Canyon Lake alum treatment starts April 22

Lake Elsinore & San Jacinto Watersheds Authority (LESJWA) announced that Canyon Lake will receive an alum treatment from April 22 through April 25. Alum will be applied to the lake in the main body, East Bay, and the area north of the causeway.

The lake will remain open during the treatment process. Recreational users will experience little disruption during treatment application and implementation.

Alum binds with phosphorus in the lake water, drops the nutrient to the lake bottom, and thereby reduces algae growth in the lake. Canyon Lake water mostly comes from stormwater runoff from the upper watershed each year and has high levels of nutrients that hurt water quality and threaten aquatic life.

In order to comply with water quality regulations enforced by the state, through the local Santa Ana Regional Water Quality Control Board, the Lake Elsinore & Canyon Lake Nutrient Total Maximum Daily Load (TMDL) Task Force, a coalition of cities, the county, and several other organizations led by LESJWA, provides funding to continue alum water treatments in Canyon Lake.

The TMDL Task Force evaluated several options during the CEQA process and determined that alum application provides the best option as a step to effectively treat the entire lake in a timely manner with minimal impact to Canyon Lake residents.

The treatment schedule is as follows (subject to change):

  • Monday, April 22: Main body from 7 a.m. to 4 p.m. p.m.
  • Tuesday, April 23: Main body from 7 a.m. to 4 p.m. 
  • Wednesday, April 24: Main boat ramp to the west end of East Bay from 7 a.m. to 4 p.m. 
  • Thursday, April 25: East Bay and area north of the causeway from 7 a.m. to 4 p.m.
  • Friday, April 26: Clean up

For more information, contact Rachel Gray at Lake Elsinore & San Jacinto Watershed Authority at 951-354-4242 or [email protected]. For daily operation updates, visit


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