Stream Water Quality as Influenced by Beaver within Grazing Systems in Wyoming

Abstract

Stream water flowing from watersheds subjected to continuous and deferred rotation grazing by livestock was sampled to enumerate bacteria for detecting differences between grazing treatments and streams. Fecal cliforms, fecal streptococci, total counts at 20 degrees C, and bacteria capable of fluorescing under long wave radiation were selected as indicators of pollution. The study was conducted two summers, 1979 and 1980, on mountain rangeland near Laramie, Wyo. Bacteria counts for different indicator groups varied in their ability to detect change between grazing treatments as well as between streams. Fluorescing bacteria and total counts were of little value in explaining nonpoint source pollution whereas fecal coliform and streptococci were. Variation in counts of fecal coliform and streptococci could not be fully accounted for by differences in grazing management but is partially explained by beaver damming of stream flow. Given that beaver impoundment of selected stream reaches is equal, variation in nonpoint pollution may be caused by differences in grazing treatments.