Linear Correlation/Regression Analysis of Forestry Models 



back on the site, the water yield is reduced over 

 time.) The ECA model used on the Flathead 

 National Forest is namedH^OY (Isaacson 1977). 



In 1990, the Montana Cumulative Effects 

 Cooperative (which includes the Flathead Na- 

 tional Forest, Department of State Lands, and 

 Plum Creek, L.P.) adopted and then updated a 

 watershed computer model for analysis of tim- 

 ber harvest effects in multiple-ownership wa- 

 tersheds. This updated model (named 

 WATSED) combines a sediment yield model 

 (Cline and others 1981) and an ECA water yield 

 predictive model (U.S.D.A. Forest Service Re- 

 gion 1 1972). WATSED predicts the natural 

 levels of water yield and sediment production 

 along with increases due to timber harvest The 

 WATSED computer model develops predic- 

 tions for a water yield model based upon an 

 ECA concept. The sediment yield portion of 

 WATSED predicts soil erosion from roads, 

 timber harvest, and fire. 



The purpose of this module was to deter- 

 mine the relationships between the quantitative 

 studies and current forest management model- 

 ing tools. We applied land use data to the three 

 computer models. Numerical outputs were then 

 applied as independent variables to linear cor- 

 relation/regression analyses. Results from the 

 water quality and fisheries modules were ap- 

 plied as dependent variables. The goal of this 

 effort was to test the statistical significance of 

 those regressions and to determine whether 

 there is a relationship between what is predicted 

 by the management models and the empirical 

 data collected in the water quality and fisheries 

 studies. 



Linear Correlation/Regression 

 Analysis 



The quantitative field measurements re- 

 viewed included the following: suspended sedi- 

 ment (Flathead National Forest database), total 

 suspended solids (Module C), streambed sedi- 



ment (Module D — McNeil sediment cores and 

 Whitlock- Vibert box sediment), nutrients (Mod- 

 ule C), maximum algae growth (Chlorophyll { 

 — Module C), and frequency of bull trout and 

 westslope cutthroat. trout redds (Module D). 

 Qualitative procedures were conducted in the 

 stream reaches immediately upstream from the 

 water quality or fishery monitoring sites. These 

 procedures included the following: Region-1 

 stream channel stability rating (Flathead Na- 

 tional Forest database, Pfankuch 1978), sub- 

 strate score (Module D), and Montana Water 

 Quality Bureau's state-wide stream reach as- 

 sessment procedure (Module E). This repre- 

 sents all available historic and current informa- 

 tion collected for each watershed. The ECA 

 model HjOY was run on the 28 fisheries study 

 watersheds. Model output for HflY is water 

 yield increase, which was used for comparison 

 to the water quality and fisheries data. The 

 cumulative watershed effects risk assessment 

 procedure. Sequoia (CRA = Cumulative Run- 

 off Acreage — Module H) was applied to the 28 

 fisheries study watersheds. 



Because WATSED was being updated, it 

 was unavailable for use until late in this coop- 

 erative effort. Therefore we did not have time to 

 run data sets on all 28 fishery watersheds. For 

 this reason, we chose from the 28 fishery water- 

 sheds, the 10 that had the longest history of 

 water quality and fish habitat monitoring data. 

 There were five variables from WATSED that 

 were used for the correlations: (1) equivalent 

 clearcut acreage — cumulative, (2) water yield 

 increase (WYI) — annual basis, (3) water yield 

 increase — 75 percent peak flow duration change, 



(4) natural sediment yield — annual basis, and 



(5) sediment yield increase — annual basis. 

 See Table J-1 for the list of study water- 

 sheds and the variables measured. Refer to 

 Figure D-1 for watershed locations. 



The Region 1 Channel Stability Ratings 

 (CSR) were conducted on the same ten stream 



Page 128 



Flathead Basin Cooperative Program Final Report 



