A new project led by researchers at Scripps Institution of Oceanography at the University of California, San Diego, aims to reduce human exposure to beach contamination through a three-pronged approach of real-time coastal monitoring, source identification, and improved management and regulation.
Scripps scientists have been awarded $750,000 by the City of Imperial Beach to study coastal pollution through a project funded by the State Water Resources Control Board as part of California Gov. Gray Davis’s Clean Beach Initiative.
The City of Imperial Beach’s coastline is often plagued by high bacteria contamination. Its beaches were closed 39 times in 2000, more than half of these closings during the peak tourist months of summer. The sources of bacterial contamination responsible for these closures are difficult to pinpoint due to the various possible sources, including the South Bay International Wastewater Treatment Plant outfall, the Tijuana River outflow, northward flow of wastewater from Mexico, and local runoff from Imperial Beach.
It is recognized that existing analysis methods are inadequate to assess and identify the effects of these disparate sources of Imperial Beach’s contamination problems.
Under the newly funded project, Scripps scientists have designed a system for monitoring coastal circulation and movement of distinct water types.
"We put together a number of emerging technologies and will apply them to water-quality problems related to coastal-transport processes," said Eric Terrill, assistant project scientist in the Scripps Marine Physical Laboratory. "This project will help identify which of the various pollution sources impact the Imperial Beach region in a manner only possible with the application of new technologies."
The "Coastal Monitoring System" combines data from radar instruments that map surface ocean currents and a suite of in-water instrumentation.
At the core of the system is CODAR (coastal ocean dynamics applications radar), a high-resolution radar instrument that produces a map of the ocean surface currents on a real-time basis. CODAR scatters radio waves across the ocean surface waves and processes their signals as they return to the instrument. The signals track the movement of the surface waters over an extended area, thus helping to identify which regions of the coastline may be impacted by pollution flows — or alternatively, from where polluted waters may have originated.
The resulting maps will be complemented by in-water instrumentation to measure currents through the water column, water-column stratification, currents in the surf zone, and water-quality parameters.
These continuous and real-time data from instruments will be combined with an enhanced program of bacteria sampling by the County of San Diego.
All information will be stored in a comprehensive database, which will help reveal how the coastal region responds to changing environmental conditions, such as tides, wind events, and precipitation, and how they correspond with beach contamination. The scientists anticipate that these "time histories" will allow officials to trace transport routes backwards in time to their pollution sources.
"This project holds the promise of a reduction in bacterial contamination and a reduction in the exposure of people to contaminated waters," said John Largier, associate research oceanographer at Scripps. "The radar mapping of surface currents over a large area, combined with data on currents through the water column, will allow us to identify the origin of contaminated water transported to the beach and provide early warning of bacterial contamination events. The improved knowledge of the source will guide regulation and management to reduce or eliminate the sources of contamination and the improved monitoring will reduce the exposure of swimmers to contaminated waters."
Although Imperial Beach will be the focus, the system has the capability to monitor the coast from the United States-Mexico border to Point Loma, and offshore to the Coronado Islands. Further, this system will be extended south across the border through collaboration with scientists in Ensenada, Mexico.
"Through an increased understanding of the real-time conditions present in the coastal environment, this system holds the possibility that we may be able to forecast days on which there is a high likelihood of beach closures due to fecal contamination," added Largier.
"Scripps is providing a service to the local community in this project by applying science to regional water contamination issues. We’re expecting that a better understanding of the complex ocean physics in the region will help us find solutions," said Terrill.