Project Area and Sampling Sites 



The project area is located in central Montana in Golden Valley County. Careless Creek 

 is a tributary of the Musselshell River. It heads in the Big Snowy Mountains south of Lewistown 

 and flows southeasterly for about 30 miles to its mouth east of Ryegate. Careless Creek begins 

 in the Middle Rockies Ecoregion but flows for most of its length through the Northwestern Great 

 Plains Ecoregion (USEPA 2000). Near its lower end, Careless Creek receives water from 

 Deadman's Basin Reservoir, an off-stream storage reservoir. This water is used to supplement 

 flows in the Musselshell River during the summer irrigation season. Although all three sampling 

 sites are located in the Northwestern Great Plains, water delivered from Deadman's Basin 

 originates in the Little Belt and Crazy Mountains (Middle Rockies Ecoregion). 



Periphyton samples were collected at three sites on Careless Creek (Table 1, Map 1). 

 Elevations at the sampling sites range from about 3730 feet above mean sea level at the site 

 above the Deadman's Basin return to about 3585 feet at the the mouth of Careless Creek. The 

 surface geology of the Careless Creek watershed consists primarily of marine shales, sandstones, 

 and siltstones of the Montana Group (Renfro and Feray 1972). Vegetation along lower Careless 

 Creek is mixed grassland (USDA 1976). All three sites are classified C-3 in the Montana 

 Surface Water Quality Standards, although Deadman's Basin Reservoir and Careless Creek 

 above Swimming Woman Creek are classified B-1 . Both of these segments are located 

 immediately upstream of the reach containing the Careless Creek sampling sites. 



Methods 



Periphyton samples were collected following standard operating procedures of the 

 MDEQ Plarming, Prevention, and Assistance Division. Using appropriate tools, microalgae 

 were scraped, brushed, or sucked from natural substrates in proportion to the importance of those 

 substrates at each study site. Macroalgae were picked by hand in proportion to their abundance 

 at the site. All collections of microalgae and macroalgae were pooled into a common container 

 and preserved with Lugol's (IKI) solution. 



