Flooding Creates Potential Human Health and Recreational Risks in Rivers Across Montana

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HELENA—River recreators should avoid contact with water during and for at least two weeks after flood events. Floodwaters have already impacted communities in the Yellowstone River basin, and more flooding is anticipated elsewhere in the state, such as in the Flathead River basin and Missoula County. Floodwaters can carry potentially dangerous debris and may contain chemicals and bacteria from damaged or overwhelmed wastewater treatment facilities and flooded homes, businesses, and agricultural fields. 

Montana Fish, Wildlife and Parks has issued closures for Fishing Access Sites along the Stillwater, Yellowstone, Madison, and Gallatin Rivers due to safety hazards related to collapsing banks, debris jams, and exposed or submerged infrastructure (myfwp.mt.gov/fwpPub/allRestrictions). Sites are being reopened on a case-by-case basis as site conditions and safety concerns allow.

Recreationists should also be aware that rivers and creeks could be contaminated with harmful bacteria. This is especially true downstream of communities where widespread flooding occurred because water treatment systems may take time to return to normal operation even after floodwaters recede.  

The Department of Environmental Quality monitors water quality across the state and will conduct additional floodwater monitoring in areas where monitoring projects are already ongoing, such as the Yellowstone River basins. While this may help identify contamination, sampling will not determine the source of contaminants – whether it is from overwhelmed water treatment facilities or general runoff from other dispersed sources.

Where public drinking water supplies are of concern, DEQ works with municipalities and certified operators to inform residents of boil orders and advisories and to ensure the safety of water systems when they return to service. Public water systems that experience or anticipate issues related to flooding should contact DEQ for support and guidance. The public can find additional flood-related resources on the DEQ Flooding Resources web page.

According to the Montana Department of Public Health and Human Services (DPHHS), ingesting floodwater that contains even small amounts of bacteria (such as E. coli) can lead to diarrhea, abdominal cramps, and sometimes vomiting or fever.

The DPHHS Environmental Laboratory is available to conduct water testing for communities as needed. For more information, contact the laboratory at 800-821-7284.