Gyn and Elaine Jones
'The Model Farm'
Kerang VIC

 

With the aid of his on-farm weather station and evaporation pan, Gyn Jones has worked out how to keep track of the water cycle on his property to within just a few megalitres. In an area with salinity problems and with caps being placed on irrigation water, this information is vital to the ongoing running of his farm. Gyn and Elaine Jones have owned 'The Model Farm', a 50 hectare irrigated-pasture beef enterprise in northern Victoria, for 26 years. Thirty-two hectares of the property are irrigated and the rest is flood liable from the Loddon River, which borders the property. A scientist by training, Gyn was an extension officer in the Department of Agriculture before his retirement. He applies a scientific approach to the management of water on his property and is able to account for almost every drop of water that goes on or comes off 'The Model Farm'.

This involved the development of a detailed measuring system and a mathematical calculation to compensate for the difference in evaporation measured by the evaporation pan and what actually happens in the paddock. Gyn developed his model using weather figures over a nine-year period, gathered from the weather station on the farm.

'During the day the sun shines on the evaporation tank and the temperature rises. The tank becomes a heat bank. Meanwhile if you had a look at five in the afternoon when things are cooling down, you'd find only a small amount of evaporation' said Gyn. 'But meantime, the pasture will have been using water all day.

'Overnight the surrounding air cools off, the tank is relatively warm and it evaporates like fury for the first part of the night until it cools down again. So it's really not mimicking the pasture.

'There is also a crop factor that must be taken into account. Until you get to about gumboot height, your oat crop will transpire exactly as much as the lucerne and clover crops next door. But once your crop starts getting taller than that, the wind starts going between the plants and you start getting what I call a clothes line effect.

'To take these factors into account I developed a pan factor which varies at different times of the year and a crop factor which also varies depending on the crop growth. These give me the correct water usage figures.

'We've got measurement of plant use, rainfall and evaporation. When that reaches the amount of water that your paddock normally takes, you irrigate.

'In the last "ordinary" year we used 352 megalitres of water and I could account for all but six of those.'

Accounting for water is becoming critical for Gyn and Elaine as water use for irrigation becomes further restricted.

'It is now getting to a stage where there is a cap on water usage. In 82-83 we only had 130%'' said Gyn.

'We irrigate for spring production so we have hay for the following winter. When we cut the hay, we sit down and work out what water we've got available out of our 130% of water right. We take away what we've used from that amount and put aside what we need for Autumn, assuming that there's no rain at all.

'We then use this to work out how much water our perennial pasture needs to get us from that date - normally around the first of December - through till the first week of April. If it doesn't rain after that, God help us!

'We divide what we've got left by the number of hectares and that tells us what we can irrigate' said Gyn.

In his quest to develop sustainable forms of irrigation, Gyn has become a specialist on salinity and is the author of a practical booklet for farmers entitled Irrigation Salinity, attack and defence.

One of the key things he advocates, along with careful tracking of the water cycle to ensure irrigation water is not leaking into the water table, is proper preparation of ground for irrigation.

'We had a community owned research farm in this area and we did work on slopes. It was basic to everything else. The work wasn't written up, but its been applied and that's what we were on about' said Gyn.

'We found that a fall of 1 in 750 was the best for this area, and it handled most of the problems.'

'At first, I worked it out by hand. The first paddock I did with another local farmer - he had it surveyed, I worked it out and he went with the recommendations. His paddock grew its first barley crop for years. He was able to get cover over the whole paddock and not waste irrigation water.'

'The first laser contractor came in 1978 and it's an everyday occurrence now. Though you still see irrigation being applied to land that hasn't been prepared' Gyn said.

As a result of Gyn's careful tracking of water to ensure it doesn't leak into the water table, the level of the water table on his property is actually falling and previously saline areas have disappeared.

As well as using weather information to make the day to day running of the farm sustainable, 'The Model Farm' is being used in another project assessing climate change.

Gyn and Elaine's son is Dr Roger Jones of the Climate Impacts Group at CSIRO Atmospheric Research.

Roger has taken the data from the farm and built a model that reproduces the irrigator behaviour, automatically watering at the same level of dryness that would prompt Gyn and Elaine to irrigate.

The model allows him to look at long sequences of artificially generated climate, based on current climate and changed climate, to see how often the cap on water usage is exceeded. The model has been used to look at the risk that irrigating may become non-viable because the farm cap is exceeded too often under climate change, due to higher evaporation and (possibly) lower rainfall.

Roger believes the risk that climate change poses to irrigation activities over the longer term is sufficient to warrant its inclusion into long-term planning for things such as salinity, environmental flows and water supply security.

The work is about to be published in an international journal, and a number of other researchers have already picked up the techniques for risk assessment illustrated by the work, and are using it to assess other impacts under climate change.

The data and records from the farm have been essential to Roger's work. He is now involved in a study to determine how the information he has gathered from 'The Model Farm' might be applied on a broader scale.

'We are very careful irrigators' said Gyn.

'We can be criticised because we've got a very small property, but I question this whole idea of getting big when you're handling natural resources.'

'We are using precious resources. There are people who wanted to just write this area off when salinity became a problem, but then you just go on and damage the next area and it just isn't sustainable.'