Planning helps save water for Stewarts
A series of dry years may have provided their challenges but they also allowed Benalla farmers David and Anna Stewart to think outside the square when it came to water management.
"We'd previously farmed in South Australia where we were used to having a bore with a windmill, or a tank and trough in every paddock," recalls David, who farms north of Benalla.
The Stewarts' run a small prime lamb enterprise on 100ha. Their undulating property has granite-based sandy loam soils rising to rocky granite outcrops. The rocky outcrops had been fenced off, leaving two main cropping paddocks and three smaller paddocks – but just two dams to water the stock.
"Having to rely entirely on surface dam water was an experience we had little knowledge of, and didn't feel very comfortable about," David said.
"The stock were allowed to walk through gateways to access paddocks with water," says David. "This essentially made grazing management impossible.
- A whole farm plan sets the scene for changes to water infrastructure, especially on a new farm
- The installation of a reticulation system has increased flexibility and improved grazing management.
With the couple intending to grow lucerne, which requires a rotational grazing system, it was clear that significant changes needed to be made to the farm layout and the watering system.
They developed a whole farm plan which included reticulating water to where it was needed in a bid to provide much improved water security.
They decided to build a larger dam in the best catchment, and install a reticulated watering system comprising a header tank, poly troughs and piping across the entire farm.
Their whole farm plan divided the property according to soil type – specifically, its suitability to grow lucerne. This resulted in the two larger cropping paddocks being subdivided into nine smaller paddocks, each requiring its own trough.
The other paddocks also required troughs, both as a back-up for when the dams run dry, but also because the stock noticeably prefer to drink the clean water from the troughs.
Working to the farm plan, they installed a 30,000-litre header tank at the highest point of the property. An electric pressure pump was installed at the dam to deliver water to the tank (a head of around 25m).
The water is then gravitated to the troughs via 40mm piping. All the lines have been set up with gate valves to isolate paddocks that are not being grazed.
In summer, the tank's capacity represents approximately 10 days' supply, but, as with any other watering system, it requires monitoring every couple of days.
Occasionally the pump has required repairs or maintenance, but there has normally been adequate water in the tank to continue watering the stock during that time. The system works well, enabling David to rotationally graze the entire farm. This is generally a maximum of five to seven days, followed by a rest period of between 28 to 37 days, depending on the season and paddock size. But it is only effective while there is an adequate water supply.
With good rains over summer and good stores of subsoil moisture David has plans to put in lucerne this August.
The dams are also full after such a good start to the season.
One system the couple did try during the dry years was to use an anti-evaporative agent in the dam.
They believe this product helped prevent them from running out of water during the dry start to 2010.
It was applied to the water in January 2010 after they realised volumes in the main dam were "disappearing at an alarming rate".
They continued to apply it every 10 days until the end of autumn.
Although he did not take any proper measurements other than to mark the water level from week to week, the product seemed to be working.
"The rate of evaporation had reduced markedly to the point that we made it through the dry 2010 summer and autumn comfortably with water remaining in the dam."
David saw no indication that the silicon-based product was harmful or distasteful to stock or wildlife.
This was one landholder's experience. CSIRO has produced a paper outlining the effectiveness of various tools to reduce evaporation on dams. This publication "New tools for measuring Evaporation from Farm Dams" can be found at www.npsi.gov.au.