Weekly Irrigation Requirements – Macalister Irrigation District (Gippsland)

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MID ETo Update

11th August to 17th August 2022


  • Flood irrigation interval for the last week was 27 days
  • Spray irrigation amount was  9 mm of irrigation water for the last week
  • The predicted weekly pasture water use:
    • MID 15 mm, Bairnsdale is 14 mm, Orbost 13 mm and Yarram 14 mm
  • Glenmaggie is at 85.3%

* These figures are approximate and do not take into account rainfall on farm*


The Odd Spot

Welcome to the first ETo update for the 22/23 irrigation season. It’s a great start to the season with 100% HRWS and Glenmaggie at 85.3% and rising.

Incentives Funding
–    Are you planning on installing a reuse system, converting from flood to spray or upgrading your flood irrigation this season? Applications are currently being accepted for onground works through the  Central Gippsland Irrigation efficiency incentive program. Applications close Wednesday 31 August and as always are subject to a selection process, limited funding and eligibility criteria.

–    Do you have a something you’ve always wanted to trial on your farm linked to irrigation? Or a question you’ve always wanted answered? There is up to $30k of funding available to investigate your puzzling irrigation questions. The irrigation demonstration project is currently accepting applications until Wednesday 31 August.

–    If you’re interested in completing an irrigation farm plan, please get in touch. There is now funding available and applications are being accepted and approved monthly.

For more information on any of the above please contact your favourite irrigation extension officers at AgVic Maffra or click this link: https://www.wgcma.vic.gov.au/for-farmers/incentives21
All of the above is made possible through the Victorian Government’s Sustainable Irrigation Program.


ETo – Last Week Totals

Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Boisdale 9 17 1 0
Cowwarr 8 27.8 1 0
East Sale  10 50.6 1 0
Tinamba 7 25 1 0
Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Bairnsdale 11 30.4 1 0
Latrobe Valley Airport 8.8 51 1 0
Orbost 9.1 30.6 1 0
Yarram 10.1 28.2 1 0

* Effective rainfall = daily rainfall minus 2mm.
ETₒ   and the “crop coefficient” (conversion factor) of 1.0 applies to a healthy productive pasture 12 cm high.
** This data is not included when doing any of the below calculations

MID average daily pasture water use over the last week was 1.2 mm/day.

The approximate MID flood irrigation interval based on last week’s daily pasture water use rate was 27 days. (This figure assumes that 30 mm of readily available water is held in the pasture root zone divided by the 1.2 mm/day = 25 days and then add an extra two days to account for waterlogging). This does not take into account any rain your farm may have got during the week which will extend the interval.


Spray irrigators in the MID needed to have applied on average 9 mm of irrigation water for the week to meet pasture water use (1.2 mm x 7). This irrigation figure does not take into account any rainfall on your farm, which must be subtracted from the required irrigation figure, and assumes that the spray irrigation system is applying water at 100% uniformity. This figure may be greater depending on the specific spray irrigation system uniformity.


For Thursday 18 to Wed 24th Aug

Location Predicted Pasture Water Use Weekly (mm/ha) Predicted Pasture Water Use Weekly (ML/ha) Predicted Pasture Water Use Daily (mm/day)
Bairnsdale 14 0.14 2.0
MID 15 0.15 2.1
Orbost 13 0.13 1.9
Yarram 14 0.14 2

This ETo update is also available as an email. Contact [email protected]

The intention of this service is not for the information to be used in isolation when making decisions about irrigation
This publication is provided solely for information purposes and no representation or warranty is made as to its quality, accuracy, completeness, suitability or fitness for any particular purpose. You should make your own inquiries as to its appropriateness and suitability for your particular circumstances. The State of Victoria as represented by its Department of Jobs, Precincts and Regions accepts no duty of care and disclaims all liability in relation to use of this publication.
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