| Nonpoint sources of bacteria are common pollutants of rangeland streams in Wyoming and throughout the United States and are often addressed through implementation of Best Management Practices (BMPs). The effectiveness of BMPs at addressing nonpoint sources of bacteria, such as E. coli,, is uncertain as very few quantitative assessments have documented responses in surface water quality. This study conducted in the Crow Creek Watershed, southeast Wyoming, investigated water quality responses to three implemented BMPs and evaluated monitoring approaches for measuring these changes. A cross-fence was installed to change the pasture shape and access to the impaired stream reach while water was diverted upstream of the cross-fence; off-stream water developments were installed within the grazing allotment to improve livestock grazing practices and wildlife distribution. Stream E. coli, bacteria levels were assessed comparing 'before vs. after' BMP implementation as well as 'above vs. below' an existing wet meadow; additional parameters (streamflow, turbidity, precipitation and stream sediment E. coli, bacteria) were measured to determine interactions between these factors and stream bacteria levels. Declines in E. coli, concentrations were statistically significant after the installation of BMPs in the 'before vs. after' analysis, indicating the cumulative effectiveness of the practices. The wet meadow provides effective on-channel treatment with statistically significant E. coli, reductions in the 'above vs. below' analysis but was ineffective in preventing elevated bacteria levels in the downstream channel. Weekly E. coli, sampling provided running geometric means useful for trend analysis throughout the seasons and from year to year; compliance monitoring alone may have missed seasonal fluctuations and would not fully represent the variety of hydrologic conditions. Assessing the effectiveness of BMPs for nonpoint sources of E. coli, is possible with long-term monitoring; yet collecting adequate data prior to implementation of management activities is a challenge. |
