It is an idea that a team of researchers at Scripps Institution of Oceanography at UC San Diego put into practice on Tuesday, launching the first version of a “Pathogen Forecast Model” that looks five days into the future, using weather, tide, wave and river flow forecasts to calculate what ocean water conditions are likely to exist hour by hour from Coronado south past the U.S.-Mexico border.
Some might wonder what’s to understand, given that persistently high sewage levels from the Tijuana River and a broken sewage-treatment plant six miles south of the border have left some areas, such as the Tijuana Slough, off limits for swimming for years now. The public has been able to look up beach closures made by the county’s monitoring program at sdbeachinfo.com for years.
Sure, agreed oceanographer Falk Feddersen, the project’s lead, locations closest to the Tijuana Estuary have had long and unbroken stretches where water quality has been too poor for swimming. But beaches further north, such as those in Coronado and Silver Strand State Beach, are far enough away that their water quality status fluctuates with complex ocean circulation patterns, especially during the summer months when the tidal surge comes from the southwest.
Drawing together multiple data streams in a special computing cluster housed at the San Diego Supercomputer Center, it is possible, researchers say, to predict how ocean water will move from south to north, mixing in whorls and eddies influenced by current, wind, temperature and many other factors, just as weather models can calculate the likely temperature, precipitation and humidity days ahead.
“I think it’s fair to say that we can predict, with 82% accuracy, five days out, whether the county will be posting a beach advisory or not in that span from (Imperial Beach) to Coronado,” Feddersen said.
The inaugural forecast, available now at pfmweb.ucsd.edu, allows users to pick a location and hit play, watching as the forecast depicts the predicted swirls and eddies of future ocean currents, graphing out expected concentrations of sewage at the ocean’s surface. While some, such as Playas de Tijuana and the Imperial Beach Pier, are never predicted to escape the yellow “moderate risk” range of the scale, others, such as Silver Strand and Coronado at Avenida Lunar, are shown to fall into or near the green range on Saturday.
For those trying to plan family outings for the weekend, this ocean pollution forecast could provide additional information on where to go and when.
“The overall goal of the project can be stated this way: We want to be able to allow (families) to know whether they can take their kids to the beach on the weekend, whether it’s going to be safe on the weekend for them or for their kids to be swimming in the water,” Feddersen said.
Skeptical parents will likely wonder why they should trust that this new model is as good at predicting ocean circulation as its creators say it is. Feddersen, who holds a doctorate in physical oceanography from Scripps, said that the model’s results compared favorably to the county’s daily pathogen monitoring, which has technicians collect samples and conduct DNA analysis in a certified lab.
“When the (county test results) get larger, our model’s percent sewage gets larger and, when it gets smaller, the other gets smaller,” Feddersen said. “In fact, these two things are highly correlated; they have a correlation (value of) 0.54 on the fifth day of the forecast, and this implies good skill in forecasting the sewage plumes.”
That is not to say that this model, as published on the university’s new website, is now the authority in South County beach closures. According to state law, the county’s environmental health department shoulders that responsibility and will continue posting notices if its own monitoring detects the presence of enterococcus bacteria in concentrations considered strong enough to increase the likelihood of infection.
“This will be used as one of the many telemetry tools viewed daily to assist with beach water quality monitoring,” a county statement said.
About $3 million in state funding paid for the work, which includes additional ocean sensors along the shore to collect more precise data on ocean currents near shore, on computing resources at the supercomputer center, and on norovirus monitoring, which is still underway. Norovirus is by far the most infectious pathogen in sewage, and by documenting concentrations and how they correlate with other environmental factors, the project plans to add a prediction of the likely infectiousness of ocean water in 2026.
State Sen. Steve Padilla pushed hard to help secure funding for the project.
“Communities like Imperial Beach have been at the epicenter of this crisis for a generation, and they deserve real, science-driven solutions,” Padilla said in a statement.
U.S. Rep. Scott Peters, who has been pushing for comprehensive repairs to the degraded sewage treatment capacity that handles Tijuana River water, said that the model is key to understanding whether the sewage situation is getting better or worse.
“As these projects move forward, this predictive model will be essential to monitor conditions during construction and ensure that those solutions are working as intended.”
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