Veldhuisen, C. and Haight, R., 2003. Regression models for estimating mean annual and low flows from Skagit tributaries. Skagit System Cooperative, La Conner, WA. pp. 3.

Mean annual and low flows (2-year 7-day) for Skagit River tributaries are useful for a variety of applications, including the establishment of in-stream flow requirements. This brief report documents the development of two relatively simple regression equations that may be useful for such purposes.
Because runoff characteristics are known to vary considerably between basins, we focused on methods that would be well suited to small to moderate-sized Skagit tributaries with basins less than 100 mi2. We determined initially that an ideal method would utilize empirical regression models based on local flow data. For ease of implementation, we judged that such a method should not require more than a small number of basin attributes that could be easily determined from topographic maps and/or GIS information. These limitations eliminated from consideration any physically-based hydrologic models, which would be prohibitively data intensive, or annual or shorter time-steps models.