2012 IAL Conference A novel technique to measure the total evaporation and its components during...
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Transcript of 2012 IAL Conference A novel technique to measure the total evaporation and its components during...
2012 IAL Conference
A novel technique to measure the total evaporation and its components during
sprinkler irrigation
Jasim Uddin
Rod Smith
Nigel Hancock
Joseph Foley
National Centre for Engineering In Agriculture (NCEA)
University of Southern Queensland,
Toowoomba QLD 4350
Australia
Presentation layout
Background Hypothesis Objectives Methodology Results Conclusions
BackgroundFigure 1: Components of evaporation losses during sprinkler
irrigation
Droplet evaporation
Canopy evaporation
Soil evaporation
Background
Components Theoretical Experimental
Canopy evaporation
8% Unable to measure
Droplet evaporation
<1% 0-45%
Soil evaporation negligible Unable to measure
Limitations of the catch-can method
Laborious and time consuming Unable to measure ET over crop
(Source : Smith, Cotton CRC)
Catch-can
Limitations of the lysimeter method
Figure 3: Measured ET using lysimeter and predicted ET (source : Thompson et al. 1997)
Lysimeter could not measure ET during irrigation
Irrigation period
Background
Hypothesis:Eddy covariance – sap flow method can be used to measure total ET and its components during sprinkler irrigation
Objectives: To measure the total ET and transpiration
To estimate the components of ET
Methodology
Figure 4: Experimental set up
Eddy covariance system
Sap flow system
Methodology
Eddy covariance (ECV) system
Sonic anemometer
Infrared Gas analyzer
Net radiometer
Sap flow system
Datalogger Hub
sensorInterface
MethodologyMeasurements
Latent heat flux (λE) and sensible heat flux (H)
Eddy covariance technique Net radiation (Rn)
Four components net radiometer Soil heat flux (G)
Soil heat flux plates Transpiration (T) measured by
Sap flow method Air temperature (Ta) and Relative humidity (RH)
Temperature and RH probe
nE ET R H G
Methodology
Data processing
Calculation of λE:
Bowen Ratio,
Calculations of ET in mm/hr :
Calculations of ETref : FAO Penman-Monteith
1nR G
E
/H E
(28.36 24)
EET
Results
Figure 3: Measurement of ET and tarnspiration over mature cotton
Results Figure 4: Components of total ET measured by ECV-sap flow
method
Conclusions
Measurement of total ET during sprinkler irrigation is possible which includes:
canopy evaporation and droplet evaporation during
irrigation reduction of transpiration during irrigation canopy interception soil evaporation
Thanks for your attendance
Questions