An Analysis of the Effect of Timber Harvest 



ON Streamflow Quantity and Regime: 



An Examination of Historical Records 



By F. Richard Hauer' 



Introduction 



The piupose of this module was to deter- 

 mine the effect, if any, of timber management 

 practices on streamflow quantity or regime. 

 The analyses were based on Flathead Basin 

 historical records of: 



(1) streamflow (United States Geological 

 Survey) 



(2) precipitation, temperature, and snow 

 pack (National Weather Service), 



(3) timber harvest quantity, location, and 

 type (Flathead National Forest, De- 

 partment of State Lands, and Plum 

 Creek Timber Co.), and 



(4) historical fire records (Flathead Na- 

 tional Forest and Glacier National 

 Park). 



I analyzed streamflow quantity and regime 

 from 22 gauging sites located throughout the 

 Flathead Basin for changes that may be attrib- 

 uted to timber harvest. These analyses were 

 conducted in light of natural interannual vari- 

 abilities of climate, past fire history, and current 

 logging practices. I focused the study on deter- 

 mining possible changes in four components of 

 annual streamflow: 



(1) discharge response to specific rainfall 

 events that are distinct and separate 

 from the influence of water stored as 

 snow pack, 



(2) spring runoff quantity or regime (for 

 example, height, breadth, and timing), 



(3) annual discharge to annual precipita- 

 tion relationships, and 



(4) the relationship of annual maximum 

 and minimum discharge. 



This report does not attempt to detail every 

 analysis that was conducted. Many of the com- 

 parative statistics that were run, particularly on 

 untransformed data (that is, data which did not 

 account for interannual variability in tempera- 

 ture, precipitation, or snow pack), were insig- 

 nificant due to high interannual variability Fur- 

 thermore, some of the databases, particularly 

 streamflow on very small creeks, spanned rela- 

 tively short time periods (typically three years), 

 which did not permit long term comparative 

 analyses. 



Results 



Results of the analyses revealed that: 



(1) There was no significant correlative 

 relationship between recorded rainfall 

 events during the summer and fall (that 

 is, not affected by snow pack) and 

 increased river discharge during the 



'Dr. F. Richard Hauer is a Research Associate 

 Professor with the Hathead Lake Biological Station 

 in Poison, Montana. 



Flathead Basin Cooperative Program Final Report 



Page 13 



