Can higher flow rates improve performance of border check irrigation in the murray dairy region
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Can higher flow rates improve performance of border-check irrigation in the Murray Dairy Region? PowerPoint PPT Presentation


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Can higher flow rates improve performance of border-check irrigation in the Murray Dairy Region?. Mike Morris, Amjed Hussain, Malcolm Gillies. The Murray Dairy Region. Image: Murray Dairy. Why fast flow irrigation?. Millennium drought (1997-2009) ↓ dairy irrigators

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Can higher flow rates improve performance of border-check irrigation in the Murray Dairy Region?

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Can higher flow rates improve performanceof border-check irrigationin the Murray Dairy Region?

Mike Morris, Amjed Hussain, Malcolm Gillies


The Murray Dairy Region

  • Image: Murray Dairy


Why fast flow irrigation?

  • Millennium drought (1997-2009)

    • ↓ dairy irrigators

    • ↑ dairy farm system complexity

    • ↓ time

  • System modernisation

    • ↓ outlets

    • ↑ flow

  • On-Farm Irrigation Efficiency Program

    • ↑ ↑ redevelopment


What were the issues?

  • Industry

    • Does faster flow save water?

    • Does it improve productivity?

  • Catchment managers

    • Are there catchment scale implications?


What is fast flow?

  • We have no standard definition

  • “Fast” is getting faster..

  • Our working definition has been

  • {conventional best practice} x 2


Field measurements

  • Paired irrigation bays

  • Managed by the farmer

  • Monitored for the full irrigation season

    • Inflow hydrograph

    • Depth hydrographs

    • Soil profile water content

    • Surface drainage

    • Watertable depth

    • Productivity


Modelling

Surface irrigation models applied to assure process understanding


Light soil site

Soil: Cobram loam

Bay length: 243 m

Bay width: 60 m

Slope 1:750

Crop: lucerne (alfalfa)

Irrigation flow rates:

High flow bay: 0.36 ML/d/m bay width

Low flow bay: 0.18 ML/d/m bay width


Heavy soil site

Soil: Moira loam

Bay length: 200 m

Bay width: 40 m

Slope 1:650

Crop: perennial pasture

Irrigation flow rates:

High flow bay = 0.33 ML/d/m bay width

Low flow bay = 0.17 ML/d/m bay width


Light soil, lucerne site

  • High flow provided limited control of infiltrated depth

  • High flow had greatest runoff variation and losses

  • Excess water applied can cause substantial deep drainage at both high and low flow rates

  • Precision of irrigation management was insufficient to capture any potential savings


Heavy soil, pasture site

  • Very low permeability subsoil

  • Very slow drainage (~10 hr)

  • All irrigations replenished soil profile moisture

  • Minimal impact on soil moisture in subsoil

  • Advantage of high flow limited to reductions in the duration of irrigations, reducing labour costs


Generalising these results

  • Analytical Irrigation Model (Austin and Prendergast, 1998)

    • Kinematic wave assumptions

    • Linear infiltration function

  • Monte Carlo analysis (100,000 model realisations)

    • Flow rate = 0.1 - 0.5 ML/d/m bay width

    • Cut-off = 20 - 400 mins

  • Keep “reasonable” irrigations (22,000 model realisations)

    • Runoff > 0 and < 10% inflow


Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr


Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr

154 min

76 min


Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr

154 ±10 min

76 ± 5 min


Flow rate and irrigation performance

  • Average infiltrateddepth vs Flow rate

  • Low quarter uniformity vs Flow rate

  • for final infiltration from 0.1 to 20 mm/hr

  • for bay length from 200 to 1000 m


Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration0.1 - 20 mm/hr


Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration0.1 - 20 mm/hr


Bay attributes

Length200 - 1000 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr


Bay attributes

Length200 - 1000 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr


Conclusions

  • Water savings with high flow rates are not supported by our data or modeling

  • Were there savings, the irrigation practice on farms measured was not precise enough to capture them

  • Outcomes were more variable at higher flow rates

  • We need airbags, not turbo-chargers!


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