Water Quality

Harmful Algal Bloom Information

A harmful algal bloom (HAB) is an overgrowth of algae in a water body that could affect water quality and aquatic life. Some HABs produced by bacteria can create toxins that may also harm people and animals.

The California Regional Water Quality Control Board has sampled some areas of the Delta and found some HABs in areas around Stockton. Due to the nature of our Delta waterways, these HABs can be in areas not sampled or even in areas previously showing no contamination. Because of this it is best to stay away from scum, and cloudy or discolored water. Keep children and pets away from algae in the water or on the shore. Do not drink the contaminated water or use it for cooking. Do not eat shellfish from this water. For any fish caught in this water, throw away guts and clean fillets with tap water or bottled water before cooking.
For more information on locations of sampling, please visit the California Harmful Algal Blooms Portal
https://mywaterquality.ca.gov/habs/index.html

Other locations with information:

CDC Harmful Algal Blooms https://www.cdc.gov/habs/index.html

Sources of Exposure and Risk Factors https://www.cdc.gov/habs/exposure-sources.html

SWAMP-Surface Water Ambient Monitoring Program

The Central Valley Water Board monitors and evaluates water quality data  for many Central valley lakes and rivers that are used for recreational activities. Throughout the summer, some of these water bodies will be sampled for Escherichia coli (E. coli) to monitor overall well-being of recreational waters. To find out where the Central Valley Water Board is currently monitoring and to see the latest results visit: