PROJECT AREA AND SAMPLING SITES 



The project area is located in Garfield County in east 

 central Montana. Big Dry Creek heads at an elevation of 3,500 

 feet south of Sand Springs in the southwestern corner of Garfield 

 county. Little Dry Creek heads south of Jordan at about the same 

 elevation. The two streams flow north and east to where they 

 join 26 miles east of Jordan along Montana Highway 200. 



The project area is within the Northwestern Great Plains 

 Ecoregion (Woods et al . 1999) . The surface geology of the area 

 consists of sandstone and shales of t-he Hell Creek formation in 

 the headwaters and near the mouth of Big Dry Creek, and rocks of 

 the coal -bearing Fort Union Formation in between (Renfro and 

 Feray 1972) . Upland vegetation is predominantly mixed grassland 

 (USDA 1976) . The main land use is livestock grazing. 



Periphyton samples were collected at one site each on Big 

 Dry Creek and Little Dry Creek (Table 1) . The site on Big Dry 

 Creek (#9) is about 2 miles upstream from Fort Peck Reservoir on 

 the Missouri River (Map 1) . The site on Little Dry Creek (Map 2) 

 is just above its confluence with Big Dry Creek, which is about 8 

 miles above Site #9 and 10 miles above Fort Peck Reservoir. 



Elevations at the sampling sites are about 2,300 feet for 

 Big Dry Creek and 2,400 feet for Little Dry Creek. Big Dry Creek 

 and Little Dry Creek are classified C-3 in the Montana Surface 

 Water Quality Standards. 



METHODS 



Periphyton samples were collected following standard 

 operating procedures of the Planning, Prevention, and Assistance 

 Division of the Montana Department of Environmental Quality. 



