Harmful algal blooms (HABs) are present on Hebgen Reservoir in the Rainbow Point
Campground area. Routine monitoring of Hebgen has confirmed the presence of anatoxin-a
which poses a risk to people, pets, and livestock.
HABs are caused by blue-green algae
that are native to Montana’s
freshwater lakes and reservoirs. Not
all varieties of blue-green algae are
harmful, but some can produce
dangerous toxins. Ingestion or
prolonged contact with the algal bloom
may result in illness, with impacts such
as muscle twitching, staggering,
convulsions, paralysis, and death.
Children and pets are more likely to
ingest HAB infested water.
Toxin exposure can occur in humans
from recreational activities where
water might be ingested such as
swimming, wind surfing, jet skiing, and
water skiing. Children and pets are
more likely to ingest HAB infested
water because they spend most of their time wading in the shallow waters where algae can
accumulate, and they have less control over how much water they ingest. Animals and livestock
that drink large amounts of contaminated water, and pets that collect scum on their fur and then
ingest it by licking, are at high risk of toxin exposure.
Blue-green algal blooms often look like pea soup, grass clippings or green latex paint. The
algae are usually suspended in the water or appear as floating mats.
Advisory signs are at public access points in the Rainbow Point Campground area warning the
public that toxic algae has been identified in the water in these areas. At this time there are no
other identified blooms affecting other areas of the reservoir.
NorthWestern Energy is monitoring the blooms and will provide updates if additional restrictions
are implemented for public safety.
A Harmful Algal Bloom is present on Hebgen Reservoir in the Rainbow
Point Campground area.
Suspect a HAB? When in doubt, stay out. Do not drink, swallow, or swim in water that shows
signs of a HAB and be sure to keep kids, pets, and livestock out too. If you suspect a HABrelated illness in a person or animal call Poison Control 1-800-222-1222 and seek medical
attention.
Report a suspected HAB at www.hab.mt.gov or call 1-888-849-2938. You may also report a
suspected HAB by calling the Gallatin City-County Health Department Environmental Health at
406-582-3120. The Gallatin City-County Health Department has resources for water quality on
their website, www.healthygallatin.org.

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