Baseflow evaluation of a logged small watershed of the Bull Run River, Oregon

Abstract

The impact of logging operation on baseflow yield on the Bull Run Municipal watershed, Oregon was examined. Daily streamflow data, from 1958 to 1984, for the three small watersheds on the Bull Run river were analyzed. The baseflow recession coefficient was determined by analyses of successive days flows. Least squares and linear regression analysis were utilized to evaluate the effect of treatments. It was shown that logging of 25 percent of total treated watershed reduced mean daily baseflow yield, but this was not significantly different at either the 0.05 or 0.01 level. Also, it was shown by the untreated watershed that there was a significant difference, at the 0.05 level, of baseflow yield between the period of pre- and post-logging. The decreased baseflow yield may have resulted from decreasing fog drip and increasing evaporation rate in the logged areas and from decreasing precipitation on the watersheds during the post-logging period.