case study of China

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ContentslistsavailableatScienceDirect

Agricultural

Water

Management

jo u r n al ho m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / a g w a t

Cost-effectiveness

analysis

of

water-saving

irrigation

technologies

based

on

climate

change

response:

A

case

study

of

China

Xiaoxia

Zou

a

_,

_Yu’e

_Li

a,∗

_,

_Roger

_Cremades

b,c

_,

_Qingzhu

_Gao

a

_,

_Yunfan

_Wan

a

_,

_Xiaobo

_Qin

a

a_Institute_of_Environment_and_Sustainable_Development_in_Agriculture_(IEDA),_Chinese_Academy_of_Agricultural_{Sciences(CAAS),}₁₀₀₈₁_Beijing,_China b_{International}_Max_Planck_Research_School_on_Earth_System_Modeling_(IMPRS-ESM),_Hamburg,_Germany

c_Research_Unit_{Sustainability}_and_Global_Change,_University_of_Hamburg,_Germany

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received6September2012 Accepted7July2013 Available online 7 August 2013 Keywords:

Cost-effectivenessanalysis Water-savingirrigation Climatechange Adaptationandmitigation

a

b

s

t

r

a

c

t

Thisstudyprovidesacost-effectivenessanalysisoffourwater-savingirrigationtechniquesthatarewidely implementedinChinatoaddresstheimpactsofclimatechange:sprinklerirrigation,micro-irrigation, low-pressurepipeirrigationandchannellining.Theaimistothoroughlyunderstandtheeconomic feasibilityofwater-savingirrigationasanapproachtocopingwithclimatechange.Basedonthe cost-effectivenessanalysis,thisstudyﬁndsthatwater-savingirrigationiscost-effectiveincopingwithclimate change,andhasbeneﬁtsforclimatechangemitigationandadaptation,andforsustainableeconomic development.Forthecost-effectivenessratioofmitigationandadaptation,onlythatofchannelliningis negative(formitigationis−43.02to−73.41US$/t,forgrainyieldincrease−34.35to−20.13US$/t,and forwatersaving−0.020to−0.012US$/m3_)._Sprinkler_irrigation_has_the_highest_incremental_cost_for

mit-igation(476.03–691.64US$/t),becausewhensprinklerirrigationisused,theremaybeadditionalenergy needstomeetwaterpressurerequirements,whichmayincreasegreenhousegasemissionscomparedto traditionalirrigation.Formitigation,indistrictswherethepumpingheadforpressureislowerthanthe criticalenergysavinghead,sprinklerirrigationshouldbeavoided.Micro-irrigationhasthehighest incre-mentalcostforadaptationfollowedbysprinklerirrigationandlow-pressurepipeirrigation,butwhen consideringtherevenuesfromimprovedadaptation,allofthemeasuresassessedareeconomically fea-sible.Theresultssuggestthatformitigationandadaptationobjectives,micro-irrigationperformsbest. Fromaneconomicperspective,channelliningisrecommended.Therefore,abalanceddevelopmentof channelliningandmicro-irrigationaccordingtodifferentgeographicalconditionsisrecommended.

1. Introduction

Agricultureis one ofthe mostvulnerablesectors to climate change(IPCC,2007a).Waterresourcesareessentialtoagriculture, butover thelast 50 years,someparts ofChina(Figs.1 and2), includingmajorgrainproducingareas,haveexperienceddeclining precipitation(Renetal.,2005).Inrecentdecades,anannualaverage of12.64millionhaoffarmlandhasbeenaffectedbydrought,with anaveragedisasterrate(i.e.,thepercentageofthetotaldrought affectedareathatsuffersdisastrousloss)of56.71%.In2008,the grainlosscausedbydroughtwasabout16milliontonsand ﬁnan-ciallosseswereabout23millionChineseyuan(CNY)(MWR,2011). Inaddition,increasingdemandforwaterfromurbanandindustrial

∗ Correspondingauthor.Tel.:+8601082105615.

E-mailaddresses:[email protected],[email protected](X.Zou), [email protected],[email protected](Y.Li).

sectorsplacesgreaterpressureonagriculturalwateruse(Fedoroff et al.,2010).Previous studies haveindicated that water-saving irrigation(WSI)contributestowatersavingandalsotothe reduc-tion ofgreenhouse gasemissions,which can easethenegative effects ofclimatechangeonagriculturalproduction (Zouetal., 2012;Karimietal.,2012).However,thecostandeffectivenessof usingWSItocopewithclimatechangeremainsunknown.Todate, therehavebeenlimitedcomparisonswithotheradaptationand mitigationmeasurestoinformidentiﬁcationofadaptationand mit-igationstrategies.Aclearpictureofthecost-effectivenessofWSI techniquesincopingwithclimatechangecanalsosupport iden-tiﬁcationofbalancedresponsestoclimatechangeandsustainable economicdevelopment.

Cost-effectiveness analysis(CEA) is a decision-making assis-tancetoolthatcomparesalternativestoachieveagoalwithregard totheirresourceutilization (cost)and outcomes(effectiveness) (BambhaandKim,2004).CEAcanbeusedtoﬁndtheleastcost meanstoachieveagoal,ortoestimatetheexpectedcostsof achiev-ingaparticularoutcome(TietenbergandLewis,2011).Itcanalso beusedtocomparetheimpactsand costofvariousalternative meansofachievingthesameobjective(Dhaliwaletal.,2012).The 0378-3774© 2013 The Authors. Published by Elsevier B.V.

http://dx.doi.org/10.1016/j.agwat.2013.07.004

Open access under CC BY license.

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Fig.1. TendencyofannualprecipitationinChinafrom1956to2002(Renetal.,2005). resultofaCEAisexpressedinaratio(cost-effectivenessratio,CER)

betweencostandoutcome(Johannesson,1995).CEAhasbeenused forestimatingthecostofmitigationintheelectricitysector(Sims etal.,2003),andindairyfarms(Vellingaetal.,2011),buildings (Hoogwijketal.,2010),agriculture(WassmannandPathak,2007), transport(Metzetal.,2001)andtheservicesector(Hoogwijketal., 2010).Despitethislargebodyofliterature,therearenospeciﬁc studiesaddressingthecost-effectivenessofWSIforclimatechange adaptationandmitigation.

Comparedto traditional irrigationpractices, WSI techniques requirehighercapitalinvestment.Revenueisamajordriverfor farmerswho pursueagriculturalproduction (Muhammad etal.,

2007).Therefore,thecostandeffectivenessareveryimportant fac-torsrelevanttothewillingnessoffarmerstoadoptWSI(Tiwari and Dinar,2000).Inthe contextof climatechange,sustainable development,mitigationandadaptationareintegralpartsofthe responsetoclimatechange.Fordevelopingcountries,mitigationis along-termandarduouschallenge,whileadaptationisapresent andurgenttask.Withglobalgreenhousegasconcentrationsrising, asuccessfulresponsetoclimatechangeisaconcernfacedbythe wholeworld(IPCC,2007a,b).

Inordertoelucidatetherelationshipsbetweenthecostsand effectiveness of WSI in the context of climate change adapta-tion and mitigation, CEA wasapplied to the fourmost widely

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implementedWSI techniquesin China:sprinklerirrigation (SI), micro-irrigation(MI),low-pressurepipeirrigation(LI)and chan-nellining(CI).OnthebasisofCEA,recommendationsaremadefor addressingdevelopmentneedswhilecontributingtoaneffective climatechangeresponseandsustainabledevelopment.

2. Methods

NeuhauserandLweicki(1975)carriedoutaCEAprovidingits resultsasanaveragecost-effectivenessratio(CER).Followingthis method,inthispaperthecostandeffectivenessofmitigationand adaptationofeachWSItechniquearecomparedwithabaseline scenarioinwhichtraditionalirrigationisemployed.The method-ologicalstepsaresummarizedinFig.3.Evaluationindicatorsand calculationmethodsaredescribedinSection2.1,anddatasources andprocessingmethodsareexplainedinSection2.2.

2.1. Evaluationindicatorsandcalculationmethods 2.1.1. Deﬁnitionofevaluationindicators

Allthecalculationsinthispaperarebasedonanon-gravity irri-gatedarea.In gravityirrigatedareas,noenergyis consumedin waterpumping,sotherearenogreenhousegas(GHG)emissions, andnoneedtocalculatethecosteffectivenessofGHGmitigation.

Baselinescenario:Thebaselinescenarioisdescribedintermsof theenergyconsumedandCO2emittedbyirrigationmachineryper

unitarea(ha)ofirrigatedfarmland,andbythewaterconsumption andgrainyieldperunitofirrigatedfarmland(ha)whentraditional irrigationisadopted.

Coststructure:Dataonproductioncostthatarenotmodiﬁed byotheragriculturalproductionconditionswhichhavenothingto dowithirrigationwerecollected. Incomparisonwiththe base-linescenario,thecoststructureofWSIconsistsof:annualaverage initialequipmentinvestment(I),annualaverageequipment oper-ationand maintenanceinvestment(OM),annualreduced water fees(SW)andenergyfees(SE)ofWSItechniquescomparedwith traditionalirrigation.

Measureofmitigationeffectiveness:TheadoptionofWSI con-tributes to CO2 emission reduction in the Chinese agricultural

sectorduetothepumpingenergysavedwhengroundwateror non-gravityconveyedwaterissaved(Maetal.,2006;LiandFu,1998; Dangetal.,2006;Zouetal.,2012).

Cost-effectivenessofmitigation:Thecostneededtoreduceeach unitofgreenhousegasemission.Inthispaper,thisreferstothe

additionalcosts duetoadoption ofWSI ofreducing one tonof CO2 emissionbelowtheemissionsinthebaselinescenario.

Cost-effectivenessisexpressedasaratioofcoststoeffectiveness(CER) (unit:US$/tCO2).

Measures of adaptation effectiveness: The adoption of WSI enablesfarmers toreducetheadverseeffectsofclimatechange in two main ways. First, research shows that adoption of WSI increasescropyieldsperunitarea(ha)(Chai,2000;Chenetal., 2009; Guoet al.,2004; Houet al.,2007; Wang,2010).Second, reducedrequirementsforwateruseperunitarea(ha)make agri-culturalproduction more resilientto drought(Loëet al.,2001; Tuongetal.,2005;Belderetal.,2005;Katoetal.,2009).Boththese beneﬁtsofWSIreduce‘thevulnerabilityofagriculturetoclimate change.

Cost-effectivenessofadaptation:Theadditionalcostneededto enhanceadaptationquantitatively,expressedasaCER.The addi-tionalcostofincreasingeachtonofgrainyield(unit:US$/t)and theadditionalcostofreducing eachcubicmeterofwater(unit: US$/m3₎_are_estimated_by_comparing_costs_and_effects_in_the

base-lineandWSIscenario. 2.1.2. Calculationmethods

(1)Formulaforcalculatinginvestments:

Cj=Ij+OMj−SEj−SWj (1)

where C, annual total cost of WSI technique for irrigating per unitareaof farmlandcompared totraditional irrigation (US$ha−1yr−1);I,averageinitialcostofinstallingwater-saving devices perunit area(US$ha−1yr−1);OM,annual operation andmaintenancecostsperunitareaofwater-savingdevices (US$ha−1yr−1); SE, annual average energy fees saved by WSItechniquesperunitareaincomparisonwithtraditional irrigation(US$ha−1yr−1);SW,annualaveragewaterfeessaved perunitareabyWSItechniqueincomparisonwithtraditional irrigation(US$ha−1yr−1);j,indexforWSItechnique.

(2)FormulaforCEAofGHGmitigation: CER_mj= _ECj

mj (2)

whereCERm,cost-effectivenessratioofmitigation(US$/tCO2);

Em,annualaverageCO2 emissionreduction perunit areaof

farmlandirrigatedbyWSItechniqueincomparisonwith tra-ditionalirrigation(tha−1yr−1). Cost CO2

Emission

Reduction Grain Yield Increase CER of Mitigation

Cost Effectiveness Analysis (CEA)

CER of Grain YieldIncrease Initial Equipment Investment Operation and Maintenance Energy Saving Fees Water Saving Fees TotalCost Mitigation _Adaptation WaterSaving CER of Water Saving

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(3)FormulaforCEAofadaptation: (i)CEAofgrainyieldincrease

CERgi=_ECj

gj (3)

whereCERg,cost-effectivenessratioofgrainyieldincrease

(US$/t);Eg,annualaverageincreaseingrainyieldperunit

areaoffarmlandirrigatedbyWSItechnique(tha−1yr−1). (ii)CEAofreducedwaterconsumption

CERwj=_ECj

wj (4)

whereCERw,cost-effectivenessratioofwateruse

reduc-tion(US$/m3_);_E

w,annualaveragevolumeofreducedwater

useperunitareaoffarmlandirrigatedbyWSItechnique (m3_ha−1_yr−1_).

2.2. Datasourcesandprocessingmethods

Dataontheinitialequipmentinvestment(I),mechanicallife(i) andtherateofincreasedgrainyieldweretakenfrompublished studies(seebelow),andtheaveragevalueofthesedatawasused. GrainpricesandexchangeratesofCNYagainstUS$andEurocome from“ChinaStatisticalYearbook”(NBSC,2008,2009,2010).Energy andwaterprices comefromNationalDevelopment andReform CommissionofChina(NDRCC,2009–2011).

Themainuncertaintyofthepaperistheinvestmentandprice data.Thepaperisbasedonprovincialdatainallitscalculations. Therecouldbedifferencesininvestmentorpricebetweendifferent regionswithinChina.Inordertoreducethisuncertainty,efforts havebeenmadetoensurethatthedatasourcesforinvestment, priceandratesofgrainyieldincreasecoversregionsatdifferent levelsofeconomicdevelopmentinChina.

Table1

InitialcostsofWSItechniques(unit:US$/ha).

CI LI SI MI

Mean 586.44 581.42 1305.13 1975.82

Min 524.80 488.88 1172.15 1770.72

Max 648.07 673.96 1438.10 2180.91

Note:MinandMaxvaluearethelowerandupperbounds,respectively,ofthe95% conﬁdenceinterval.

2.2.1. StatisticsoninitialinvestmentinWSIdevices

Reliablepublishedpapers including reportsof initial

invest-ment in WSI techniques were identiﬁed (see Appendix A and

Fig. 4). The data identiﬁed covered both the more economi-callydeveloped eastern regionand the less developed western regionofChina.Theaveragecostreportedineachcasestudywas adoptedandconvertedintoUS$(seeTable1)usinganexchange rateof1US$=7.12CNY,whichistheaverageexchangerateover 2008–2010(NBSC,2008,2009,2010).

2.2.2. MechanicallifeofWSIdevicesandtheiroperationand maintenancecosts

Accordingtopublished papers, theservice lifeof MI ranges between5and15years(WangandWu,2006;Dangetal.,2006; Dongetal.,2000;Huang,2001),SIbetween10and20years(Wang andWu,2006;Zhang,2006),LIbetween10and15years(Li,1991) andCI15–30years(Wu,2000;GaoandZhang,2004;Meng,2006). Inthispaper,thefollowingdurationsofservicelifeareassumed: MIis10years,SIis15years,LIis12yearsandCIis20years.Byusing theservicelifedata,theannualinitialinvestmentofWSItechnique wasobtained.Collectedinitialinvestmentdatacoveredaseriesof yearsthatfrom1980stopresentandtheaverageofthesedatawas used,sothepresentvaluewasignored.

The average annual operation and maintenance cost of SI accountsforabout5%ofitsinitialequipmentcost(LiandWang,

Fig.4.DistributionofdataonWSIinitialinvestmentcostsinthepublishedliteratures.Notes:Theverticallinebisectingdatapointsindicatestherangeofinitialinvestment costsreportedineachpaper,andthetriangleindicatestheaverageoftherange.Atrianglewithnobisectinglineindicatesthatthepapergaveonlyonevalueforinitial equipmentinvestmentcosts.ThelettersindicatingeachpapermatchesthecodingofpapersinAppendixA.

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Fig.5.Provincescoveredbytheirrigationwaterpricesurvey.

2001;WangandGao,2001),thatofCIabout3%(LiandFu,1998), MIabout8%andLIabout5%(WangandWu,2006).Theaverage valueoftheinitialequipmentcostwasusedinthecalculationof operationandmaintenancecosts.

2.2.3. Irrigationwaterandenergyprices

InChina,irrigationwaterpricesvaryfromregiontoregion.In someregionstherearenowaterfees(SCNPC,2002),whileinsome waterconservancyprojectareasthewaterpriceishigherdueto highoperationand maintenance fees(SDPC,2001).Toquantify waterprices, 12irrigationdistrictslocatedinShaanxi,Xinjiang, Qinghai,Shandong,Hunan,Sichuan,Heilongjiang,Hebei, Gansu, Jilin,JiangxiandBeijing(Fig.5)weresurveyed,onthebasisofwhich 0.03US$/m3_was_taken_as_the_water_price_for_all_calculations_in_this

paper.

ThesourcesoftheenergyrelevanttoWSItechniquesaremainly electricityanddiesel(Zouetal.,2012).Attheendof2010,theprice ofdieselinChinawasapproximately980US$/t(NDRCC,2010).The priceofelectricityforirrigationwasabout0.056US$/kWh(NDRCC, 2009–2011).

2.2.4. MitigationandadaptationeffectsofWSItechniques

GHGmitigationeffectsofWSIaremainlyduetoreducedCO2

emissionsfromreducedenergyuseinwaterpumping.Water sav-ingsmaybecausedby reducedevapotranspiration,percolation, runofforbyotherfactors.Irrespectiveofthespecificcauseofwater savings,thetotalvolumeofwatersavedisdirectlyreflectedina reductioninpumpedwater,whichreduceswaterpumpingenergy needsandGHGemissions.Wepreviouslyquantifiedthe mitiga-tioneffectsofWSItechniquescomparedtotraditionalirrigation (Zouetal.,2012),andinthispaperweusetheaveragedatafrom theevaluatedperiod(2007–2009).

Regardingadaptationeffects, previousstudieshavereported thatWSItechniquescanincreasegrainyieldandreduce agricul-tural waterconsumption (Belderetal.,2005; Katoet al.,2009; Wang,2010). Data on reduced agriculturalwater consumption derivedfromourpreviousstudy(Zouetal.,2012).Inthispaper,the

Table2

RateofincreaseingrainyieldduetoadoptionofWSItechniques(unit:%).

CI LI SI MI

Mean 14.28 19.33 22.15 23.41

Min 10.53 17.66 18.95 21.35

Max 18.03 21.00 25.35 25.48

Note:MinandMaxvaluearethelowerandupperbounds,respectively,ofthe95% conﬁdenceinterval.

rateofincreaseingrainyieldsforeachWSItechniquecompared

totraditional irrigationwasreviewedby selectingdatasources

reportingyieldsunderconditionsequivalenttothosereportedin

thepapersreviewedoninitialinvestmentcosts.Alldataongrain

yieldincreasesderivedfromﬁeldexperimentscomparingthenet

increaseingrainyieldwithWSItechniquestoyieldsunder

tra-ditionalirrigationmethods(seeFig.6,Table2andAppendixB).

Additionalgrainyieldthatmightbeachievedthroughreuseofthe savedwaterwasnotconsideredinthisanalysis.Basedonthe three-yearaveragegrainyieldduring2007–2009,adaptationeffectsare calculatedaccordingtoformula(5).

G=G∗R (5)

whereG,annualincreasedgrainyield;G,three-yearaveragegrain yield;R,annualrateofincreaseingrainyield.

TheeffectsofWSItechniquesinclimatechangemitigationand adaptionaresummarizedinTable3.

3. Results

3.1. AdditionalcostofWSItechniques

The additional costs of adopting WSI techniques, compared withtraditionalirrigation,areshowninTable4.Amongthefour measures,onlyCIhasanegativecost,i.e.,comparedtotraditional irrigationCIcostsless.Thisisduetolargersavingsofenergyand watercoststhantheinvestmentandmaintenancefeesunderCI.In

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Fig.6. DistributionofdataonrateofincreaseingrainyieldinresponsetoWSIs.Note:GraphicalindicationspleaserefertoFig.4.

Table3

Three-yearaverageeffectsofWSItechniquesonmitigationandadaptationindicators. Electricitysaved (kWhha−1_yr−1₎ Dieselsaved (kgha−1_yr−1₎ Emissionreduction (kgha−1_yr−1₎ Watersaved (m3_ha−1_yr−1₎

Grainyieldincreased (kgha−1_yr−1₎

SI 169.93 −6.49 143.92 2169.63 1075.73

MI 1362.33 15.98 1379.86 2524.05 1136.92

LI 178.67 0.97 177.22 1408.11 938.77

CI 281.56 15.14 324.53 1173.42 693.52

descendingorder,theCERofMIisgreaterthanSI,whichinturnis

greaterthanLI,andCIwasfoundtohavethelowest(negative)ratio.

Statisticaltestsindicatesigniﬁcant(˛=0.05)differencesbetween

CERsofeachWSImeasure.

Table4

AnnualaveragecoststructureofWSItechniques(unit:US$ha−1_yr−1_).

IE IW I OM C SI Mean 3.16 65.09 87.01 65.26 84.02 Min 3.16 65.09 78.14 58.61 68.51 Max 3.16 65.09 95.87 71.91 99.54 MI Mean 91.95 75.72 197.58 158.07 187.98 Min 91.95 75.72 177.07 141.66 151.06 Max 91.95 75.72 218.09 174.47 224.89 LI Mean 10.96 42.24 48.45 29.07 24.32 Min 10.96 42.24 40.74 24.44 11.98 Max 10.96 42.24 56.16 33.70 36.66 CI Mean 30.60 35.20 29.32 17.59 −18.89 Min 30.60 35.20 26.24 15.74 −23.82 Max 30.60 35.20 32.40 19.44 −13.96

Notes:IE,annual energy feesavedper haby WSIcomparedwith traditional irrigation;IW,annualwaterfeesavedbyWSIperhacomparedwithtraditional irrigation;I,annualinitialcostperhaofinstallingWSIdevices;OM,averageannual operationandmaintenancecostofWSIdevicesperha;C,annualaveragetotal incrementalcostperhaofWSI.

3.2. Cost-effectivenessanalysisofWSItechniquesbasedon

climatechangemitigationandadaptation

TheCERsofGHGmitigationforeachWSItechnique,obtained

byEq.(2),aregiveninTable5.Ofthefourmeasuresassessed,SI hasthehighestGHGabatementcost,followedbyLI,MI andCI. Therearesignificant(˛=0.05)differencesbetweenSIandLI,but nosignificantdifferencesbetweenMIandSI.TheCERofadaptation foreachWSItechnique,obtainedbyEqs.(3)and(4),aregivenin Table6.MIhasthehighestratioonbothoftheadaptationeffects assessed,followedbySI,LIandCI.Therearesignificant(˛=0.05) differencesamongMI,SIandLI.

IfthepresentgrainpriceinChinaisconsidered,theaveragecost ofincreasingeachunitofgrainyieldofeachWSItechniqueislower thanthevalueoftheadditionalgrainyield.Thatistosay,compared totraditionalirrigation,itisproﬁtableforfarmerstoincreasegrain yieldsbyadoptingWSItechniques.

Table5

Costs-effectivenessratioofgreenhousegasmitigation(US$/tCO2).

SI MI LI CI

Mean 583.84 136.23 137.24 −58.22

Min 476.03 109.47 67.61 −73.41

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Table6

Costs-effectivenessratiosofadaptation.

SI MI LI CI

Forwatersaving(US$m−3₎ _Mean _0.039 _0.074 _0.017 _−0.016 Min 0.032 0.060 0.009 −0.020 Max 0.046 0.089 0.026 −0.012 Forgrainyieldincrease(US$t−1₎ _Mean _78.11 _165.34 _25.91 _−27.24

Min 63.68 132.87 12.76 −34.35 Max 92.53 197.80 39.06 −20.13

3.3. Sensitivityanalysisofthecost-effectivenessofmitigationand

adaptation

Therearesourcesofuncertaintyintheselectionofthe

param-etersusedintheanalysis.Inordertoquantitativelyanalyzethe

inﬂuenceof parameters onthe cost-effectiveness ofadaptation

andmitigation,uncertaintyanalysiswasconducted.Intheanalysis,

parametervalueswerechangedby10%,25%and50%.Theresulting

ratesofchangeintheCERofmitigationandadaptationareshown

inFig.7.

TheCERofCIismostsensitivetochangeinthewaterprice(WP), followedbyenergyprice(EP),IandOM.TheCERofLIismost sen-sitivetoI,followedbyWP,OMandEP,andthesensitivitytoWP andIaresignificantlyhigherthanthatofEP.MIismostsensitive toI,followedbyOM,EPandWP,andthesensitivitytoIis signif-icantlyhigherthansensitivitytotheotherparameters.SIismost sensitivetoI,followedbyWP,OMandEP,andsensitivitytoIis significantlyhigherthansensitivitytotheotherparameters.With theexceptionofCI,thecosteffectivenessofWSItechniquesare mostlyinfluencedbyinitialequipmentinvestment.Reducinginitial equipmentinvestment costs therefore hasthe most significant impactontheCER.

3.4. MitigationandadaptationpotentialsofWSItechniques The “National Water-SavingIrrigation Program” (MWR PRC, 2008)proposesthatby2020,comparedwithabaseyearof2005, anadditional4.29millionhawillbeequippedwithSI,1.30million hawithMI,8.08millionhawithLIand17.82millionhawithCI. Statisticaldatafrom2009conﬁrmsthatthetargetforMIhasbeen exceededmainlyduetotherapiddeploymentofMI inXinjiang AutonomousRegion.AssumingthatMIwillnotbefurtherscaled upinXinjiang,itwillbenecessaryforotherprovincesandregions toincreasetheareaunderMIbyatotalof0.76millionhaby2020. Theadditionalareasrequiredfor theotherthreeWSI measures comparedto2009are3.87millionhaforSI,6.51millionhaforLI and13.24millionhaforCI,respectively.

AssumingthecurrentperformanceofWSItechniquesremains unchanged,themitigationandadaptationpotentialsthatcanbe achievedby2020areshowninFigs.8and9.Theannualaverage totalGHGmitigationpotentialofthefourmeasuresby2020is7.06 MtCO2,whileachievementofthetargetsinthenationalplancould

increasegrainoutputby20.32Mtperyearandsave35.01billion m3_of_water_per_year._Subtracting_reduced_energy_and_water_costs

fromtheinitialinvestmentcosts,anetinvestmentofaboutUS$ 0.14–0.61(0.38onaverage)billionwillbeneeded.Withouttaking intoconsiderationwaterandenergycostsavings,theequipment investmentplusmaintenancecostwillbearoundUS$1.75–2.22 (1.85onaverage)billionfrom2010to2020,oranannualaverage costofUS$0.185billion.OutofthefourWSImeasures,CI con-tributesmosttothemitigationandadaptationpotentials,whilethe requiredinvestmentsinCIarelowerthantheinvestmentsrequired fortheothermeasures.However,CIisinferiortotheotherstudied WSItechniquesintermsofperunitareamitigationand adapta-tioneffects.Fromthelong-termperspective,itisrecommended

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Fig.8.MitigationpotentialofWSItechniques.

thatMIisdeployedinareasirrigatedwithgroundwaterordiverted pumpedwater,sinceinsuchsituationsMIaddressesboth mitiga-tionandadaptationobjectivesmoreeffectively.

4. Discussion

4.1. Cost-effectivenessofmitigationandadaptationthroughWSI techniques

Therehavebeenmanystudiesonthecost-effectivenessof miti-gation(Simsetal.,2003;Vellingaetal.,2011;Hoogwijketal.,2010; WassmannandPathak,2007),butfewstudiesevaluatingthe cost-effectiveness of adaptationmeasures. Thisis because assessing theeffectivenessofadaptationisinhibitedbysignificant uncer-taintyinfutureclimatetrends,difficultiesindeterminingcriteria foradaptationeffectiveness,anddifficultiesinattributingspecific causalfactors.ForWSItechniques,manystudieshavefocusedon itseffects on water savingand grainyields, both of which are strongly affected by climatechange (IPCC, 2007a,b). Soin this papertheeffectsofWSIonreducedwaterconsumptionandgrain yieldincreasesweretakenasthecriteriatoevaluatethe adapta-tioneffectivenessofWSI.Althoughtheresultsofourstudyhave someuncertainties (such as theinvestment costsof WSI tech-niquesandpricesforenergyandirrigationwater),dataongrain yieldresponsesandwaterusederivefromcontrolledfarm exper-imentsinwhichtherewerenodifferencesinmanagementfactors

otherthantheirrigationmethod.Dataontheseadaptationeffects isthereforelikelytoberobust.

IntermsoftheCERofmitigation,SI(583.84US$/t)hasthe high-estCER,followedbyLI(137.24US$/t),MI(136.23US$/t)andthen CI(−58.22US$/t).Comparedwitha varietyofpublishedstudies (seeTable7),exceptfor theestimatedCERfor CI,thecostsper tonCO2ofWSItechniquesestimatedinthisstudyarehigherthan

thosereportedintheliterature.BuritisworthnotingthatWSI techniquesarealsoeffectiveinreducingwaterconsumptionand increasinggrainyield,sotheycancontributetoeasingpotential foodandwaterscarcity(HanjraandQureshi,2010;Tejeroetal., 2011).

EstimationoftheadaptationCERofWSItechniquesunder cur-rentclimateconditionsshows thatMI hasthehighest costper increasedunitofgrainyieldandperunitofwatersaved,followedby SI,LIandCI.Ifincreasedgrainyieldissoldatthecurrentnational averagegrainprice,thenetcostofeachWSItechniqueis nega-tive.Hence,whentheincomeeffectsareconsidered,alltheWSI techniquesaremoreproﬁtablethantraditionalirrigation.Forthe developmentofWSI,itmustbenotedthatalthoughCIhasthe low-estcostamongallfourmeasures,CIalsohasthelowestpotential perunitareaofirrigatedlandtoreducewaterconsumptionand increasegrainyield.AlthoughMIhasthehighestcost,italsohas ahighincreaseingrainyieldandreductioninwaterresourceuse (Romeroetal.,2006a,b;Rajaketal.,2006;YohannesandTadesse, 1998).ChoiceofWSItechniquesinareasfacingwaterresources scarcity,shouldconsidernotonlythecostbutthemultipleeffects ofirrigationtechniques.

4.2. CostofWSItechniquesforclimatechangeadaptation

ThisstudyconfirmedthefindingsofXiongetal.(2010),which indicatesthefeasibilityofWSIasameasuretomaintainfood pro-ductionandsavewater.Comparedwithotherresearch,ourstudy estimatesamuchlowerWSIinvestmentcostforadaptingto cli-matechange(US$0.14–0.61billionperyear)(Table8).Thereare three mainreasonsfor this discrepancy.Firstly, climatechange risksareuncertain(IPCC,2007a,b),anddifferentstudiesuse dif-ferent assumptions regardingfuture climatechange.Thisstudy assessedadaptationcostsandeffectsundercurrentclimate condi-tions.Secondly,differentassumptionsandmethodswereusedto estimateadaptationcosts(AgrawalaandFankhauser,2008).Major reportsfromStern(2006),Oxfam(2007)andUNDP(2007)were basedontheWorldBankmethod(2006).Thistakesthefractionof currentinvestmentthatisclimatesensitiveandappliesa‘mark-up’ factortothisfractiontoreflectthecostof‘climate-proofing’(Parry

Fig.9.AdaptationpotentialofWSItechniques.Notes:InFigs.8and9,eachhorizontallinerepresentsameasure.Theverticalcoordinatethatthehorizontallinecorresponds toisthemitigation/adaptationcostofthemeasure.Thelengthofthehorizontallineisthemitigation/adaptationpotentialofthemeasure.

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Table7

Cost-effectivenessratioofgreenhousegasmitigationfrompublishedstudies.

Fields CERofmitigation(US$/t) Source

Largeandmedium-sizedbiogas 49.4 Suetal.(2002)

Agriculturalwasteandcoalco-ﬁredpowergeneration 106.18–123.60 Luoetal.(2008)

Municipalsolidwasteincinerationpowergeneration 36.98–52.67 YangandMa(2006),Huetal.(2002) Medium-sizedbiomassgasiﬁedpowergeneration 22.47–26.54 Heetal.(2006)

Biomassandcoalco-ﬁredpowergeneration 87.78–129.35 Maetal.(2006)

Windpower 17.23 Maetal.(2006)

Biomasscogenerationsystemswithintegratedgasiﬁcationandcombinedcycletechnology 57.3 GustavssonandBörjesson(1998) Natural-gassystemswithdecarbonizationtechnology 95.45–114.54 GustavssonandBörjesson(1998)

CO2captureandstorageoptions 27.3–40.9 Simsetal.(2003)

Nuclearpowerversuscoal 13.6–27.3 Simsetal.(2003)

Typicalfarmingsystems 18.33–349.68 NeufeldtandSchäfer(2008)

Mitigationapproachesintheresidential,commercial,transportandagriculturalsectors 40.9–136.4 Metzetal.(2001)

etal.,2009).TheUNFCCCstudywasbasedontheIPCC(2007a,b) A1Bscenarioandusedatop-downanalyticalapproach.Ourstudy usedabottom-upapproach,andisbasedonthenationalWSI devel-opmentplanfrom2010to2020.Thirdly,previousstudieshave includedmorethanonetypeofadaptationmeasure.Forexample, thestudybyNACWA(2009)onwateradaptationcostsincludes newwatersources,sustainablewatersupplyandextreme precip-itationevents.Ourstudyfocusedsolelyonwater-savingirrigation techniques.

4.3. SuggestionsforthedevelopmentofWSItechniquesbasedon climatechangeresponse

Effectiveresponsetoclimatechangeshouldincludeboth miti-gationandadaptation(IPCC,2007a).Soifboththemitigationand adaptationeffectsofWSItechniquesareconsidered,foreachcubic meterofwatersaved,1.01kgofCO2emissionscanbereducedby

MI,0.58kgbyCI,0.57kgbySIand0.43kgbyLI.Foreachkilogramof increasedgrainyield,2.25kgofCO2emissioncanbereducedbyMI,

1.15kgbySI,0.97kgbyCIand0.64kgbyLI.Overall,amongthe4 WSItechniquesassessed,MIhasthebesteffectswhenboth mitiga-tionandadaptationeffectsareconsidered.Sointhedevelopmentof theWSI,MIisstronglyrecommendedforclimatechangemitigation andadaptation.ItshouldbenotedthatSIandLIhavelargereffects ongrainyieldincreaseandwaterconservationthanCI,butwhen mitigationandadaptationarebothconsidered,SIandLIarenot superiorbecauseSIandLIincuradditionalenergyneedstoattain acertainwaterpressure,andwhenthepumpingheadforpressure islowerthanthecriticalenergysavinghead,moreenergywillbe required,thuscausingmoreGHGemissionsthanwithtraditional irrigationmethods(Zouetal.,2012).

China is a developing country facing the challenge of cli-matechangeresponsewhilealsopursuingsustainableeconomic development.Theeconomicfeasibilityofclimatechangeresponse measuresisofgreatimportance.Cost-effectivenessanalysisfound thatonlyCIhasanegativecost,whichwasduetoenergyandwater costsavings.Sointhelong-term,investmentsinCIarethe least-costoptionCurrently,CIaccountsfor42.40%ofthetotalWSIarea

inChina(MWRPRC,2011)andaccordingtothe“National Water-savingIrrigationProgram”bytheendof2020theproportionofCI willincreaseto50%(MWRPRC,2008).However,thereisaneed toalsoconsideradaptationeffectiveness,energyconsumptionand GHGemissions.MIperformsbetterthanCIinthisregard.However, sensitiveanalysisshowsthatMIismostsensitivetotheenergy price,andalthoughwaterandenergypricescanpartlybe deter-minedbyChinesegovernmentpolicies,theenergypriceisstrongly inﬂuencedbyinternationalmarketprices,sothecost-effectiveness ofMIisvulnerabletotheimpactsofglobalenergymarkets.This suggeststhatabalanceddevelopmentofCIandMIshouldbe con-sidered.

AdoptionofWSIstillfacesconsiderablebarriersinChina.High infrastructureinvestmentcosts,technicaldemandsandstringent operatingconditionsmake itdifficultforfarmerstodeployand disseminateWSI(Romeroetal.,2006a,b;Srivastavaetal.,2003; Fangetal.,2010).Overcomingthesebarrierswillrequirefinance, technologyandcapacitybuildingsupport.Accordingtothe sen-sitiveanalysisinthisstudy,reducingtheinitialinvestmentcosts ofWSItechniqueswillhavethegreatesteffectontheprofitability ofinvestments.UnderthecurrentChinesepolicyonWSI devel-opment, the government contributes the majority of financial investments,whilefarmersprovidelaborandlimitedcapitalwhere possible(MWR PRC,2008).Thispracticehasproven very effec-tiveinsupportingdisseminationofWSItechniquesandcouldbe transferredtoothercountries.

4.4. Additionalremarks

Thecurrentstudydidnotconsidertheeconomiccostsand ben-eﬁts ofreuseof watersavedbyWSIadoption. Becausethereis acompetitionforwateronlargerscales,“losses”orsavedwater fromonelocationcanbe“sources”inanother(Perry,2011),andthe savedwatercouldbeusedforexpandingtheirrigatedarea(IWMI, 2006).Assumingthat62.08% (i.e.,thepercentageofagricultural waterconsumptionintotalnationalwaterconsumptionbetween 2007and2009)ofsavedwaterisusedtoexpandtheareaunder irrigation,andassumingaveragewaterconsumptionperunitarea Table8

Adaptationcostsfrompublishedstudies.

Field Totalcost(109US$) Annualcost(109US$) Source

Forclimatechangeby2050,globally 160–4360 4–109 WorldBank(2009)

Forclimatechangeby2030,globally 980–3420 49–171 UNFCCC(2007)

Fordrinkingandwastewaterservicesthrough2050,US 448–944 11.2–23.6 NACWAandAMWA(2009) Costofclimate-proofingFDI,GDIandODAflows 45–205 9–41 WorldBank(2006) Update,withslightmodificationofWorldBank(2006) 20–185 4–37 Stern(2006) BasedonWorldBank,plusextrapolationofcostsfromNAPAsandNGOprojects >250 >50 Oxfam(2007) WorldBank,pluscostingofPRStargets,betterdisasterresponse 430–545 86–109 UNDP(2007)

Notes:FDI=foreigndirect investment; GDI=gross domesticinvestment; ODA=ofﬁcialdevelopmentassistance;NAPA=NationalAdaptation ProgrammeofAction; PRS=povertyreductionstrategy.

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between2007and2009,thewatersavedthroughWSI dissemina-tionin2009wasenoughtoirrigateanadditional5.70(3.80–7.80) millionha.Suchexpansionwouldincreasegrainoutputby22.04 (14.68–30.15)billiontonsandwouldemit5.83milliontonsofCO2.

However,inpracticethereislargeuncertaintyaboutthesectorsin whichsavedwaterisreused;investmentcostsandCO2emissions

associatedwithwaterreusewillvarybysectorandtechnology;and reusedwatermaybesavedandreusedsuccessively.Giventhese uncertainties,wedidnotconsiderthereuseofthesavedwaterin thiscost-effectivenessanalysis.

Secondly,Chinais alargecountrywithdiversegeographical andeconomicconditions.FurtherexperimentalresearchonWSI performanceisnecessarytoprovideabroaderevidencebasedon performance and costs under diverseconditions. Despite these shortcomingsofouranalysis,thisstudyprovidesabasisfor priori-tizingWSImeasuresanddesigningincentiveprogrammestocope withclimatechange.

5. Conclusions

Water-savingirrigationisacost-effectivemeasuretopromote adaptationtoandmitigationofclimatechangewhilepursuing sus-tainableeconomicdevelopment.Themainﬁndingsofthisstudy are:

(1)Regarding the cost-effectiveness ratio of mitigation, only channellininghasanegativecost-effectivenessratio(_−43.02 to −73.41US$/tCO2), and the cost-effectiveness ratio of

the other measures in descending order are: sprinkler irrigation (476.03–691.64US$/tCO2), low-pressure pipe

irrigation (67.61–206.88US$/tCO2) and micro-irrigation

(109.47–162.98US$/tCO2);

(2)Regardingthecost-effectivenessratioofgrainyieldincrease, only channel lining has a negative cost-effectiveness ratio (−34.35to−20.13US$/t),and thecost-effectiveness ratioof theothermeasuresindescendingorderare:micro-irrigation (132.87–197.80US$/t),sprinklerirrigation(63.38–92.53US$/t) and low-pressure pipe irrigation (12.76–39.06US$/t). Regarding the cost-effectiveness ratio of reduced water consumption, only channel lining has a negative cost-effectiveness ratio (−0.020 to −0.012US$/m3_), _and _the

cost-effectivenessratioof theothermeasuresindescending order are: micro-irrigation (0.069–0.089US$/m3_),

sprin-kler irrigation (0.032–0.046US$/m3₎ _and _low-pressure _pipe

irrigation(0.009–0.026US$/m3_);

(3)Therefore, when ﬁnancial resources are available, micro-irrigationispreferredformitigationandadaptation.Channel lining has the lowest (negative cost), and also has notable mitigationandadaptationbeneﬁts,sofromtheeconomic per-spectivechannelliningisrecommended.Insomedistrictswith pumping heads lower than thecritical energy savinghead, sprinklerirrigationandlow-pressurepipeirrigationshouldbe avoidedinordertoavoidincreasinggreenhousegasemissions. Furtherresearchshouldbeundertakentobetterunderstand theperformanceofwater-savingirrigationmeasuresindifferent environmentalandeconomicconditionsthroughoutChina.

Acknowledgements

TheresearchforthispaperwassponsoredbytheNon-proﬁt Research Foundation for Agriculture (201103039) and the CAS StrategicPriority ResearchProgram(XDA05050602-02). We are verygratefultoAndreasWilkes,DeclanConwayandMarkTebboth fortheirassistanceinrevisingthepaper.

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