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