New Report on San Lorenzo River Water Quality Shows "Little to No" Human Bacteria Present

Bacteria are everywhere, in the environment and in our bodies. Many of them are beneficial; some not so much. The San Lorenzo River has historically recorded high levels of fecal indicator bacteria, but how much of that is due to human sources? The Coastal Watershed Council (CWC) and San Lorenzo River Alliance released a technical memo on Monday, June 8 indicating little to no human contribution to bacteria levels in the lower San Lorenzo River.

Results from six months of testing during last year’s recreational season (May-October) showed that bacteria associated with human sewage was rarely if ever present. Additional testing is warranted to verify these results under varying conditions, but the findings represent a challenge to the notion held by many that the river and watershed supplying two-thirds of Santa Cruz’s drinking water are badly polluted.

The report details the efforts of eighteen months of work by the San Lorenzo River Alliance’s Water Quality Working Group, including the City and County of Santa Cruz, the Surfrider Foundation Santa Cruz Chapter, the Central Coast Regional Water Quality Control Board and CWC. Epidemiologists recognize bacteria from humans as posing high threats to public health, but traditional tests required of municipalities can’t tell scientists the origin of bacteria found in rivers and creeks. The working group tested for specific sewage-associated chemical and microbiological constituents to learn more useful information, with the intention of identifying and addressing human sources of bacteria in the watershed.

Laboratory tests for caffeine, human DNA, and cholesterol were run on samples from the lower San Lorenzo River and Branciforte and Carbonera Creeks. Multiple tests indicated a significant preponderance of bird inputs, and provided little evidence of human inputs.

The group plans to repeat the series of tests during a normal, non-drought year, which will have to wait until 2016 at the earliest. The working group’s ongoing efforts include source identification and control and reduction of bacterial contaminants, with an emphasis on human and other anthropogenic sources that are deemed to be controllable. The goal is to reduce human bacteria inputs to the lowest levels possible.


San Lorenzo River Alliance/Coastal Watershed Council
http://coastal-watershed.org/