Authorities have discovered a rise in recent blue green algae alerts in NSW.

An audit of the Greater Sydney Catchment has revealed a 56 per cent increase in blue green algae alerts in the 2016-2019 audit period when compared to the 2013-2016 audit period.

The auditor stated that this increase is due to ongoing drought conditions experienced within the region in 2017-2019, which generally promotes favourable conditions for algal bloom growth including reduction in flow and high-water temperatures.

Only two sites reported red alerts during 2016-2019 – Lake Wallace and Lake Lyell. These are owned and managed by Energy Australia associated with Mt Piper power station and are lakes where raw water for drinking water and subsequent treatment is not directly sourced.

Due to drought conditions during the period of the audit it is important to note that apart from small required environmental releases, minimal flows from these lakes would have been released into Coxs River.

WaterNSW says it constantly monitors water quality in Warragamba dam.

“Our extensive monitoring program is designed to provide early warning of potential increases in algal activity, allowing us to proactively manage changes in raw water quality. For example, if required we can move to take water from different levels in the storage to avoid blue green algae which generally sits on the surface,” the authority said this week.

WaterNSW also says it has instigated a range of monitoring and science projects to gather data about any compounds which have washed off the areas of the catchment burnt by the recent fires, “to ensure we build an understanding of any other changes in the characteristics of the water in the dam over the longer term and can develop adequate mitigation strategies if required”.