The original stream order system assigns the upper-most perennial streams to a stream order of 1. However, the WDFW bull trout data, and other commonly used data, are at a scale where not all perennial streams are identified. These data are from the Washington Hydrography Framework Layer, and are at the 1:100,000 scale. Given this limitation, the upper-most streams identified in the data is assigned a stream order of 1.