Due to drought conditions, Arthurs Lake level was drawn low in 2008. The lake started refilling in 2009 and has since reached very high levels.

Hydro Tasmania has been monitoring Arthurs Lake periodically since 1991 and every year since 2008. The data indicates that there have been significant increases in phytoplankton, nutrients and turbidity levels following the low levels in 2008. These increases have remained during the recent high water levels and there are a number of possible reasons for this.

A die back of macrophytes during the low lake levels may have resulted in more nutrients being available for algae growth in Arthurs Lake. Wind resuspension of sediments as a result of low water levels may also have contributed to the pool of nutrients in the water column. Input of nutrients from dying terrestrial vegetation following the increase in water level may have fuelled the on-going raised nutrient and algae levels. A fire within the Arthurs Lake catchment in December 2012 may also continue to influence water quality as a result of nutrients from burnt vegetation being washed into the lake.

Water quality results from Arthurs Lake indicate that a change from low nutrient concentrations towards moderate nutrient concentrations has occurred. It appears unlikely that in the next few years the water quality in Arthurs Lake will return to conditions similar to pre 2008. Monitoring of water quality will continue this year.

Written by Hydro Tasmania