During the recent drought, when the waters of Lake Alexandrina receded, rye grass was sown on the dry lake bed in front of Trevor Harden’s home to stop the soil blowing away. Mr Harden would have preferred the barrages to have been opened, and the lake allowed to reconnect with the sea.
When I first visited Lake Alexandrina, at the bottom of the Murray River, it was during the drought and the so-called Murray mouth had to be kept open by a sand dredge. During my recent visit the lake was full of water, and still more water flowed in at Wellington, and out at Goolwa, out to the Southern Ocean.
According to lake-front resident, Trevor Harden, more than 50,000 megalitres per day has been flowing past his home and down the Goolwa channel to the Southern Ocean since November 2010 – more than 70,000 was flowing past on the day I visited, on March 14, 2011.
The view from Mr Harden’s veranda on that day was of black swans and pelicans sailing past on a broad expanse of brown water. But the screen saver on his computer showed wheel tracks from a quad bike across the dry lake bed. The photograph had been taken at the height of the drought in April 2009.
“During the drought, water levels in the narrow Goolwa channel to the far side were 1 metre below sea level and falling,” explained Mr Harden.
Back then, a remediation program was initiated with lime spread over the exposed acid sulphate soils of the dry lake bed in front of Mr Harden’s home and rye grass planted in an attempt to stabilize the soils.
“The acid soil was exposed and blowing in the wind and onto my new galvanized iron house and in one 24 hour period I had a very visible set of surface corrosion,” said Mr Harden. “Acidic soil doesn’t become a problem until it is exposed to air. The problem could have been averted by opening the barrages and letting some seawater in to mix with the fresh and maintain levels.”
The remediation program did stop some of the soil blowing and a government scientist won awards for his work managing the problem, but it was all unnecessary according to Mr Harden.
“When the water level in Lake Alexandrina fell to sea level, then the barrages should have been opened and tidal pressures used to maintain an estuarine system at sea level until the floods came. Freshwater will always end a drought. At issue was what to do while we waited for the rains.
“In reality, the work of spreading lime and sowing with rye grass to stop the soil from the lake blowing away would have been unnecessary if the barrages had been opened.
“The irony is that all of that remediation was required only because the water level had been allowed to drop lower than it had ever got to before.
“They kept saying we want to revegetate the lake bed,” said Mr Harden. “I said, call it ‘vegetate’ if you must, but not ‘revegetation’, because this lake bed has never had vegetation before. This lake bed has never been allowed to dry out before.”
Read the rest of this story in The Land: http://theland.farmonline.com.au/news/nationalrural/agribusiness-and-general/general/dry-dilemma-opens-barrage-of-questions/2128380.aspx?storypage=0
Read more about the history of the lakes at Quadrant Online: http://www.quadrant.org.au/blogs/doomed-planet/2010/11/jennifer-marohasy