Weekly Irrigation Requirements – Macalister Irrigation District

Macalister ETo Update

6 to 12 December 2018

  • Flood irrigation interval for the last week was days
  • Spray irrigators needed to have applied on average 32 mm of irrigation water for the week
  • The predicted weekly pasture water use for the MID in the next week is 36 mm
  • Lake Glenmaggie is at 72.7

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

The Odd Spot

Irrigation discussion groups Tuesday 18
The start up meeting for flood and spray irrigators is on next Tuesday. Open to all age and experiences, from across Gippsland. Get together, share ideas, and compare systems with other irrigators. If interested, please RSVP to Janice or Alexis on 5147 0800.

SRW temporary allocation auction – December 18 to 20
SRW will be holding an online allocation auction from 11 am Tuesday December 18 to Thursday December 20. Put this date in your calendars! More information contact Pam Crawford or Gavin Prior on 1300 139 510.

Drought infrastructure grants
Just a reminder that drought infrastructure grants are still available for those in Wellington and East Gippsland, and can be used to upgrade irrigation systems. more information here: https://bit.ly/2LbTKSW

 ETo – Last Week Totals

Location ETo mm Effective rainfall mm (R) Dairy pasture coefficient Required irrigation mm (ETo – R)
Tinamba 29.5 5.8 1 23.7
East Sale 38.6 3.8 1 34.8
Boisdale 29.7 5.2 1 24.5

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 4.6 mm/day.
The approximate MID flood irrigation interval based on last week’s daily pasture water use rate was 9 days.

(This figure assumes that 30 mm of readily available water is held in the pasture root zone divided by the 4.6 mm/day = 7 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 32 mm of irrigation water for the week to meet pasture water use (4.6 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 13 to Wednesday 19 December.

The predicted weekly pasture water use for the Macalister Irrigation District is 36 mm per hectare (0.36 ML/ha), or a pasture water use rate of 5 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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