Ocean currents mean sewage pollution potential persists
Mike Lee
San Diego Union-Tribune
01/19/2011
A day after concerns broke on both sides of the U.S.-Mexico border about a major sewage spill in Playas de Tijuana, a coastal water expert in San Diego said weak ocean currents off the South County coastline have mostly flowed to the south for the past few days.
That's welcome news for South County residents -- but it's not all good. There have been periods during the past 36 hours when currents have shifted north, said Eric Terrill, director of the Coastal Observing Research and Development Center at Scripps Institution of Oceanography.
His group tracks flows near the mouth of the Tijuana River mouth here.
On Wednesday afternoon, a nearshore eddy had formed on both sides of the border that could pump water north, though Terrill cautioned that predicting currents in tricky. “They can change in a couple hours time,” he said.
Northern flows expose Imperial Beach to sewage-tainted water in the Tijuana River and from the ongoing sewage spill of roughly 1.3 million gallons a day just south of the border fence at Playas. Read the initial story.
If the nearshore current is powerful enough, it can carry polluted water all the way to Coronado, but that hasn’t happened in the past five days.
“We haven’t seen the strong northern flows that we occasionally get,” said Terrill.
His online plume tracker shows where the plume from the Tijuana River mouth has been in recent days. Blue dots represent water flowing today, orange shows two days ago and red shows three days ago.
The plume tracker is based upon ocean current measurements made continuously with a network of radar systems. It is managed by the Southern California Coastal Ocean Observing System and was installed in the early 2000s with funding from California’s Propositions 40 and 50 to assist with oil spill response, tracking wastewater discharges, search and rescue, and assessing local climate changes.
