FECAL COLIFORM BACTERIA AS AN INDICATOR OF WATERSHED HEALTH; A COMPARISON AMONG VARIABLES DURING WATERSHED ASSESSMENT, CARROLL AND HEARD COUNTIES, GEORGIA

Fecal coliform bacteria (FCB) is one of a number of laboratory analyses performed during assessment of watershed health. FCB are ubiquitous in the guts of warm-blooded animals and are therefore present at low levels in most surface waters. Because FCB are potentially hazardous to human health, levels exceeding 200 colonies/100 mL in recreational waters or drinking water sources are considered to be unacceptable by Georgia’s EPD. Many streams in Carroll and Heard counties are listed by the EPD as partially supporting their designated uses (fishing, recreation, water supply) due to seasonally elevated FCB counts.

FCB may be introduced to surface waters in a number of ways: (1) direct introduction by warm-blooded animals; (2) runoff from pastures during rainfall; (3) bacterial growth during times of elevated nutrients. Therefore, FCB content in surface waters represents a complex microbiological response to a variety of parameters. By simultaneously measuring 21 field and laboratory parameters, the West Georgia Watershed Assessment (WGWA) permits us to simultaneously evaluate a variety of parameters.

The overall goal of the yearlong WGWA project is to better characterize surface waters in Carroll and Heard Counties, Georgia. Samples were collected from 71 sites in Carroll and Heard counties. The studied watersheds represent a diverse mixture of agricultural, recreational, commercial, and residential land use. Twenty-eight sites were sampled weekly (52 samples); 43 were sampled 12 times. FCB levels correlate most strongly with rainfall, runoff, seasonal temperature change and nutrient concentration. In general, FCB maxima correlate with high levels of total suspended solids. Major rainfall events typically result in elevated FCB levels. High levels of FCB occur periodically downstream of urban areas, and are particularly pronounced during the summer months. A detailed understanding of the relationship among these variables is necessary in order to develop a predictive model of watershed evolution.