Western Narrows Lake, Western Australia – A shift away from blue green algae with the use of Phoslock

The Western Narrows Lake is one of a series of lakes in the Narrows Lakes Interchange located next to Mitchell Freeway and to the south of the CBD of Perth, WA. The City of Perth manages the Narrows Interchange area as parkland for passive recreation and tourism purposes. Water from one of the lakes is used to irrigate the parkland. Historically the Lakes frequently experienced algal blooms. The primary cause of these blooms was excessive levels of nutrients, particularly soluble phosphorus.

Phoslock was applied to the Western Narrows Lake on an annual basis from 2009-2015 and was used as the primary management tool to address recurrent blue green algal blooms. From 2006 to 2010 there were three major blue-green algal blooms. However, since 2010 (after commencement of Phoslock applications in 2009), there have been no blue-green blooms in the Western Narrows Lake.

Before and after photos of the Western Narrows Lake are displayed below. The first photo shows the Western Lake with an algal bloom and was taken prior to the Phoslock application in 2009. The second photo was taken recently (early 2017) and shows clear water. The improvement in water quality has promoted the growth of native aquatic macrophytes in the lake and enabled the aquatic environment to recover. Results from successive annual applications have highlighted the importance in reducing the concentration of internal phosphorus over time in order to return the lakes health and aesthetic appeal.