title: Relationship between rainfall and beach bacterial concentrations on Santa Monica bay beaches.
abstract: Rainfall effects on beach water quality in southern California are large enough that county health departments typically issue warnings for the public to avoid recreational water contact for 3 days following a storm. To enhance the scientific foundation for these preemptive public health warnings, we examined the relationship between rainfall and beach indicator bacteria concentrations using 5 years of fecal coliform data taken daily at 20 sites in southern California. There was a countrywide increase in ocean bacterial concentrations associated with almost all storms larger than 6 mm and with every storm larger than 25 mm. Only for storms less than 2.5 mm was there no observable rainfall effect. Bacterial concentrations remained elevated for 5 days following a storm, although they generally returned to levels below state water quality standards within 3 days. The length of the antecedent dry period had a minimal effect on this relationship, probably reflecting a quickly developed equilibrium between the decay of older fecal material and the introduction of new fecal material to the landscape.
authors.affiliation: Southern California Coastal Water Research Project, Westminster, CA 92683, USA.
authors.forename: Drew
authors.initials: D
authors.lastname: Ackerman
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Weisberg
mesh_terms: D001493:Bathing Beaches; D002140:California; D004755:Enterobacteriaceae / Q000302:isolation & purification; D004784:Environmental Monitoring / Q000379:methods; D005243:Feces / Q000382:microbiology; D019015:Geologic Sediments / Q000382:microbiology*; D006801:Humans; D011322:Primary Prevention / Q000379:methods; D011891:Rain; D018570:Risk Assessment; D012623:Seawater / Q000382:microbiology; D013997:Time Factors; D014871:Water Microbiology; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical