Evaluation of the Impacts of Grazing Management and off-Stream Watering Facilities On Bacterial Runoff.

Runoff of E. coli and other fecal indicator bacteria from grazing lands has been identified as a significant source of bacterial contamination in need of reductions to improve water quality. Development of best management practices to address these bacterial issues is critical to the success of watershed restoration efforts. Two best management practices, grazing management and providing alternative off-stream watering facilities, were evaluated to assess their effectiveness for reducing E. coli loading.

E. coli levels in runoff from grazed and ungrazed rangeland, improved pasture, and native prairie sites were monitored from November 2007 through October 2010. Results show that rotational grazing, if timed appropriately, is a very effective practice for reducing E. coli runoff. Further, the impact of grazing timing was more significant than the impact of grazing pressure or stocking rate. As a result of these findings, it is recommended that creek pastures and other hydrologically connected pastures be grazed during periods when runoff is less likely and upland sites be grazed during rainy seasons when runoff is more likely to occur.

To assess the effect of providing alternative off-stream watering facilities, an upstream-downstream, pre-/post-treatment monitoring design was used to evaluate E. coli levels in Clear Fork of Plum Creek in central Texas from July 2007 to July 2009. Further, global positioning system collars were used to track cattle movement. The study found that when alternative off-stream water was provided, the amount of time cattle spent in the creek was reduced 43% from 3.0 to 1.7 minutes per cow per day. However, this study could not conclusively attribute E. coli loading reductions to providing alternative water because of the lack of statistical significance of observations, the decrease in flow observed during the post-treatment period, and the observed increase in E. coli levels during the post-treatment period.