Project Area and Sampling Sites 



The project area is located at the intersection of the Canadian Rockies, Northern Rockies, 

 and Montana Valley and Foothill Prairies Ecoregions (USEPA 2000) in Lewis and Clark County, 

 Montana. Mountain vegetation is mainly mixed conifer forest, with alpine tundra on the highest 

 peaks. On the foothill prairies, vegetation is mainly mixed grassland, with both subirrigated and 

 wetland areas and shrub- and tree-lined mountain streams descending into the ecoregion (Woods 

 et al. 1999). The main land uses are recreation, logging, and wildlife production in the mountain 

 regions and ranching and wildlife winter range on the foothill prairies. 



The study streams are in the Upper Missouri-Dearborn River (HUC 10030102) USGS 

 hydrologic unit. The Dearborn River and its Middle and South Forks head along the east side of 

 the Continental Divide. The main stem Dearborn River heads on the east face of Scapegoat 

 Mountain (elev. 9204 ft.) in the Scapegoat Wilderness Area. From here it flows southwesterly to 

 its junction with the Missouri River near Craig. The Middle Fork Dearborn River heads on the 

 east side of Rogers Pass (elev. 5610 ft.) and flows northeasterly to its confluence with the main 

 stem Dearborn River at Highway 200 (Map 1). The South Fork Dearborn River heads on the 

 east side of Anaconda Hill (elev. 7153 ft.) and also flows in a northeasterly direction, meeting 

 the main stem Dearborn River about midway between Highway 200 and Highway 287 (Map 1). 

 In the project area, these streams are classified B-1 in the Montana Surface Water Quality 

 Standards. The upper Dearborn River in the Scapegoat Wilderness Area is classified A-1 . 



Periphyton samples were collected at 6 sites, two each on the Dearborn, the Middle Fork, 

 and the South Fork (Table 1 ; Map 1). The upstream sites on the Dearborn and on each of its 

 forks are located in or on the edge of the Canadian Rockies and Northern Rockies Ecoregions. 

 The downstream sites are in the Montana Valley and Foothill Prairies Ecoregion. Elevations at 

 the sampling sites range from 4850 feet (Middle Fork Dearborn River near Rogers Pass) to 4030 

 feet (Dearborn River below Highway 200). 



