High levels of fecal-indicator bacteria in rivers and streams can indicate the possible presence of pathogenic (disease-causing) microorganisms. Cholera, typhoid fever, bacterial dysentery, infectious hepatitis, and cryptosporidiosis are some of the well known waterborne diseases that spread through water contaminated with fecal matter. Eye, ear, nose, and throat infections also can result from contact with contaminated water. In general, methods are not routinely used to directly detect pathogens in water. Instead, bacteria such as total coliforms, fecal coliforms, fecal streptococci, Escherichia coli (E. coli), and enterococci are used as indicators of sanitary water quality, because they are present in high numbers in fecal material and have been shown to be associated with some waterborne disease-causing organisms. Indicator bacteria usually are harmless, more plentiful, and easier to detect than pathogens. The concentration of bacteria in a sample of water is usually expressed as the number of colonies per 100 milliliters (col/100 mL).

As part of the U.S. Geological Survey National Water-Quality Assessment Program, 145 samples were collected and analyzed for selected water-quality constituents, fecal coliforms, and fecal streptococci at 17 sites in North and South Carolina from October 1995 through September 1996. Of the original 17 sites, 4 in South Carolina were sampled for E. coli and total coliforms from April through September 1997. At two sites, this sampling continued from October 1997 through April 1998.

Significant findings include:

• Samples collected at 11 of 17 stations had fecal coliform concentrations above the North and South Carolina water-quality single monthly sample standard of 400 col/100 mL.
  
  
• Of the 17 stations sampled, the highest single fecal coliform concentrations were observed in samples from two predominantly agricultural basins, Indian Creek, N.C. (21,600 col/100 mL), and Cow Castle Creek, S.C. (12,000 col/100 mL).
  
  
• Samples with the highest single fecal streptococcus concentrations were from the South Fork Catawba River, N.C. (>20,000 col/100 mL), and Cow Castle Creek, S.C. (10,000 col/100 mL).
  
  
• Statistically significant correlations (alpha = 0.05) were found between some fecal-indicator bacteria concentrations and streamflow, water temperature, pH, sediment, nitrate, ammonia, organic nitrogen, total phosphorus, organic carbon, silica, and percent saturation of dissolved oxygen.
  
  
• Correlations of water-quality constituents with fecal-indicator bacteria concentrations suggest that surface-water runoff is a significant source of fecal contamination at Cow Castle Creek, S.C.

--- March 1999

To order SANT NAWQA publications, please email or call:

Celeste A. Journey
SANT NAWQA Project Chief
cjourney@usgs.gov
(803) 750-6141