Southern Californians commonly misinformed about beach water quality, study finds

03/24/04

Data show state warning system fails 41 percent of the time

Irvine, Calif., March 24, 2004 -- Scientists at The Henry Samueli School of Engineering at UC Irvine have found serious flaws in the methods used for warning Southern Californians about the quality of coastal water.

By analyzing water quality data and beach warnings posted in the summer of 2001 for Huntington Beach a popular coastal resort reputed to have inspired Jan and Dean's "Surf City" researchers found that the public was incorrectly notified about coastal water quality as much as 41 percent of the time.

Errors were caused by a combination of factors, including infrequent sampling and testing, rapid changes in water quality and a state warning system that only allows water to be determined safe or unsafe.

The research was headed by Stanley Grant, chair of the chemical engineering and materials sciences department at UCI. Results were published in three companion papers this week on the Web site for Environmental Science & Technology, a publication of the American Chemical Society.

"Our existing warning system fails at precisely the moment it's needed most," said Grant. "When water quality is relatively good, the warning system works fine. But when it's not, the warning system is so error prone, you'd do just as well to base your decision to go in the water on the flip of a coin."

As part of a solution, the researchers have proposed that coastal states like California adopt a warning system that provides the public a range of risk, much like the forecasts provided by daily weather reports. "We're all pretty comfortable with interpreting weather reports, in which information is conveyed to the public as a probability for example, there's a 30 percent chance of rain today," Grant said. "Of course, a lot of science goes into the generation of weather forecasts, and water quality forecasts will be no different."

The research also provided new insights into the causes of coastal pollution, such as fecal bacteria, that typically close area beaches. Investigating the infrastructure currently used to divert urban runoff, the researchers found that 99 percent of the pollution occurs during rainstorms, when diversion systems such as water drains are not operating because the infrastructure cannot handle large volumes of runoff. The systems are more effective during the dry season, when the volume is smaller, originating primarily from sources like irrigation systems and car washes.

"This result has public policy ramifications because the current strategy for managing surface water runoff involves capturing and treating the dry-weather surface runoff, also referred to as urban slobber," Grant said. "The idea that urban slobber might constitute only 1 percent of the problem is staggering. The results point to the importance of developing new approaches for treating storm runoff. At present, there aren't any obvious solutions out there."

In addition, the researchers offered an approach for locating the sources of coastal pollution, as well as estimating the physical sizes of these areas and the rates they are generating pollution. The approach involves collecting shoreline water quality data and then running them through a mathematical model. When applied to Huntington Beach, the approach points to tidal outlets the Santa Ana River and the Talbert Marsh outlet as being major contributors to the pollution problem along the shore. The study also notes that a large fraction of the shoreline pollution is coming from a region where there are no obvious sources of fecal indicator bacteria. "We answered a lot of questions, but a few mysteries remain," Grant said.

Source: Eurekalert & others

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