Combie Reservoir tests clear for toxic cyanobacteria

September 23, 2019

Test results of water samples from Combie Reservoir have returned non-detectable levels for toxic cyanobacteria, also called blue-green algae.

NID took water samples on Sept. 16, after a report of a possible algae bloom in the upper portion of the reservoir.

An independent laboratory conducted tests on samples taken at three different locations. Potentially toxigenic cyanobacteria were not observed in any of the samples. The lab did find levels of the normal green algae.

As a precaution, the District will continue to visually inspect the reservoir throughout the week to see if any floating algae mats re-appear.

Cyanobacteria occurs most often during late summer or early fall, and can release toxins especially harmful to pets and children. Around the state, algal blooms have become more common in waterways, such as reservoirs and rivers.

NID has been working with the Central Valley Regional Water Quality Control and Nevada County officials since the first reported algae sighting.