Responses of Fecal Coliform in Streamwater to Four Grazing Strategies

Abstract

Concentrations and loadings (output, number day-1 km-2) of fecal coliform (FC) indicator bacteria were measured from 1979 through 1984 in streamflow from 13 forested watersheds under the following range management strategies: (A) no grazing; (B) grazing without management for livestock distribution; (C) grazing with management to obtain livestock distribution, and (D) grazing with management to obtain livestock distribution and cultural practices to increase forage. Both FC concentrations (number/100 ml) and instantaneous loadings differed significantly among strategies, seasons, and water years. Differences among strategies for mean concentrations were A<C=B<D. For instantaneous loadings, significant differences were A<C, B or D; and C<D. FC concentrations were the same for winter and for snowmelt runoff seasons but concentrations of both were significantly lower than during the summer period. Loadings were different for each season with winter<summer<snowmelt runoff. A definite relationship was established between the presence of cattle on the pastures and FC concentrations. Elevated FC counts in strategy D watersheds and loadings in excess of 10^4 organisms day-1 km-2 in the winter season provide evidence that organisms live into and through the winter period in animal feces, sediment, and soil. Results provide evidence that livestock removal may not provide an immediate solution to elevated levels of FC in streamwater.