Potentially harmful blue-green algae found at Twin Valley Reservoir north of Claresholm

Alberta Health Services says blue-green algae can cause skin irritation, rash, sore eyes, sore throats, nausea, vomiting and diarrhea in people that come into contact with it. (File)

Alberta Health Services (AHS) is warning people to avoid the water at the Twin Valley Reservoir, north of Claresholm, Alta., due to the presence of blue-green algae.

Blue-green algae, also known as cyanobacteria, is naturally occurring but can potentially produce toxins that are harmful to people and pets.

It looks like scum, grass clippings, fuzz or globs on the surface of water and can be blue-green, greenish-brown, brown and/or pinkish-red in colour. It often smells musty or grassy.

Those visiting the area are advised against swimming or wading in the water, or letting pets swim or wade in it.

Exposure to the bacteria may be fatal to pets, AHS warns.

As such, it's advised you do not feed whole fish or fish trimmings from this reservoir to your pets, and consider limiting human consumption of whole fish and fish trimmings.

If contact with the algae occurs, it's advised you wash with tap water as soon as possible.

People who come in contact with cyanobacteria or who ingest water containing it may experience skin irritation, rash, sore throat, sore red eyes, swollen lips, fever, nausea and vomiting and/or diarrhea.

AHS says symptoms usually appear within one to three hours and resolve in one to two days.

Symptoms in children are often more pronounced.

Weather and wind conditions can cause algae blooms to move from one location in the reservoir to another. As such, the advisory will remain in effect for Twin Valley Reservoir until further notice.

The town of Claresholm is located roughly 80 kilometres northwest of Lethbridge. The Twin Valley Reservoir is about 45 kilometres northeast of Claresholm.