Seasonal forecasting for irrigators

Irrigators will be better equipped to manage precious water resources thanks to a CSIRO project that investigated seasonal climate forecasting for  water supply and demand.

The CSIRO project aimed to reduce some of the guesswork for irrigation farmers and focused on cropping farms in the New South Wales Riverina region, with potential for future testing on farms across Australia.

Recent decades and future climate projections suggest history is likely to be a poor guide for future conditions.

The study looked at how early seasonal climate forecasting information can be used by irrigation farmers to:

  • more effectively manage their water resources
  • improve on-farm management decisions.

Forecasting was used to estimate how much water may be allocated in any one season, combined with how much is likely to be used.

This was done by looking at:

  • the on-farm climate
  • forecasted rain
  • evapotranspiration.

Combining supply and demand forecasts is a relatively new idea. Most irrigation farmers currently use historical guidelines to make educated guesses at the beginning of an irrigation season.

The study compared:

  • whole-farm returns ($profit/farm)
  • water productivity ($profit/ML of irrigation water)
  • risk associated with both, based on scenarios where forecasting is used, and is not used.

Water availability is expected to be further affected by a changing climate and may also be impacted by policy changes. Reducing the risk in bad years and maximising gains in good years is critical for irrigation farmers facing such uncertainty.

In the Riverina, irrigation farms and water-supply dam catchments can be up to 500 km apart, so independent forecast models for both water supply and demand are expected to be important.