Transcript Document

A Spatial Analysis of the influence of a rain event on Fecal Coliform Concentrations
and Turbidity in a small N.E. Ohio Freshwater Stream
Ian Santino, Glennon Beresin, & Andrew Fenster
Oberlin College, Systems Ecology 2008
Background
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• We chose our sample sites to be consistent with sampling in a previous
study of water quality of Plum Creek (Feeser and Soong, 2006). Based on
extenuating circumstances, only eleven sample sites are included in our
study (See diagram of stream pictured below).
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Average
We sampled during a low flow period on 11/5/08 and a high flow period,
after 12 hours of rain, on 11/15/08. We used standard methods and
procedures to collect stream water (Basic Laboratory Procedures for
Wastewater Examination, 2002), conduct FC analysis (Basic Laboratory
Procedures for Wastewater Examination, 2002), and measure turbidity (R.
Johnson et al. 2002).
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Low-flow R2=0.08
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Fecal Coliform Counts (100s of colonies)
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= turbidity
High-flow day (1000s C)
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Low-flow day (100s C)
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x 0
x
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500 m
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Oberlin
City
Limits
2000 ft
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The above graph depicts FC colony plate averages for each sample site.
Samples are ordered from upstream to downstream as indicated by the
stream map. This figure reveals that FC is variable both spatially and during
different flow conditions.
The highest FC counts for both days are within the Oberlin city limits.
However, the high flow day had significantly higher FC than the low flow day.
The circles on the graph depict the turbidity levels on the high flow day.
Patterns evident in the graph above lead us to speculate that there may be
different factors driving FC and turbidity in different stretches of the river; it
may be that an urban landscape has more FC moving into the stream but
less soil and organic matter in comparison to the headwaters, where the
stream is surrounded by an open, recently disturbed agricultural field.
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When data from low and high flow periods are analyzed as a
unit, a moderately strong positive trend is evident between
turbidity and FC (in orange), indicating that turbidity induced by
storm events generally delivers FC to the stream.
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However, if data are analyzed for either of the individual days
in isolation, no clear trends are evident between FC and
turbidity (blue = low flow, purple = high flow). We interpret this
to mean that turbidity is indirectly related to increased FC in the
water. It seems more likely that the storm event both increased
turbidity due to an increase in flow and increased runoff
carrying FC into the creek, producing a positive correlation.
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We also only captured the change between low flow and high flow,
where a more complete understanding of how weather affects FC would
call for sampling several times before, during and after the same weather
event.
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Although we can see that the portions of the stream running through the
more highly populated, urban landscapes had higher FC both during a
high and low flow period, the mechanism for those high levels is unclear.
We can only speculate that the FC is entering the stream in those
locations and that the increase during a rain event brings in runoff from
the surrounding areas. However, it is also possible that it is flowing
downstream from a different location.
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North
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80
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Turbidity (FTU)
The temporal and spatial variability of FC concentrations in Plum Creek
displayed in our data signifies that further testing needs to be done at
this high resolution. We only captured the patterning during the course of
two autumn days, instead of having a full year picture of the fluctuations.
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Conclusions and Future Research
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0
High-flow
R2=0.22
R2=0.61
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Results and Discussion
2. In addition, we expected a positive correlation between turbidity and FC
due to increased sediment disturbance in the water.
3. Finally, we expected stretches of the Plum Creek through urban areas to
have the highest FC levels because of increased impermeable ground
surfaces, and prevalence of FC sources associated with use by humans
and animals.
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0
FTU’s
1. We expected an increase in FC during a rain event due to increased
runoff carrying FC delivered from the land.
The locations of the sample sites are within agricultural, forested, and
urban/residential landscapes and all have easy road access, except the
location within the arboretum.
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The health of Plum Creek has been a particular environmental concern
over the past several decades (USGS 1977). Two years ago, Oberlin
began a regular water quality monitoring program in Plum Creek.
However, the focus of data collection and analysis in the past has
been on how nutrient concentrations change over time, at different
locations along the stream and following storm events (e.g Feeser
and Soong, 2006, Cummings et al.,2006). No studies have yet
focused on FC dynamics in relation to spatial variability
and weather conditions. The goal of our study was to analyze FC
at high spatial resolution during autumn along the four miles of Plum
Creek that run through Oberlin city limits on a low flow day and a high
flow day.
Mechanistic hypotheses
Turbidity vs. Fecal Coliform
FC (1000s of colonies)
Plum Creek is a tributary of the Black River watershed which flows
directly into Lake Erie. The creek passes through agricultural, forested,
and urban landscapes and thus makes it similar to many other streams
In the NE Ohio bioregion. Therefore, Plum Creek is an ideal place for
studying the effect of land use on measures of water quality including
nutrients, turbidity, and bacteria concentrations. Fecal coliforms (FC)
are naturally occurring bacteria that help break down food in the guts
of most mammals. Thus, they serve as an indicator for fecal
contamination and are associated with the presence of pathogens in
water, such as Hepatitis A.
FC colonies (C)
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Methods
Literature Cited
Cummings, J., Reed, T., and Weinberger, K. December, 2004. The city of Oberlin’s
effect on the Plum Creek watershed during a storm event: variation in upstream and
downstream water quality during and after storm water run-off as a function of urban
land cover. Oberlin College, Systems Ecology (ENVS 316).
Feeser, J., Lauterbur, E., and Soong, J. December, 2006. Nutrient concentrations along
an agricultural/urban stream during low flow and post-storm periods as a function of
varying land-use and biological processing. Oberlin College, Systems Ecology (ENVS
316).
Johnson, R., S. Holman and D. Holmquist. 2002. Water quality with calculators. Vernier
Software and Technology.
Basic Laboratory Procedures for Wastewater Examination, Fourth Edition, Water
Environment Federation, 2002.
U.S. Geological Survey flow and water quality data for Plum Creek for a 3 month period
in 1977