Summary of Conclusions 



b. The largest sedimentation in- 

 creases occurred in the early 1 930s 

 when substantial logging and as- 

 sociated road and rail line con- 

 struction were concentrated in the 

 Lazy Creek drainage and Lower 

 Swift Creek, near the head of 

 Whitefish Lake. (*B) 



c. Sedimentation rates also were el- 

 evated from the 1950s through the 

 mid-1970s. These increases were 

 attributed to substantial logging 

 and associated road building ac- 

 tivity, which extended to upper 

 portions of the Whitefish Lake 

 drainage. (*B) 



d. Recent logging activity in the 

 Whitefish watershed was not ac- 

 companied by increased sedimen- 

 tation in Whitefish Lake. Possible 

 explanations for reduced sediment 

 impacts include use of preexisting 

 roads, logging on less-erodible 

 lands , improved logging and road- 

 building practices, and a series of 

 comparatively mild runoff years. 

 (*B) 



6. Results from the two study lakes sug- 

 gest that roads represent the greatest 

 disturbance activity resulting in in- 

 creased sediment transport and deposi- 

 tion in the downstream lakes. Once 

 road surfaces stabilize (especially when 

 paved), additional delivery of road- 

 related fine sediment was not detected 

 from sediment core analysis in 

 McDonald Lake and road stabilization 

 is probably also responsible for declin- 

 ing sediments in Whitefish lake. (*B) 



7 . Changes in lake sedimentation directly 

 attributed to floods, fires, and other 

 natural erosion processes during the 

 past 150 years were much smaller than 



changes attributed to human distur- 

 bance activities in the two lake basins. 

 Previous speculation that erosion of 

 naturally unstable stream banks and 

 other natural sources may mask sedi- 

 ment inputs attributed to human activi- 

 ties appear unfounded for the White- 

 fish Lake and Lake McDonald basins 

 in light of data collected in the present 

 study. (*B) 



Water quality and Fisheries 



l\ broad array of streams in the Flathead 

 Basin were evaluated by monitoring various 

 physical, chemical, and biological variables 

 and conducting controlled field experiments. 

 Evaluated stream sites included watersheds with 

 no timber harvest and no roads, no timber 

 harvest with roads, and with timber harvest and 

 roads. Among those watersheds with timber 

 harvest and roads, stream sites were selected to 

 represent different levels of percentage harvest 

 within the basin. Source module for each con- 

 clusion is identified as: 



*C = Module C: The Effect of Timber 

 Management on Stream Water Qual- 

 ity. 



*D = Module D: Fisheries Habitat and Fish- 

 eries Populations. 



8. Monitoring data collected from this 

 research indicated the following statis- 

 tically significant relationships (p < 

 0.1, or better) between timber harvest 

 activity (that is, road building, harvest, 

 etc.) and several physical, chemical, or 

 biological measures of stream ecosys- 

 tem quality. 



a. Timber harvest activity was posi- 

 tively correlated with suspended 



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Flathead Basin Cooperative Program Final Report 



