I NPARTIA LFULFILMEN TFO RTH EREQUIREMENT S OFTH EDEGRE EO FMASTERO FSCIENC EI NIRRIGATIO NENGINEERIN G

Abstract

Thestudyarea,theAbayachamoBasinisasubbasinoftheEthiopianRiftValleylake s Basin.ItcomprisestwolakesAbayaandChamo,perennialrivers,andotherephemeral riversareenteringatChamoandanoverflowfro mchamojoin sSermalerivertojoi n Segenriver,whichinturnendsupinLakeChew-bahiratborderofEthiopiawith Kenya.Thestudythu sinvestigate sEvapotranspiration(ET)ofthebasinwhichisamajor componentofthehydrologiccycle. Asoneofuniversallyacceptedandwellunderstoodevaporationestimationmethod,it hasbeenassumedtha tFACPenman-Monteithmethodperformbettertha nother availablemethod.Thusinthisstudy.Inordertosynchronizeestimatesfro mvarious evaporationmethodstheconceptofPenmanequivalentestimate(PEE)isintroduced . Naturally,dueto^thedifferenceinth econceptualizationanditsintende doriginaluse, differentevaporationmethodsgivedifferentestimates.TheconceptofPEEiscoinedto reducepartoferrorintroduce dasaresultofusingdifferentevaporationmethodsin estimationofasingletimeseriesofevaporation.Inthisregard ,estimatesfro mvarious methodswerestandardizedtopenmanmethodbyintroducin gregressioncoefficientto eachmethod.Therefore,inthisstudyastandardizedvalueofth ePEEisusedinthe estimationoftheEvapotranspirationofthebasin. ThemeanDailyestimatesofEvapotranspirationbyFACPenman-Monteithwas obtainedas3.7mm/dayatHageremariamto4.5mm/dayatMirabAbaya.Aftermethods (HargreavesandBlanney-Criddle)havebeenregressedwithpenmanestimate improvemen testimatearedoneforstations.ForMirabAbaya,Dila,Arbaminchand Konsotheimprove destimatefo rHargreavesproducesR ^valueof0.98,0.96,0.98and 0.93respectively.Calibrationwithth eFACPenman-Monteithwasdonebyimprovin g theKhscoefficientoftheHargreavesequation.Similarlycalibrationwithth eFAC penman-Monteit hwasdonebyimprovin gthePvalueoftheBlaneyandCriddle equation