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SemesterReport

TheTémezModel:

ApplicationwithGIS

GISinWaterResources,Fall2013Dr.DavidR.MaidmentandDr.DavidG.Tarboton

By:

AntonioCañamásCatalá

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Table of Contents 

1. Introduction......................................................................................................................................................3

1.1. WaterResourcesAssessment.........................................................................................................3

1.2. Objectives.................................................................................................................................................3

2. TémezModelDescription...........................................................................................................................4

2.1. Definition..................................................................................................................................................4

2.2. Watercycleparameters.....................................................................................................................4

2.3. Formulation.............................................................................................................................................5

2.4. Implementation.....................................................................................................................................6

3. Subbasins...........................................................................................................................................................7

3.1. Spanishsubbasin..................................................................................................................................7

3.2. U.Ssubbasin..........................................................................................................................................8

4. DataSources......................................................................................................................................................8

4.1. PrecipitationandStreamflows.......................................................................................................8

4.2. PotentialEvapotranspiration..........................................................................................................9

5. Results................................................................................................................................................................10

5.1. SpanishWatershed.............................................................................................................................10

5.2. U.S.Watershed.....................................................................................................................................12

6. ClimateChangeSimulation......................................................................................................................15

7. Conclusions......................................................................................................................................................17

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1. Introduction 1.1. Water Resources Assessment 

WaterResourcesassessmenthasawiderangeofspatialandtemporalscales.Themethodologyapplieddependsonthegoalsoftheanalysis,andofthevariabilityofmeteorologicalandhydrologicalinputs‐outputstargets.Watersupplysystems,onwhichthisreportwillfocus,useamonthlyorseasonaltimestep.

In order to implement a correctWater Resources assessment, it is necessary tocharacterize the Natural Regime. This means water resources underpredevelopment,thatis,iftherewerenotanyinfluencesupstreamfromthelocationstudied.Thetwomainreasonsforthisstepare:

‐ Toperformacorrectassessmentoftheavailableresources‐ ToobtaintheInflowTimeSeriesforriverbasinmanagementmodels

TheBasinhydrologyisrepresentedinamanagementmodelasaninputsequenceofstreamflowsateachspecificlocation.Inthisreport,wewillsimulatelongtimeseriesofstreamflows(andotherhydrologicalparameters)todeterminehowwellasystemmightperforminthefuture.

1.2. Objectives  

Themainobjectivesofthisreportareenumeratedasfollows:

1. DescriptionandcharacterizationoftheTémezModel.

2. GIS application of the TémezModel on twowater basins of two differentcountries:SpainandUnitedStates.

3. ResearchofthedifferentGISdatabasesinSpainandhowtheycomparewiththeexistingonesintheU.S.

4. Discussionofwhethertheresultsobtaineddescribethebehaviorofthesubbasinsstudied.

5. Application of the model: streamflow prediction with a climate changescenario.

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2. Témez Model Description 

2.1. Definition 

Hydrologicalmodelsrespondtothefollowingclassification:

As it canbe seen in Figure1, theTémezRainfall‐RunoffModel is aMathematicalDeterministicHydrologicalmodel:

‐ Continuous:simulatescompletelytheHydrologicalCyclecontinuouslyintime.

‐ Conceptual:basedonwaterbalances.‐ Lumped‐Parameter:variablesandparameterslumped.

2.2. Water cycle parameters 

Thefollowingparameters,whichexplaintheHydrologicalCycle,arecontained intheTémezModel.

Figure2:TémezModelParameters

Figure1:HydrologicalModelsClassification

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AsshowninFigure2,twodifferentstoragesareconsidered:

1. Superior:non‐saturatedzone(soil,H).2. Inferiororaquifer:saturated,undergroundreservoirwithdischargeintothe

drainagebasin.

Theparametersthatcharacterizethebasin,whichwewillcalibratetosimulatethebasin’sbehavior,arewritteninredinthesketch:

HmaxMaximumsoilmoisture

ImaxMaximuminfiltration

CExcesscoefficient

αGroundwaterdischargeparameter

2.3. Formulation 

The expressions, based on mass water balance equations, necessary to run themodelandthatcharacterizeeachoftheembeddedparametersare:

1.RainfallExcess(T):

Pi≤P0 Ti=0

Pi>P0 Ti=(Pi‐P0)2/(Pi+δ‐2P0)where:δ=Hmax–Hi‐1+PETi

P0=C(Hmax–Hi‐1)

Where,

Pi:precipitationinmonthi Ti:waterexcessinmonthi Hi‐1:soilmoistureinmonthi‐1 PETi:potentialevapotranspirationinmonthi

2.SoilmoisturebalanceandactualET:

ETi=min(PET,Hi‐1+Pi–Ti)

Hi=max(0;,Hi‐1+Pi–Ti–ETi)

3.Infiltration(aquiferrecharge):

Ii=Imax(Ti/Ti+Imax)

whereIiistheinfiltrationinmonthi

4.DirectRunoff(Qsupi)

Qsupi=Ti‐Ii

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5.GroundwaterDischarge(Qsubi)

LinearReservoirmodel:Theaquiferisassumedtobehaveasatankwhere theoutflowdependsonthevolume.

Ri=A*Ii

where A is the area of the basin andRi the recharge inmonthi.

Vi=Vi‐1e‐α+Ri(1–e‐α)/α;whereViisthewatervolumeoftheaquiferinmonthi

Qsubi=Vi‐1–Vi+Ri

6.TotalRunoff

Qi=Qsupi+Qsubi

whereQiisthetotalrunoffinmonthi.

2.4. Implementation 

The equations associated with the model are implemented in an Excel file (orsimilar),withadistributionsimilartoFigure4:

A)Steps

1. Datacollection,analysisandpreprocessing.2. Calibrationof theparameters: theobjective is tominimize thedifference

betweentheobservedstreamflowsandthosethatarecalculated(atleast20yearsofdata).Thisisaccomplishedby:

a)Previousparameterestimations. b)Parameteradjustmentbycomparison:useofmonthlyvalue

graphs,annualvaluesgraphsandmeanmonthlyvaluesgraph.

3. Validation of the model: comparison with values of recent years (5‐10years).

4. ScenarioSimulation

Figure3:LinearReservoirModel

Figure4:SampleImplementationinMicrosoftExcel

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B)NecessaryInputData

Theinputdataforthemodelare

MonthlyTimeSeriesofatleast25yearsforthePrecipitation(Pi) PotentialEvapotranspiration(PETi) ObservedStreamflows

ItwillalsobenecessarytoobtaininformationrelevanttotheSurfaceofthebasin,theinitialSoilMoisture(H0)andtheinitialAquiferVolume(V0).

The effects of the initial Soil Moisture and Aquifer Volume are confined to thestreamflowsof the first fewmonths. The values of these twoparameters canbeapproximated by observing the initial differences between the calculated andobservedstreamflows.

3. Sub basins 3.1. Spanish sub basin 

AsexplainedintheWaterResourcesAssessmentsection,fortheproperfunctioningofthemodel,theremustnotbeanyinfluencesupstreamfromthedrainagepointofthebasin.Itwasquitedifficulttofindabasinthatfulfilledthisrequirementandhadtherequireddataforthemodelavailable.Afterextensiveresearch,itwasdecidedthat theUpperMijares in the East Coast of Spain (Figure 5) bemodelled for theSpanishsubbasin.Inthedelimitationofthewatershed(seesection4),areservoirjustdownstreamoftheoutflowgagecanbeobserved.

UsingGIS, the area of the sub basinwas found to be 1396 km2 and the outflowstreamflow gage, as well as the rain gages located inside the sub basin, wereidentified.

Figure5:UpperMijaresSubBasininSpain

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3.2.   U. S sub basin 

FortheU.S.,awell‐knownsubbasinwaschosen:UpperBlancoRiverintheareaofAustinandSanAntonio(Figure6).Thesurfaceofthissubbasinisfoundtobe921.16km2.

4. Data Sources 4.1. Precipitation and Streamflows 

GIShasbeenusedinthisreportasadataextractiontool.

For the Spanish sub basin, a GIS desktop (developed by the Agricultural,Alimentation and EnvironmentalSpanishGovernmentDepartment)hasbeenusedfortheextractionofboththePrecipitation and Streamflow TimeSeries.Thiswasmadepossiblethanksto the identification of the gageslocated within the Upper Mijares subbasin through the Shapefiles obtainedfrom the same Spanish GovernmentDepartment. At this point, it isnoteworthythatthedatafoundforthissubbasinwasavailableonly fromtheyear1990onward.

Figure6:UpperBlancoRiverSubBasinintheAustinandSanAntonioArea

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Ontheotherhand,theNLDAStoolenablesustoextracthourly,monthlyandyearlydata for several parameters from the Hydrological Cycle. In this case, thePrecipitationmonthlyTimeSerieswereextracted inpackagesof10years(moreyearsoversaturatedthecomputercapacity).TheZonalAveragewasdonewiththephytoncodeprovidedbyDr.TarbotoninExercise5.TheStreamflowTimeSerieswereobtainedusingtheUSGSdatabasewhichcontainsalargenumberofrecordsofmonthlyStreamflowdatafordifferentsites.Inourcase,theutilizedsitewascalled:BlancoRvatWimberley,Tx

Thefollowingtablesummarizesthedatasources:

4.2. Potential Evapotranspiration 

ThePETdatawasnot founddirectly foranyof thesubbasins.Toovercomethisobstacle,thesimpleThornthwaiteformulawasemployed:

PETi=16(L/12)(N/30)(10Ti/I)α

Where,

Listhemeandaylighthoursofthemonth Nistheno.ofdaysinthemonth Tiisthemeanmonthlytemperature IandαtwoparametersthatdependonTi

Variable Spain U.S

P

LDAStool

Streamflow

PET Nodirectsource Nodirect source

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ThetemperaturedatawasobtainedfromaSpanishmeteorologicalwebsite.Ontheother hand, for theU.S., the LDAS tool also allowed us to extract themean skintemperatureinthesubbasin.

5. Results 5.1. Spanish Watershed 

Thestepsexplainedinsection2(Implementation)werefollowedtosimulatethebasin’sflows.

A) Calibration

Thetwomethodsfollowedtocalibratetheparametersofthesubbasinare:

1) Visual analysis: adjust the calculated streamflow to the data streamflowusingtheMonthlyValuesandMeanMonthlyValuesgraphs

2) Optimization: minimize the error (mean square difference) between thecalculatedstreamflowandthedatastreamflowusingtheSolverToolwiththefollowingconditions:c,Hmax,Imax,α>0andc<1.

Thevaluesobtainedfortheparametersarethefollowing:

Hmax(mm) c Imax(mm) α H0(mm)  V0(mm)

Area (Km2)  1396  200  0.01  500  0.5  20  60 

Thegroundwaterdischargeparameteristhemajorparameterthatcontributestothebaseflowofthebasin(flowduringperiodswithoutstorms).Thevalueobtainedforα(0.5)isveryhigh.Thiscanmeanthattheaquiferlocatedbelowthebasinishighlypermeable.Thisisconsistentlyrelatedtothevalueofthesurfacecoefficient(c=0.01),whichisverylow,andtheImaxvalue(500mm).

Thegraphbelowshowstheresultsfromthecalibrationprocess:

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FromtheMonthlyStreamflowValuesgraph,wecanconcludethatthemodelhasnotyetreachedagoodcalibration,duetotheinsufficientdataavailable(onlyfrom1990onwards).TheTemezmodelisprimarilydevelopedtomodelthebaseflowandnotto simulate well the peak flows. This is evident for October 2000 where thedifferenceinthecalculatedstreamflowandthedatastreamflowisnoticeable.

On theotherhand, themeanmonthlyvaluesadjustveryprecisely to thedataasshowninthechartbelow.

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Mm3

Monthly Streamflow Values

Calculated Streamflow Data Streamflow

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December

January

February

March

April

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Mm3

Mean Monthly Values

Calculated Streamflow Streamflow data

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The main differences can be found in October and November. Due to theMediterraneanClimate,majorstormsoccurduringthesemonths.Thesestormsarestronginmagnitude(mmofrain)andshortinduration,makingtheerrorbetweenthecalculatedandtherealstreamflowslarger.Fortherestofthemonths,assaidbefore,theresultsarequitesatisfactory.

B) Validation

InordertovalidatetheparametersobtainedduringtheCalibrationprocess,thelast5yearsofdata(2005‐2010)havebeenusedasshowninthechartbelow.Itcanbeobserved that for the last year (2010) the model is starting to simulate thestreamflowsverywell(needformoredata).

5.2. U.S. Watershed 

ThesameprocedureexplainedfortheUpperMijaresSubbasinhasbeenusedintheUpperBlancoriversubbasin.

A) Calibration

Inthiscase,theresultsoftheparameterscanbeusedtoconcludethatthesubbasinhasasmallercontributiontotheaquifer(α=0.013)andabiggertothesurfacerunoff(c=0.1789)thantheUpperMijaressubbasin.Themaximumsoilmoisturecontent(Hmax=426mm)hasbeenfoundtobeveryhighintheareaofthesubbasin.

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Mm3

Validation

Calculated Streamflow Data Streamflow

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TheMonthlyStreamflowValuesgraphshowstheverygoodcalibrationofthemodel.Even though the peaks are again badly simulated, the baseflow is found toapproximateaccuratelythestreamflowdata.

Thedataavailableforthisbasinwasmoreextensive(1979–2013)andthisexplainsthebetterperformanceofthemodel.

IntheMonthlyMeanValuesplotshownbelow,moreorlessallmonthsadjustedtothedata,butwithbiggerdifferencesthanfortheUpperMijaresbasin.However,ahugedifferencebetweentheresultsofthemodelandtherealdatawasfoundinMay.

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Jul‐2006

Jun‐2007

Monthly Streamflows Values 

Calculated Streamflow Data Streamflow

Hmax(mm)  c  Imax(mm)  α 

H0(mm) 

V0(mm) 

 Area (Km2)  921.16  426  0.1789  290  0.013  260  300 

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Todeterminethesourcesoferrorduringthismonth,theresultsanddataforMaywereplottedinaseparategraph:

Apossibleexplanationcanbethattheerrorsusuallycompensateinapositiveandnegativematter(sometimesthemodelgivesabiggerresultandothersasmallerone),butforthismonthalltheresultsseemtobeoverestimated.Nevertheless,nospecificexplanationtowhythisishappeninghasbeenfound.

B) Validation

The last fouryearswereplotted tovalidate themodel.Theresultsshowamuchbetterapproximationofthebasin’sbehaviorthanfortheUpperMijaressubbasin.Theavailabilityofmoredata(12yearsmore)justifiesthebetterqualityofmodeloutputs.

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Februar

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ber

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Monthly Mean Values

Calculated Streamflow Data Streamflow

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1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011

May 1979‐2012

Calculated Streamflow Data Streamflow

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6. Climate Change Simulation 

AClimateChangeScenariohasbeensimulatedfortheUpperBlancoRiverSubbasin.

To simulate the conditions of this hypothetical scenario, the precipitation andpotential evapotranspiration input data has been decreased and increased,respectively. Thedata obtained from theZonalAverage from1996onwardshasbeenmultipliedby0.9(10%decrease).Ontheotherhand,theevapotranspirationdatahasbeenmultipliedby1.12(12%increase).Thesemodificationssimulatethereductioninrainandtheincreaseinevapotranspiration,duetotheincreaseintheglobaltemperature.

Inordertoanalyzetheresults,thecalculatedstreamflowwiththeclimatechangesimulation data has been plotted against the calculated streamflow for the basescenariointhegraphbelow.

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80

Jan‐2008

Apr‐2008

Jul‐2008

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Jan‐2009

Apr‐2009

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Apr‐2010

Jul‐2010

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Jan‐2011

Apr‐2011

Jul‐2011

Oct‐2011

Jan‐2012

Apr‐2012

Jul‐2012

Oct‐2012

Validation

Calculated Streamflow Data Streamflow

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Intheabovegraphitcanbeobservedthattheclimatechangeeffectsinthebaseflow(depletion)starttobenoticedafter,moreorless,2yearsofdata(1998).TheMeanMonthlyValuesshowsusmoreclearlytheimportanceofthedepletion:

Intermsofnumbersthemeandepletionpermonthlyvaluewas:

Mean depletion per month: 

5.69 Mm3 35.30%

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Jan‐1996

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Mm3

Monthly Values since the start of the climate change

Calculated Streamflow Calculated Streamflow (climate change)

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30

Mm3

Depletation in Mean Monthly values

Calculated Streamflow Calculated Streamflow (climate change) Depletion

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7. Conclusions 

TheTemezModelhasbeenshowedtoperformagoodsimulationoftheriverbasin’sbaseflowwhenthenecessarydataisavailable.ThedatafoundfortheU.S.subbasinranges from 1979 to 2013 (i.e 33 years), and at the end of this period, we canconcludethatthemodelisworkingproperly.Ontheotherhand,theSpanishdatawasonly20years long (1990‐2010),and theperformanceof themodelwasnotsatisfactory(theCalibrationstepisnotyetoverwiththatnumberofyears).

The application of this model to simulate hypothetical scenarios (e.g. ClimateChange, Pumping…) is a useful tool forWater Resources Management. One cananalyzetheimpactofthenewconditionsinthebasinandhowthisaffectsthewaterresourcesavailableforsupply.InthescenarioproposedinSection6,theimpactofareductioninrainandanincreaseinpotentialevapotranspirationreducesmorethana35%theavailabilityoftheWaterResourcesinthebasin.SuchanalysiscanhelptheWaterAuthoritiestoprioritizetheallocationofWaterResourcesandtakepreventivemeasurestoavoidscarcity.

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8. References  WaterResourcesPlanningandManagementcoursedocuments,Universidad

PolitecnicadeValencia

Ministerio de Agricultura, Alimentacion y Medioambiente, Spanish

GovernmentDepartment(http://www.magrama.gob.es)

ConfederaciónHidrográficadelJúcar,(http://www.chj.es)

IMPLEMENTACIÓN DEL MODELO HIDROLÓGICO DE TÉMEZ PARA LA

EVALUACIÓNDERECURSOSHÍDRICOSCONGRASSGIS.FASESUPERFICIAL

YSUBTERRÁNEA;A.PontencianodelasHerasyJ.J.VillaverdeValero

USGSwebsite(http://www.usgs.gov)