Fir Creek (Bull Run River tributary)

Fir Creek is a tributary, about 5 mi long, of the Bull Run River in the U.S. state of Oregon. Part of the system that provides drinking water to the city of Portland, it flows generally northwest through a protected part of the Mount Hood National Forest in Clackamas and Multnomah counties. It joins the Bull Run River at the upper end of Bull Run Reservoir 1, about 14 mi from the larger stream's confluence with the Sandy River.

Course
The creek arises in the Mount Hood National Forest in northern Clackamas County near its border with Multnomah County. The stream flows north, crossing the border almost immediately and entering Multnomah County. Turning west, it receives an unnamed tributary from the right before turning gradually northwest. It passes under Forest Road 1211 and by a United States Geological Survey (USGS) stream gauge 0.6 mi from the mouth. The creek joins the main stem Bull Run River near the upper end of Bull Run Reservoir 1, about 14 mi from where the river joins the Sandy River.

Discharge
Since 1975 the USGS has monitored the flow of Fir Creek at a stream gauge 0.6 mi from the mouth. The average flow between then and 2009 was 34.5 cuft/s. This is from a drainage area of about 6 sqmi. The maximum flow recorded during this period was 1690 cuft/s on November 25, 1999. The minimum was 1.4 cuft/s on September 5–7, 2003.

Watershed
The Bull Run River watershed, which includes Fir Creek, drains 139 mi2. The basin, which is the main source of Portland's drinking water, is largely restricted to uses related to water collection, storage, treatment, and forest management. The Fir Creek basin of about 6 mi2 amounts to about 4 percent of the total Bull Run River watershed, which is managed by the Portland Water Bureau and the United States Forest Service.