We all know it’s been hot this summer. Records have been dropping like flies. But we may not have noticed that it has also been dry, and this is having a dramatic impact on flows in rivers across Victoria.
The wet weather of the last couple of years has been absolutely fantastic for rivers and the improvement in their condition following the drought years has been wonderful to see. Birds, fish and trees have been busting out all over the place. But in our excitement we seem to have forgotten that the last two summers were very unusual and the rainfall unprecedented, due to extreme La Nina conditions.
According to the Bureau of Meteorology, summer 2013 is supposed to be ‘neutral’ (neither El Nino nor La Nina), yet rainfall in Victoria in the past few months has been way below average. What is going on? Could it be that this is the new ‘normal’ and that under the influence of climate change conditions in Victoria are drier than they used to be? Time will tell but the impact on our rivers has been dramatic.
Let’s have a look at the difference a year can make. Every month the Department of Sustainability and Environment (DSE) puts out a monthly water report that looks at the status of Victoria’s water resources, including streamflows – how much water is going down each river. A year ago the streamflow map looked like this:
Victoria was dry in the west but plenty of water was flowing out from the Alps both to the north and the south. Some rivers had more than 100% of their November average flows.
Fast forward to a year later (November 2012 is the latest map available) and this is what we get:
Apart from a couple of small patches, streamflows across the whole state were less than 40% of the average for the time of year – and that was before the heatwave! Imagine what January 2013’s map will look like…. I bet those blue bits will be gone. The Bureau of Meteorology seems to agree.
Unfortunately for our rivers, there is a nasty multiplier effect between decline in rainfall and its impact on river flows. Changes in rainfall have around a threefold impact on streamflows . This means a 10% decline in rainfall can result in up to 30% decline in the amount of water flowing in the river. No wonder a drier future spells bad news for rivers.
As the temperature rises, demand for water goes up. Water use in Melbourne has rocketed up in the last few weeks and per capita use is currently higher than it’s been in years. And summer’s only halfway through.
It’s good to hear Water Minister Peter Walsh saying that he does not intend to use the Wonthaggi desalination plant to supply water for Melbourne. But if he is going to stick to his plan he is going to have to up his effort elsewhere to keep demand for water in check – cancelling Target 155 was not a smart move.
Water use is also increasing in northern Victoria where farmers are irrigating more than in recent years. While there’s still plenty of water in our dams, our rivers are already feeling the pinch.
2013 will be an interesting year for Victoria’s rivers. With a return to drier conditions, will we remember what we learnt during the last drought? Or will demand for water continue to increase? How will the implementation of the Murray-Darling Basin Plan play out? And will the Victorian government show any concern for the state of our rivers or just continue on its merry way of prioritising consumption over environment?
Here at Environment Victoria we’ll be taking a look at the condition of rivers around the state and assessing the major threats and opportunities for action. We’ll be looking for interesting and innovative ways of presenting the information to inform and inspire, and developing an action plan in the lead-up to the next state election. We aim to have the state of our rivers firmly on the agenda. And to do that we will need your help, so stay tuned!
Happy New Year!