Danger warning issued at Crowley Lake after tests identify harmful algal blooms

The Lahontan Regional Water Quality Control Board is urging visitors to stay out of the water at Crowley Lake in Mono County.

Areas of the lake were tested to confirm that the lake is being impacted by harmful algal blooms and a “WARNING and DANGER” advisory has been posted to alert lake users of the elevated risk. Those who may be visiting the area are encouraged to follow the below guidance until further notice.

Warning – Hilton Creek Drainage

  • No swimming;
  • Do not let pets and other animals go into or drink the water, or eat scum on the shore;
  • Stay away from scum, and cloudy or discolored water;
  • Do not eat shellfish from this water;
  • Do not use this water for drinking or cooking; • Boiling or filtering will not make the water safe; and
  • For fish caught here, throw away guts and clean fillets with tap water or bottled water before cooking.

Danger – South Landing Marina

  • Stay out of the water until further notice, including watercraft;
  • Do not let pets and other animals drink or go into the water, or go near the scum;
  • Stay away from scum, and cloudy or discolored water;
  • Do not eat fish or shellfish from this water;
  • Do not use this water for drinking or cooking; and
  • Boiling or filtering will not make the water safe.

Water Board staff monitored Crowley Lake on Aug. 16 as part of the Labor Day Pre-Holiday Assessment. These assessments are done before Memorial, Independence, and Labor Days to inform the public of current harmful algal bloom levels within popular waterbodies across the state.

Water Board staff noticed signs of a harmful algal bloom longer than a football field along the shoreline near the South Landing area of the Lake at both the Marina and the Hilton Creek Drainage. Sample results confirmed toxin levels were present at Danger levels within the Marina, and Warning levels at Hilton Creek Drainage.

An image of a harmful algal bloom. Photos submitted

Note that cyanobacteria, a group of organisms that form harmful algal blooms, can produce potent toxins. Health risks are associated with HABs as they produce dermatoxins that can cause skin inflammation, which can cause itching skin and rashes, as well as gastrointestinal distress, headaches, agitation and weakness, or abnormal breathing if HAB material is swallowed while swimming.

Dogs and children are most susceptible to exposure because of their smaller body size, increased potential to swallow water while swimming and tendency to stay in the water longer. If you suspect exposure, wash your children and dog immediately. Due to the size and toxicity of the bloom with increasing temperatures and decreased precipitation this time of year, the bloom may proliferate and alter its potential to produce toxins.

The bloom occurring in the lake appears suspended on the water’s surface. Bloom conditions can change rapidly, as the winds and waves move or concentrate the bloom into different regions of the lake. In some areas, the bloom may concentrate and form a film or scum on the water surface. The color of the water may also appear discolored as bright or dark green and brown.

Advisory signs have been posted to notify recreational users of the bloom. The Water Boards will provide regular updates to inform the community when postings are removed on the California HAB Reports Web Map.

Here’s another image of a harmful algal bloom.

The Water Boards recommend that people practice healthy water habits while enjoying the outdoors this summer at your local lake, river or stream: 

  • Heed all instructions on posted advisories if present;
  • Avoid algae and scum in the water and on the shore;
  • Keep an eye on children and pets. If you think a harmful algal bloom or toxic algal mats are present, do not let pets and other animals go into or drink the water or eat scum/algal mats on the shore;
  • Don’t drink the water or use it for cooking;
  • Wash yourself, your family and your pets with clean water after water play;
  • If you catch fish, throw away guts and clean fillets with tap water or bottled water before cooking;
  • Avoid eating shellfish if you think a harmful algal bloom is present;
  • Get medical treatment immediately if you think that you, your pet, or livestock has gotten sick after going in the water. Be sure to alert the medical professional to the possible contact with cyanobacteria. Also, make sure to contact the local county public health department.

To report a bloom, do one of the following:
Fill out the Bloom Report form on the HABs Portal:

https://mywaterquality.ca.gov/habs/do/bloomreport.html

Email: CyanoHAB.reports@waterboards.ca.gov

Call the HABs hotline: (844) 729-6466 (toll free).

Contact your county Public Health Office

For more information about HABs, visit: California Harmful Algal Blooms Portal.