New forecasting models offer hope for future water planning
GroundCover™ Issue: 103 | 04 Mar 2013 | Author: Tom Dixon
Grower: David Cattanach
Region: Darlington Point, near Coleambally, in south-west New South Wales
Commodity: wheat, barley and maize Farming area: 600 hectares
Annual rainfall: 50 to 500 millimetres
In January, David Cattanach saw his temperature gauge do something it had never done before – reach 50ºC.
Darlington Point, New South Wales, was not unique in this new record: the Bureau of Meteorology (BoM) had to update its temperature maps with two new colours – pink and purple – to extend the previous temperature range that was capped at 50ºC.
These temperature extremes are another challenge that low-rainfall-area growers such as David are learning to adapt to.
“In recent years, we have seen fairly out-of-the-ordinary temperature extremes,” David says. “If you look at average temperatures for this region, they don’t look all that unusual,” he says. “But the extremes make such a difference day to day.”
South-east Australia’s climate normally varies a lot – but is increasingly experiencing extremes in temperature and an increased incidence of very wet and very dry years.
“For example, in February 2010, we had two very hot weeks and two relatively cold weeks,” David says.
David grows wheat, barley and maize near Coleambally in south-west NSW. The hotter-than-normal two weeks of that February 2010 hurt his harvest, but for others in the region it was the two cooler-than-average weeks that made the difference.
“My neighbour, a fruit grower, didn’t get the sugar levels up in his plums because it was too cool, so he remembers that. Those different extremes impact us differently depending on what we’re growing.”
These extremes in weather (especially rainfall) make accurate forecasting more difficult and have flow-on effects for irrigation budgeting. “Because of increasing variability in rainfall – especially during winter – I have been budgeting to use more water than I did 20 years ago,” David says.
“In the past, I would budget to use two megalitres per hectare to grow wheat, and about eight to nine megalitres to grow maize. During the drought of recent years we were using 4.5 to five megalitres for a hectare of wheat and 10 megalitres for maize.”
David’s interest in rainfall stretches beyond his own property. He has been working with researchers from CSIRO on ongoing climate projects. “CSIRO data from the nearby Hanwood Research Station in Griffith has shown an increase in the water deficit figure (the amount of water a plant needs to grow versus the amount of rainfall received) for the May to October cereals growing season of around 30 per cent over 50 years,” David says.
In 2004, David was awarded a Nuffield Scholarship to investigate agricultural emissions and the impact of climate change on production. He is a participant in the 2012–13 ‘climate change adaptation in agriculture’ master class through the National Climate Change Adaptation Research Facility’s Primary Industries Adaptation Research Network.
With this water deficit in mind, David carefully works out returns based on water availability.
“We have only a very small amount of water, so I have to budget how much water I will need to get a crop through to harvest. I also have to decide what crop, or variety of crops, will give me the best return per megalitre,” he says.
“I cannot afford to run short of water, because in drought years water use is higher. And when water use is higher, there’s no surplus tradeable water anywhere.”
Tools for the future
Improved seasonal forecasting methods would help growers such as David to better budget water for the coming growing season. It is the promise of more accurate forecasting that has driven his interest in forecasting tools.
David is working with CSIRO researchers to review existing seasonal forecasting tools and develop new ones. He hopes the tools will help develop more accurate water budgets based on forecasts.
“In the past I was more interested in what the weather was going to be this week,” he says. “However, over the past 10 years I have become more interested in what the weather is likely to be at the end of the season, because of limited irrigation allocations.”
South-east Australia has a highly variable climate, which is difficult to forecast accurately because there is no one dominant climate driver. Forecasting for the region needs to take into account the interaction of several climate systems including the Indian Ocean Dipole, the subtropical ridge and the El Niño Southern Oscillation (ENSO).
David likes to keep an eye on these drivers. “I tend to look more at the Indian Ocean Dipole in the Indian Ocean and the ENSO Index in the Pacific Ocean because these seem to give an indication of longer-term weather patterns.”
The BoM has several seasonal forecasting tools available online, including ENSO wrap-ups (www.bom.gov.au/climate). These are the types of tools that David is looking at in conjunction with CSIRO.
David regularly looks at BoM’s Predictive Ocean Atmosphere Model for Australia (POAMA) models for predicting rainfall. “If POAMA is combined with other models, it may well be more accurate. The outlook for the summer favoured an El Niño in the Pacific Ocean, but that never really happened," he says.
“This is where composite models become very valuable,” David says, “and why it is so crucial to look at all of the different systems together and how they interact.
“New, more accurate seasonal forecasting tools based on this composite approach would mean more efficient use of water. A high-water-use season means we end up cutting crops off and that’s a waste. Ending up with excess water at the end of a season is just as inefficient,” he says.
The GRDC’s Climate Champions program provides early access to research assessing the impact of climate variability in different agricultural regions and helps growers adapt their production systems. Participants have been selected for their willingness to learn more about the influences of climate variability and to provide leadership to other farmers by sharing their experiences and what they have learnt.
“If we can produce an accurate seasonal forecast, and relate this back to water deficit, it will influence which crops we can grow and the area of crops we can grow.”
The research project will have significant benefit to rain-fed systems too. “If you know you’ll have a dry spring, you may change your cropping mix accordingly, or if you’re a livestock farmer, you may reduce stock levels earlier than you’d planned,” David says.
Although it is a critical element, water is only part of the equation, and sometimes the economics of putting in one crop over another outweighs the risk of loss due to extreme weather events.
“Grain markets play a huge part in our decision-making,” David says. “If the price of wheat goes high enough, then we’ll put more wheat in. It’s worth the risk. However, if the wheat price drops, we’ll put more summer crops in, such as maize, sunflowers and soybeans.”
David finds the GRDC-supported Climate Champion program a great way to network with other growers and researchers in Australia who have a shared interest in adapting to a more variable and changing climate.
GRDC Project Code EC00003
Region South, North
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