A simple Coorong solution requiring no freshwater.


10 September 2008

The Secretary

Senate Standing Committee on Rural and Regional Affairs and Transport

Parliament House

Canberra ACT 2600

A simple Coorong solution requiring no freshwater.

It is of concern that people when discussing the lower lakes refer to the Coorong needing

freshwater. The Coorong is saltwater currently up to 6 times as salty as the sea at the

southern end. It’s problem is it is too salty. By diluting with seawater we can reduce its

salinity to the required level, no more than 3 times saltier than the sea.

If I may quote David Patton, Adelaide University.

“In the past, when fresh waters typically flowed over for several months per year, the

salinities were kept at levels that allowed hyper marine organisms to survive. They

struggle once salinities get about 3 times saltier than sea water.

What has happened for the last 7years, is that increasing amounts of salt have moved into

the southern Coorong because of the lack of flows down the river. As a consequence, the

salinity levels have reached six times higher than sea water. The tidal prism has no ability

to influence the water levels for the southern part of this system.”

See http://www.envict.org.au/file/Winter_2005_Coorong_report.pdf

Ruppia Tuberosa is an annual plant that exploits the ephemeral mudflats around the

shores of the southern Coorong. It is a major provider of food resources and habitat for

waterbirds and fish. Ruppia Tuberosa does not survive once salinity exceeds 3 times the


By admitting seawater to the Southern Coorong we can lower the salinity to a suitable


By controlling the seasons when we admit seawater to the Southern Coorong we can

control the water level to provide Ruppia Tuberosa with the drying mudflats in summer

and the required rising water level in late autumn and winter needed for it to germinate

and spread.

By admitting seawater to the Southern Coorong during autumn, winter, spring we can

establish a flow from the Southern area to the Northern and on out the mouth flushing the

excess salt from the system.

By setting up a flow out through the mouth we will reverse the current inflow which is

bringing in sand which clogs the mouth. Enough outflow current and the mouth will

become self cleaning.

Currently the Murray Mouth Dredging is costing $5m/yr. In the 5 yrs to 27/4/07 dredging

has cost $27m.

If the $5m/yr was put into getting seawater into the Southern Coorong I believe we could

save the whole Coorong environment and keep the mouth clear.

Seawater need to be moved from the Southern Ocean a distance of about 1km over the

peninsula and into the Southern Coorong around Salt Creek. The exposed open surf

beach there will be a challenge but ultimately we could come up with a solution which

uses the power of the surf to push the ocean water on its way.

A temporary solution may be to move seawater in using the existing dredging equipment.

Ultimately a larger version of the system as used at West Lakes, South Australia, needs to

be in place. West Lakes have inlet pipe at one end with auto opening gate at high tide,

through which 500meg/litres per day flows in. A similar system is needed which will

allow water at high tide to flow through into the Southern Coorong. This water then

makes its way thru the Coorong to eventually flow out the mouth, whilst at West Lakes it

flows into the Port River and the sea.

Thank you for considering this solution and I urge to speed it implementation

Sincerely yours,

George Bennett