CHANGES IN A STREAM’S PHYSICAL AND BIOLOGICAL CONDITIONS FOLLOWING LIVESTOCK EXCLUSION

Abstract

Runoff from dairy cow pastures can degrade the quality of surface waters. Weekly grab samples were collected for 7.5 years from a small stream draining a 56.7–ha, mostly dairy cow pasture and analyzed for fecal coliform and enterococci (streptococci). In situ measurements of pH, dissolved oxygen, temperature, conductivity, and turbidity were made during most grab sampling events. Fecal coliform and enterococci levels for samples collected during the 2.25 years prior to the installation of livestock exclusion fencing were more than 300% greater at the downstream monitoring station compared to the upstream station. After fencing, fecal coliform and enterococci levels decreased 65.9% and 57.0%, respectively. The decreased bacteria levels were significantly different, indicating that livestock exclusion fencing was effective at reducing bacteria levels in the stream. While the levels of dissolved oxygen, pH, temperature, and specific conductivity downstream relative to upstream following fencing generally documented improved water quality, the changes were not statistically significant. Conversely, decreases in turbidity and suspended sediment levels following fencing were significantly different. Levels of most of the physical parameters and bacteria were not significantly different at the upstream monitoring site following the installation of the alternate water supply in the pasture upstream. Thus, the alternate water supply, without fencing, was not effective at improving water quality in the upper pasture.