Earlier this year, harmful algae was detected in the off-season in several Central Texas lakes. In light of this, the Watershed Protection Department is expanding our monitoring plan to be year-round and include all three lakes in Austin’s jurisdiction. As the summer approaches, harmful algae may be more prevalent and more toxic than it was in the winter and spring. Dog owners should treat all algae as though it contained toxins and not allow their dogs to touch or ingest algae in any Central Texas waterways.
Starting this week, we will be monitoring three sites on Lake Austin and three sites on Lady Bird Lake, visiting them every other week throughout the summer. We will continue monitoring throughout the year, but may scale back the frequency as the year progresses. We will also begin monitoring one site on Lake Walter E. Long, visiting it at least three times during the summer and fall. Results from the initial round of testing should be available mid-June at AustinTexas.gov/Algae.
In addition, we have spent the past several months planning a pilot project to try to prevent the growth of harmful algae, using a phosphorus-binding clay called Phoslock. Pending Austin City Council approval, the pilot project would consist of applying Phoslock by boat over 20 acres of water around Red Bud Isle. There would be three applications over the course of nine weeks, starting June 21. For 2021, the cost is $300,000 and includes the material, the application and extensive laboratory testing.
Phoslock works by binding phosphorus both in the water and in the sediment. Once bound, the phosphorus remains in the lake sediments in a mineral form that is unavailable to the blue-green algae as a nutrient source. It is safe for humans, wildlife and the environment.
The applications should result in a decrease in the amount and/or toxicity of blue-green algae in the area treated. However, we do not know how effective it will be and Austin residents and visitors should continue to treat algae in this area with caution.
Map of Monitoring Sites