Effects of Rainfall on E. coli Concentrations at Door County, Wisconsin Beaches

Table 1

Overall impact of rainfall on E. coli concentrations in beach water. Mean E. coli concentration in beach water during a rainfall event was compared with the seasonal mean E. coli concentration at the same beach by analysis of variance. All beaches, except Nicolet Bay Beach, had a total of ten rain events with 7 samples collected per 24-hour sampling event. Nicolet Bay Beach had four rain sampling events. Bolded 𝑃-values indicated significantly higher E. coli concentrations during rain events (𝑃<.05).

Beach name	Mean E. coli during rain event	Seasonal E. coli mean	Significant difference
	(MPN/100 mL)	(MPN/100 mL)	(𝑃 value)
Baileys Harbor	225.4	53.4	.000
Egg Harbor	41.0	61.4	.849
Ellison Bay	447.7	43.3	.000
Nicolet	19.4	26.4	.041
Murphy Park	191.0	115.9	.000
Sister Bay	778.3	276.0	.000
Sunset Park	187.5	102.1	.011
Whitefish Dunes	39.8	48.3	.110