Cyanotoxins in Oregon’s Cascade Range Rivers that are Tapped for Drinking Water Supply
A study conducted by the U.S. Geological Survey (USGS) in collaboration with multiple water utilities and research partners revealed widespread cyanotoxin occurrence in Cascade Range rivers that provide municipal drinking water to over 1.5 million Oregonians.
A study conducted by the U.S. Geological Survey (USGS) in collaboration with multiple water utilities and research partners revealed widespread cyanotoxin occurrence in Cascade Range rivers that provide municipal drinking water to over 1.5 million Oregonians.
Cyanotoxins produced by harmful algal blooms (HABs) threaten people, pets, recreation, and aquatic ecosystems. Exposure through drinking, swimming, and dialysis can cause illness, liver damage, neurological effects, and even death. HABs, whether they produce cyanotoxins or not, impact aquatic habitats and impair water quality by blocking sunlight, depleting oxygen, and may cause fish kills. Recreational advisories at popular waterbodies occur each summer, harming local economies, and HABs can sometimes make drinking water unusable.
The 2016-20 study examined sources and downriver transport of four cyanotoxins—microcystins, cylindrospermopsins, anatoxins, and saxitoxins —across reservoir-river systems in northwestern Oregon that supply 18 drinking water treatment plants. The study utilized direct sampling of cyanobacterial mats and materials collected with plankton net tows, and the deployment of Solid-Phase Adsorption Toxin Tracking (SPATT) samplers to assess toxin presence in reservoirs, rivers, and tributaries. Over 300 samples from 65 sites across seven river basins, including the Clackamas, North Santiam, McKenzie, and North Umpqua rivers, were assessed.
Key findings indicate that cyanotoxins were frequently detected in cyanobacteria from both reservoir and river environments, with over 90% of concentrated samples containing at least one toxin. The research identified both planktonic (drifting in the water) cyanobacteria in reservoirs and benthic (occurring in the riverbed) cyanobacteria in rivers as primary sources of these toxins, which can persist in the water column and be transported into drinking water supply intakes.
“This study provides critical insights into the types of streams and specific locations supporting toxin producing cyanobacteria” said Kurt Carpenter, USGS lead scientist on the study. “The occurrence of multiple cyanotoxins in raw source waters for several drinking water supply plants highlights the need for continued monitoring to protect public health.”
Funding for the study was jointly provided by the Clackamas River Water Providers: the Cities of Estacada, Clackamas, Gladstone, Oak Lodge, Oregon City, Tigard and West Linn, the Sunrise Water Authority and South Fork Water Board, Clackamas County Water Environmental Services, City of Salem, Eugene Water & Electric Board, and the Congressionally Directed USGS Cooperative Matching Funds (Directed HABs) Program.
For more information, access the full study: Reservoir and Riverine Sources of Cyanotoxins in Oregon’s Cascade Range Rivers Tapped for Drinking Water Supply