21 July 2011 in Jamie’s View
Correspondents to The Land continually claim the Lower Lakes are estuarine with a natural state alternating between fresh and salt depending on river flows and tidal movements.
Your columnist and Myth and the Murray mouthpiece, Jennifer Marohasy, insists the great majority of scientists, who agree the lakes are not naturally estuarine, are all wrong.
The truth is that salt water incursion into the lakes is rare between one and five per cent of the last 7000 years. This does not mean that every year there are between four and 18 days the lakes were salt; it means that at certain rare times over the eons due to extraordinary conditions there were prolonged salt incursions.The last major incursion was some 1700 to 2000 years ago. Diatoms from the lake bed confirm this and that most incursions did not progress past Point Sturt, which is at the south west corner of Lake Alexandrina only 20 kilometres from the mouth.
The fact is the lakes perform a vital role in maintaining the health of the entire river system, which accumulates two million tonnes of salt each year much of it from over the border. The barrages were constructed to maintain the lakes' fresh water status in the face of ballooning extractions for irrigation upstream, as discussed in the SA parliament in the late 1880s. They did not "create" a freshwater environment they restored and preserved one.
If it was as simple as pulling out the barrages and letting the sea in, why was it necessary to dredge the mouth continuously from 2002 to 2010, (at vast expense), to keep the mouth open during low or non-existent outflows? No science is needed to know that without a reasonable outflow the mouth will silt up completely.
Ms Marohasy has constantly ignored the weight of scientific evidence against her claims. Let her list the scientists who support her argument that the Lower Lakes have been a fully estuarine water body for more than five per cent of the past 7000 years particularly the past 1700 years.
In the past 40 years, SA has made better use of limited water resources than any other State. We had to. We have not increased our take of river water since 1969. Yet Myth and the Murray would have your readers believe we in SA are the water wasters.
Instead of focusing solely on the bottom end of the river system, perhaps Ms Marohasy could draw attention to water inefficiencies in other States still using archaic, inefficient irrigation systems. Irrigators and communities across the entire basin should be working cooperatively to preserve the health and viability of the waterway upon which we all depend. Only in this way can we sustainably maximise the opportunity the Murray-Darling Basin presents us to grow food for ourselves and others in the world less fortunate than ourselves.
Preserving the river system is also imperative to maintaining the culture and lifestyle of all who live and work with this irreplaceable waterway. Ms Marohasy and her cohorts should stop creating myths and focus on protecting the long-term sustainability of our greatest environmental asset so we all benefit and not just a chosen few.
*Written by Jamie Briggs MP, Patrick Secker MP, Mitch Williams MP and Adrian Pederick MP