| North Fork Bull Run River | |
| Name Etymology: | Possibly after cattle that escaped and ran wild along the river between 1849 and 1855[1] |
| Map: | Bull run river oregon watershed map.png |
| Map Size: | 300 |
| Pushpin Map: | USA Oregon |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of the mouth of the North Fork Bull Run River in Oregon |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Oregon |
| Subdivision Type4: | County |
| Subdivision Name4: | Multnomah County |
| Length: | 6miles[2] |
| Discharge1 Location: | mouth[3] |
| Discharge1 Min: | 8.6cuft/s |
| Discharge1 Avg: | 72.6cuft/s[4] |
| Discharge1 Max: | 9700cuft/s |
| Source1: | Mount Hood National Forest |
| Source1 Location: | Palmer Lake, Multnomah County, Oregon |
| Source1 Coordinates: | 45.5644°N -121.9964°W[5] |
| Mouth: | Bull Run River |
| Mouth Location: | Bull Run Reservoir 1, Multnomah County, Oregon |
| Mouth Coordinates: | 45.4939°N -122.035°W |
| Mouth Elevation: | 1096feet |
| Basin Size: | 8.32sqmi |
The North Fork Bull Run River is a tributary, about 6miles 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 south through a protected part of the Mount Hood National Forest in Multnomah County. It joins the Bull Run River at Bull Run Reservoir 1.
The river, which begins at Palmer Lake, slightly southeast of Palmer Peak, flows south and slightly west through Multnomah County and the Mount Hood National Forest within the Bull Run Watershed Management Unit (BRWMU). It receives an unnamed tributary from the right as it passes through Latourell Prairie. Another unnamed tributary enters from the left just before the North Fork reaches a United States Geological Survey (USGS) stream gauge and enters Bull Run Reservoir 1, which is part of the Bull Run River mainstem. The North Fork has no named tributaries. Its mouth is roughly 13.5miles from the confluence of the Bull Run River with the Sandy River.[6]
Since 1965, the USGS has monitored the flow of the North Fork Bull Run River at a stream gauge at the river mouth. The average flow between then and 2007 was 72.6cuft/s. This is from a drainage area of 8.32sqmi. The maximum flow recorded during this period was 9700cuft/s on January 20, 1972, probably affected by a surge of water related to a landslide. The minimum was 8.6cuft/s on October 19 - 29, 1987.[3]
The Bull Run River watershed, which includes the North Fork Bull Run River, drains 139mi2.[7] 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 North Fork Bull Run River basin of 8.32mi2 amounts to about 6 percent of the total Bull Run River watershed,[3] which is managed by the Portland Water Bureau and the United States Forest Service.[8]