Weekly Irrigation Requirements – Northern Victoria



Wednesday 13 Oct 2021


Weekly Irrigation Requirement$ Summary – Driving Water Productivity

This update provides ‘reference evapotranspiration’ (ETo) information to assist with improved irrigation scheduling for top yields and high water productivity.


In this update:

  1. Weekly irrigation requirements – summary.
  2. Commentary
    – Seasonal climate update webinar
    – Farm Crime Stoppers campaign.
  3. Soil temperature.
  4. Last week’s irrigation requirement.
  5. Next week’s irrigation requirement.
  6. Daily ETo and rainfall.
  7. Seven-day weather forecast – Nanneella.



Water requirement for our reference crop of pasture (ETo) at Kyabram*:

Past 7 days

6 – 12 Oct

Previous 7 days

29 Sep – 5 Oct

Next 7 days

13 – 19 Oct

Long-term Oct average
Water requirement – ETo** 26mm 15mm 22m 30mm
Water requirement – ETo** 0.26ML/ha 0.15ML/ha 0.22ML/ha 0.30ML/ha

** Rainfall is not included in these estimates.  The figures presented are cumulative daily reference evapotranspiration (ETo).

* See the tables and graphs below for ETo (and rainfall) at more locations.



Seasonal climate update webinar

A Seasonal Climate Update webinar will be conducted at 12 noon on Wednesday 20th October.  Agriculture Victoria seasonal risk agronomist Dale Grey will focus on the current seasonal climate outlook for Victoria, South Australia, Tasmania and southern New South Wales.  The outlook will be based on model projections for rainfall using current oceanic, atmospheric and soil moisture conditions.

 Farm Crime Stoppers campaign

Crime Stoppers Victoria has launched a new campaign “Putting a Spotlight on Farm Crime” to highlight the importance of reporting farm crimes, whether its’s stolen livestock, harvested animals, firearms, equipment, tools or chemicals.  To further help boost security on rural properties, Crime Stoppers Victoria has produced new farm gate signs, available to order for free through www.crimestoppersvic.com.au/farm-crimeThe signs are 1 x per person and available ONLY at Benalla Police Station, Warragul Police Station, Bendigo Police Station, Hamilton Police Station. Rural property owners are also encouraged to download the Farm Security checklist via the same link: www.crimestoppersvic.com.au/farm-crime/



  • The soil temperature measured by a capacitance probe at 9am today (Wednesday 13 Oct) under ‘surface irrigated pasture’ at 10cm depth at Wee Wee Rup (near Leitchville) was 14oC, 1oC more than the same time last week (6 Oct).
  • This time last year (13 Oct 2020), the soil temperature at Lancaster (near Kyabram) was 12oC.

Soil temperature under pasture at 10cm depth at Wee Wee Rup, as measured by a capacitance probe.




Pasture Irrigation Requirement$

 Weekly Totals – Wednesday 6 Oct to Tues 12 Oct 2021 

Location ETo+





ETo – R

(mm irrigation required) 

Dairy x pasture crop coefficient Average^ ETo
 (mm /DAY)
Required@ Surface Irrigation Interval (days) Spray> irrigators needed to apply (mm)
Deniliquin* 32 2 30 1 4.5 11 30
Kyabram* 26 0 26 1 3.8 13 26
Tatura*   26 0 26 1 3.8 13 26
Kerang# 28 0 28 1 4.0 11 28
Echuca# 26 0 26 1 3.7 12 26
Yarrawalla# 26 0 26 1 3.7 12 26
Numurkah# 23 0 23 1 3.3 13 23
East Sale~ 23 11 12 1 3.3 14 12

~ This location is listed as a feature of interest and changes each week.

Tip:  To convert mm to megalitres /ha, divide by 100.  Eg. 50mm = 0.5ML /ha.

Important:  The “required surface irrigation interval” shown in these tables is calculated only using cumulative ETo and needs to be considered in conjunction with rainfall on your farm.  For example, this time of the year (October) for each 4mm of effective rain on your property, typically an extra day can be added to the “required surface irrigation interval” for pasture.




Pasture Irrigation Requirement$¥

Weekly Totals – Wed 13 Oct to Tues 19 Oct 2021  

Location ETo



R <


ETo – R

(mm irrigation required)

Average ETo
(mm /DAY)
Required Surface Irrigation Interval (Days) > Spray irrigators will need to apply (mm)
Deniliquin 27 16 11 3.8 12 11
Kyabram 22 25 -3 3.2 15
Tatura 22 28 -6 3.1 15
Kerang 28 12 16 4.0 12 16
Echuca 24 20 4 3.5 14 4
Yarrawalla 25 15 10 3.5 13 10
Numurkah 23 24 -1 3.3 14

< Only daily forecast rainfall events 2mm or greater are listed in the above tables and in the ETo graphs below.



6.  DAILY ETo and rainfall – last week & next week




7.  SEVEN-DAY FORECAST for Nanneella (near Echuca)

  SWAN system free daily email service for practically any location.





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 Here’s a top offer!  If you would like 7-day forecast ETo (and rainfall, temperature and wind) for any selected location/s emailed to you daily for free, please click here.

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 irrigations or this scientific booklet.

 The intention of this service is not for this information to be used in isolation when making decisions about irrigation timing.  ETo data provides another handy tool in your irrigation ‘tool box’ and needs to be used in conjunction with other preferred scheduling methods and updated weather information.

IrriSAT is an Australian web-based irrigation scheduling tool that uses satellite ‘vision’ to tailor irrigation scheduling for your crops.  Alternatively, IrriPasture or the SoilWater app are relatively simple and user-friendly apps that use regional weather based measurements to assist with scheduling irrigations on your farm.


+ Reference evapotranspiration (“ETo”).  Refers to the evapotranspiration from an actively growing, well-watered, grass stand 120mm in height.

* ETo and rainfall data sourced from the  Bureau of Meteorology

# ETo and rainfall data sourced from the Queensland government’s SILO web site based on climate data provided by the Bureau of Meteorology.  This is “triangulated” data – based on calculations and measurements from the closest weather stations which are not on-site.  Comment: SILO ETo data generally appears to be slightly lower than BOM ETo data.

~Rainfall R.”  Where a rainfall event is less than 2mm it is usually not ‘effective’ and is unlikely to be listed.  Any rain in excess of that which fills the soil profile (or reduces ‘cumulative ETo-R’ back below the estimated RAW,) also needs to be disregarded.  Because rainfall can vary over short distances, irrigators are encouraged to collect and use their own rainfall figures for their farm.

x  “Dairy pasture crop coefficient.”  For crops other than pasture refer to this Tech Note for discussion of an appropriate crop coefficient “What is evapotranspiration and how do I use it to schedule irrigations?”  Alternatively, use the Irrigation Scheduling Tool embedded in this Update which provides guidance on which crop coefficient to use for your particular crop and it’s stage of development.

^ The “Average (daily) ETo” is simply calculated by dividing the total weekly cumulative ETo by 7 days.
@ To calculate the “Required surface irrigation interval” it is assumed there is 40mm of ‘readily available water’ in the pasture root zone.  eg.  Required surface irrigation interval = 40mm  ÷  average (daily) ETo, plus 2 days to allow for excess water to drain away following a surface irrigation event.  (Where SILO ETo data is used – Kerang, Echuca, Yarrawalla and Numurkah, 1day is added rather than 2 days because SILO ETo figures are appearing to be slightly lower than BOM ETo figures.)
> Spray irrigators need/ed to apply.”  This figure is based only on evapotranspiration minus rainfall (“ETo – R”) and assumes a good spray uniformity and, application efficiency.  If a spray irrigation system has compromised spray uniformity or application efficiency, then more water will need to be applied to best meet plant needs.   Typically, with pressurised irrigation systems, irrigations will be applied more regularly than once per week in summer to optimise plant growth.

¥Next weeks forecast reference evapotranspiration – pasture irrigation requirement.”  These figures are sourced from the BOM.  This is a ‘fee for service’ arrangement and these specific forecast ETo figures are currently not publicly available.  If you would like 7-day forecast ETo (and rainfall, temperature and wind) for any selected location/s emailed to you daily, click here.


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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