Drought Fears – Walk Across The Murray
There’s always something to be scared about. But in the history of things to be scared about, this has to be at the very bottom of the list.
The Murray is Australia’s largest and longest river. It’s not all that spectacular by world standards, but we’re quite fond of it.
Before European intervention, The Murray was what most Australian rivers are – a series of inter-connected waterholes along a dry bed, which were linked during flood times, when water would spread out over a wide area. After the floods, water in the river would gradually dry up, returning the river to its normal dry bed. For almost all of its history, except for the last seventy years, it has regularly been possible to walk across The Murray.
Over the last century flows in and out of the river have been increasingly carefully managed, so that for much of its length water is maintained at a fixed level, and there is always some flow, even in times of prolonged drought. Testing at centres along the river, including Morgan in its lower South Australian reaches, show that salinity and turbidity (the amount of suspended matter in the water) are both decreasing.
In other words, even during times of low rainfall and consequent low inflows, the river’s health has been good. The river is a major source of tourism income, and supports vast areas of irrigation where grapes and citrus fruit are grown. It will never be returned to its ‘natural’ state.
The lower lakes are similarly an entirely artificial creation. The Coroong, the name of the estuary and lower lakes, was a tidal, that is, salt water estuary, which was occasionally filled with fresh water in times of flood. The flow of water in and out to the sea was blocked when barrages were built across the mouth of the river about seventy years ago, and the current permanent fresh water lake system created
About 500 gigalitres of water is lost from these artificial lakes each year through evaporation. This leads to higher levels of salinity, but levels which still do not approach those of the sea water which used to fill the lakes. There are questions about whether this loss is sustainable, or whether the barrages should be removed and a weir built across the real mouth of The Murray, where it enters the lower lakes at Wellington.
This would reduce loss of fresh water through evaporation and make management of the river in its lower stretches (from Morgan to Wellington) easier. But it would create considerable difficulties for the communities which have grown up around the lower lakes, and especially for the town of Meningie.
Further study and debate will help to clarify the best solution. But scare-mongering headlines will not help.