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

Background Figure 1: Components of evaporation losses during sprinkler irrigation Droplet evaporation Canopy evaporation Soil evaporation

Background ComponentsTheoreticalExperimental Canopy evaporation 8%Unable to measure Droplet evaporation <1%0-45% Soil evaporationnegligibleUnable 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 sensor Interface

Methodology Measurements  Latent heat flux (λE) and sensible heat flux (H) Eddy covariance technique  Net radiation (R n ) 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

Methodology Data processing  Calculation of λE: Bowen Ratio,  Calculations of ET in mm/hr :  Calculations of ET ref : FAO Penman-Monteith

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

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