Evaporation and Evapotranspiration: Measurements and Estimations

219 Pages·2013·6.185 MB·English

by  Wossenu Abtew, Assefa Melesse (auth.)

Evaporation and Evapotranspiration

Wossenu Abtew • Assefa Melesse
Evaporation and
Evapotranspiration
Measurements and Estimations
123
Dr.WossenuAbtew Prof.Dr.AssefaMelesse
SouthFloridaWaterManagementDistrict DepartmentofEarthandEnvironment
WestPalmBeach,FL FloridaInternationalUniversity
USA Miami,FL
USA
ISBN978-94-007-4736-4 ISBN978-94-007-4737-1(eBook)
DOI10.1007/978-94-007-4737-1
SpringerDordrechtHeidelbergNewYorkLondon
LibraryofCongressControlNumber:2012946197
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Preface
Waterlossthroughevaporationfromopenwaterandevapotranspiration(ET)from
vegetationisoneofthe majorcomponentsofthehydrologiccycleaffectingwater
resourcesavailability.Measurementandestimationofthesetermshaveinitiatedthe
developmentofthetheoryoftheprocess,measurementtechniques,andestimation
equations.Perceptionshavecontributedtobiasesofestimation.Adryingpondtaken
overbyvegetationgivestheperceptionthatthevegetation’sincreasedETresulted
inthedryingofthepond.Successionofvegetationinawetlandmayhidetheimpact
ofchanginghydrologybysuggestingwaterlossesareduetoinvadingvegetation.
The evapotranspiration process is controlled by the availability of moisture to
evaporate.Energyisrequiredtodetachwatermolecules.Amechanismisrequired
tomovethevaporintotheaircolumn.Theairhastohavethecapacitytoholdthe
vapor.Whentheairhasnomorecapacitytoholdmoisture,thereverseprocess,dew
formation,occurs.Inthisbook,dewevaporationispresentedinachapter.Achapter
onvaporpressureandvaporpressuredeficitestimationmethodsis presentedwith
known quality data from a monitoring network. ET processes and mechanisms
arepresentedinasimplifiedwaywithoutcompromisingcomplexity.Ineachcase,
examplesofapplicationsfromtheauthors’experiencearepresentedforcomparing
estimation methods. Meteorological monitoring and data quality, input into ET
estimationmethods,is vastlydiscussedina chapterwithillustrationsfroma large
monitoring network. The design and application of a lysimeter system for open
waterevaporationandwetlandvegetationEThasprovidedmeasureddatatogauge
the performanceof various estimation equations. The advantageand limitation of
simple ET estimation methods,when inputdata is limited, are addressed.Remote
sensingapplicationtoETestimationissufficientlyaddressedinthreechapterswith
applicationcasestudies.Anintroductionintotheexpectedimpactofclimatechange
on ET rates is included as a chapter with climate model application results. This
book is a useful resource for hydrologists, scientists, meteorologists, engineers,
water resource managers, agricultural and environmental professionals, students,
andteachers.
WossenuAbtew
vii

Contents
1 Introduction................................................................. 1
1.1 OverviewofEvaporationandEvapotranspirationStudies......... 1
References.................................................................... 3
2 MeteorologicalParameterMonitoringandDataQuality.............. 5
2.1 Introduction........................................................... 5
2.2 MeteorologicalParametersMonitoringNetwork................... 5
2.2.1 SourcesofErrorinMeteorologicalParameters........... 7
2.3 AirTemperature...................................................... 7
2.3.1 DewPointTemperature .................................... 10
2.4 Humidity.............................................................. 12
2.5 WaterTemperature................................................... 13
2.6 AtmosphericPressure................................................ 13
2.7 WindSpeedandWindDirection .................................... 15
2.7.1 WindProfile................................................. 18
2.7.2 WindBarrier’sImpactonWindSpeedandPattern....... 19
2.8 SolarRadiation....................................................... 20
2.9 NetSolarRadiation .................................................. 23
2.10 Summary.............................................................. 27
References.................................................................... 27
3 EvaporationandEvapotranspirationMeasurement ................... 29
3.1 Introduction........................................................... 29
3.2 PanEvaporation...................................................... 29
3.3 Lysimeters............................................................ 32
3.3.1 WeighingLysimeter ........................................ 32
3.3.2 WaterBalanceLysimeter................................... 32
3.4 EddyCorrelation..................................................... 37
3.5 BowenRatio.......................................................... 38
3.6 Lidar(LightDetectionandRangingMethod) ...................... 40
3.7 Satellite-BasedMethods............................................. 41
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