» 



In two of the four subreaches the WSP pxedicted water 

 surface elevations were significantly diffeifent (p £.05) from 

 the measured elevations. None of the IFG-4 predicted eleva- 

 tions were significantly different from the measured values. , 

 Neither model produced statistically superior velocity or 

 depth predictions. The velocity predictions for both models 

 were significantly different from the measured velocities in 

 three of the four subreaches. The WSP predicted depths were 

 significantly different from the measured depths in three sub- 

 reaches while the IFG-4 predicted depths were significantly 

 different from the measured depths in all four siibreaches. 

 On a statistical basis, the IFG-4 model was superior to the 

 WSP model in the prediction of only water surface elevations. 



The above statistical analysis does not provide a measure 

 of the bias of the predictions nor does it indicate which 

 model provides the better velocity and depth predictions. The 

 differences between means for the IFG-4 predicted versus the 

 measured data and the WSP predicted versus the measured data ^-^ 

 does provide some measure of the magnitude of the bias. An 

 indication of the better model can be obtained by comparing 

 these differences (Table 30) . The model having the smaller 

 difference is considered the better predictor. f ■ 



% Table 30. Differences between the means for the IFG-4 predicted 



versus the measured water surface elevations, mean segment 

 velocities, and mean segment depths and the WSP predicted 

 versus the measured water surface elevations, mean segment 

 velocities and mean segment depths for subreaches of the 

 ' Madison, Beaverhead, Gallatin and Big Hole Rivers. The 

 standard error is in parenthesis. 



Difference Between Means 



' Madison (#1) Beaverhead (#2) Gallatin (#2) Big Hole (#l) 



Water Surface Elev. (ft) 



IFG-4 vs. .Measured .007(.006) .007(.009) .007(.010) -.003(.012) 



WSP vs. Measured .030(.021) -.026{.033) -.215(.027) -.117(.025) 



Velocity (ft/sec) 



IFG-4 vs. Measured .046(.031) .253(.062) -.238(.033) -.154(.023) 



WSP vs. Measured .100(.052) .670(.082) .222(.052) .225(.036) 



Depth (ft) 



IFG-4 vs. Measured -.105(.016) -. 135 ( .026) -. 066 ( . 021) -.099(.015) 



WSP vs. Measured -.018(.020) -.159(.032) -.192(.021) -.146(.015) 



84 



