Canyon Lake is part of the Lake Elsinore and San Jacinto Watersheds. Throughout the year, naturally occurring algal blooms take place in the lake and change the color of the water.


Found naturally in marine and freshwater throughout the world. Exists at varying levels in all natural water bodies.

Algal blooms occur when there is an oversupply of nutrients in a lake, such as phosphorus and nitrogen coming from excess lawn and agricultural fertilizer, pet waste and overwatering. High temperatures enhance and thicken blooms.

Low oxygen levels in water, lack of water movement and low water levels contribute to blooms. Algal blooms reproduce rapidly and cause dense buildups.


Harmful algal blooms (HABs), occur when colonies of algal reproduce rapidly, producing toxins that can harm humans, animals and aquatic life. When in doubt, stay out.

Range from microscopic, single-celled organisms to large seaweeds.

Even nontoxic algal can eat up all of the oxygen in water. The decay can clog the gills of fish and invertebrates, or smother aquatic vegetation. They can discolor water, form large, smelly piles on beaches or contaminate drinking water.


During algal blooms, residents should stay out of the water that is foamy, scummy, pea-green, blue-green, brownish red or looks like floating paint.


Alum applications reduce the phosphorus levels (food for algal). Alum was recommended by water quality lake experts advising the Lake Elsinore and Canyon Lake Nutrient TMDL Task Force.

Residents can reduce algal blooms by curtailing overwatering that leads to nutrient run off from soils and lawns by reducing the use of fertilizers, picking up pet waste, and avoid littering.

Alum applications are effective in reducing algal growth, however in small coves where there is little water movement and temperatures are warm, algal blooms can still occur.


The Lake Elsinore and Canyon Lake Nutrient TMDL Task Force, composed of cities, the county and other organizations in the upper watershed, work jointly under the Lake Elsinore and San Jacinto Watersheds Authority (LESJWA) to help improve water quality of Lake Elsinore and Canyon Lake.


Canyon Lake Property Owners Association | (951) 244-6841

Lake Recreation

Algal Sampling


Lake Warnings


City of Canyon Lake

Assists with resident communications and notifications.

Elsinore Valley Municipal Water District | (951) 674-3146

Water and sewer services for Canyon Lake residents and businesses.

Lake Elsinore and San Jacinto Watersheds Authority | (951) 354-4221

Overall lake water quality improvements and alum applications.