Postcards from the Drought: Invasive plants growing in Russian River due to low, slow water

Frequent visitors to the Russian River will have observed a marked change in the way the water looks as a second year of historic drought settles in.

The river is lower and slower than in the past as regulators restrict its flow to keep as much water as possible behind the dams in Lakes Sonoma and Mendocino.

The river is also covered in places with a thick green blanket of plant life. Stagnant water allowed Ludwigia, or water primrose, to take root in the river. The primrose in turn created a safe haven for small, floating aquatic ferns called Azolla.

Both are harmless, though something for swimmers and paddlers to get used to.

But there is a hint of peril in the Russian River waters. Low levels of toxic blue-green algae have been detected in some areas of the watershed since midsummer — enough to prompt authorities to install CAUTION signs warning visitors to avoid floating algae mats that might contain the cyanobacteria or toxins they can produce.

While they tell people (and their pets) not to drink the water, they say that when real rain finally comes, it should be enough to flush out the system.

Postcards from the Drought is an occasional photographic series aimed at reflecting the impact living with the drought continues to have on us each day. We welcome your suggestions. Email us at

Editor’s note: This story has been updated. A common name incorrectly used for Azolla has been removed.

Mary Callahan

Environment and Climate Change, The Press Democrat

I am in awe of the breathtaking nature here in Sonoma County and am so grateful to live in this spectacular region we call home. I am amazed, too, by the expertise in our community and by the commitment to protecting the land, its waterways, its wildlife and its residents. My goal is to improve understanding of the issues, to find hope and to help all of us navigate the future of our environment. 

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