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| Titel |
Microbial water quality in streams as affected by high flow events |
| VerfasserIn |
Andrey Guber, Yakov Pachepsky, Daniel Shelton |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250045562
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| Zusammenfassung |
| Bottom sediments in surface water sources were shown to serve as reservoirs of
pathogen and indicator microorganisms. Resuspension of these sediments during the
high flow events strongly modifies microbial quality of recreation and irrigation
waters. Therefore, changes in microbial water quality are expected due to climatic
changes that affect the precipitation frequency-duration-intensity relationships. The
objective of this work was to summarize results of three years of artificial high
flow experiments at the perennial first-order creek in riparian zone. The artificial
high flow events were created at the USDA-ARS OPE3 research site by releasing
80T of tap water with tracers in four allotments during 20 min and monitoring
streamflow, and E. coli and PFBA tracer concentrations at four stations with automated
refrigerated samplers along the 630 m stream reach. Sediment texture and E. coli
concentrations were measured before the event and on the next day. The E. coli
concentration in stream water during and after the event far exceeded the limits
recommended for recreation and irrigation waters. Based on bacteria mass balance, E.
coli were released on average from the top 5 mm of the sediment layer. E. coli
concentrations in sediments were one order of magnitude larger days after the experiment
than before the event. Semivariograms of E. coli concentrations before events were
periodic indicative to the extreme patchiness, whereas no spatial structure was found
in E. coli concentrations day after the event. Tracer breakthrough concentrations
suggested a slow return of bacteria from stagnant zones near stream banks to the
flow zone in the creek. On one of the years, A high concentration of streambed E.
coli (“hotspot”) resuspended within the first reach caused a pulse of high E. coli
concentrations that propagated along the creek without substantial attenuation.
Functioning of environmental reservoirs of E. coli such as bottom sediment, bank soils,
periphyton, and algae will change as the climate changes, and this change needs to be
understood to foresee the changes in microbial quality of irrigation and recreation waters. |
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