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Escherichia coli Loading at or Near Base Flow in a Mixed‐Use Watershed
Author(s) -
Gentry Randall W.,
McCarthy John,
Layton Alice,
McKay Larry D.,
Williams Dan,
Koirala Shesh R.,
Sayler Gary S.
Publication year - 2006
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0243
Subject(s) - base flow , watershed , escherichia coli , environmental science , base (topology) , flow (mathematics) , hydrology (agriculture) , chemistry , geology , computer science , geography , mathematics , drainage basin , geotechnical engineering , physics , mechanics , biochemistry , cartography , machine learning , mathematical analysis , gene
This study analyzed the occurrence of Escherichia coli in a mixed land‐use watershed with human, cattle, and wildlife fecal inputs located in a karstic geologic region using synoptic monitoring (samples taken throughout the watershed system) during base‐flow conditions. The objective of the study was to evaluate the occurrence of E. coli during base‐flow conditions for several months at seven different main channel and nine different tributary sampling sites in the Stock Creek watershed, a 49.3‐km 2 basin located in Knoxville, TN. Escherichia coli densities were measured using the Colilert (Defined Substrate Technology) method. The instantaneous loads for E. coli were determined from measured flow rates and E. coli densities, with the highest loading rates observed in the late fall. The study indicated a strong correlation between E. coli load rate (colony‐forming units [CFU]/d), 7‐d antecedent precipitation, and turbidity. Water quality data, however, also exhibited a spatial dependency; for example, the E. coli load rate was better correlated with turbidity in the slower draining basin tailwater sampling sites than in the faster draining upstream headwater sampling sites. In the headwater sites, the E. coli load rate was better correlated with 7‐d antecedent precipitation than turbidity.