How a drainage network started in 1863 transformed South Australia's south

Dec 26, 2023

Across South Australia's south-east, large stretches of wetlands and swamps sprawl across the landscape, soaked from what locals say is a classic, old-fashioned, wet winter.

"When it comes to SA, nowhere does a wet winter quite like we do," says Evan Pettingill, former chief executive of the Drainage Board.

"We know a thing or two about surface water down here."

From above, the point is well made.

The swamps, wetlands, creeks, waterways and drains of the state's south-east – from the Coorong to the coast and inland towards Keith — are "well worth seeing from the air" to appreciate just how much water lies in the region in a good wet year, Mr Pettingill says.

And this year, the network of more than 2,500 kilometres of human-made drains and natural waterways is alive and flowing — allowing this once waterlogged region to flourish as an agricultural engine room.

David Williamson, manager of south-east drainage operations at the state's environment department, explains where the water is heading.

"As flows increase, water is moving right around the region and even into parts of the upper south-east and wetlands that haven't seen much of a drink in recent years," he says.

"We're diverting about 400 megalitres a day from Blackford to Tilley Swamp and into Taratap which is 6,000 hectares of wetlands that we're rehydrating – and this is the water course that goes to the southern Coorong.

"At this stage we haven't had any requests to send it to the Coorong so we're just hydrating wetlands along the route, but if we do [get a request] we are in a good position."

Mr Williamson says as the drains fill and flow, so too do creeks and swamps that make an appearance in a "really good wet year".

"We're getting some good flows in the Tatiara region; Nalang Creek is flowing into Poocher Swamp and we're seeing some flows into Bool Lagoon via Mosquito Creek," he says.

"We sent about 2 gigalitres into Bool Lagoon in the last week, and that's sitting at about 30 centimetres deep currently. It is a massive storage and can take about 18 gigalitres.

"Cockatoo Lake at Padthaway is also full.

"We had a mild summer and late spring, so there has been a lot of water already in the ground and if the rain keeps coming, it should be a really good year for waterways."

While the region lays claim to its share of volcanic mountains and ranges, much of the south-east is low-lying and comparatively flat.

But with reliable annual rainfall of between 500 and 800mm, and proximity to important ports and trade routes, the region came under the eye of pioneering South Australians and governments which sought to "open up" the area for productive agriculture and later, post-war soldier settlement.

In 1863, renowned surveyor George Goyder, along with engineer and architect William Hanson and public works commissioner William Milne, travelled to the region to assess its potential and develop a vision that would define its future.

The first drains in the lower south-east, around Port MacDonnell and Kingston ports, commenced in 1863 but it wasn't until after World War II that the majority were constructed.

The early efforts "were true pioneering grit" says Mr Pettingill.

"It was wheelbarrow and shovel," he says.

"It would have been pretty hard going, no doubt about it. Horse and cart, hammers and chisels."

But in 1913, the first steam powered excavator was brought in to expedite things.

The majority of the drains in the lower south-east were constructed between 1949 and 1972, largely to remove waterlogging, drive agricultural productivity and improve accessibility.

"It was land development for soldier settlement and agricultural production after the Second World War where the bulk of the work occurred," Mr Pettingill explained.

The majority of drains in the upper south-east were constructed from the late 1990s following a focused effort on environmental flows and as part of the Upper South East Dryland Salinity and Flood Management Program.

With the exception of some private works, drainage has been designed and constructed under the authority of the government.

"The relationship between government and landholder has always been a robust one," Mr Pettingill says.

"We've had some visionary and strong-minded landholders like Tom Brinkworth and the McCourt family who have made a significant contribution to water flow and management.

"The Woakwine cutting, and Tom Brinkworth's Wetlands and Wildlife, have been remarkable achievements and are an important part of the history of south-east drainage."