The USGS and the water bureau operate a stream gauge at RM 4.7 (RK 7.6), which is 1.8 miles (2.9 km) downstream from Bull Run Reservoir 2 and the water system intake.
Measurements are for the river only and do not include water diverted upstream of the gauge to the city water supply or to a former power plant.
The maximum flow at this station was 24,800 cubic feet per second (700 m³/s) on December 22, 1964, and the minimum flow was 1.1 cubic feet per second (0.031 m³/s) on October 4, 1974.
The drainage area above this gauge is 107 square miles (280 km²), about 77 percent of the whole watershed.
The maximum flow occurred during the floods of December 1964 and January 1965, rated by the National Weather Service as one of Oregon's top 10 weather events of the 20th century.

Since 1966, the USGS has monitored the flow of the Bull Run River at a stream gauge 14.8 miles (23.8 km) from the mouth.
The average flow between then and 2008 was 404 cubic feet per second (11.4 m³/s).
This is from a drainage area of 47.90 square miles (124.06 km²), about 34 percent of the entire watershed.
The maximum flow recorded during this period was 15,800 cubic feet per second (450 m³/s) on November 5, 1999.
The minimum was 30 cubic feet per second (0.85 m³/s) on October 28–31, 1987.

The uppermost stream gauge on the main stem is at RM 20.9 (RK 30.6), 1 mile (1.6 km) downstream from the outlet structure at Bull Run Lake.
In operation since 1992, the gauge recorded an average flow of 26.1 cubic feet per second (0.74 m³/s) between then and 2009.
This was from a drainage area of 5.08 square miles (13.2 km²), about 4 percent of the total watershed.
The maximum flow recorded during this period was 148 cubic feet per second (4.2 m³/s) on February 7, 1996.
The minimum was 8.2 cubic feet per second (0.23 m³/s) on October 28, 1992.

In addition to the three main-stem gauges, the USGS operates five other stream gauges in the Bull Run watershed.
Each of the following tributaries has one gauge: Fir Creek, Blazed Alder Creek, the North Fork, the South Fork, and the Little Sandy.

Near the outlet structure of Bull Run Lake, a USGS water-stage recorder at RM 21.9 (RK 46.8) has collected data on lake levels since 1992.
The maximum lake content between then and 2009 was 48,340 acre feet (59,630,000 m³) on February 9, 1996, and the minimum was 31,080 acre feet (38,340,000 m³) on October 29, 1992.
The two Bull Run reservoirs are also equipped with water-stage recorders.
The USGS and the water bureau operate a stream gauge at RM 4.7 (RK 7.6), which is 1.8 miles (2.9 km) downstream from Bull Run Reservoir 2 and the water system intake. Measurements are for the river only and do not include water diverted upstream of the gauge to the city water supply or to a former power plant. The maximum flow at this station was 24,800 cubic feet per second (700 m³/s) on December 22, 1964, and the minimum flow was 1.1 cubic feet per second (0.031 m³/s) on October 4, 1974. The drainage area above this gauge is 107 square miles (280 km²), about 77 percent of the whole watershed. The maximum flow occurred during the floods of December 1964 and January 1965, rated by the National Weather Service as one of Oregon's top 10 weather events of the 20th century.
Since 1966, the USGS has monitored the flow of the Bull Run River at a stream gauge 14.8 miles (23.8 km) from the mouth. The average flow between then and 2008 was 404 cubic feet per second (11.4 m³/s). This is from a drainage area of 47.90 square miles (124.06 km²), about 34 percent of the entire watershed. The maximum flow recorded during this period was 15,800 cubic feet per second (450 m³/s) on November 5, 1999. The minimum was 30 cubic feet per second (0.85 m³/s) on October 28–31, 1987.
The uppermost stream gauge on the main stem is at RM 20.9 (RK 30.6), 1 mile (1.6 km) downstream from the outlet structure at Bull Run Lake. In operation since 1992, the gauge recorded an average flow of 26.1 cubic feet per second (0.74 m³/s) between then and 2009. This was from a drainage area of 5.08 square miles (13.2 km²), about 4 percent of the total watershed. The maximum flow recorded during this period was 148 cubic feet per second (4.2 m³/s) on February 7, 1996. The minimum was 8.2 cubic feet per second (0.23 m³/s) on October 28, 1992.
In addition to the three main-stem gauges, the USGS operates five other stream gauges in the Bull Run watershed. Each of the following tributaries has one gauge: Fir Creek, Blazed Alder Creek, the North Fork, the South Fork, and the Little Sandy.
Near the outlet structure of Bull Run Lake, a USGS water-stage recorder at RM 21.9 (RK 46.8) has collected data on lake levels since 1992. The maximum lake content between then and 2009 was 48,340 acre feet (59,630,000 m³) on February 9, 1996, and the minimum was 31,080 acre feet (38,340,000 m³) on October 29, 1992. The two Bull Run reservoirs are also equipped with water-stage recorders.
Bull Run River (Oregon)