The underlying purpose of this report is to provide ^P 



information that will help the state determine whether Big Spring 

 Creek is water-quality limited and in need of a TMDL . 



PROJECT AREA AND SAMPLING SITES 



Big Spring Creek is located in Fergus County near the city 

 of Lewistown in central Montana. Big Spring, a few miles 

 southeast of Lewistown, is the source of Big Spring Creek and 

 generates most of its streamflow. Major tributaries of Big 

 Spring Creek head in the Big Snowy Mountains, an outlier of the 

 Middle Rockies Ecoregion (Omernik and Gallant 1987) . 



Periphyton samples were collected at five stations on Big 

 Spring Creek (Table 1) . The two sites above Lewistown are 

 classified B-l in the Montana Surface Water Quality Standards. 

 Recreation, fish and aquatic life uses in upper Big Spring Creek 

 are threatened by land development and discharges from a fish 

 hatchery (MDEQ 1998) . 



Below Lewistown, aquatic life, fish and recreation uses are 

 partially impaired by agriculture, channelization, domestic 

 wastewater, the Lewistown wastewater treatment plant, stormwater 

 runoff, animal confinement facilities, and silviculture (MDEQ 

 1998) . The three sites below Lewistown are classified B-2. 



METHODS 



Periphyton samples were collected in August 1998 using the 

 composite, multi-habitat technique described by Bahls (1993). 

 All samples were collected by MDEQ personel as one component of a 

 suite of biological, habitat, and water quality assessments. 



