9th wettest year on record in the Bull Run watershed.
The Bull Run watershed -- Portland’s primary source of drinking water -- had a lot of rainfall in 2012, far more than in most years.
The precipitation in 2012 was 100.73 inches of rainfall at the Headworks Treatment Facility, where records have been kept since 1899. It was the 9th wettest calendar year on record, which puts the year in the 90th percentile.
To put the rainfall in perspective, the last time there was over 100 inches in a calendar year was in 1996 -- during the big February flood -- when the level reached 112.14 inches. Before that, it was in 1953 with 102.06 inches. As seen on the graph, most of the years with over 100 inches of rain recorded at the Water Bureau’s Headworks facility were between 1933 and 1953.
Precipitation is also measured at three SNOTEL* sites in the watershed: at the South Fork of the Bull Run River, the North Fork of the Bull Run River, and at Blazed Alder Creek. These precipitation records do not date back as far, but 2012 was a very wet year:
- 146.5 inches at South Fork (2690’ elevation)
- 195.8 inches at North Fork (3060’ elevation)
- 145.8 inches at Blazed Alder (3650’ elevation)
When compared with the 1996 precipitation, there were 196.0 inches at North Fork and 179.0 inches at Blazed Alder (South Forth was not yet established in 1996).
So, all the rain in 2012 was not just in your imagination.
* SNOw TELemetry. Stations operated by the Natural Resources Conservation Service (NRCS) Snow Survey. Each station measures air temperature, precipitation, snow depth and snow water equivalent (SWE, pronounced “swee”), which is based on the weight of the snowpack and reflects the depth that the snow would be if it all melted in place. The station takes hourly readings and uploads them via radio to the Snow Survey’s data facility from where it’s put out on the web.