Central Valley Water Board Harmful Algal Bloom Projects

The Central Valley Water Board began a partnership with Restore the Delta (RTD) in 2022 to monitor Delta waters near Stockton for HABs.

HAB monitoring typically runs May through September, when HABs are most likely to occur and recreators spend the most time in the water. RTD staff visit seven sites weekly to conduct a visual inspection, record water quality parameters using a sonde, and conduct a field test to screen the water for the presence of microcystins. Additional water samples are collected for laboratory analysis of microcystins using the ELISA method 1-2 times per month, depending on conditions observed during the field visit.

Visit the Restore the Delta webpage to learn more about their organization and their Water Quality and HAB Monitoring efforts.

The Central Valley Water Board is partnering with Tulare County Environmental Health to monitor Kaweah Lake and River for HABs after a series of bloom reports were submitted by members of the public in 2022. Due to extremely high flows in 2023, a full season of monitoring began in 2024.

HAB monitoring during 2024 occurred every two weeks from late June through early October. Tulare County collected water grabs and benthic algal mat material (when present), and deployed solid phase adsorption toxin trackers (SPATT). Samples were analyzed for microcystins, anatoxin-a, cylindrospermopsin, and saxitoxins.

Project title: New technologies and a coordination framework for an integrated HAB detection and monitoring system across the San Francisco Estuary.

Central Valley Water Board staff will serve on a team of co-investigators to advance an integrated HAB detection and monitoring system across the San Francisco Estuary. The project is led by scientists at the San Francisco Estuary Institute (SFEI), US Geological Survey (USGS), and CA Department of Water Resources (DWR). This work is funded by the NOAA MERHAB Program through 2028.

Popular recreational lakes H.V. Eastman and Hensley are located within 15 miles of each other in the Sierra Nevada foothills and each have experienced annual HAB events. This study took a multifaceted approach to investigate the patterns and drivers of HABs at these lakes. In situ sampling from the lakes and upstream tributaries was conducted between May 2021 and December 2022.

Products:

• Manuscript in prep
• Presentation at 30th Annual California Aquatic Bioassessment Workgroup (CABW) 2023 Meeting (Video will open in YouTube)

Comprehensive information about the CVWB's work in the Delta can be found on the Delta Water Quality webpage.

The highest priority information gap identified in the CVWB's Delta Nutrient Research Plan is to improve understanding of causes, trends and potential for management of HABs in the Delta. Staff are involved in several collaborative projects advancing HAB monitoring and research.

A select list of CVWB HAB-related projects and efforts in the Delta are highlighted below. HAB-related publications from CVWB work in the Delta can be found on the Central Valley Water Board HAB Documents webpage.

The State Water Resource Control Board (State Water Board) is developing a statewide plan for biostimulatory substances and cyanotoxins under the Biostimulation, Cyanotoxins, and Biological Condition Provisions.

In an effort to provide additional information, the Central Valley Water Board contracted with the Southern California Coastal Water Research Project (SCCWRP) to complete additional analysis focused in the Central Valley.

Products:

• Technical reports and a memo from Central Valley Water Board executives can be found here: Surface Water Ambient Monitoring Program (SWAMP).

Clear Lake is the largest natural freshwater lake in California. HABs have been observed in Clear Lake throughout the 20th century with blooms well documented and described since the early 1970s.

Links:

• Visit the Clear Lake Nutrient Control Program and TMDL webpage to learn more about the Central Valley Water Board's work at Clear Lake.
• Visit the Big Valley Band of Pomo Indians Clear Lake Cyanotoxins webpage to view current HAB advisory levels and learn about the tribe's monitoring program.