HAB Reports Map

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Overview: The HAB Reports Map is maintained by the State Water Resources Control Board (CA Water Boards). This map displays locations where harmful algal blooms (HABs) are reported through the online Report Form or from water monitoring data that is submitted to the CA Water Boards. Voluntary on-line submitted reports may include suspected bloom locations that are later verified as not a bloom. Updates based on investigations are noted on the map. Note that drinking/potable water advisories and marine blooms in coastal areas are not displayed on this map.

Guidance for recreational notifications and advisories: The CA Water Boards coordinates response to reports with other state and local agencies and may conduct follow-up field investigations and water testing to inform a recreational advisory. Where noted, recommended recreational advisories and corresponding signage are based on California voluntary guidance for recreational waters.

What you can do: Practicing Healthy Water Habits while outdoors is recommended even for waterbodies with no information noted on the map below. When in doubt, avoid contact with water impacted by HABs. For questions, please contact the HAB Hotline by email (CyanoHAB.Reports@waterboards.ca.gov) or phone (1-800-222-1222).

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How to use the map: Colored dots on the map represent reported locations with pop-up windows that provide additional details for each report. Dots are symbolized based on the current advisory status and the date since the report was last verified by staff (refer to map legends for details). These details are also available in the adjacent table sorted by county. Updates for a location are added to this map when available. However, when updates are not shared with the CA Water Boards, the location's dot symbol will fade in color after 30 days since the last update (refer to map legend for details).

Disclaimer: The exact location, extent, and toxicity of the reported bloom may not be accurate due to changing environmental conditions. Reported blooms can be localized to a portion of waterbody (specific shorelines or confined coves), move with the water current, or impact the entire waterbody (lake-wide). Please use data presented in this map for general purposes only. The data are subject to change as new information is received; check back for daily updates. If a HAB location is missing from this map, notify the HAB Hotline. To learn more on identifying a HAB, please consult our visual guide.

Alert: San Francisco Bay and estuary marine HAB event – A marine HAB (also known as a red tide due to discolored red/brown water) is currently impacting the San Francisco Bay and Estuary in multiple areas. Reports from the public for this event are displayed on this map. Comprehensive updates on areas impacted by this red tide is available at: Toxic Phytoplankton Observations Map (arcgis.com).Toxic Phytoplankton Observations Map (arcgis.com). For questions please contact redtide@cdph.ca.gov. For illness reporting, contact: marinehab@oehha.ca.gov.

Latest HAB Weekly Updates List

HAB Reports Map - data and reports voluntary shared



Water monitoring organizations that share data: Several routine water monitoring programs share water testing data to display in this map including the following locations: Klamath BasinEast Bay Regional Parks, Clear Lake, Lake Isabella, Lake Henshaw, and reservoirs along State Water Project. Please reach out to cyanoHAB.reports@waterboards.ca.gov if your organization would like to participate in our program.

Download data: To download the full data set, including reports from all years, go to the California Open Data Portal. The HAB Reports Tracking Map is populated by data in the Freshwater and Estuarine HAB Program's Reports and Monitoring Data System and maintained by the CA Water Boards.