Summary of Conclusions 



d. 



sediment concentrations 

 streams. (*C) 



Timber harvest activity was posi- 

 tively correlated with concentra- 

 tions of nutrients (nitrogen and 

 phosphorus). (*C) 

 Timber harvest activity was posi- 

 tively correlated with the percent- 

 age of fine sediment in trout 

 spawning gravels. (*D) 

 Timber harvest activity was posi- 

 tively correlated with gravel im- 

 beddedness in streams. (*D) 

 Field surveys indicated the following 

 statistically significant relationships 

 (coixelations analyses; p < 0.1, or bet- 

 ter), 



a. Timber harvest activity was posi- 

 tively correlated with algal growth 

 in the streams. (*C) 

 Imbeddedness was negatively cor- 

 related with juvenile bull trout 

 densities in streams. (*D) 

 The mean percentage of fine sedi- 

 ments in spawning areas of undis- 

 turbed watershed streams in the 

 Flathead Basin was 31.7% (range 

 24.8% to 39%) while in water- 

 sheds subject to timber harvest the 

 mean percentage of fine material 

 was 39% (range 32.8% to 50.3%). 

 (*D) 

 10. Experimental studies showed that in- 

 creases in the amount of fine sediment 

 in spawning gravels caused a signifi- 

 cant reduction in embryo survivorship 

 of bull trout and westslope cutthroat 

 trout. When the percentage of fine sedi- 

 mentreached40%, survivorship of both 

 species was reduced below 30%, and 

 with 50% fine sediments, embryo 

 survivorship was only 4%. (*D) 



in Stream Reach Assessment 



b. 



c. 



1 he Water Quality Bureau's statewide 

 nonpoint source stream reach assessments were 

 conducted on 30 study streams containing 95 

 reaches. The qualitative visual survey results 

 were evaluated by comparison with the results 

 of the other modules. The source module for 

 conclusions is identified as: 



*E = Module E: Application of the Montana 

 Nonpoint Source Stream Reach As- 

 sessment in the Flathead Basin. 



11. Tree blowdown (due to inadequate 

 streamside management zones or pre- 

 scription), sediment from poor road 

 maintenance, logging slash in the 

 stream channel, and bank trampling by 

 livestock were observed by the sur- 

 veyor to be the primary causes of stream 

 problems related to management prac- 

 tices. (*E) 



12. Quantitative fisheries study results that 

 identified impairment to fish spawning 

 or rearing habitat did not correlate well 

 with impairment values derived from 

 the assessment procedure. The assess- 

 ments generally identified less impair- 

 ment than the results from the fisheries 

 study. This indicates that the assess- 

 ment procedure either does not identify 

 or underestimated impairment to bene- 

 ficial uses. (*D and *E) 



Forest Practices 



1"^ orest practices are often viewed as poten- 

 tial threats to water quality and fisheries. Direct 

 measurement of nonpoint source pollution from 

 specific practices is too cosdy to be used for 

 routine evaluation on all activity areas. There- 



Flathead Basin Cooperative Program Final Report 



Page 147 



