Application of the Montana Nonpoint Source Stream 

 Reach Assessment in the Flathead Basin 



By Steve Tralles^ 



Introduction 



Nonpoint source pollution is the major cause 

 of aquatic degradation in Montana (Montana 

 Water Quality Bureau 1990). Nonpoint source 

 pollution originates from diffuse runoff primar- 

 ily during extreme rains or snowmelt and is 

 generally caused by land management activity. 



In order of significance, the following land 

 management activities are the major causes of 

 nonpoint source pollution in Montana: agricul- 

 ture, stream modification, mining, and forest 

 practices (Montana WaterQuality Bureau 1990). 



Forest practices only impair approximately 

 13 percent of Montana's streams. However, 

 those streams are usually located in areas with 

 the highest aquatic resource value. Streams in 

 the Flathead Basin are no exception. 



The Flathead Basin exhibits some of Mon- 

 tana's highest water quality and supports a 

 variety of aquatic life, including westslope cut- 

 throat and bull trout (both species of special 

 concern). In the Flathead Basin, siltation is the 

 leading cause of stream pollution and forest 

 practices are the leading causes of nonpoint 

 source pollution (Flathead Basin Commission 

 1990). 



Montana has developed a nonpoint source 

 pollution management plan to identify and re- 

 solve nonpoint source pollution problems. The 

 Montana Department of Health and Environ- 

 mental SciencesAVater Quality Bureau has de- 

 signed a nonpoint source pollution stream reach 

 assessment procedure. We use it as an initial 

 screening method to identify and prioritize 



moderate and severe nonpoint source pollution 

 problems across the state. 



In conducting the stream reach assessment, 

 surveyors walk the stream and visually evaluate 

 stream conditions. They note perceived impair- 

 ment to beneficial uses caused by nonpoint 

 source pollution and by natural or hydrologic 

 influences. Impairment is the degree to which a 

 stream or stream reach will support designated 

 beneficial uses. For the purpose of this study, 

 the primary beneficial use is fisheries. The 

 surveyors also evaluate land management ac- 

 tivities and application of best management 

 practices. 



Since agency resources (people and money) 

 are limited, the assessment procedure is rela- 

 tively quick and easy — designed primarily to 

 identify the most significant problems. Conse- 

 quentiy, the assessment procedure is subjective 

 and nonquantitative. 



Goals of the nonpoint source pollution 

 stream reach assessment study were ( 1 ) to evalu- 

 ate impairment to beneficial uses in the Flat- 

 head Basin and (2) to evaluate the accuracy of 

 the assessment procedure by comparing its re- 

 sults with the results of quantitative studies 

 performed by other Cooperative Program mem- 

 bers. 



'Steve Tralles is an Environmental Specialist 

 with theWater Quality Bureau of the Montana De- 

 partment of Health and Environmental Sciences in 

 Helena, Montana. 



Flathead Basin Cooperative Program Final Report 



Page 71 



