INDICATOR BACTERIA CONCENTRATIONS OF 2 NORTHWEST ARKANSAS STREAMS IN RELATION TO FLOW AND SEASON

Concentrations of indicator bacteria: such as fecal coliform (FC) and fecal streptococcus (FS) are open used to assess the suitability of wa ters for their intended use(s) and to allocate resources for water qua lity improvement measures. There is evidence, however, that concentrat ions of FC and FS can be influenced by variables such as season and fl ow rate during sampling, which could lead to biased results. The objec tive of this study was to assess the impacts of season and flow rate o n concentrations of FC and FS. Fecal indicator bacteria concentrations were measured for approximately three years at five sites on two Nort hwest Arkansas streams. Flow data were collected at two of the five si tes. Land use in the basins draining the streams was primarily pasture (57-90%) and forest (6-40%); Significant seasonal influences on FC an d FS concentrations were detected for all sampling sites, with the hig hest concentrations occurring in summer On the two sites with flow dat a, pow rate generally had a significant effect on FC and FS concentrat ions during all seasons, with FC and FS concentrations increasing with flow rate. Ratios of FC and FS, which have been used in the past to d ifferentiate between animal and human sources of fecal pollution, did not appear to reliably indicate the major sources of fecal indicator b acteria. The findings of this study suggest a potential for fixed samp ling intervals to contribute to biased results. The issue of biased re sults might be avoided by sampling during times of year and flow condi tions that support the intended use(s) of the waters.