spawning, clog irrigation intakes, create tastes and odors in 

 drinking water, and cause other problems. 



The federal Clean Water Act directs states to develop water 

 pollution control plans (Total Maximum Daily Loads or TMDLs) that 

 set limits on pollution loading to water-quality limited waters. 

 Water-quality limited waters are lakes and stream segments that 

 do not meet water-quality standards, that is, that do not fully 

 support their beneficial uses. The Clean Water Act and EPA 

 regulations require each state to (1) identify waters that are 

 water-quality limited, (2) prioritize and target waters for 

 TMDLs, and (3) develop TMDL plans to attain and maintain water- 

 quality standards for all water-quality limited waters. 



One purpose of this report is to provide information that 

 will help the State of Montana to determine whether Box Elder 

 Creek is water-quality limited and in need of TMDLs. Another 

 purpose of this report is to evaluate the sensitivity of 

 periphyton metrics to grazing levels in riparian areas. 



PROJECT AREA AND SAMPLING SITES 



The project area is a section of Box Elder Creek north of 

 Winnett in Petroleum County in central Montana. Box Elder Creek 

 heads in the Judith Mountains northeast of Lewistown and flows 

 southeasterly for about 70 miles to the point where it meets the 

 Musselshell River upstream from Mosby, Montana. The watershed 

 encompasses 1,184 square miles. 



The project area is in the Central Grassland Subregion of 

 the Northwestern Great Plains Ecoregion (Woods et al . 1999). The 

 surface geology consists mainly of marine shales of the Colorado 

 Group (Taylor and Ashley, undated) . Upland vegetation in the 

 study area is mixed grassland (USDA 1976) . Riparian vegetation 



