EPISODIC EVENTS
Extremely high concentrations of E. coli for the 15 Mad River sites monitored in 1998 coincided with storm events. However, other E. coli peaks, identified in the seasonal figures, do not occur in association with storm events but may correspond to human activities in the drainage basins of particular sites. Anomalous events in which E. coli concentrations spike on a particular date and site were observed over the course of this study. Three episodic events have been tied to activities occurring in the watershed. |
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When the Warren village site (13) is compared to a control site (6), overall E. coli concentrations for the village site were significantly higher than the control site. However, three peak E. coli concentrations for Warren coincided with storm events (8/11, 8/25, 9/16). Two other peaks (circled in blue) coincided with stream bank restoration work (10/16 and 10/20). At low streamflow, E. coli concentrations for the two sites were not significantly different. These results suggest that storm events may flush E. coli through the waterway, and resuspension of stream sediments by streambed disturbance may increase downstream E. coli concentrations.
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| Data and analysis by Deb Sargent under the direction of Dr. Leslie Morrissey, School of Natural Resources, University of Vermont. Cooperator: Friends of the Mad River. |
| The impact of septic systems on water quality can be
assessed by comparing E. coli concentrations above and below
residential areas. In this example, site 13 in Warren village is
compared to site 14 above Warren village. E. coli concentrations for both sites were close
on every date with the exception of 10/16 and 10/20. On these
particular dates, earth-moving equipment was observed working upstream in the brook to repair streambanks
damaged by flooding. Suspended sediment, a reservoir for bacteria,
released during the streambank work may have caused the increase in E. coli
concentrations. Therefore, high concentrations noted in the
village during storm events appear to have originated from the drainage
area upstream of site 14.
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| Data and analysis by Deb Sargent under the direction of Dr. Leslie Morrissey, School of Natural Resources, University of Vermont. Cooperator: Friends of the Mad River. |
| An assessment of the contribution of agricultural regions to water
quality can be made by comparing agricultural sites to control
sites. In this example, site 11, representing an agricultural area,
is compared to control site 6. On most dates, E. coli concentrations
were higher at the agricultural site than the control
site. E. coli concentrations were consistently and considerably
higher than corresponding values at the control site on peak streamflow dates (6/16, 8/11, 8/25,
9/16, shown circled in blue) and also on two intermediate stream flow dates that had small
hydrograph peaks (7/20 and 10/29). E. coli peaks unrelated to peak
stream flow events were
observed on 9/22 and 9/29, shown circled in green. During these two dates, cows and horses
were observed on pasture and may account for the high E. coli
concentrations observed on those particular dates.
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| Data and analysis by Deb Sargent under the direction of Dr. Leslie Morrissey, School of Natural Resources, University of Vermont. Cooperator: Friends of the Mad River. |
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