Trigger Level

(2) The -1.5 AHD ‘trigger’ level for intervention is much too low and much too late. 


  • The draft EIS clearly indicates that this ‘trigger for action’ has been determined solely by considerations of water quality concerns and the point at which modelling indicates risk of irreversible acidification of the lake water body.


  • It takes no account of the fact that exposed acidic soils are not remaining in situ but are moving in large quantities whenever winds exceed low velocities, with significant and potentially extreme environmental and human consequences.


  • With lake water levels at about -1.0 AHD in March 2009 there are already large expanses of exposed soils (sands and mud) exposed around the shores of the lakes and in channels in the vicinity of Goolwa, Currency Creek, the Finniss River and Clayton. As levels have dropped over the past six months the shallow waters have receded rapidly.


  • Ecological and human consequences are already serious.


  • Anticipated further lowering of lake water levels over the next ten months, towards the -1.5AHD trigger will escalate these problems with Lake Alexandrina then only half its original size and huge expanses of lake bed exposed to wind.


  • To then use sea water, in February 2010, to hold the level at -1.5 AHD would allow the current wind erosion and deposition damage to continue.


  • Water levels need to be returned to at least 0.0 AHD to alleviate these problems.