Weekly Irrigation Requirements – Macalister Irrigation District (Gippsland)

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MID ETo Update

06th May to 12th May 2021


  • Flood irrigation interval for the last week was 25 days
  • Spray irrigation amount was  9 mm of irrigation water for the last week
  • The predicted weekly pasture water use:
    • Bairnsdale is 12 mm, MID 11 mm, Orbost 13 mm and Yarram 10 mm
  • Glenmaggie is at 32.5%

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


The Odd Spot

Last ETo newsletter for the irrigation season

This will be the last ETo newsletter for the 2020/21 irrigation season. The AgVic team hope you have a good winter that leads into a nice productive spring. The Eto newsletter will commence for the 2021/22 irrigation season in mid-August to continue to provide ETo rates, irrigation scheduling and updates relevant to irrigation in the area.

Recent timely rain will set up late autumn/winter growth

On average 29.5 mm of rain has fallen across the district. The average evapotranspiration rate for last week was 1.2 mm/day. Providing the evapotranspiration rate remains similar, the recent rain will last 28 days before we will require further rain or irrigation (if possible to irrigate)

Free Farm Safety Assistance

The Victorian Government has provided funding under the Making Our Farms Safer initiative to enable the Victorian Farmers Federation to provide free assistance to help you establish a simple safety process for your farm.

For further information please go to https://www.vff.org.au/project/making-our-farms-safer/


ETo – Last Week Totals

Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Boisdale 8 35.8 1 0
Cowwarr 9 23 1 0
East Sale 9 41.8 1 0
Nambrok 10 19.8 1 0
Tinamba 8 29.8 1 0
Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Bairnsdale 9 35.4 1 0
Latrobe Valley Airport 9.7 3.6 1 6.1
Orbost 7 66.4 1 0
Yarram 10.2 10.4 1 0

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

MID average daily pasture water use over the last week was 1.3 mm/day.

The approximate MID flood irrigation interval based on last week’s daily pasture water use rate was 25 days. (This figure assumes that 30 mm of readily available water is held in the pasture root zone divided by the 1.3 mm/day = 23 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 (1.3 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 13th May to Wednesday 19th May

Location Predicted weekly pasture water use (mm/ha) Predicted Weekly Pasture water use (ML/ha) Predicted daily pasture water use (mm/day)
Bairnsdale 12 0.12 1.7
MID 11 0.11 1.6
Orbost 13 0.13 1.9
Yarram 10 0.1 1.4


This ETo update is also available as an email. Contact james.paulet@agriculture.vic.gov.au

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.
If you know someone who you think would like to receive this weekly update, please forward this email to them so they can subscribe if they wish.
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