To wrap up the 2019-20 irrigation season we’ve analysed the weather data from the Lincoln and Winchmore climate stations and then estimated how much water an efficient irrigation system would have used. The following table provides a summary of average daily and monthly water use for pasture (Potential Evapotranspiration – PET) alongside monthly rainfall.

The 2019-20 irrigation season was characterised by a cold start with regular rainfall, a relatively warm and dry peak of season and a warm end to the season but again with regular rainfall.

Using the data summarised above, a daily timestep water budget was used to determine how much irrigation an efficient system would have applied. To calculate this, some simple irrigation rules were used:

  • An irrigation application depth of 10mm for soils with a Profile Available Water (PAW) of 60mm and 80mm, and 15mm for soil with an PAW of 100mm and 120mm.
  • An irrigation trigger point of 50{d63bd7a1bfb28fa6de66fde08e78ca1ad36bbb55755b6aa7dcff30a97ce0b189} PAW for the shoulder seasons and 60{d63bd7a1bfb28fa6de66fde08e78ca1ad36bbb55755b6aa7dcff30a97ce0b189} PAW at the peak of the season

The ‘efficient irrigator’ results are shown in the table below.

For Lincoln, due to the much lower rainfall, an efficient irrigator would have used between 390mm and 450mm depending upon PAW, and for Winchmore between 300mm and 390mm. For all scenarios there was no reason to irrigate in September or April.

The take home from the above is, if you have applied greater than 450mm this irrigation season or have irrigated in September or April, it would be prudent to review your irrigation management and explore ways to improve. A basic review of your irrigation is simple to undertake; a water budget spreadsheet alongside your irrigation and rainfall records is all that is required to gain valuable insight. A few hours analysis work over winter could result in saving you thousands in operating costs for next season.

If you would like specific support, advice or a review of your irrigation management (including practical suggestions around how your irrigation practice could be improved), or you are having issues with your irrigation equipment, give the team of practical specialists at Water Strategies a call to book in your Irrigation WOF.


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