Influence of Stream Characteristics and Grazing Intensity on Stream Temperatures in Eastern Oregon

Stream temperatures were measured during summer months, 1978 to 1984, at 12 forested watersheds near John Day, Oregon, to determine temperature characteristics and assess effects of three range management strategies of increasing intensity. Maximum temperatures in streams of the 12 watersheds ranged from 12.5 to 27.8 °C. Maximum stream temperatures on four watersheds exceeded 24 °C, the recommended short-term maximum for rainbow trout (Oncorhynchus mykiss) and chinook salmon (O. tshawytscha). Streams with greater than 75 percent stream shade maintained acceptable stream temperatures for rainbow trout and chinook salmon. Lowest temperatures were observed in streams from ungrazed watersheds. Although highest temperatures were observed in the most intensively managed watersheds (2.8 hectares per animal unit month), the effect of range management strategy was not definitive. It was confounded by watershed characteristics and about 100 years of grazing use prior to initiation of this study.