Summary of Lower Lakes Situation
DROUGHT or CHANGE
by Ian Rowan
Since 2002 inflows to the River Murray have been about 4000GL per year or less than half the long term median inflows. Demand for water has remained the same and as a consequence there has been no outflow of water to the sea and water levels below Lock 1 and the Lower Lakes have declined to below sea level.
This situation has produced serious impacts amongst the worst of which are:
No outflow to the sea has meant that continuous dredging of the Murray Mouth has been necessary to keep it open and allow tidal flow to the northern end of the Coorong.
Water levels have dropped to 0.5m below sea level in the summer of 2008/09 and 1.05m below sea level in 2009/10. A further 0.5m drop could be expected this coming summer.
Acidification as a result of oxidation of newly exposed sulphidic lake beds has occurred. The worst of the acidification has been in Currency Creek, Loveday Bay and parts of the Finniss River. The Clayton regulator has temporarily alleviated the problem in Currency Creek and the Finniss but Loveday Bay in the south-eastern part of Lake Alexandrina has been left untreated.
Slumping and cracking of river banks downstream of Lock 1 has resulted in the loss of several cars and orders to evacuate some riverside homes have been given.
Plans for Lake Albert have changed over time. The original pumping to keep the Lake full was stopped in June, 2009 and it was decided to let the Lake dry out. More recent information has suggested that the threat of acidification is so great that pumping will now recommence when water levels drop below 1m below sea level. They are currently 0.4m below sea level.
Water salinities in the Lower Lakes have increased and the water cannot now be used for irrigation. Some irrigators can now access water from a new pipeline from Tailem Bend. This supply could also be under threat this summer from saline Lake water intrusion which even last summer went past Tailem Bend at times when conditions were unfavourable.
There has been a marked impact on wildlife. Bird numbers are significantly lower and turtles have been encrusted by a tubeworm that has proliferated with rising salinities.
Strong winds have at times caused dust storms from the exposed lake beds. Health problems have been attributed to the dust which comprises fine Aeolian sands and possible corrosive material.
These and other impacts, including the human costs and desperation, are likely to worsen this summer and in the future as predictions are that river flows will decline as a result of global warming. This and the predicted rise in sea level will mean that the concept of maintaining a large, 800 km2, freshwater lake system will be untenable.