Weekly Irrigation Requirements – Macalister Irrigation District (Gippsland)

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MID ETo Update

15th to 21th April 2021


  • Flood irrigation interval for the last week was 13 days
  • Spray irrigation amount was  19 mm of irrigation water for the last week
  • The predicted weekly pasture water use:
    • Bairnsdale is 15 mm, MID 14 mm, Orbost 14 mm and Yarram 13 mm
  • Glenmaggie is at 39.3%

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


The Odd Spot

Emptying re-use dams and effluent ponds leading into winter
Having your re-use dams as empty as possible at the start of winter allows for a greater capacity to capture rainfall run-off into your re-use system. This significantly reduces any rainfall run-off leaving your farm and carrying nutrients and sediments into waterways.
Effluent systems are generally designed to have the storage ponds empty going into the winter. Having the ponds empty increases effluent storage capacity as rainfall exceeds evaporation in this period and paddocks are generally too wet to apply effluent as it increases the risk of nutrient run-off and waterlogging. Plus applying an autumn application of effluent will provide a free boost to winter pasture growth.

East Gippsland Field Days
The irrigation team will be at the East Gippsland Field Days, on Friday 23rd April and Saturday 24th April.
The irrigation team will be at site G19 this year and will have our salinity meter there again, so bring along a water sample, and we can advise you on it’s suitability for use.
For general information about the field days click here

Agriculture Energy Investment Plan
The Victorian Government has announced a $30 million extension to the Agriculture Energy Investment Plan.
The plan supports agricultural businesses to reduce energy costs, improve energy efficiency and explore alternative energy options, helping to sustain Victoria’s adaptable and internationally competitive agriculture sector.  The plan is made up of assessments, grants, demonstrations, skills and education, and research.
To find out more information, click on the link below


ETo – Last Week Totals

Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Boisdale 19 6.4 1 12.6
Cowwarr 18 0.2 1 17.8
East Sale  21 0 1 21
Nambrok 20 0.4 1 19.6
Tinamba 16 0 1 16
Location ETo (mm) Effective Rain * mm (R) Dairy pasture coefficient Required Irrigation mm (ETo – R)
Bairnsdale 21 0 1 21
Latrobe Valley Airport 18.6 1.8 1 16.8
Orbost 16.4 0 1 16.4
Yarram 18.4 0 1 18.4

** 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 2.7 mm/day.

The approximate MID flood irrigation interval based on last week’s daily pasture water use rate was 13 days. (This figure assumes that 30 mm of readily available water is held in the pasture root zone divided by the 2.7 mm/day = 11 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 19 mm of irrigation water for the week to meet pasture water use (2.7 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 22nd April to Wednesday 26th April

Location Predicted weekly pasture water use (mm/ha) Predicted Weekly Pasture water use (ML/ha) Predicted daily pasture water use (mm/day)
Bairnsdale 15 0.15 2.1
MID 14 0.14 2.0
Orbost 14 0.14 2
Yarram 13 0.13 1.9

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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