Australia Weather News

Farmers who have signed up to two new irrigation schemes in Tasmania are anxiously looking to the sky for signs of good rainfall.

The Swan Valley Scheme near Swansea on the east coast, and the Southern Highlands Scheme around Bothwell, both need rain to fill the newly built dams.

There has been a little rain in the past week but not nearly enough at this stage.

Richard Hallett, a Bothwell farmer and chairman of the Southern Highlands Scheme, said no one thought that 2017 would see a one in 20 to 25-year event where rainfall to date had been less than the same period in 2015, which had been an incredibly dry year.

"It's been the driest start to winter in 120 years," he said.

Low flow unexpected

Mr Hallett said it was almost unheard of for flows in the Shannon River, which feeds the scheme's Southernfield Dam, to be as low as they were at present.

"For the scheme to operate properly, we need a good 50 to 60 days or more pumping from the Shannon and, at the moment, we're nowhere near even getting the flows to be able to start," he said.

If those rains do not come, irrigators who have signed up for the scheme and invested heavily in water and on-farm infrastructure may have to look to what would be an expensive alternative supply.

"That may include Great Lake, which was always going to be part of the scheme as a back-up, but it's a very expensive water source," Mr Hallett said.

"If we're talking about water that's pumped from the Shannon, we're probably talking about $100 to $120 a megalitre applied, whereas [we're] talking towards $300 per megalitre for water which is from Great Lake."

Ambitious plan uses precision agriculture techniques

Among the many other farmers preparing for the Southern Midlands Irrigation Scheme is Will Bignell, whose family has been farming in the area for many years.

He is preparing part of the family farm known as The Square for the advent of water from the scheme.

It is an ambitious plan involving a huge single pivot and the use of a large amount of precision agriculture technology and techniques, not to mention that dependence on rainfall to fill the Southernfield Dam.

That single pivot is nearly 1 kilometre long and will irrigate 150 hectares.

"This new water allowed us to open up new country and put in this big pivot, so the efficiency gains and the control it will give us is pretty much what I'm working towards," he said.

Precision agriculture techniques have played a large part in the planning and development of The Square.

"It's allowed us to make informed decisions for big dollars with a high degree of confidence," Mr Bignell said.

But what happens if the rainfall needed in the catchment does not happen this season?

"That puts the wind up me most nights when I go to bed at the moment," he said.

"What a combo of the perfect damned storm, to put it mildly — we've got no flow down the Shannon so we're looking at buying expensive water at the start of the season with an empty dam.

"We've just got to hope it rains and look at some options just to get this scheme going and moving."