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Irrigation – Does Variability Matter? Ian McIndoe Fraser Scales

Irrigation – Does Variability Matter? Ian McIndoe Fraser Scales. Background. With irrigation, we have to get SMARTer ! Production Drainage (due to irrigation AND rainfall) Allocation limits/ water use Other factors, e.g. energy We need irrigation to be well-designed and well-managed

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Irrigation – Does Variability Matter? Ian McIndoe Fraser Scales

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  1. Irrigation – Does Variability Matter?Ian McIndoeFraser Scales

  2. Background • With irrigation, we have to get SMARTer! • Production • Drainage (due to irrigation AND rainfall) • Allocation limits/ water use • Other factors, e.g. energy • We need irrigation to be well-designed and well-managed • Design sets the platform for high performance

  3. The challenge • We live in an imperfect world • Variability is a fact of life • Variability has to be accommodated in both design and management • Optimum solutions are site specific

  4. What variability? • Climatic – rainfall, wind, humidity, temperature • Agronomic – crop, stage, physical composition, actual water use • Soils – PAW, infiltration, depth to pans, surface storage • Topographical – shape, slope, infrastructure, natural features

  5. What variability? • Water supply – reliability, quantity, quality • Irrigation system – components, pressure, flow, uniformity, application intensity • Management – timing, depth applied • Given this, how can we deal with variability to deliver SMART irrigation?

  6. Climate • Generally, good historical data is available – useful for determining design specs and overall need • For rainfall, need to make full use of local data

  7. Wind speed

  8. Wind speed

  9. Temperature

  10. Agronomic • Currently, mostly standard values used to determine crop water need • Improved data is being produced – e.g. grazed pasture crop factors • Need for irrigation systems to be designed to better match crop needs

  11. Soils • Currently, soil maps often used (e.g. S Map) • Need better information on soil properties and variability of soils on farm • PAW and its variability • Depth to pans/ lower hydraulic conductivity horizons • How much does PAW variability matter?

  12. Soil PAW variability

  13. Soil PAW variability

  14. Topography • Slope matters more than you might think • Very few paddocks are actually flat • Surface redistribution is very common • Need to tailor design and management to maximise benefits • Land levelling under spray irrigation?

  15. Application uniformity • Is about how evenly water is being applied to the ground surface • Easily checked using bucket tests • Low uniformity usually leads to low efficiency

  16. Spray irrigation bucket test

  17. Application uniformity

  18. Application uniformity

  19. Ponding and surface redistribution • Probably the biggest contributor to low irrigation performance • Can generally be observed • Driven by application intensity and depth applied • Particularly an issue on slopes • Needs full consideration in irrigation design and management.

  20. Ponding under pivot

  21. Ponding

  22. Application intensity

  23. Application intensity

  24. Supply reliability • Impacts on irrigation mind set – just in case versus just in time • Impacts on production, water use, drainage • Need to have high reliability to achieve high performance

  25. Irrigation system • Irrigation method • Pressure variability - tradeoffs • Flow variability • issue with VRI, corner arms, multiple pumps • Voltage variability • INZ Codes of practice – design, installation

  26. Performance – 60 mm PAW

  27. Performance – 60 mm PAW

  28. Performance – 120 mm PAW

  29. Performance – 120 mm PAW

  30. Irrigation management strategies • Depth of water applied • Return interval • Seasonal limits • Where and how irrigation is scheduled • A lot of work has been done and is being done in this area. • Weather forecasting will be critical!

  31. Effect of scheduling location

  32. Conclusions • We need to become SMARTer irrigators • Variability does matter in some areas • We need to focus on production, water use and drainage • Better engineering will be required • in the factory: new or improved irrigation methods • in the design shop • We need to target application uniformity • We need to target surface redistribution

  33. Priorities • What is easy and cost-effective to implement? • Some things are well understood • Some things need to be better communicated to end users • Some things require further investigation • We can achieve our targets, but its not going to be easy.

  34. Questions

  35. Temperature

  36. Centre-pivot

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