An algal mat alert is listed for Rio Dell based on a visual finding and testing that detected cyanotoxins.
California State Water Resources Control Board FHABS program · advisory 2026-08-14 · observation 2026-07-23River conditions and notices
Choose a location on the homepage for its relevant weather, gauge, access details, and matched notices.
Current algae records
An algal mat alert is listed near the South Fork confluence based on a visual finding and testing that detected cyanotoxins.
California State Water Resources Control Board FHABS program · advisory 2026-09-03 · observation 2026-08-11An algal mat alert is listed near Fortuna based on a visual finding and testing that detected cyanotoxins.
California State Water Resources Control Board FHABS program · advisory 2026-09-03 · observation 2026-08-11A May 21 public report near Myers Flat remains listed as under investigation. It is not a confirmed current site test.
California State Water Resources Control Board FHABS program · advisory 2026-05-29 · observation 2026-05-21Humboldt County advises visitors to watch for harmful algal blooms, especially in slow or stagnant water. This is regional guidance, not a test of every river spot.
Humboldt County DHHS Environmental Health · advisory 2026-07-24 · observation 2026-07-23How these records are used
Official advisory labels remain as issued. A record applies only to its documented geographic scope. Weather and gauge observations do not determine algae or swimming safety, and a missing test is not an all-clear.
The statewide reports system is voluntary and is not a comprehensive testing program.
California HAB response guidance ↗Live weather and gauges
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Flow measures how much water passes the gauge. Gauge height is measured from a fixed reference; it is not the depth at your swimming spot.
