Remediation by seawater

6 January 2010

Some call it "flooding the lakes with seawater", seawater "the S word" around these parts.  The taboo topic not brought up in polite conversation anywhere near the Lower Lakes of South Australia. 

This time the technique is being called 'tidal inundation'.  And guess what, it works.  At the 18th NSW Coastal Conference in November 2009 a paper was submitted titled, "Remediation of coastal acid sulfate soils by tidal inundation: Effectiveness and geochemical implications".  This paper was presented by scientists from the Centre for Acid Sulfate Soil Research, Southern Cross GeoScience, Southern Cross University, NSW.

An excerpt from the abstract of this paper says; 

"This study demonstrates that marine tidal inundation can be an effective method for remediating acid sulfate soils at a landscape-scale. However, there are a range of potential geochemical complexities which need to be considered prior to implementing this technique."

And

"Tidal inundation of ASS is a potentially lowcost, landscape-scale remediation technique which has recently been trialled in far north Queensland. It is well suited to situations where the site is close to a large marine source, where the elevation of ASS is close to mean sea level and conventional agricultural landuse has been abandoned."

A recent announcement on the 3rd of January from CRCCare, claims success in rehabilitating 800 ha of tidal wetlands near Cairns using planned releases of seawater over acidic soils and treatment with lime.  Along with the restablishment of mangroves, the wildlife has returned and exceeded scientists' expectations.

Scientists say that this technique can be applied to the Lower Murray-Darling area.

As of August 2009, over 200 ha at Loveday Bay has been classified officially as acidic. So far no remediation plan has been made public

Loveday Bay, SA- 200 ha of acidic water as of August 2009

Lake Albert is also at serious risk of turning acidic. The plan currently in place for Lake Albert is to resume pumping water from Lake Alexandrina and trial the use of lime and vegetation.  

Lake Albert covers 15,000 hectares, and Lake Alexandrina covers 56,000 hectares when full.  Lake Albert has already surpassed one acidification 'trigger level' while Lake Alexandrina is rapidly approaching it's estimated trigger. 

This method of using tidal innundation to remediate the affects of acid sulphate soil problems is proven; compared to the current trials of 'bio-remediation' which are not proven at all. In fact as far back as the 1930's cropping Lake Albert was not advised. 

If the Lower Lakes are allowed to 'turn acidic', it will be more than a 'landscape-scale' type of remediation effort required, it will be an environmental disaster of the scale that this lucky country has yet to experience.