Abstract:
TheSWATmodelishydro-dynamicandphysically-basedmodelforapplicationincomplexand
largebasins.Modelinputsarea sfollows:rainfall,airtemperature,soilcbaracteristics,
topography,vegetation,bydrogeologyandotherrelevantphysicalparametersand.TheSoiland
WaterAssessmentTool2005(SWAT2005)wasdevelopedbytheAgriculturalResearchService
o ftheUnitedStatesDepartmento fAgricultureanddistributedbytheUSEnvironmental
ProtectionAgencyforwatershedmanagement.Themainobjectiveo fthisstudyistoestimate
overallflowyieldo fHawasaacatchmentwhichislocatedintheMainEthiopianRiftvalleyin
Ethiopia.Afterthedataqualitytest,meteorologicalandhydrologicaldataforcalibrationand
validationwereusedtoestimatetheparametersintheSWATmodel.Theevaluationo fthe
SWATmodelresponsetorainfall-runo frelationshipfromsensitiveanalysiswetakethemost
tensensitiveflowparameterwhichaffecttherainfallrunoffrelationshipo fthecatchment.
AmongthesensitiveflowparametersthesoilevaporationCompensationfactor(ESCO)were
foundtob emoresensitiveparametertorunoff.WhileThresholdwaterdepthintheshallow
aquiferforflow(GWQMN) ,BaseflowAlphaFactor(ALPHA-BF) ,thresholdwaterforwateri n
theshallowaquiferforflow"revamp"percolationtodeepaquifertoaccrue(REVAPMN) ,Soil
depthinmeter(SOLZ)andSCSrunoffcurvenumber(CN-2)themostinfluentialflow
parametero fthecatchmentandotherflowparameterles sinfluencethanother.Themean
monthlyandannualwateryieldsimulatedforabas eperiodfoundtobe25.8mmand309.0mm,
respectively.Seasonalwateryieldsimulationresulted56.6mm,89.7mmand155.0mmfordry,
intermediateandwetseason srespectively.Wateryieldisthetotalamounto fwaterleavingthe
HRUandenteringmainchannelduringthetimestep.(WYLD )=SURQ+LATQ+GWQTLOSS.Fromourresult,thetotalamounto fwaterleavingtheHRUandenteringmainchannel
duringthetimestep(WYLD )i s769.8mmH2O.Thepredictedhydrographwascalibrated
againstobservedoneandthemodelparameterswereoptimizedforgoodsimulation.The
calibrationandvalidationresultshowthatthecoefficiento fdeterminations(R^)andtheNashSutcliffesimulationefficiency(ENS)are0.76and0.72forcalibrationand0.77and0.73for
validationthisshowsitisgoodsimulation.
