The City of Austin will conduct its fourth year of a five-year pilot program aimed at reducing harmful algae blooms on parts of Lady Bird Lake. Harmful algae blooms occur when Cyanobacteria, or blue-green algae, produce toxins. The pilot program involves applying lanthanum-modified clay in specific areas of the lake. This clay binds to phosphorus, a key nutrient for algae, making it unavailable and thereby reducing algae growth.
The first application this year is scheduled for Monday, June 3, in three locations. If additional time is needed, the contractor will continue the work on June 4. A second and third application are planned for July and August. The material is applied from a barge and appears as a gray slurry that temporarily clouds the water. Although safe, recreational boaters are advised to stay away from the barge.
The lanthanum-modified clay will be applied at:
- Red Bud Isle
- The boat ramp on the north shore of the lake, just west of I-35
- The north shore of the lake between I-35 and the lagoon behind Festival Beach Boat Ramp
The second location is new and chosen for research purposes to identify any unforeseen impacts on aquatic insects; no impacts are expected.
Results over the past three years have been mixed. At Red Bud Isle, there has been a reduction in harmful algae after each June application. However, subsequent applications in July and August have only maintained this reduction without further improvement. By June of each following year, algae typically return. This year saw an early recurrence in spring but was mitigated by recent rains.
East of I-35, results have been less promising due to new sediments covering up the clay and introducing more nutrients.
The pilot program costs $300,000 annually and is funded through drainage charges assessed on utility bills.
Reducing nutrient runoff into the lake remains a critical solution. Residents can help by limiting fertilizer use and picking up after pets. Planting native vegetation along creeks can also filter pollutants from stormwater.
Nutrient sources upstream of Austin contribute significantly to the problem, including fertilizers, leaking septic tanks, and treated wastewater effluent. Climate change and zebra mussels may also affect nutrient cycling dynamics that promote harmful algae blooms.
Fortunately, most harmful algae blooms in Austin are not as widespread as elsewhere; thus far it has not been necessary to close lakes to recreation because toxins remain confined to patchy algae mats rather than being released into water bodies.
Harmful algae blooms were first documented on Lady Bird Lake in 2019 and have occurred annually since then. Blooms have also been reported on Lake Austin, other Highland Lakes, and Barton Creek.
Harmful algae can be fatal to dogs and cause illness in humans. Other risks include bacteria and parasites associated with natural water bodies. The City advises avoiding contact with algae-laden water for both people and pets; swimming is prohibited in Lady Bird Lake.
In case of sudden unexplained symptoms after swimming or pet exposure to lake water:
- Contact your medical provider or Texas Poison Control Center at 1-800-222-1222.
- For pets: Contact your veterinarian.
Report incidents via AustinTexas.gov/Algae.