Woods Lake - blue green algae update

Hydro Tasmania

In 2023, we saw algal concentrations ramp up during Autumn and while we hope this doesn’t occur, it won’t be unexpected if this happens again and be assured we are monitoring the situation and implementing management advice from the expert scientific panel. 

Why do we think this happened? 

Woods Lake is pretty shallow with a maximum depth of only five metres. It is not out of the ordinary for shallow lakes to naturally cycle between a clear, aquatic plant-dominated state and a turbid or murky state dominated by algae.  

Some of you might remember Woods Lake being quite murky back in the 1990s. Then through the early 2000s and up to around 2016 the lake was clear with large aquatic plants. This was the lake cycling between these two states; clear and turbid. 

What makes the lake change state? 

A shift in states can sometimes be driven by a change in nutrient load, such as nitrates and phosphates from agriculture, forestry and other industries. At Woods Lake, consecutive years of La Nina may have contributed to a larger amount of naturally occurring nutrients entering the lake through higher runoff. However, there are also a range of other possible contributing factors and given the complexity of the problem, we’ve been working with a scientific panel to investigate the potential drivers and best options for ongoing management.  

What have we been doing? 

-Water level management 

We’ve drawn water levels down at the lake based on expert advice from our scientific panel, which suggested that ‘flushing’ some of the turbid water from the lake and adding clear, algal-free water may increase the amount of light reaching the sediment and therefore promote aquatic plant growth. This may assist in shifting the state from an algal-dominated state to plant-dominated state. If managed appropriately, this approach won’t negatively impact anything and may be a valuable step to keep further algal blooms at bay. 

-Regular monitoring 

We’re still undertaking regular monitoring to ensure we pick up changes quickly and can react accordingly.  

-Scientific panel 

We’re meeting with the scientific panel every month to progress our understanding of the algal bloom, its drivers and the best management approaches available.  

-Scientific modelling 

A scientific model is being produced through the University of Western Australia and Griffith University to help with the early identification of drivers of the current and future algal blooms which will help target our management actions. 

Feel free to contact engagement@hydro.com.au if you have any queries or would like to know more.   

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