Submitted to: Georgia Water Resources Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/30/1999
Publication Date: N/A
Interpretive Summary: Contamination of surface water with fecal bacteria from grazinglands is a component of pollution related to agriculture. Urban development has resulted in an increased demand for water for domestic use and recreation. This increases the importance of identifying and controlling agricultural pollution. Exclusion of cattle from creeks and rivers by fencing is effective in limiting fecal contamination of creeks and rivers but it is expensive. Additional methods of reducing microbe numbers are needed for beef production systems in the southeastern USA. Some commonly used tests for fecal contamination count some microbes that are not fecal in origin and can yield high estimates from natural areas due to wildlife. The objectives of this work were first to compare three assays for fecal microbes in the surface water of an area grazed by cattle with surface water of a wooded area. Secondly, our objective was to test the impact of a pond on the level of bacterial contamination of water leaving the grazing area. Two assays were sensitive to the presence of cattle in the watershed. Either of these assays would be more likely to differentiate the impact of cattle from wildlife than a more traditional analysis. Locating grazing animals in the landscape above a pond was an effective means of reducing numbers of fecal bacteria in surface waters leaving grazinglands.
Technical Abstract: Contamination of surface waters with fecal bacteria from grazinglands is a component of non-point source agricultural pollution and increased demand for surface water to supply domestic and recreational needs means that movement of pollutants from agricultural lands must be controlled. Exclusion of cattle from surface water by fencing is partially effective but expensive. Additional methods are needed for reducing microbe numbers in surface water leaving beef production systems in the southeastern USA. Tests for total or fecal coliform bacteria have been used to indicate fecal contamination but these tests enumerate some microbes that are not fecal in origin and often yield high estimates from natural areas. We compared numbers of total coliform, E. coli, and enterococci bacteria in the surface water of a grazed watershed with surface water of a wooded watershed. We also tested the impact of a retention pond on the numbers of microbes in water leaving the grazed watershed. Assays for E. coli and enterococci wer more sensitive to the presence of cattle in the watershed than total coliforms. Either an assay for E. coli or enterococci would be more likely to differentiate the impact of cattle from wildlife than an analysis for total coliforms. Locating grazing animals in the landscape above a pond was an effective means of reducing fecal bacteria in surface waters leaving grazinglands.