Sources and persistence of fecal coliform bacteria in a rural watershed

Water quality within the Thomas Brook watershed, which is a small catchment located in the headwaters of the Cornwallis River drainage basin, was assessed through an integrated monitoring program. The Thomas Brook watershed is approximately 1000 ha and is characterized by both agricultural and residential land uses. Fecal coliform. concentrations and stream flow were monitored at several points throughout the watershed during an eight-month period (May to December, 2001). Thomas Brook was seriously degraded with respect to microbial water quality. Fecal coliform. levels frequently exceeded recreational water quality guidelines. At the watershed outlet, 94% of the collected samples exceeded the recreational water quality guideline during low flow conditions. Substantial bacterial loading was observed along stream reaches impacted by livestock operations. Bacterial loading was also observed along a stream reach that was not impacted by agricultural activities. A dense clustering of residences, using on-site septic systems, was the suspected source. Results from this study indicate the presence of a reservoir of fecal microorganisms within the stream sediments. The release of fecal microorganisms from the stream sediments to the water column during both low and high flow conditions could be a major source of bacterial loading.