Association of Urban Runoff with Coastal Water Quality in Orange County, California

• Published in: Water environment research 2002-01, Vol.74 (1), p.82-90
• Main Authors: Dwight, Ryan H., Semenza, Jan C., Baker, Dean B., Olson, Betty H.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bacteria; Bathing Beaches; Beaches; California; CLIMATE CHANGE; Coastal water; COASTAL WATERS; Earth sciences; Earth, ocean, space; EL NINO; Engineering and environment geology. Geothermics; Enterobacteriaceae - growth & development; Exact sciences and technology; Fresh Water - analysis; Fresh Water - microbiology; Government agencies; Greenhouse Effect; Health risk assessment; Health risks; INDICATOR BACTERIA; Investigations; Natural water pollution; Nonpoint source pollution; OCEAN; Oceans and Seas; PCB; Pollutants; Pollution; Pollution, environment geology; Polychlorinated biphenyls; Precipitation; Public health; Rain; Rainwaters, run off water and others; Recreation; Research Papers; River water; Rivers; Seawaters, estuaries; STORM DRAINS; Stormwater; Urban runoff; URBAN STORMWATER RUNOFF; Urbanization; USA, California; Water Microbiology; Water Movements; Water pollution; Water Pollution - analysis; Water Pollution - statistics & numerical data; WATER QUALITY; Water treatment and pollution; Watershed management; Watersheds
• ISSN: 1061-4303; 1554-7531
• DOI: 10.2175/106143002X139776

The associations between storm events, urban runoff, and coastal water quality have not been well investigated. A temporal and spatial analysis of 2 years of data was conducted to determine associations between urban river discharge and indicator bacteria levels for Southern California beaches and evaluate the contribution of anomalous precipitation to the association. Data show beaches next to rivers had the highest bacterial levels in both wet and dry seasons. Bacterial levels rose substantially across all sites during wet months, and river discharge and bacterial levels were all highest during the winter with the most rainfall. Precipitation was significantly associated (Spearman rank bivariate correlation, P < 0.01) with water discharged from the rivers. River discharge was significantly associated with bacterial levels at 20 out of 22 beaches, with the strongest associations at sites next to rivers. The results indicate that urban river discharge is a primary source of Southern California's coastal water pollution and, as a result, swimming at beaches near rivers may pose a significant public health risk. The strong association found between precipitation and water pollution may be relevant to studies of potential health effects associated with climate change.