Data Analysis for Source ID: Examples of Statistical Methods and Results Julie Kinzelman, City of Racine Beach Management Workshop April 14 – 15, 2005, Egg Harbor, WI

Association of Bacterial Indicator Levels to Coastal Conditions Can we tell when E. coli will be elevated?

Potential Associations Wind Direction Wave Height Estimation Precipitation Surface Water Temperature Presence of Algae

Wind Direction Wind Vector Containing Direction East

YEARNUMBER OF DAYS INCLUDING WIND VECTOR EAST (90°) MayJuneJulyAugust 20020* ** ***910 Number of Sampling Events

Winds East = High Waves

Influence of East Wind In 2 out of the 3 years the increased number of days including wind vector E also reflected an increase in the number of days per month with poor water quality failures This translates to a correlation of ~ 50% Onshore winds frequently increased wave height as noted in field observations

Wave Height Estimated Visually (low, medium, or high)

YEARDAILY FREQUENCY OF WAVE HEIGHT BY MONTH May/JuneJulyAugust/September LowMed.HighLowMed.HighLowMed.High Frequency of Wave Height

The number of days with moderate or high waves increased as the summer progressed. The total number of days designated as having high waves increased in August

Local Mathematical Model Best Predictor: E. coli today = (yesterday's E. coli count) (wave height) [p = 0.009] Second Best Predictor: Wave Height + Easterly Wind Vector [p = 0.02]

Precipitation Wet Weather Advisories

Average Daily Precipitation AVERAGE DAILY PRECIPITATION BY MONTH (CM) YEARMONTH JUNEJULYAUGUST

Monthly Precipitation MONTHLY PRECIPITATION TOTALS (CM) YEARTOTAL MONTHLY PRECIPITATION SEASON TOTAL JUNEJULYAUGUST

Although June had high amounts of ppt. it always had the least number of BWQF.

2004

Rainfall can have an immediate impact on surface water quality

Storm Water Discharge to Lake Michigan after Rain Event

Rainfall vs. BWQF Rainfall preceded about 50% of all BWQF in Racine in 2004 The impacts of rainfall can be sudden and immediate Pre-emptive advisories may be appropriate Rainfall can impact surface in a variety of ways: –CSO, SSO, Runoff, Storm water discharge

Surface Water Temperature Did Warmer Water = More Bacteria?

Upwelling can change surface water temperature

Scatter plots of the data demonstrate that a strong correlation did not exist between E. coli and surface water temperature [R2=0.04(2004)]

Algae (Cladophora) Was there more E. coli when there was more algae?

High Amounts of Algae

Low Amounts of Algae

ALGAL PRESENCE VS. E. COLI CONCENTRATION ALGAL PRESENCE

Association of Algae to BWQF The concentration of E. coli isolated from North Beach did not correlate with the amount of algae noted in the field at the time of collection Neither was there a higher incidence of water quality advisories on days when moderate or high levels of algae were noted

Association of Algae to BWQF E. coli concentration, ranked by code relating to Cladophora presence and subjected to ANOVA showed no significant difference (p = 0.64) Limited by the small number of degrees of freedom (n = 27) Correlation may have been noted if the degrees of freedom were higher, i.e. more samples collected

Best Predictors of Water Quality in Racine, WI Wave Height (> 1.0 ft.) Wind Direction (East)

Acknowledgements S. C. Johnson, A Family Company WI DNR Richard Whitman, USGS City of Racine Health Department University of Surrey, RCPEH

Too Many Statistics!!!