He says despite the increased debate on the future of the Murray-Darling Basin and how best to manage its precious water resources, the situation is going from bad to worse.
"We had reasonable rainfall, but there’s been absolutely no run-off into the storages, because the catchments are so dry," he said.
"We now face a situation where the storages of the Murray-Darling are about half what they were at this time last year, and irrigators are facing an even more desperate situation as they just had no water, and we’re seeing permanent plantings now die."
Professor Cullen says not enough progress has been made since the Government called the states together 12 months ago to ensure continuity of water supplies in the Murray-Darling Basin.
"The Government has passed the Water Act, which gives the Commonwealth power to do serious planning for the Murray-Darling Basin," he said.
"But that planning hasn’t got under way as yet and there hasn’t yet been agreement amongst the states as to how it’s all to proceed – so I would like to think that that planning could be accelerated."
He says working out how to spend the resources in a cost-effective way to achieve the right outcomes will be challenging, and requires more discussion amongst urban and rural users of water.
And according to Professor Cullen, a lot of resilience in the aquatic ecosystems and the flood plane ecosystems of the Murray has been lost as a result of the natural drought.
"We’ve lost a lot of red gums in the lower Murray, and the Coorong is now at hyper-saline areas, heading towards the Dead Sea, and so I hope that can be recovered but I’m not sure about that," he said.
Professor Cullen now hopes that after the election the focus will again return to the River Murray, and how best to ensure cities such as Adelaide at the end of the system have enough water.
"It’s important that we get on and do some of the things that have to be done, in particular securing a diversity of sources to keep Adelaide secure," he said.
"I think there is already rising salinity in the lower Murray, and as the levels drop and salty groundwater flows in, there could well come a time when the Murray becomes unusable by Adelaide.
"Alternative supplies urgently need to be explored and developed, and got onto line."