Scientists raise the spectre of salinity

Report number eight on agriculture, Industry development and adjustment, raises concerns about salinity in the basin affecting agriculture, if stream flows were to reduce due to climate change.

“For example, a three per cent reduction in average rainfall has been modelled to result in a 17 per cent increase in temporary market prices in the southern MDB (Gupta & Hughes 2018),” the report said.

“Added to this is a potential challenge of increased salinity and reduced water quality due to declining in-flows with the remaining water potentially less fit-for-purpose.

“Industries and businesses will need to continue to evaluate the use, quality, security and price of water relative to other input costs and commodity prices, as this will ultimately govern the profitability and sustainability of irrigated agriculture in the Murray-Darling Basin.”

However, the latest independent audit on salinity across the Murray-Darling Basin notes that following action taken in the 1980s and 1990s, when crops were under threat from raised salinity, the situation has changed.

“The irrigation induced salinity problems of the 1980s are now mostly controlled and dryland salinity problems are confined to local sub-catchments that pose a low risk to the shared resources of the River Murray,” the audit says.

“There is currently no need for additional salt interception schemes, noting that there are no known sites to build additional cost-effective salt interception schemes.”

The scientific report notes that the primary water quality issue for irrigated agriculture is salinity with excessive concentrations causing a reduction of production and potentially damaging plant health.

The introduction to the series of essays says: “Reduced river flow has resulted in more salt in the basin’s rivers.”

However, the report does not analyse the changing salinity levels measured in the Murray-Darling Basin.

It simply notes that water quality varies across the basin and is impacted by external environmental conditions.

“Fluctuations in water flows (ie. floods and droughts) has major impacts on parameters such as: Salinity, Acid sulfate soils, Blackwater events, Thermal stratification and Blue-green algae,” the report said.

The independent audit on the Murray-Darling Basin Authority released last year, raised concerns about future effects of climate change.

“... the potential effects of climate change on the Basin Salinity Management Program are not well articulated,” it said.

The academy essays may help to illuminate the possible future threats to water quality.

One of the essay authors, Professor Robert Fitzpatrick, said the reference to increasing salt loads in rivers was intended to indicate that under climate change scenarios, salt load would increase as river flows decreased.

Prof Fitzpatrick, from Adelaide University, said while salt interception schemes had their place there was some good research into ways of using natural wetting and drying cycles which were addressing salinity and acid sulphate soils, which could be applied in the future.