Weekly Irrigation Requirements – Macalister Irrigation District (Gippsland)

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MID ETo Update

7 January 2021 – 13 January 2021


    • Flood irrigation interval for the last week was 8 days
    • Spray irrigation amount was 36 mm of irrigation water for the last week
    • The predicted weekly pasture water use:
      • Bairnsdale is 38 mm, MID 38 mm, Orbost 35 mm and Yarram 37 mm
    • Glenmaggie is at 77.7%

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


The Odd Spot

Dairy, Horticulture, sheep and broadacre cropping farmers now eligible for Internet of Things Trial
Grants are currently available for farmers in the Wellington Shire to invest in IoT technologies matched to their on-farm needs.
Applications close at 5pm on Friday 29 January 2021. More info: https://agriculture.vic.gov.au/farm-management/digital-agriculture/victorias-onfarm-internet-of-things-trial

Blue green algae (BGA) Outbreak
Visual monitoring indicates Blue Green Algae (BGA) may be present in local drains at Serpentine Creek near Maffra. Contact SRW for more information. For current SRW warnings and for more information go to http://www.srw.com.au/current-bga-warnings/

Cowwarr weather station offline
The Cowwarr weather station is experiencing technical difficulties and is currently offline. We will endeavour to get it back up and running ASAP


ETo – Last Week Totals

Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Boisdale 33 0 1 33
Cowwarr 32 3.8 1 28.2
East Sale  41 0 1 41
Nambrok 42 0 1 0
Tinamba 33 2 1 31
Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Bairnsdale 38 10.6 1 27.4
Latrobe Valley Airport 41.1 2.8 1 38.3
Orbost 32.6 14.6 1 18
Yarram 40 7.2 1 32.8

Tip:  To convert mm to megalitres/ha, divide by 100.  Eg. 50mm = 0.5ML /ha.
* Effective rainfall = daily rainfall minus 2mm.
ETₒ   and the “crop coefficient” (conversion factor) of 1.0 applies to a healthy productive pasture


MID average daily pasture water use over the last week was 5.2 mm/day.

The approximate MID flood irrigation interval based on last week’s daily pasture water use rate was 8 days. (This figure assumes that 30 mm of readily available water is held in the pasture root zone divided by the 5.2 mm/day = 6 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 36 mm of irrigation water for the week to meet pasture water use (5.2 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 14 January to Wednesday 20 January

Location Predicted weekly pasture water use (mm/ha) Predicted Weekly Pasture water use (ML/ha) Predicted daily pasture water use (mm/day)
Bairnsdale 35 0.35 5.0
MID 39 0.39 5.6
Orbost 34 0.34 4.9
Yarram 37 0.37 5.3

This ETo update is also available online at https://extensionaus.com.au/irrigatingag/macalister-eto-update/

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.
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