Annual Streamflow 



A high degree of correlation (r^ = 0.878) existed between the water-year (October 

 through September) streamflow from the Halfway Creek drainage and that from the Miller 

 Creek drainage prior to trenching, A covariance analysis compared the regression 

 obtained before trenching with that after trenching. That analysis indicated no signi- 

 ficant change in the slope of the regression line after trenching and no significant 

 shift in the data either above or below the original regression line (fig. 9). Years 

 of below average streamflow come closer to conforming to the before-trenching regression 

 line than years of high streamflow. Apparently, years of low streamflow are closely 

 alined by such relatively constant factors as consumptive use and watershed character- 

 istics, whereas years of high streamflow are influenced more by such variable factors 

 as precipitation storm patterns and snowpack distribution prior to runoff (Gartska et 

 al. 1958). A slight reduction observed in streamflow from Halfway Creek in wetter 

 years is indicated by triangles that represent the 4 years since trenching. 



Some of the scatter of points in figure 9 are explained by multiple regression 

 analysis that includes Rice Climatic Station precipitation data. With this precipita- 

 tion included, the r^ increased to 0.932, but did not alter the previous conclusion 

 that trenching had no significant effect on annual flow. 



10 



