Summary of Conclusions 



1 he following section represents a con- 

 sensus of the study team leaders on the conclu- 

 sions most relevant to the general objectives of 

 the cooperative program. They are arranged in 

 the same general order as the presentation of 

 study modules. 



Historical Record, Water Quality, 

 AND Fisheries 



v-^hanges in stream flow and the transport 

 and deposition of fine sediments over the past 

 140 years were evaluated by examining two 

 sources of historical records." mean daily dis- 

 charge at stream gaging sites and sediment 

 accumulation on lake bottoms. These evalu- 

 ations indicated the following relationships 

 between lake/stream measures and timber har- 

 vest, and other land use activities. Source mod- 

 ule for each conclusion is identified as: 



*A = Module A: An Analysis of the Effect 

 of Timber Harvest on Streamflow 

 Quantity and Regime: An Examina- 

 tion of Historical Records. 



*B = Module B: Evaluation of Historical 

 Sediment Deposition Related to Land 

 Use through Analysis of Lake Sedi- 

 ments. 



Historical Record 



1. Comparison of spring runoff regimes 

 among major river drainages in the 

 Flathead between 1940 and present 

 indicated that drainages having experi- 



enced extensive timber harvest also 

 have spring runoff occurring earlier in 

 the year than similar drainages having 

 little timber harvest. (*A) 



2. It appears that timber harvest may re- 

 sult in a higher peak in spring discharge 

 during above normal runoff years, but 

 not in major flood years. (*A) 



3. Lake coring analyses indicated thatpast 

 human land disturbance activities in- 

 creased fine sediment deposition up to 

 10-fold in Whitefish Lake in the 1930s 

 and 4- to 5 -fold in Lake McDonald 

 between 1930 and 1960. (*B) 



4. Lake McDonald 



a. Initial road construction and up- 

 grading of the Going to the Sun 

 Road from Lake McDonald to the 

 continental divide at Logan Pass 

 during the 1930s and 1940s were 

 accompanied by substantial in- 

 creases in sediment deposition in 

 Lake McDonald. (*B) 



b. After the road was paved in the 

 early 1950s the sediment deposi- 

 tion rate in Lake McDonald re- 

 turned to background levels and 

 has remained at background lev- 

 els over the last 25 years. (*B) 



5. Whitefish Lake 



a. Large increases in sediment depo- 

 sition occurred during the early 

 part of this century (1900-1910) 

 and were attributed to railroad 

 construction along the lakeshore 

 and logging activity around the 

 lake. (*B) 



Flathead Basin Cooperative Program Final Report 



Page 145 



