EFFECTIVENESS OF BEST MANAGEMENT PRACTICES IN IMPROVING WATER QUALITY AND STREAM MORPHOLOGY ON CATTLE FARMS IN CENTRAL VIRGINIA

Cattle with stream access tend to spend much of their time in streams and riparian zones seeking water and forage. Best management practices (BMPs) are structural and managerial practices intended to keep cattle out of stream areas to reduce erosion, surface runoff, and non-point source water pollution. In this study, the effectiveness of cattle exclosures were evaluated by comparing stream channel morphology and water quality on three beef cattle farms with BMPs and two without. Two non-pasture reaches located upstream and downstream of the main study area were also evaluated for water and habitat quality for comparative purposes. All study sites are located in the Blue Ridge foothills of central Amherst County, Virginia, in the Graham Creek and adjacent Muddy Creek watersheds. On average, pasture stream reaches with BMPs exhibited lower concentrations of total nitrogen and phosphorus, higher entrenchment ratios, lower bankfull width/depth ratios, and higher aquatic habitat assessment scores than reaches without BMPs. Turbidity, bank angle, and total coliform and E. coli bacterial counts did not demonstrate consistent differences between sites with and without BMPs. The age of exclosures ranged from three to six years, with older exclosures showing improved nutrient concentrations, channel form, and habitat quality over younger exclosures. While the older exclosures demonstrated characteristics similar to non-pasture reaches, younger exclosures were more comparable to pasture sites without BMPs. Results indicate that BMPs are moderately effective at mitigating cattle impact on streams, but at least six to ten years may be required before significant positive changes are seen in stream channel morphology and water quality.