Del Valle Regional Park

Cyanobacteria (Blue-Green Algae)

Cyanobacteria (Blue-Green Algae) Information

Cyanobacteria (blue-green algae) are natural organisms that are present in most lakes. Certain conditions – low water levels, limited water circulation, increased heat and light, among other factors – can cause cyanobacteria to bloom and, in some cases, release toxins. The most common cyanobacteria toxins are Anatoxin-A, a neurotoxin, and Microcystin, which affects the liver. Scientists do not know what causes the cyanobacteria to become toxic. 

The Park District had never before seen toxic algae blooms in its lakes, but in 2014, recorded three, most likely due to the drought.  The first and third toxic blooms were in Lake Temescal in Oakland, both blooms resulted in its closure for a total of about nine weeks over the summer and fall, and a second bloom was discovered in September in Lake Chabot and still remains.

Exposure to toxic algae, either through ingestion or skin contact, can cause rashes, skin and eye irritation, allergic reactions, gastrointestinal problems or, at high doses, serious illness or death, according to the California Department of Public Health. Several dog deaths around the state have been attributed to toxic algae poisoning in the past two years.

Blooms usually run their course and dissipate in a week or two, but rainstorms and cold temperatures can speed up the process. At Lake Temescal, the Park District used an organic chemical called GreenClean to control the algae. The chemical is safe for water used for drinking, swimming, and fishing, and does not harm other aquatic life. The District has only used the chemical in Lake Chabot at the Marina because the lake is very large in size. The water in Lake Chabot is under the jurisdiction of the East Bay Municipal Utility District. 

Swimming – by dogs or people – is not allowed at Lake Chabot. Several signs at the lake warn visitors to stay out of the water due to the algae, rinse skin with tap water after contact, and keep pets away from the water. Fish should be rinsed in tap water and the guts discarded.

Media Coverage

Current Water Quality Conditions

Due to the drought and unusually warm weather conditions, toxic blooms of cyanobacteria (blue-green algae) and other water-quality issues are occurring more frequently in the East Bay Regional Park District and elsewhere. We monitor our lakes and shorelines regularly and post warnings and closures when appropriate. Here’s a current update of which lakes and shorelines are affected: 

Alert LevelParksDescription
Water Warnings Posted
Water Quality Notice

Cyanobacteria (blue-green algae) is present in the reservoir and a Caution Advisory is posted. See Cyanobacteria (Blue-Green Algae) Updates for more info.

Caution Advisory Posted
Shinn Pond

Cyanobacteria (blue-green algae) is present and a Caution Advisory is posted at Shinn Pond. Swimming is never allowed and water contact is currently not permitted at Shinn Pond. Due to the presence of toxic algae in the pond, please keep dogs away from the water. Cyanobacteria (Blue-Green Algae) Updates

Danger Advisory Posted
Water Quality Notice

Cyanobacteria (blue-green algae) is present in the reservoir and a Danger Advisory posted. No swimming is allowed. See Cyanobacteria (Blue-Green Algae) Updates for more information. Conditions [PDF]

Water Warnings Posted
Water Quality Notice

Cyanobacteria (blue-green algae) is present at Horseshoe Lake, but no toxins have been detected. There are no advisories posted at Horseshoe Lake or the swim beach this time. See Cyanobacteria (Blue-Green Algae) Updates for more info.
Conditions [PDF] |  Monitoring Program | Cyanobacteria (Blue-Green Algae) Updates

Water Warnings Posted
Water Quality Notice

Cyanobacteria (blue-green algae) is present at the lake, but no toxins have been detected recently. There are no advisories posted at this time. See Cyanobacteria (Blue-Green Algae) Updates for more info.
Monitoring Program | Cyanobacteria (Blue-Green Algae) Updates
The District regularly monitors Lake Temescal to ensure the water quality meets acceptable levels for fishing and swimming.  Water quality samples are taken from four locations around the Lake; including the swim beach.

The Swim Facility/Area is CLOSED until further notice.

Water Warnings Posted
Notice

Lake Anza Swim Area: CLOSED - No Swimming. Cyanobacteria (blue-green algae) is present in lake, but no toxins have been detected recently. There are no advisories posted at the lake. As a precaution, keep dogs away from water.
Lake Anza Lawn Area: CLOSED, until further notice, for a construction project. Please use alternative lawn areas at the Brazil Room and at Meadows on Lone Oak Rd. Restrooms at lake facility closed with portable restrooms available in the parking lot during the project. The Lake Anza Trail and picnic sites are open for use. 

Water Quality Notice
Water Conditions [PDF] | Monitoring Program | Cyanobacteria (Blue-Green Algae) Updates

Water Warnings Posted
Cyanobacteria

Cyanobacteria (blue-green algae) is present at the shoreline, but toxins detected recently have been below California advisory guidelines. There are no advisories posted at this time. See Cyanobacteria (blue-green algae) for more info.

Caution Advisory Posted
Water Quality Notice

Cyanobacteria (blue-green algae) is present at the lake and toxins have been detected recently. A Caution Advisory is posted around the lake.
See Cyanobacteria (Blue-Green Algae) Updates for more information.

Water Warnings Posted
Water Quality Notice

Shadow Cliffs swimming is CLOSED for the 2021 season due to low water levels. There are no cyanobacteria advisories at this time.
Cyanobacteria (Blue-Green Algae) Updates

Water Warnings Posted
Water Quality Notice

Keller Beach is OPEN for swimming.
Conditions [PDF] 

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