The Scripps Institution of Oceanography model predicts forecasts of sewage concentration along the southern San Diego coast up to five days in advance.

With the Tijuana River sewage crisis causing beach closures from Coronado south to the Mexican border daily, researchers at La Jolla’s Scripps Institution of Oceanography have developed a predictive tool beachgoers can use to plan ahead.

The 120-mile Tijuana River flows from Baja California, Mexico into the US just south of Imperial Beach, discharging millions of gallons of wastewater, including sewage, industrial waste and runoff, into the Pacific Ocean every day, causing extreme water pollution as well as air pollution.

Called the Pathogen Forecast Model, the new SIO tool, administered via a website, will allow families “to know whether they can take their kids to the beach on the weekend,” said SIO physical oceanographer Falk Feddersen. 

The PFM provides detailed forecasts for Playas Tijuana, Imperial Beach, Silver Strand State Park and Coronado, showing shoreline sewage concentrations as well as estimated risk of illness for ocean swimmers.

Currently, there are no plans to extend the model to predict water quality in La Jolla, Feddersen said, though The Children’s Pool, La Jolla Cove and other local shorelines are occasionally closed or under San Diego County Department of Environmental Health and Quality water advisory.

The PFM works by collecting weather information including winds and heating; the offshore ocean and tide forecasts; wave models; and river flow forecast, generating a video image of sewage contours moving along the shoreline. 

The transitions are shown in colors, with greens and yellows indicating lower contamination risks and red indicating high concentrations of pollution.

The PFM five-day forecast can predict future beach advisories with an 82 percent accuracy, Feddersen said, “a pretty good accomplishment.” 

The forecasting model improves upon the current testing methods, which culture and measure the concentration of the fecal indicator bacteria Enterococcus in water samples. 

This is tricky, however, as Enterococcus dies rapidly in sunlight, Feddersen said. Furthermore, it’s norovirus that sickens people, a virus hard to measure in ocean water.

Additionally, measuring bacteria on a given day will lead to advisories and closures, but “you can’t see what’s going to happen five days out,” he said.

The PFM is the “first ocean sewage model forecast of its kind,” Feddersen added. “The ultimate goal is … to have better information.”

A second phase of the PFM, coming summer 2026, will include a norovirus ecology model, he said.