When Steve Posselt dragged and paddled his kayak down the Darling and Murray rivers from Toowoomba to the Murray mouth, he specifically set out to understand the impact of drought on the river system.
In the resulting book, Cry Me A River, he records the conversations he had with farmers, irrigators, mayors and water engineers along the length of the river system. In the process he came to two simple but alarming conclusions.
Firstly, any water stored in open storage is rapidly lost. The rate of evaporation in western NSW is more than a metre every year – it has regularly exceeded 1600mm in recent years – where rainfall is less than half a metre each year, generally closer to 100mm a year. The rate of evaporation in Bourke, for instance, is about 2000mm per year. Average rainfall, not counting climate change, is less than 400mm per year. That is a deficit of more than a metre and a half per year of all water in storages. They are, in effect, evaporation ponds.
The corollary of this is that the safest place to store water is in the ground. The ground acts as a sponge, soaking up water and releasing it in dry times. Up to 60 percent of the water in our rivers, traditionally comes from ground water, not from surface run-off.
Secondly, our water engineering practices – lining irrigation channels, creating impervious dams, straightening out rivers, etc – all speed up the rate at which water runs off the landscape, reducing the opportunity for that water to soak into the ground, thereby robbing the river basin of its natural water storage system to protect from drought.
The Murray Darling Basin Management scheme was predicated on the modernisation of water management which supposedly “created” additional water by these very mechanisms that reduce ground water.
As a water engineer, Steve is shocked that the profession which he proudly joined last century has actively reduced ground water in the name of increasing water storages to enable irrigation.
“These delusional water management practices have contributed directly to the creation of drought and thus the Menindee fish kill,” Posselt said in May 2019.
His book, Cry Me A River, is available through his website, Kayak4Earth.