Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/1996
Publication Date: N/A
Interpretive Summary: Indicator bacteria like fecal coliform (FC) and fecal streptococcus (FS) can be used to measure water quality. However, the season and the amount of rain may bias sampling results. The objective of this study was to assess the impacts of season and flow rate on FC and FS. Three years of data were collected on two streams in NW Arkansas. Season made a big difference, with most bacterial runoff occurring in summer. Flow rate als had a significant effect on bacterial concentrations.
Technical Abstract: Concentrations of indicator bacteria such as fecal coliform (FC) and fecal streptococcus (FS) are often used to assess the suitability of waters for their intended use(s) and to allocate resources for water quality improvement measures. There is evidence, however, that concentrations of FC and FS can be influenced by variable such as season and flow rate during gsampling, which could lead to biased results. The objective of this study was to assess the impacts of season and flow rate on concentrations of FC and FS. Nearly three years" FC data were collected from five sites on two Northwest Arkansas streams; flow data were collected on two of the sites. Land use in the basins draining the streams was primarily pasture (57-90%) and forest (6-40%). Significant seasonal influences on FC and FS concentrations were detected for all sampling sites, with the highest concentrations occurring in summer. On the two sites with flow data, flow rate generally had a significant effect on FC and FS concentrations during all seasons. Ratios of FC and FS, which have been used in the past to differentiate between animal and human sources of fecal pollution, did not appear to reliably indicate the major sources of fecal indicator bacteria. The findings of this study suggest a potential for fixed sampling intervals to contribute to biased results. The issue of biased results might be avoided by sampling during times of the year and flow conditions that support the intended use(s) of the waters.