J Water Health 01 (2003) 23-31

Storm effects on regional beach water quality along the southern California shoreline

Rachel T. Noble, Stephen B. Weisberg, Molly K. Leecaster, Charles D. McGee, John H. Dorsey, Patricia Vainik and Victoria Orozco-Borbón

UNC at Chapel Hill, Institute of Marine Sciences, 3431 Arendell St., Morehead City, NC 28557, USA Tel.: +1 252 7266841 x150 Fax: +1 252 7262426 E-mail: rtnoble@email.unc.edu

Southern California Coastal Water Research Project, 7171 Fenwick Lane, Westminster, CA 92683, USA

Idaho National Environment and Engineering Laboratory, Idaho Falls, ID, 83415, USA

Orange County Sanitation District, 10844 Ellis Avenue, Fountain Valley, CA 92708, USA

Department of Natural Sciences, Loyola Marymount University, One LMU Drive, Los Angeles, California 90045, USA

City of San Diego Metropolitan Wastewater Department, 4918 North Harbor Drive, San Diego, CA 92106, USA

Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Km. 103 Carretera Tijuana-Ensenada, Ensenada, México

Two regional studies conducted during dry weather demonstrated that the Southern California Bight (SCB) shoreline has good water quality, except near areas that drain land-based runoff. Here, we repeat those regional studies 36 h after a rainstorm to assess the influence of runoff under high flow conditions. Two hundred and fifty-four shoreline sites between Santa Barbara, California and Ensenada, Mexico were sampled using a stratified-random sampling design with four strata: sandy beaches, rocky shoreline, shoreline adjacent to urban runoff outlets that flow intermittently, and shoreline adjacent to outlets that flow year-round. Each site was sampled for total coliforms, fecal coliforms (or E. coli), and enterococci. Sixty percent of the shoreline failed water quality standards after the storm compared to only 6% during dry weather. Failure of water quality standards increased to more than 90% for shoreline areas adjacent to urban runoff outlets. During dry weather, most water quality failures occurred for only one of the three bacterial indicators and concentrations were barely above State of California standards; following the storm, most failures were for multiple indicators and exceeded State of California standards by a large margin. The condition of the shoreline in Mexico and the United States was similar following rainfall, which was not the case during dry weather.

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