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 performance of border check irrigation in the murray dairy region

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

Mike Morris, Amjed Hussain, Malcolm Gillies


The murray dairy region

The Murray Dairy Region

  • Image: Murray Dairy


Why fast flow irrigation

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

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

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

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


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Modelling

Surface irrigation models applied to assure process understanding


Can higher flow rates improve performance of border check irrigation in the murray dairy region

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


Can higher flow rates improve performance of border check irrigation in the murray dairy region

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

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

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

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


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr

154 min

76 min


Can higher flow rates improve performance of border check irrigation in the murray dairy region

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

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


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration0.1 - 20 mm/hr


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Bay attributes

Length400 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration0.1 - 20 mm/hr


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Bay attributes

Length200 - 1000 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr


Can higher flow rates improve performance of border check irrigation in the murray dairy region

Bay attributes

Length200 - 1000 m

Width50 m

Slope1:750

Roughness0.25

Crack fill37.5 mm

Final infiltration2 mm/hr


Conclusions

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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