Streamflow changes after logging 130‐year‐old Douglas fir in two small watersheds

Abstract

Timber harvest in two small watersheds in western Oregon containing 130‐yr‐old timber increased annual water yield up to 42 cm. For 4 years after logging, yield increases averaged 38 cm at a 13.0‐ha clearcut watershed and 20 cm at a 15.4‐ha watershed where timber was shelterwood cut. Increased summer flows were indicated by much fewer low‐flow days after logging, particularly at the clearcut watershed. During the 1977 drought year, only eight and two low‐flow days occurred at the clearcut and shelterwood cut watersheds, respectively, compared to 143 and 135 low‐flow days predicted by the calibration relationship. Neither the size nor the timing of peak flows changed significantly after logging at either watershed.