Precipitation events in California, USA, are projected to become more volatile: less frequent but more extreme as global warming pushes mid-latitude frontal cyclones further poleward while bolstering the atmospheric rivers (AR), which tend to produce the region’s extreme rainfall. Pollutant accumulation and delivery to coastal waters can be expected to increase, as lengthening dry spells will increasingly tend to be punctuated by more extreme precipitation events. Coastal pollution exposes human populations to high levels of fecal bacteria, which could cause gastrointestinal, eye and ear infections, and lead to exposure to pathogens causing life-threatening conditions such as hepatitis A. The aim of this study is to quantitatively assess the effect of extreme precipitation events on coastal water quality in California.We used historical daily precipitation and weekly fecal bacteria indicators (total and fecal coliforms, enterococci, and <i>Escherichia coli</i>) at ~ 500 monitoring locations in California’s coastal waters to explore weekly associations between precipitation and water quality during 2003–09 by means of canonical correlation analysis (CCA). We then verified, using a recently published catalog of atmospheric rivers, that these observed associations are driven by atmospheric river storms.  The temporal evolutions of associated patterns for precipitation and fecal bacteria were highly correlated and their association was strongest in Southern California. Moreover, two-thirds of coastal water pollution spikes exceeding one standard deviation were associated with AR landfalls. This work highlights the importance of skillful AR landfall predictions in reducing vulnerability to extreme weather and delineate measures, such as an early warning system, that improve the response and resilience of human populations to a varying and changing climate.

Atmospheric rivers and public health: Observed links between extreme precipitation events and California’s coastal water quality

2019 Fall National Meeting

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