North Dakota expands harmful-algae advisories and warnings to seven waterbodies

The North Dakota Department of Environmental Quality added Lake Tschida in Grant County to the state’s harmful algal bloom advisory list on July 30, bringing the number of waterbodies under an active advisory or warning to seven.

The update matters for residents planning to swim, boat or fish near the listed lakes and dams, as well as people bringing pets or livestock to the water. DEQ advises visitors to check current conditions before traveling, avoid suspected blue-green algae, keep pets away from affected water and rinse with fresh water after contact.

What DEQ’s advisory means

Lake Tschida was posted as an advisory on July 28, according to DEQ’s statewide update issued July 30. An advisory means a bloom is present in portions of a waterbody. It is not a closure or a determination that the entire lake is unsafe.

A warning reflects a more extensive condition: the bloom covers a significant portion of the waterbody and toxin levels exceed the recreational threshold. DEQ’s current list includes four advisories and three warnings, so the seven waterbodies do not all have the same status.

The seven waterbodies on the current list

DEQ’s list was current as of July 29, 2026:

• Advisories: Devils Lake, Ramsey/Benson counties, posted July 16; Lake Brekken, McLean County, posted July 16; Lake Darling, Renville County, posted June 29; and Lake Tschida, Grant County, posted July 28.
• Warnings: Bowman-Haley Dam, Bowman County, posted June 29; South Golden Lake, Steele County, posted June 29; and Warsing Dam, Eddy County, posted July 1.

Prairie Public reported July 31 that Lake Tschida was the seventh report of a harmful algal bloom this year. That description refers to reports during 2026; DEQ’s count is the number of waterbodies currently under active advisories or warnings.

What residents should do

DEQ says harmful algal blooms, also called HABs or blue-green algae, can develop quickly in warm, sunny weather. Some blooms produce cyanotoxins that can make people, pets and livestock sick if the water is swallowed or touched. That does not mean every bloom contains toxins or that contact will necessarily cause illness.

Residents should:

• Check DEQ’s current HAB conditions before traveling to a listed waterbody.
• Do not swim in or drink from water suspected of containing blue-green algae.
• Keep pets away from affected water and prevent livestock from using it as a drinking source.
• Bring plenty of fresh water for people and animals.
• Rinse people and animals with fresh water as soon as possible after contact.

North Dakota State University Extension reported June 29 that cyanobacteria growth is accelerated by warm to hot temperatures and that some cyanobacteria can produce toxins harmful to people, livestock and wildlife. Blooms may appear as scum or colored material on or just below the water’s surface, but appearance alone does not establish whether toxins are present.

How to report a suspected bloom

DEQ relies on public reports to identify possible blooms and determine where additional sampling or updates are needed. Suspected blooms can be reported by calling 701-328-5210, using the state HAB reporting tool or emailing DEQ-HAB@nd.gov.

DEQ posts HAB updates from May 1 through Dec. 31. Because bloom conditions can change quickly, residents should verify the current status before each visit rather than relying on an earlier advisory or warning.

Sources

• North Dakota DEQ harmful algal bloom advisory update, July 30, 2026
• Blue-green algae advisory issued for Lake Tschida
• NDSU Extension: Summer heat brings increased risk of toxic cyanobacteria