Weekly Irrigation Requirements – Macalister Irrigation District

Macalister ETo Update

12 to 17 October 2018

  • Flood irrigation interval for the last week was 11 days
    · Spray irrigators needed to have applied on average 24 mm of irrigation water for the week
    · The predicted weekly pasture water use for the MID in the next week is 27 mm

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

The Odd Spot

Are Irrigation Upgrades really worth it? Find out at McArthurs field day 24 October
A field day is being run at Waverly Pastoral farms next Wednesday 24, to look at the returns on investment for a flood to spray conversion. Topics covered will include production increases, irrigation scheduling, water savings and total costs. Come to 292 Bundalaguah Road in Maffra from 10:45am to 1pm. A BBQ lunch will be provided (BYO chair). Please RSVP to Alexis on 0428 387 869.

On-farm Drought Infrastructure support grants
On-farm infrastructure grants linked to drought conditions in Wellington and East Gippsland Shires were launched yesterday. Grants of up to $5,000 per eligible farm business are available (dollar for dollar co-contribution) for increasing drought preparedness. Funded items include stock containment areas, fodder storage, feeding system upgrades, upgraded irrigation or stock water infrastructure, and farm monitoring technology. For more information go to: http://bit.ly/2QTXBqk

Tinamba soil temperature
The soil temperature is high enough to plant millet and nearly high enough to plant sorghum. The Tinamba soil temperature for the week averaged 15 degrees.

 ETo – Last Week Totals

Location ETo mm Effective rainfall mm (R) Dairy pasture coefficient Required irrigation mm (ETo – R)
East Sale 29.7 0 1 29.7
Tinamba 21.5 16.4 1 5.1
Cowwarr 20.9 3.6 1 17.3

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 12 cm high.

MID average daily pasture water use over the last week was 3.4 mm/day.
The approximate MID flood irrigation interval based on last week’s daily pasture water use rate was 11 days.

(This figure assumes that 30 mm of readily available water is held in the pasture root zone divided by the 3.4 mm/day = 9 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 24 mm of irrigation water for the week to meet pasture water use (3.4 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 specific spray irrigation system uniformity.


For Thursday 18 to Wednesday 24 October.

The predicted weekly pasture water use for the Macalister Irrigation District is 27 mm per hectare (0.27 ML/ha), or a pasture water use rate of 3.8 mm/day.


The intention of this service is not for the information to be used in isolation when making decisions about irrigation scheduling.
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 Economic Development, Jobs, Transport and Resources accepts no duty of care and disclaims all liability in relation to use of this publication.

AgVic also provides weekly ET email updates for North East Victoria (contact dennis.watson@ecodev.vic.gov.au), Northern Victoria (robert.oconnor@ecodev.vic.gov.au) and the Mallee (maxine.schache@ecodev.vic.gov.au).

You can also follow on Twitter and Facebook.

Further information:

For more detail about using evapotranspiration data refer to this Agriculture Victoria fact sheet “What is evapotranspiration and how do I use it to schedule irrigationsor this scientific paper.


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