Is the water in our streams, rivers, and lakes toxic to aquatic life?

This map shows data generated by:



To measure how well a water body supports aquatic life, we can perform a toxicity test. Water samples from a given water body are taken to the laboratory and test organisms are exposed to that water to see if they exhibit any adverse effects .  Toxicity tests are especially useful in water quality monitoring because they show the overall effect on aquatic life of all of the chemicals found in the water sample.  Toxicity tests can assess mortality, behavioral changes, reproductive status or physiological and biochemical changes.  Follow-up tests called Toxicity Identification Evaluations are used in the laboratory to identify the probable cause of toxicity.  In California, pesticides have been a common cause.

The assessment of toxicity displayed here is based on methods used to summarize nine years of toxicity testing data collected by the Surface Water Ambient Monitoring Program (SWAMP) and partner programs (click here to view the report). The process used to characterize the magnitude of toxicity at each site was designed to integrate results from multiple samples taken at a site and multiple tests conducted on the samples. Note that the assessment displayed here does not completely match the SWAMP report due to differences in statistical methods and additional data assessed in this portal.

Statewide Statistics - Condition of State's Waters