State of California Department of Water Resources Studying Downtown McLeod Lake for Harmful Algal Blooms Using Dye

The California Department of Water Resources (DWR) will conduct two studies in Downton Stockton McLeod Lake beginning this summer. The first study will take place next week. The studies will apply a non-harmful dye to the water to record water flow and monitor the interaction of McLeod Lake and the San Joaquin River. The purpose of the studies is to establish the cause of harmful algal blooms (HABs) in the Stockton Waterfront. McLeod Lake was selected by the State as one of the study sites due to the impact of HABs in the area, particularly during drought years.

To conduct the studies, crews hired by the State will use rhodamine dye. Recognized by the U.S. Environmental Protection Agency (EPA) as non-harmful to humans and the environment, rhodamine may turn the water noticeably bright pink or a purplish color depending on weather and water conditions at the time of the application. The coloring is temporary and poses no harm to McLeod Lake, people, boats, or wildlife.

The first dye study is scheduled to begin on August 26, 2024, and anticipated to be completed by Friday, August 30, 2024. Crews will use a Port of Stockton boat to apply the dye and record data between McLeod Lake at Weber Point and Interstate 5. The second study is expected to be scheduled in early 2025. Data collected during the studies will provide information about conditions that are present between the Stockton waterfront and the San Joaquin River that result in the harmful algal blooms that cause the water to turn green and odors that occur during hot months.

For additional information, please contact the City of Stockton Community Relations Officer or visit Municipal Utilities webpage.