This review looks at nonpoint source pollution in watersheds caused by cattle excrement, and how rangeland managers must address certain concerns regarding impacts on water quality due to nutrient and pathogen loading to these water bodies. Nader suggests that water quality data should be examined carefully before assigning a cause and effect relationship between cattle grazing and nonpoint source pollution. Natural background levels of nutrient and pathogen loading can be quite high during storm events. Nonpoint source pollution from pastured and rangeland livestock depends on stocking rate, length of grazing period, the season of use, manure deposition sites, and concentration. Normally, pastures and rangelands have not presented water quality problems caused by cattle excrement, except under special circumstances. Several studies have concluded that cattle excrement contributes negligible nutrient pollution to waterways. Unfortunately, none of the studies defined the treatments well enough to describe the intensity and timing of grazing. The main water quality concerns are from cattle feces and urine deposited directly into the water. Potential problems occur in cases where animals congregate for feeding, watering and resting, in proximity to waterways. There is little scientific evidence that excrement from beef cattle on rangelands significantly impacts water quality. When significant nutrient contamination does occur, especially phosphorus, they are more likely explained by erosion and sediment processes in the watershed. The scientific evidence implicating beef cattle as a significant source of C. parvum or G. duodenalis for surface water is incomplete and contradictory. Given the lack of scientific investigation, it would be premature to claim that rangeland cattle production is the leading source of C. parvum or G. duodenalis for surface water contamination. Rangeland beef cattle excrement may increase pathogen contamination in waterways beyond background levels, but studies have shown that background levels are not zero. High counts of indicator bacteria are often found upstream from grazed areas and are attributed to wildlife. Nader concludes that rangeland water quality can be managed by implementing spatial distribution of cattle through salting, upland water developments. fences for pasture rotation, and even by training or selection of the cattle grazed. Future research needs to be focused directly on monitoring grazing impacts on nutrient and pathogen dynamics at the watershed scale.
Citations and enhanced abstracts for journals articles and documents focused on rangeland ecology and management. RSIS is a collaboration between Montana State University, University of Idaho, and University of Wyoming.