1. 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

2. Presentation layout  Background  Hypothesis  Objectives  Methodology  Results  Conclusions

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

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

5. Limitations of the catch-can method  Laborious and time consuming  Unable to measure ET over crop (Source : Smith, Cotton CRC) Catch-can

6. 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

7. 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

8. Methodology Figure 4: Experimental set up Eddy covariance system Sap flow system

9. Methodology Eddy covariance (ECV) system Sonic anemometer Infrared Gas analyzer Net radiometer

10. Sap flow system Datalogger Hub sensor Interface

11. 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

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

13. Results Figure 3: Measurement of ET and tarnspiration over mature cotton

14. Results Figure 4: Components of total ET measured by ECV-sap flow method

15. 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

16. Thanks for your attendance Questions