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| Titel |
Temporal stability of E. coli concentration patterns in two irrigation ponds in Maryland |
| VerfasserIn |
Yakov Pachepsky, Rachel Kierzewsky, Matthew Stocker, Walter Mulbry, Patricia Millner, Daniel Shelton |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140382
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| Publikation (Nr.) |
 EGU/EGU2017-3763.pdf |
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| Zusammenfassung |
| There are about nine million ponds in U.S., and many of them serve as important
agricultural surface water source. E. coli concentrations are commonly used to
evaluate microbial water quality for irrigation and recreation. Our hypothesis was that
temporally stable patterns of E. coli concentrations exist across irrigation ponds, i.e.
there are zones where E. coli concentrations are mostly or always lower than the
average concentration across a pond for any sampling event, and there are other
zones where E. coli concentrations are mostly or always higher than the average
concentration across a pond for any sampling event. Two irrigation ponds in Maryland
were sampled biweekly in summer of 2016. Samples were taken in 22 locations
across one pond and at 34 locations across another pond on grids. Temperature, pH,
turbidity, and concentrations of dissolved oxygen, nutrients, chlorophyll a, and
generic E. coli were determined. Methods of temporal stability assessment included
estimating Vachaud’s mean relative differences, computing the Spearman correlation
coefficient, and deriving empirical orthogonal functions. All three methods indicated the
presence of temporally stable patterns in E. coli concentrations and environmental
covariates. The distance from the shore seemed to serve as one of controls. Temporal
stability was found for the most of environmental covariates. Smaller mean relative
differences of E. coli concentrations corresponded to larger mean relative differences of
chlorophyll a. Presence of temporal stability in E. coli concentrations across ponds
means that (a) the selection of sampling locations may strongly affect the microbial
quality assessment, (b) the microbial quality of water at the pumping intake for
irrigation can be affected by the intake location, and (c) one or more locations can
be found where E. coli concentrations remain close to the median concentrations
across the pond, and can be used to characterize the overall microbial water quality. |
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