Scripps’s New Tool Predicts Ocean Contamination Days in Advance

For years, San Diegans near our southern beaches have learned to treat the Pacific with suspicion.

On a day when the water looks inviting, invisible pathogens may be drifting north from Tijuana, where a water treatment plant struggles to contain its outflow. Swimming in these conditions can feel less like a rite of warm weather and more like a wager. But oceanographers at the Scripps Institution of Oceanography have devised a way to tip the odds.

March 5, 2025

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The new Pathogen Forecast Model translates the complexity of oceanic physics (currents, winds, tides, waves) into something as simple as a weather report. Scientists have long been able to measure norovirus levels in the surf, but, until now, those measurements told only where the danger had been, not where it was going. The new model can project, up to five days in advance, where contaminated water is likely to travel and how risky it might be to take a swim at various San Diego beaches.

The results appear on a map, rendered in various hues of caution.

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The hope is that the model will restore a measure of trust to the shoreline. County water monitors, armed with advance warning, could open beaches more often and with greater confidence. For San Diego families who have lived with closures that can stretch for weeks or months at a time, the prospect is a promise of better beach days ahead.

Find your beach at pfmweb.ucsd.edu