88 - 



Lower Clark Fork River Basin 



From the nx)uth of the Flathead River to the Idaho state! ine (approximately 

 90 miles), the Clark Fork River receives tributary flows from the Bitterroot 

 Range to the southwest and the Cabinet Mountains to the northeast. The 

 DNR&C basin designation is 76N. The DHES has classified all streams as 

 B-Di, except Ashley Creek (A-Closed) and Pilgrim Creek (A-Open-Dj). 



USFS ownership dominates the area, except in the Thompson River drainage. 

 Timber- harvest activities have been extensive, both on USFS and other 

 forestlands; related water quality impacts are discussed. 



Along the Clark Fork River and in the area of the Flathead River, highly 

 erosive (silt and clay) glacial lake deposits contribute to non-point 

 water pollution. These areas are especially susceptible to impacts from 

 forestry activities. The steep terrain found in this area also contributes 

 to the sensitivity of watersheds. Local Conservation Districts (1977), 

 estimated that three percent (11,500 acres) of the commercial forestland 

 acreage contributed to sediment pollution of streamcourses (USGS drainage 

 basin 17010213). Approximately 75 percent of these problems were con- 

 sidered correctible. 



9. Mainstem Clark Fork River Drainage (Lower) 



This drainage segment is characterized by the narrow valley of the Clark 

 Fork River. Tributary flows drain the adjacent slopes. Ownership within 

 the drainage is predominantly USFS; private and state holdings are con- 

 centrated in the valley bottoms. Significant checkerboard ownership 

 patterns exist in the Thompson River drainage (discussed in following 

 section), Weeksville Creek, Lynch Creek (and tributaries), and in the Vermillion 

 River watershed. 



