Although, for this period, no apparent change in streamflow resulted from trench- 

 ing, it is possible that redistribution of the streamflow did occur. Peak streamflow 

 during the period reflects the most change. 



Based on daily streamflow measurements, a comparison was made of the highest single 

 day of streamflow from Halfway Creek each year and the highest single day of streamflow 

 from Miller Creek each year. Thus compared, the 2 days of each year do not necessarily 

 coincide, but do reflect the peak of snowmelt-generated streamflow each year. An 

 analysis of the 12 years of records prior to trenching resulted in 86 percent of the 

 variance of Halfway Creek streamflow being explained by Miller Creek streamflow (fig. 

 12). After trenching, all peaks were lower than predicted by the regression line. 



A comparison of peak flows and snowpack water content indicated that after trench- 

 ing the peak flows closely followed the regression they followed before trenching; only 

 a slight reduction was noted (fig- 13) . For the year 1968, the peak flow, compared to 

 snowpack conditions, was less than expected on both drainages. 



Less obvious changes in peak streamflow since trenching include less fluctuation 

 in the peak height and a shift of the peak to a later date. Of interest, too, is the 

 fact that peak flow each year on Miller Creek usually occurs within a week of May 21; 

 on Halfway Creek, it can take place any time between March 24 and May 27 (mean, April 

 24), nearly a month ahead of the peak Miller Creek flow. 



Peak streamflow cannot be influenced without showing some change in the subsequent 

 recession. Recession streamflow is characteristic of a particular watershed and more 

 or less independent of current precipitation. Consequently, a change in the recession 



13 



